Planetary Sciences and Exploration Programmerajiv/planexnews/oldPlanexpdf...11 Volume -5, Issue-4, Oct 2015 c to otets Volume -5, Issue-4, Oct 2014 EDITOR’S DESk Dear Readers This

N e w s l e t t e r

Planetary Sciences and Exploration Programme

PPPLLLAAANNNEEEXXX Volume -5, Issue-4 OCTOBER 2015

ISSN: 2320-7108

Back to Contents

Mission Updates Events

Editor’s Desk Reader’s Column

News Highlights

Flash News

ARTICLES Solar system through the eyes of ASTROSAT Shyama Narendranath K C, ISRO Satellite Centre, Bangalore, India

Complex molecules in the star forming regions Ankan Das, Indian Centre for Space Physics, Kolkata, India

Emergence of statistical behavior in many particle mechanical systems: Boltzmann’s ideas on macroscopic irreversibility Navinder Singh, Physical Research Laboratory, Ahmedabad, India

NEW HORIZONS

1

1

2

6

7

11

15

20

25

30

31

24

Multi-Application Solar Telescope (MAST) at Udaipur Solar Observatory of PRL Srivastav N, Mathew S K & MAST Team, Udaipur Solar Observatory (PRL), Udaipur, India

List of Reviewers

Announcements and Opportunities

26

CONTENTS

Cover Design: K. Durga Prasad(Image Credits: www.isro.gov.in, personal communication)

The front page mosaic depicts two recent historic events - Inauguration of India’s biggest Solar Telescope, MAST and Launch of India’s first Multi-Wavelength Space Observatory, ASTROSAT. Image of MAST dome is shown at the centre. Images of inauguration are seen in inset. The historic launch of ASTROSAT onboard PSLV-C30 is shown on left while the top panel shows an artist impression of ASTROSAT spacecraft.

EDITORIAL BOARD

Co-Editor:Durga Prasad Karanam

Editor: Neeraj Srivastava

Members:Subhadyouti Bose Jinia Sikdar Poornima K. V. Samarpita Sarkar Nambiar K. Rajagopalan

Associate Editors: Rishitosh Kumar SinhaJayesh P. PabariVijayan Sivaprahasam

Web Manager:Rajiv R. Bharti

Advisors: Prof. S.V.S. Murty Dr. Debabrata Banerjee

COvER pAgE

Mission Story

31 Awards and Honours

1

Volume -5, Issue-4, Oct 2015

Back to Contents 1


1

EDITOR’S DESk Dear Readers

This last week of Sept. 2015 has been very exciting and eventful. MOM has completed one year in the orbit on Sept. 24, with a promise of staying longer; MRO has clinched the evidence of liquid water on Mars at present, NASA announc-ing the result on Sept. 28; and the most exciting event, ISRO created a landmark on Sept. 28, 2015 with the text book launch of much awaited ASTROSAT mission - the first ever space observatory capable of observing the sky in multiple wave-lengths, from optical to hard X-rays. The present issue cel-ebrates the same with an educative and informative article on ASTROSAT by Dr. S. Narendanath KC of Space Astronomy Group, ISAC, highlighting the design concept, configuration specialties and some of the important scientific objectives which could be achieved with this multi-wavelength, multi-institutional space bouquet.

On Aug. 4, 2015, PRL added another feather in its cap with the inauguration of the MAST facility at Udaipur. MAST is an acronym for Multi-Application Solar Telescope. Dr. Nandita Srivastava, Dr. Shibu K. Mathew along with the other mem-bers of the MAST team present an appealing article giving an account of the conception, realization and configuration of this state-of-the art facility along with some important sci-ence issues that can be addressed with this new mace in our armory for solar studies.

Formation of molecules in ISM & concept of time are some of the fundamental but yet to be fully understood problems in cosmology. Dr. Ankan Das of Indian Centre for Space Physics, Kolkata presents a detailed account of complex molecules in the star forming regions exploring their development and link-ing them to the plausible source of life on the Earth. Catering to your inquisitiveness, Dr. Navinder Singh of PRL, further attempts to de-mystify the paradox between microscopic time reversibility and macroscopic time irreversibility; eventually, pondering over the concept of time through a brief discussion over the origin of cosmological arrow of time.

Regular columns News highlights, Mission Updates and Announcement of Opportunities continue to notify about the developments and opportunities in the field of Planet. Sci. & Exp. and a Mission Story on New Horizons mission has been included that has recently sent breathtaking pictures from the outskirts of our solar system.

Before signing off, a farewell bid to our valued team members Ms Varatharajan I and Ms Aarthy E. I would like to extend my heartiest wishes for their future research endeavors. Besides, I welcome into the team - Ms S. Sarkar & Ms. Poornima KV as members and Dr. J. Pabari as Associate editor. We look forward to their esteemed contributions in future.

With this issue, we complete five years of publication of PLANEX Newsletter. Thank you dear readers, for your

unvarying support, encouragement and appreciation that helped us reach this far. Obviously the celebration of success is mutual. Please keep us fuelled by your sup-port so that we can set more milestones in our journey…..

“.....Excellent. You are doing a wonderful job of bringing out a news letter of Planex regularly. I am delighted to read the recent issue. It is full of so much interesting information and articles......I am also happy to note that the circulation in the country is widespread and many from smaller places are evincing keen interest....”

- Ranganath NavalgundInstitute of Advanced Studies

Indian Institute of Science CampusBangalore

“.....I enjoyed the contents of the newsletter. Please keepus in your mailing list, so that we receive future newsletters. I will also inform my students to go through the newsletter. We should get young minds excited about these develop-ments.....”

- R. BaskarDepartment of Environmental Science and Engineering

Guru Jambheshwar University of Science and Technology, Haryana

“..... Thanks for the newsletter. It’s very informative and interesting. Keep the good work up.....”

- A.S. AryaSAC-Ahmedabad

“.....Thank you so much for sending the very informative volume of PLANEX newsletter. The article on “Dark Matter in our Universe” and “The Coldest place of solar system” were very impressive. Overall the issue was very informative and it helped to know our solar system very vividly.....”

- Sarmistha BasuM.P. Birla Institute of Fundamental Research, Kolkata

Happy ReadingEnjoy !

Neeraj Srivastava

READER’S COLumN

Back to Contents

2


Back to Contents

NEwS HIgHLIgHTS

Indian Mars Color Camera captured the un-precedented far side of DeimosMars has almost four decade long history of orbital imag-ing, enabling identification of features as big as Olympus Mons (~18 km) and as small as a rock boulder (~meter) on its surface. Although cameras onboard various spacecrafts sent to orbit around Mars have been able to capture almost every intriguing aspects of Mars, what has been left un-explored in a detailed and focused manner is the Martian Moons (Phobos and Deimos). Until Mars Orbiter Mission (MOM) was sent to orbit Mars, the far side of Deimos has never been viewed. Such a gap has been recently bridged by the Indian Mars Color Camera (MCC) that while taking advantage of the large elliptical orbit of MOM captured what has been hiding behind Deimos. MCC has captured four image frames of the far side of Deimos to generate a high dynamic range product having enhanced image details. The shape of Deimos, as inferred from the MCC images, matches well with the proposed models thus con-firming its far side imaging. As far as the magnitude of Deimos is concerned, the MCC images give a fairly small variation from the reported values, which could be a factor controlled by the surface characteristics of far and near side. Therefore, detailed imaging in future is imperative. In addition, MOM MCC has paved the way to figure out the relevance of the far side of Deimos after its first sighting ever in more than four decades by any other Mars missions.

View of Deimos acquired by MCC onboard MOM (Image Credit: Mars Atlas- ISRO)

Source: http://www.sciencedirect.com/science/article/pii/S0032063315002482

Crater Theophilus exposes hydroxyl bearing features on MoonOne of the important findings of Chandrayaan-1 onboard Moon Mineralogy Mapper (M3) has been to dethrone the long standing theory that suggested Moon to be bone dry. This was manifested by identifying a sharp 2800 nm hydroxyl absorption feature in the M3 spectral products. The spectral observations became even more interesting when it was noticed that the hydroxyl absorption features are bound to magmatic materials excavated from Moon’s interior. One of the evidences for this intriguing geological scenario has been brought to notice in a recent research, wherein from few localized zones of the Theophilus crater central peak, strong 2800 nm hydroxyl features associ-ated with materials consistent to crystalline plagioclase and olivine-crystalline plagioclase-bearing anorthositic and/or troctolitic units have been found. Such a finding churns up the need for further detection of localized sites wherein similar geologic associations could be explored in detail, as the finding has a great scientific implication in constraining the anhydrous ambiguity and improving our understanding of geological evolution of Moon.

Source:http://www.sciencedirect.com/science/article/pii/S0019103515003048

Evidence for late-stage flow of habitable water on MarsDetection of chloride minerals has been often challenged and controversial due to the lack of characteristic absorp-tion features of anhydrous chlorides in VNIR wavelengths. In return, this has limited our understanding of chloride deposits, their geochemical environment, formation sce-nario, age, and relationships to other hydrous minerals and aqueous processes in the history of Mars. To address the importance of chloride salts and discuss their geochemi-cal implications, a group of researchers have analysed the chloride deposits emplaced near Meridiani Planum. It has been suggested that the chloride deposits detected in the confined basin is possibly an outcome of fluviolacustrine processes, wherein the late-stage flow of water has incised a valley that led to accumulation of water and infilling of the basin to form a lake. The accumulated water in the lake subsequently evaporated and thereby precipitated the chloride salts in the interior. From crater count, the maximum age is estimated as ~3.6 Ga. In addition, the study has indicated that this hydrogeological episode was possibly active after widespread water flow and incision in the region and even pointed out that these chloride depos-its reflect some of the last remnants of habitable surface water flowing in the history of aqueous activities on Mars.

Source: http://geology.gsapubs.org/content/43/9/787

3


Back to Contents

NEwS HIgHLIgHTS

Polyphase glaciation on MarsMartian mid-high latitudes have preserved several land-form evidences that suggest a long history of debris-covered glaciation on Mars. Recently, these landform evidences have been compared on the basis of their morphology, stratigraphic sequence, scale, and extent to emphasize that multiple phases of glacial activities are re-corded in the exposed landforms. The study reveals that the region has been reworked by at least two, or may be three, phases of glaciation, wherein, the major and/or extensive glaciation is recorded in the regional scale lobate debris aprons (LDA) and the minor, or more confined glaciation is recorded in the small-scale glacial-like features (GLFs).

Source: http://www.tandfonline.com/doi/full/10.1080/17445647.2015.1047907#.Vgt3A_nvPcs

Discovery of twin craters in JämtlandPossible traces of two meteoritic impacts, a twin strike that occurred 458 million years ago, have been discovered in the Swedish county of Jämtland by a team of researchers. Two craters, one with a diameter of 7.5 km and other of 0.7 km, have been detected in the Jämtland region, a region that was under the 0.5 km deep sea at the time of impact. Drilling operations carried out in these craters revealed presence of identical geologic sequence and the sediment overlying impact sequences is reported as of the same age. Further, to explain the observations, it is hypothesized that water was gushed out during the impact for a hundred seconds, leaving behind the craters dry; however, water eventually came back in the craters along with the frag-ments ejected during the impact. This finding has great implications to understand the disruption event occurred 470 million years ago in the asteroid belt between Jupiter and Mars, which has generated several fragments of as-teroid debris and dust, causing increase of the magnitude in the influx of smaller fragments to Earth by two-folds.

Source: http://www.sci-news.com/geology/science-ordovician-impact-craters-sweden-03231.html

Limits of Extraterrestrial lifeOn the basis of bizarre life forms discovered on Earth, planetary scientists have predicted the nature of lives else-where in the universe, i.e. Mars and Titan. A hypothesis was put forth which suggests that the Earth like life forms can survive on Mars with necessary adaptations to suit itself to the Martian environment, i.e. by making use of water-hydrogen peroxide mixture instead of using water as intracellular liquid. Whereas, on Titan, life might be possible through the utilization of extensive liquid hy-drocarbon like methane or ethane present on the Titan’s surface, which might help the non-water based life forms to thrive on the Titan. It is believed that if we don’t hunt for various life options in the universe, we may never be able to understand what to look for when we really go for exploration. However, these hypotheses can be further tested only upon the discovery of extraterrestrial life and a second biosphere.

Source: http://www.mdpi.com/2075-1729/5/3/1472h t t p : / / w w w . s c i e n c e d a i l y . c o m /releases/2015/08/150826101656.htm

Episodic erosion of Medusae Fossae Formation on Mars Elysium Planitia is the youngest volcanic province on Mars, and second largest volcanic region on the planet, after Tharsis. Recent analysis of SHARAD radar stratig-raphy of this region showed multiple layers of overlapping lava flows. On applying 3D technique on SHARAD data to visualize the subsurface structure of Elysium Planitia, it was found that the source of lava flows and subsequent formation of sedimentary layers are from Medusae Fos-sae Formation (MFF). This implied that the episodes of obliquity controlled atmospheric activity periodically erode materials from MFF and redeposit it across a large region on Mars.

S o u r c e : h t t p : / / o n l i n e l i b r a r y . w i l e y . c o m /doi/10.1002/2015GL065017/abstract

Self-lifting of dust layers on MarsPhoenix landed on Mars in 2008 to search for evidence of water and understand its history, and explore environ-ments suitable for microbial life on Mars. Along with the other onboard instruments, a LIDAR (LIght Detection And Ranging) was kept on Phoenix to collect information about time-dependent structure of planetary boundary layer by studying vertical profile of ice, fog, dust and clouds in the local atmosphere. A team of researchers has reported

Illustration of a twin meteorite impact in Jämtland, Swe-den (Image Credit: Don Dixon/Erik Sturkell/University of Gothenburg)

4


Back to Contents

detection of dust layers in the Martian atmosphere by LI-DAR on Phoenix. The results were studied in the context of dust storm activity near the edge of the north polar ice cap. Atmospheric dust is heated by solar radiation, caus-ing buoyant instability at the planetary boundary layer and detaching dust layers, which arrived at the landing site with altitudes corresponding to the observations given by the LIDAR. This self-lifting of dust layers may be found similar to the “solar escalator” mechanism, occurring in the stratosphere of the Earth.


LADEE spacecraft detected Neon in Moon’s thin atmosphereThe exosphere of the Moon is derived from solar wind, comprising of hydrogen and helium, possibly along with other elements like neon. The elements from solar wind strike the lunar surface and reside there, except helium, neon and argon, which are volatile in nature and bounce back to the space. However, the presence of neon in the Moon’s exosphere is a subject of speculation starting from the Apollo missions, but there were no credible detections about it. Recently, it has been reported that exosphere of the Moon is made up of mostly helium, argon as well as neon, with relative abundance dependent on the time of day, and these results have come from the Neutral Mass Spectrometer (NMS) of the Lunar Atmosphere and Dust Environment Explorer (LADEE) mission, launched in 2013. However, there is no enough neon to make the Moon visibly glow, due to the tenu-ous nature of the lunar atmosphere; NASA’s LADEE spacecraft has confirmed its existence for the first time.


NEwS HIgHLIgHTS

Insitu mineralogical information posted from Yutu rover traverseChina’s 3rd lunar mission (Chang`E-3) consists of a lander and a rover (named Yutu) to traverse around the area in close vicinity to the landing location. It landed on Dec. 14, 2014 in the northern portion of Mare Imbrium, a region well known for its young titanium rich lava flow content. A recent study utilised the VNIS (Visible and near-infrared spectroscopy) and Active Particle X-ray Spectrometer (APXS) instrument onboard the rover to understand the chemical composition. The VNIS instrument operating frequency range is 450-950 nm (100 bands) and 900-2400 nm (300 bands, non-imaging), which is placed under the rover, enabling it to measure the surface reflectance at a distance from ~1m. Four spectral signatures were acquired at four different locations. The in situ measured spectra reveals less matured surface than those reported by the Moon Mineralogy Mapper (M3) (onboard Chandrayaan-1) and Spectral Profiler (onboard Kaguya) for the same re-gion. To decipher the mineralogy over the landing site, the team used a radiative transfer model coupled with spectral look up table. The analysis suggests that the regolith over the landing site contains high abundance of olivine. The onboard APXS instrument suggesting that the northern part of the Mare Imbrium basalt, where Yutu rover traversed, has a higher olivine content that its surroundings also confirmed this high abundance.

S o u r c e : h t t p : / / o n l i n e l i b r a r y . w i l e y . c o m /doi/10.1002/2015GL065273/fullhttp://www.hou.usra.edu/meetings/lpsc2014/pdf/2816.pdf

Simulation of ground ice and its effects on the ice table depth on MarsOn present day Mars, ice in the form of a thin layer of frost

An artistic view of NASA’s LADEE spacecraft in Moon’s orbit( Image Credit: NASA Ames / Dana Berry)

Chang’e 3’s landing site (Image Credit: NASA)

5


Back to Contents

is known to exist on the surface at a few places (mostly beyond ±40° latitudes) and at particular occasions. After Phoenix landed in the Northern Plains of Mars in 2008, frost was observed by a camera on the surface very close to the lander, on the legs of the lander, as well as on a small trench dug by the robotic arm, which exposed the near-surface ice that later sublimated to space. In recent times, surface ice was observed in a few small fresh craters around the landing site of Viking Lander 2 (48° N and 134° E). In order to explain this phenomenon, modeling of ground ice involved atmospheric water of ~20 pr µm (precipitable mi-crometers), a value that turned out to be much higher than previously observed values. It has been said that the pres-ence of snow/ice on the surface acts a source of humidity and that it also reduces the chances of sublimation of sub-surface ice. Using the NASA Ames Mars General Circula-tion Model (MGCM), recent research claims that with the inclusion of a thin layer of seasonal frost, ice table depths of substantially lesser depths would be produced vis-à-vis a model that doesn’t include surface frost. With a maximum frost albedo of ~0.35, an ice table depth of ~64 cm was produced from Ls=182° to Ls=16°, which was found to be 24 cm less deep than the frost-less situation. Moreover, it was found that albedo plays a minor role with respect to the depth of the ice table in the model used by the scientists.

Source: http://www.sciencedirect.com/science/article/pii/S0019103515003498 http://science.journalfeeds.com/astronomy-astrophysics/icarus/modeling-the-effects-of-martian-surface-frost-on-ice-table-depth-2/20150822/

Image Credit: http://nssdc.gsfc.nasa.gov/imgcat/hires/vl2_p21841.jpg

NEwS HIgHLIgHTS

80 lava flows topographically misaligned around Olympus MonsOlympus Mons, the tallest volcano on the solar system, has undergone numerous eruptions since its origin to the recent few hundreds of millions of years. It hosts numerous lava flows around its flanks, which are stratigraphically distin-guishable. It is natural, that the lava flow emanating from the source will follow the down slope topography. However, there are few flows (~ 80 in numbers) on the southern part of the Mons that didn’t follow the down slope direction, but diverged/tilted by an average of 15.4° ± 9.8° in the counter clockwise direction. Ina recent study, attempts were gath-ered to analyse and solve the cause for this non-orientation of flow with respect to the topography. The original lava flow followed the down slope direction, but subsequently due to magmatic loading, flexural subsidence took place on the Olympus Mons region. On a quantitative scale, this could be possible on addition of 1.33 x 105 to 1.35 x 106 km3 of volcanic material, or about 1-10% of the total volume of the present-day edifice. To decipher the age of this subsid-ence event, crater counting over the selected region within the 80 lava flows were carried out. It was found that the subsidence took place around 210±40 Ma, suggesting Late Amazonian volcanic and tectonic events around Olympus Mons region.

S o u r c e : h t t p : / / o n l i n e l i b r a r y . w i l e y . c o m /doi/10.1002/2015JE004875/abstract

Mercury’s chaotic orbit around the Sun ex-plainedData from MESSENGER spacecraft has shed new light about Mercury’s rotation characteristics. A new study suggests that the planet does not rotate smoothly but experiences some rather chaotic oscillations during its 88-day cycle. The oscillations are supposed to be caused by Mercury’s interactions with the Sun during its orbit wherein, Sun’s gravity increases or decreases its rotational velocity depending on where Mercury is on its elliptical orbit. MESSENGER recorded that Mercury is spinning on its axis about 9 seconds faster than previously estimated. Earlier studies calculated that Mercury rotates three times on its axis for every two solar revolutions and scientists think Jupiter’s gravity field might be influencing its spin. Scientist also suggested that Jupiter has imposed a 12-year oscillation period over Mercury’s own orbital period, which correlates well with Jupiter’s orbit around the Sun. This long-term oscillatory lock by Jupiter might help explain the chaotic orbit that Mercury exhibits.

Source: http://blogs.agu.org/geospace/2015/09/09/mercurys-movements-give-scientists-peek-inside-the-planet/

This image, taken by Viking 2 Lander camera 2 at Uto-pia Planitia, shows a thin layer of water ice frost on the martian surface. The image was taken on 18 May 1979, almost exactly one martian year (687 days) after frost first appeared at this spot and was imaged by Viking 2. The layer is thought to be only a couple thousandths of a centimeter thick. The view is looking towards the southeast, the dark boulder at left is roughly one meter across. (Viking 2 Lander, P-21841)

6


Back to Contents

Present-day liquid water activity on MarsWater cannot exist in the liquid state on contemporary Mars due to extremely low surface temperature (average surface temperature ~211 K) and surface pressure (average surface pressure 6.1 mbar). However, some salts can depress the freezing temperature and reduce the evaporation rate of water thereby allowing it to flow like a liquid. This theory is helped by the fact that a large amount of various salts like sulphates, chlorides and perchlorates have been found at different locations on Mars. But, till date, no clear spectral signature of liquid water was detected by spectrometers like CRISM and OMEGA since the previous attempts at spectroscopic analysis of such salty water lacked good correlation with respect to brines’ spectral signatures. Recently, a team of researchers claimed to have found evidence for flowing liquid water on Mars which was at-tributed to a briny feature called Recurring Slope Lineae (RSL). These RSLs have been defined as thin streaks of relatively lower albedo compared to the surrounding sur-face, which appear and lengthen down slopes of craters and steep hill sides when local surface temperatures reach at least 250 - 300 K, thereby indicating the role of season in the formation of these features. The difference between the recent study and the earlier ones is that CRISM data was used to study the spectra from four different locations which strongly suggests the presence of hydrated salts at all the four locations and at times that match the seasonal appearance of RSLs. The salts that have been identified from the observed spectra include magnesium perchlo-rate (Mg(ClO4)2), magnesium chlorate (Mg(ClO3)2), and sodium perchlorate (NaClO4). The presence of these salts has therefore led the team to conclude that RSLs form on Mars due to present-day water activity.

Source: http://www.nature.com/ngeo/journal/vaop/ncurrent/Image Credit: http://planets.ucla.edu/news/top-scientists-debate-whether-life-could-survive-on-mars/

NEwS HIgHLIgHTS FLASH NEwS

A colour-enhanced image of the inside rim of Newton Crater on Mars. The dark streaks, called Recurring Slope Lineae (RSL), may represent current subsurface liquid water activity. The image was taken by an instrument onboard the Mars Reconnaissance Orbiter.

• Nitrogen content in Pluto’s Atmosphere http://www.sciencedaily.com/releases/2015/08/150811132550.htm

• Particle distribution of Saturn’s rings Link:http://www.sciencedaily.com/releases/2015/08/150805075742.htm

• New Horizons unveil new facets of Pluto Link: http://www.sciencedaily.com/releas-es/2015/07/150722014337.htm

• Rosetta and Philae recent discoveries about Comet 67P/Churyumov-Gerasimenko Link:http://sci.esa.int/rosetta/31211-/?farchive_objecttypeid=12&farchive_objectid=3091

• Thermal stability of Ceres ice Link:http://onlinelibrary.wiley.com/doi/10.1002/2015JE004887/abstract

• Chang’E-3 landing site in Mare Imbrium: Photomet-ric properties Link: http://onlinelibrary.wiley.com/doi/10.1002/2015GL065789/abstract

• A new black hole about 5,000 times the mass of the sun Link: http://www.nasa.gov/feature/goddard/astronomers-identify-a-new-mid-size-black-hole

• NASA’s Cassini mission found global ocean beneath Saturn’s Moon Enceladus Link: https://www.nasa.gov/press-release/cassini-finds-global-ocean-in-saturns-moon-enceladus

• Excess ice detected beneath Arcadia Planitia, Mars Link: http://onlinelibrary.wiley.com/doi/10.1002/2015GL064844/abstract

• Potentially habitable climates Link: http://www.sciencedaily.com/releas-es/2015/09/150914102753.htm

• Fractured and porous regions on the far side of the Moon

Link: http://onlinelibrary.wiley.com/doi/10.1002/2015GL065022/abstract

• A close look at a star that is still forming Link: http://mnras.oxfordjournals.org/con-

tent/453/2/2126

7


Back to Contents 7


7


7

Solar System through the eyes of ASTROSAT

Since the beginning of humanity, the motions of the planets have been traced by nameless observers across the civiliza-tions. Records of these lead to speculations on the nature of these objects since then. With the remarkably clever use of telescopes, the Italian scientist Galileo Galilei paved the way for a more serious study of the till then point like objects in the night sky. But we had to wait until the space age to understand the real nature of planets. Rocky, gas-eous, hot, cold, light and dense, today we know that planets in the Solar System and beyond can form and evolve in many ways.

As the space age began, our vision improved, we could go beyond the opaque atmosphere and see the planets in a new light. Visible light is reflected from a planet and it helps us to take a picture of its surface or atmosphere. Infrared observations are best used to identify minerals on the surface or composition of the atmosphere. As we go to shorter wavelengths/higher energies, we can probe high energy processes that are invisible in the optical and IR. UV and X ray emission especially in the outer regions of the atmosphere tells us that planetary atmospheres extends far beyond what is observed in the optical or IR. Figure 1 shows the X ray image of Mars as measured by XMM-Newton showing that the outer atmosphere or exopshere extends to almost 6 to 7 times the radius of Mars.

Multiwavelength observations: How it helps The power of multi wavelength observations has been firmly demonstrated in astrophysics. Take the case of the most familiar object in the sky, Sun. In the visible light, Sun appears as a steady source with the total output hardly undergoing any change. But use an X ray telescope and we find a dynamic surface where magnetic field lines rise and sink, there is emission of particles and radiation and the plasma rises to a whooping million Kelvin. Add in a UV observation, we can trace the origin of the coronal plasma to the chromospheres and the so called ‘transition region’. For example, measuring the composition of the plasma in the chromosphere in UV and that of the corona in soft X rays provide important clues to an age old mystery, how does the corona of the Sun gets heated up.

Of course to see the Sun or any other object in other bands in the electromagnetic spectrum we need to go above the Earth’s atmosphere. Though made with good intentions, Earth’s atmosphere prevents us from measuring high energy radiation from Earth. Hence space platforms are a must if we are to probe the many wonders that unveil under multi wavelength observations. Recently launched Indian As-tronomy satellite provides very good opportunity to carry out such observations.

ASTROnomy SATellite (ASTROSAT)

From optical to hard X-rays, ASTROSAT is a multi-wavelength space observatory conceived and realised in our country for all of us who care to look up the skies. AS-TROSAT will survey the sky in X rays for transients using the Scanning Sky Monitor (SSM) which will provide an alert to the rest of the co-aligned payloads when an event is encountered. Detailed pointed observations of a variety of sources in multi wavelength would be possible with the payloads in optical, UV, soft X rays and hard X rays. Figure 2 shows a model of ASTROSAT in the deployed condition.

Figure 2: ASTROSAT in deployed configuration (Image Credit: ISRO)

Figure 1: X ray image of Mars with XMM-Newton space observatory. The red circle at the center the size of Mars in optical wavelengths (Image Credit: http://www.esa.int/Our_Activities/Space_Science/Exploring_space/X-ray_view_of_the_Red_Planet)

Back to Contents

8


Back to Contents 8


8


8

There are five major scientific payloads on ASTROSAT along with a charged particle monitor that will monitor the radiation environment:

Large Area X ray Proportional Counters (LAXPC): consists of three large area proportional counter detectors in the energy range 3-100 keV

Cadmiun Zinc Telluride (CZT) Imager: consists of 64 CZT detectors arranged in four quadrants and operates in the 15 to 100 keV energy range. There is a coded mask for imaging as well.

Scanning Sky Monitor (SSM): consists of three proportional counters in the 2-10 keV energy range along with coded masks to detect transient X ray events. SSM continuously scans the sky on a rotating platform.

Ultraviolet Imaging Telescope (UVIT): consists of two telescopes in the optical, NUV and FUV range.

Soft X ray telescope (SXT): consists of a grazing incidence Wolter type 1 X ray telescope with a X-ray CCD at the focal plane and operates in the 0.3- 8 keV energy range.

From a Low Earth Orbit (LEO) at an altitude of 650 km, ASTROSAT will perform pointed observations for over five years. Though primarily designed for astrophysical sources, ASTROSAT has immense potential for studying our own neighbourhood, the solar system in particular with SXT and UVIT (and hence described in some more detail below; overview of Astrosat can be found on the back cover). Si-multaneous measurements of UV and Soft X ray emission of objects in the solar system thus could be possible from a single platform.

The Ultra-Violet Imaging Telescope (UVIT)

The Ultra Violet Imaging Telescope (UVIT) simultane-ously images in three channels: FUV (130-180 nm), NUV (200-300 nm) and VIS (320-550 nm) in a circular field of 28’ using a set of filters on a filter wheel. There are two gratings one in FUV and the other in NUV for low resolu-tion slitless spectroscopy. A high spatial resolution of 1.8” is achieved for the FUV and NUV channels while it is 2.2” for the VIS channel. UVIT is realised as two telescopes of focal length 4.75 m as shown in Figure 3. There are three focal plane intensified CMOS imagers that can be operated in a photon counting mode (i.e, count every photon as a

Figure 3: Ultraviolet Imaging Telescopes (courtesy: ISRO)

Back to Contents

Back to Contents 9


function of time) or integration mode (collect photons for a fixed time and read out).

Made by the Indian Institute of Astrophysics (IIA) in Bangalore, UVIT is the highest angular resolution UV telescope ever flown. Thus, it offers a unique opportunity to do potentially new science.

The Soft X ray telescope

One cannot make lenses or reflecting mirrors like in the vis-ible or UV for an X-ray telescope. X rays are almost fully absorbed at the reflecting surface. To reflect and focus X- rays Wolter designed in a very clever way optics whereby X- rays can be reflected when the angle of incidence is very small, almost grazing the surface. Such telescopes have been built and flown in NASA and ESA missions but until now none was ever made in India.

The Soft X-ray Telescope (SXT) made at the Tata Institute of Fundamental Research (TIFR) is the first of its kind to be flown on an Indian satellite. SXT consists of a Wolter Type 1 grazing incidence optics with a X ray CCD at the focal plane (provided by University of Leicster). SXT im-ages in the energy range 0.3 to 8 keV as well as provide the energy spectrum. An area of over a hundred cm2 at 1.5 keV (since the area is dependent on the photon energy) would ensure sufficient photon collection for typical sources. The soft X ray range of SXT is ideal to measure planetary X ray emissions as well.

Thus a combination of SXT and UVIT measurements would provide a unique opportunity to study several processes around the outer gas giant planets and the inner planet Mars whose emission spreads over the entire UV to soft X ray range and has possible common origins.

The power of two eyes

High energy processes reveal their existence through the emission of UV and X ray radiation in planetary atmo-spheres. Planets with a magnetosphere such as Earth and

Figure 5: Composite image of Jupiter in optical, UV and X rays. The X-ray and UV emission from the poles can be seen. (Credit: http://astrosat.iucaa.in/http://chandra.harvard.edu/photo/2002/0001/0001_xray_opt_uv.jpg)

Figure 6: ASTROSAT in the clean room (coutesy: ISRO)

Figure 4: The Soft X ray telescope (Courtesy: ISRO)

Back to Contents

Back to Contents 10

Volume -5, Issue-4, Oct 2015Jupiter exhibit strong X ray and UV emissions especially in the polar regions. The all-pervading solar wind interacts with the upper atmosphere of planets resulting in time variable emissions at these wavelengths. Heavy ions in the solar wind though in miniscule amounts, undergo charge exchange reactions with the exosphere of planets. This is one of the ways heavier atoms escape from the gravitational field of the planet forever resulting in atmospheric erosion over geological time scales. Mars glow in X rays to several radii as seen in Figure 1 because of this solar wind charge exchange emission. This also happens in Comets making comets one of the brightest X ray sources in the Solar System.

Jupiter is one of the strongest X ray emitter in the solar system. The complex Jovian magnetosphere especially at the poles emit soft X –rays that has been shown to have a strange 45 minute periodicity believed to be associated with a hot spot at high northern latitudes. Simultaneous observations of the Jupiter auroras with the Chandra X ray observatory and the FUV channel of the Hubble Space Telescope revealed that the excitation of the same energetic electrons are responsible for both UV and X ray emissions though the source of ions is unclear (Gladstone et al, Nature, 2002, 415, p 1000). It was the ‘simultaneous’ observation that lead to this conclusive evidence. But it is not often that two observatories in space can be co-ordinated to observe a source for the same time period. It is here that an observa-tory like ASTROSAT can work wonders.

Earth also has a magnetosphere that is dynamic often cor-relating with the solar activity. It has been shown that the soft X ray emission lines in the geo-corona (above ~ 500

km of Earth’s surface) are produced by solar wind charge exchange reactions. The spatial and temporal variability of this emission adds in an unwanted component to the spec-trum of interest. A systematic study of the geo-coronal UV and X ray emission would provide a new data set to model the geocorona as well as to eliminate this component from the actual spectrum of the source.

Exciting times ahead

On the 28th of September 2015, on PSLV C-30, India’s first dedicated astronomy satellite has been successfully launched into an orbit of 650 km above the Earth’s surface carrying five sophisticated instruments. It will from this day begin its life of five years or more providing a wealth of data that our country can be truly proud of.

For the hundreds of people who have worked hard to realise this it would be a moment of bliss and so would be for those who look forward to the many scientific breakthroughs this great effort would bring forth. May dreams come true!

Further Reading:

1. http://astrosat.iucaa.in/ 2. http://astrosat.iucaa.in/~astrosat/astrosat_handbook_ ver1.6.pdf

Shyama Narendanath K CSpace Astronomy Group

ISRO Satellite CentreBangalore

E-mail: [email protected]

ASTROSAT is the first ever space observatory that carries instruments from optical to hard X rays

The Ultraviolet Imaging Telescope (UVIT) is the highest angular resolution UV telescope ever flown!

ASTROSAT is the first multi institutional space project (TIFR, IIA, IUCAA, RRI, PRL, Univ of Leicester, Canadian Space Agency and ISRO)

The gold coated reflecting foils on SXT are so smooth that the roughness is only about 7 Angstroms! And 328 of such identical foils had to be made to make the telescope optics

After a specified period from launch, ASTROSAT would be at the disposal of anyone interested in science: Proposals would be accepted (based on scientific merits and feasibility) and the data made public

Back to Contents

Back to Contents 11

Volume -5, Issue-4, Oct 2015Complex Molecules in Star forming Regions

The Big Bang theory is the prevailing cosmological model that describes the start of the Universe. At this point in time all matter and energy of the discernible universe was focused in one point of nearly infinite density. After the Big Bang, the universe began to expand and reached its pres-ent form. To our present knowledge, it is still expanding at an accelerated rate. Most of the matter and energy of the Universe is presumably is in the form of dark matter and dark energy. Universe consists of planets, stars, galaxies, the content of intergalactic space, the smallest subatomic particles and all matter and energy. Areas between the star systems in a galaxy is not empty, it consists of an especially dilute (by terrestrial standards) mixture of ions, atoms, molecules, larger dust grains, cosmic-rays, and (galactic) magnetic fields. The matter consists of 99% gas and 1% dust by mass. This can be referred to as the interstellar medium (ISM). After Big-Bang, some heavier isotopes of hydrogen and helium were created. No heavier elements, known as metals, were fashioned since the universe expanded apace and have become too cold. The heavier elements were created through numerous stages of the stellar evolution. The interstellar gas is primarily composed of hydrogen and helium with traces of alternative species, such as carbon, nitrogen and oxygen etc.. These are the essential elements of the ISM from that the complex molecules (species with 6 or more atoms) are formed via chemical evolution.

Various stages of Star formation

To understand the chemical evolution of a molecular cloud it is not adequate to study only the cloud chemistry; it is also necessary to understand the physical properties of the cloud. Stars are mainly formed in the relatively densest part of the interstellar cloud called as pre-stellar core. These regions are extremely cold (temperatures are about 10 to 20 K). At these temperatures and densities, gases are mainly in the molecular form. A proto-star is the central region of a col-lapsing cloud fragment which is in the process of formation of a star. This has not yet become hot enough (107 K) and does not have enough mass in the core to initiate the process of nuclear fusion in order to halt its gravitational collapse. When the density reaches above a critical value, stars are formed. Since the star formation regions are dense and are opaque to the visible light, we use IR and radio telescopes to investigate them. Star formation begins when the dense parts of the cloud core collapse under their own gravity. The cores are more denser than the outer cloud. As a result, the cloud collapses rapidly.

Various stages of low mass protostars are mainly classi-fied into four categories namely, Class 0, Class I, Class II and Class III. Class 0 stage is the earliest stage of young stellar objects which occurs typically after 104 years after

the onset of collapse. At this stage, accretion is still going on and its central protostar is yet to acquire its final mass. Envelope is more massive than the central protostellar mass. The spectral energy distribution (SED) of a class 0 object gives a black body spectrum at a temperature below 15-30K and peaking at submillimeter wavelengths beyond 100 µm. Protostellar phase resulting from the evolution of a Class 0 object is named as Class I object. Typically protostellar phase arises after 105 years of the onset of collapse. At this stage, envelope becomes less massive than the core mass. Peak of SED shifts to far infrared wavelengths (below 100 µm). Emission from the envelope (about 100K) and the thick disk (a few 100K) are observed. Class I object further evolves into the form of Class II. This stage appears about 106 years after the collapse has started. At this stage most of the mass in the envelope has been removed since most of the materials are accreted in the central object. A flattened circumstellar disk or protoplanetary disk is present at this stage which contributes only about 1% of the total mass of the system. Remaining material of the envelope may still accrete onto the outer part of the disk. At this stage, embedded objects become visible at infrared and optical wavelengths. SED of class II object shows peaks around 2 µm, corresponding to temperatures around 1000-2000K. Actually this stage initiates the pre-main sequence stage of a star. At longer wavelengths an infrared excess is observed which is originating from the disk. Class III stage is the evolutionary stage in the formation of low mass protostars which resulting from the Class II object after 1-10 million years from the onset of initial collapse. At this stage, accre-tion has stopped and what remains from the circumstellar disk is a debris disk. A debris disk is developed around a star after the dissipation of the circumstellar/protoplan-etary disk. The debris disk mainly composed of residual planetesimals analogous to asteroids, comets, and Kuiper Belt Objects in the Solar System. Density and temperature gradually increases as the object contracts. SED of class III object resembles a stellar blackbody peaking at optical and infrared wavelengths. Very small infrared excess is still observed.

Molecules observed around the ISM serve as probes around their physical surroundings. For example, high resolution rotational and vibrational spectra of the observed species are utilized to demonstrate the density and temperature of the gas as well as any large scale motions (collapse and rotation) and vibrational spectra of molecules in dust give the information about the nature of the grain mantle (whether it is polar or non-polar). Study of the interstellar molecules helps to classify various evolutionary stages of star formation just mentioned above. This classification is mainly based on the observational evidences along the low mass stars having luminosity ≤ 102 times the solar luminos-ity because till now we have very limited understanding about the formation of higher mass stars. Low mass stars (initial size of the cloud 0.l-0.3 parsec) mainly started to

Back to Contents

12


Back to Contents 12

Volume -5, Issue-4, Oct 2015form around the cold environments having number density of hydrogen in all forms (nH) ~ 2 x 104 cm-3 and T=10 K. Since the atoms and molecules release energy in the form of radiation as collapse proceeds, it belongs to the isothermal phase initially. When the radius of the cloud reaches nearly ~0.02-0.05 parsec and central density reaches ~ 105-107 cm-

3, cloud becomes opaque and temperature increases rapidly as the collapse progress further. A complete knowledge about the chemical complexity requires a time dependent simultaneous study of physical and chemical properties of a collapsing cloud.

Gas phase chemistry:

The properties of the gaseous complex species are solely dependent on the sources where they are found. Obser-vational evidence suggests that around the dense, cold regions, molecules are mostly unsaturated (hydrogen-poor) and exotic, whereas in young stellar objects, molecules are found to be quite saturated (hydrogen-rich) and terrestrial in nature. Strong evidences of polycyclic aromatic hydro-carbons (PAHs), consisting 30-100 carbon atoms have been assigned to a number of broad emission features in infrared, arising from the re-emission in regions with strong UV or visible radiation such as around the photon dominated

regions (regions strongly affected by the radiation from the newly formed stars). PAHs are also claimed to be re-sponsible for some unassigned series of diffuse interstellar bands (DIBs). A single PAH molecule is yet to be detected because these molecules could easily coagulate to produce a larger cluster. PAHs are much larger than the normally detected gas phase molecules.

Most of the detected gas phase molecules are observed by the rotational spectral lines. Table 1 shows the list of molecules detected in the Interstellar Medium or Circum-stellar Shells as of July, 2015. Molecules whose rotational transitions are observed in the space are first detected in the laboratory by the rotational spectroscopy. The determination of precise rotational and distortional constants then enables the observational prediction. The detection, recording and interpretation of the experimental data can be extremely facilitated by the theoretical predictions of the rotational and distortional constants. Accurate theoretical predictions could guide the experimental investigation to carry out searches in relatively narrower regions of the frequency spectrum. Theoretical predictions have also been shown to be effective in guiding successful astronomical detection of molecules with no laboratory measured transitions such as HNC, HCO+, HOC+, N2H

+, C3N, HCNH+, C2H, etc..The Table 1: Molecules in the Interstellar Medium or Circumstellar Shells (as of 07/2015, Courtesy: https://www.astro.uni-koeln.de/cdms/molecules)

Back to Contents

13


Back to Contents 13

Volume -5, Issue-4, Oct 2015basis of gas phase chemistry lies in the classes of reactions which could progress efficiently under the low temperature and low density conditions of interstellar clouds. Obviously, these reactions do not possess any activation barrier and are highly exothermic in nature. Positive ion-molecule, radia-tive association, dissociative recombination, radical-radical and radical-stable process are of this kind. Positive ions are mainly produced by the cosmic rays. Typical ionization rate (ζ)= 10-17 s-1 is adopted by following the rate of ionization and dissociation of H2. Dominant ion in the ISM is H3

+ which is produced by the following sequence:

H2 + cosmic ray -> H2+ + e-

H2+ + H2 -> H3

+ + H

Since H3+ does not react with molecular hydrogen, it is

abundant enough in the ISM. These ion-molecular reac-tions involving non-polar neutral species posses large rate coefficient (~ 10-9 cm3 s-1) and are independent of temperature. Reactions with the polar neutral species are even faster and rate coefficients are inversely proportional to the temperature. Radiative association reactions often occur in the absence of a normal exothermic product chan-nel. Here, two reactants collide together in the formation of a temporary complex and emission of radiation for the stabilization. Simple statistical approach as well as some experimental measurements found that this type of reaction is very fast (10-9-10-10 cm3 s-1). Dissociative recombination reactions, in which molecular ions and electrons recombine to form smaller neutrals, have rate coefficients 102-3 times larger than the ion-molecular reactions with weak inverse temperature dependence. Though the reactions involving neutrals often possess high activation barriers, reactions involving radicals (species with odd number of electrons) are often found to be highly reactive. Radical-radical and radical-stable reactions can have rate coefficient as high as few times 10-10 cm3 s-1.

In order to study the chemical composition, thousands of reactions of above classes are considered. Large gas phase chemical network is available in a number of databases like, UMIST, OSU etc. These database consist of several thousands reactions along with their rate coefficients. Rate coefficients enlisted in these databases are either obtained from the experiments or by the theoretical calculations. Depending on the assorted targeted regions, physical pa-rameters are chosen for chemical modeling.

Ice phase chemistry:

Complex molecules are detected mainly around the dense sources. Though most of them are detected in the gas phase, there is strong evidence that they can be formed on interstel-lar grains as well. Interstellar dusts are mainly composed of silica (SiO2), magnesium and iron silicates (e.g. Olivine,

orthopyroxene, forsterite), amorphous carbon (do not have the crystalline structure) or water ice. Although by mass the dust consists of only 1% of the total Interstellar medium, it plays a crucial role to govern the physics and chemistry of the interstellar medium. For instance, it is well established that H2, the most abundant molecule in the interstellar medium, forms on dust grains. Actually the formation of complex molecules in the gas phases started after the ejec-tion of H2 molecules from the ice phase. Probably grain chemistry plays a significant role for the formation of other chemical compounds in the ISM. The dust contains significant amount of heavy elements and have a large opacity. It obscures all but the relatively nearby regions at visual and ultraviolet wavelengths and re-radiates the absorbed energy in the far-infrared part of the spectrum. It provides a major part (~30%) of the total luminosity of the Galaxy. The far-infrared radiations from the dusts remove the gravitational energy of collapsing cloud and allow the star formation to occur.

For simplicity, a topologically smooth surface having square size grain is considered for the modeling purpose. Applying periodic boundary conditions on square grain effectively makes it a spherical grain. There are four basic processes which are occurring on the interstellar grains. First step is the accretion of gas phase species, second step is the dif-fusion of the adsorbed species, third step is the reaction between the surface species and fourth and last step is the evaporation of the surface species. Accretion rate of the incoming species depends on gas phase concentration of that species, thermal velocity of the medium, grain size, grain number density and sticking coefficient of the incoming species. Langmuir-Hinshelwood (LH) mechanism is the best studied diffusion process where two adsorbates could diffuse, either by thermally activated random walk or by quantum mechanical tunneling. During this walking if two adsorbates land on same well they could react. At the low temperatures, LH mainly occurs by physisorption or weak binding to the surface. At least one of the two reactants requires to move over or pass through small barriers for any reaction to happen and the size of the barrier against diffusion is related to the size of binding energy. At much higher temperatures, even strongly bound, or chemisorbed species are also able to diffuse and react. There is another reaction mechanism named as Eley-Rideal (ER) mecha-nism. In this mechanism incoming species could strike any adsorbed atoms and might lead to a reaction. ER type reaction is more probable around the high surface coverage region. Due to the high barrier energies around the low tem-peratures, only lighter species like H atom could evaporate after competing with the LH mechanism. Among the other evaporation mechanism, cosmic ray induced desorption is a very efficient means to transfer surface molecules into gas phase during late stage of chemical evolution. It is as-sumed that relativistic Fe nuclei with energies 20 – 70 MeV could deposit 0.4 MeV energy on an average dust particle

Back to Contents

14


Back to Contents 14


of radius 0.1µm. Grains could be cooled down due to thermal evaporation and radiation processes. It is assumed that grains could spend some fraction of time around the elevated temperature having peak around 70K. For the easy inclusion of cosmic ray induced photo-evaporation into the model calculations, thermal evaporation rate at an elevated temperature (~70 K) is calculated and multiplied by the fraction of time spent at the vicinity of 70 K. Another type of evaporation is the non-thermal evaporation. This process assumes the immediate desorption of the adsorbed species because of the energy released during some of the reactions.

A cartoon of the interstellar chemical process is shown in Fig. 1. Fig. 1 shows that gas and grains are continuously interacting with each other to exchange their chemical components. Due to these continuous processing over ~106 years, several complex molecules could be synthesized in the ISM. It is believed that some parts of the complex interstellar species could be synthesized on the interstellar grain which could populate the gas phase by several means (thermal evaporation, cosmic ray induced evaporation, non-thermal evaporation or by the sublimation of grain mantle due to the heat generated from newly born stars). These complex gas phase species then further recycled in the gas phase for their further evolution for the formation of prebiotic molecules (thought to be the species leading to the origin of life). Currently, different absorption bands have been detected in the infrared spectra of cold, dense interstellar and circumstellar environments. These are at-tributed to the vibrational transitions of various molecules frozen on dust grains. Thus interstellar dusts are the key ingredients of interstellar chemical process. H2O is the most abundant interstellar ice component. CH3OH, CO2 and CO also covers a reasonable portion of the interstellar grain mantle. Composition of a simulated grain mantle is shown in Fig. 2 for better understanding. In order to mimic the exact chemical composition of the ISM, it is essential to consider the reaction occurring on both the phases (gas

phase and grain phase) simultaneously.

Prebiotic molecules

Some prebiotic molecules are recently been observed. Various forms of sugar molecules (glycolaldehyde, ethylene glycol etc.) are observed by Hollis et al. (2002). Amino acetonitrile which is the precursor of the simplest amino acid glycine, has recently been observed by Belloche et al. (2008). Kuan et al. (2003) claimed that they detected the interstellar glycine but similar observation by Snyder et al. (2005) ruled out this possibility. They claimed that the lines which were identified for the glycine most likely would be from the ‘weeds’ such as C2H5CN, C2H3CN and gauche ethanol. Weeds are the species having high fractional abun-dances around the hot cores (a relatively small, dense and hot molecular clump occurring in regions of massive star formation) and corinos (a warm, compact molecular clump found in the inner envelope of Class 0 protostars. This is the low mass analogs of hot cores) often lead to composite spectra which are reasonably dense and often creates a big challenge for the identification of new species.

Formation of pre-biotic molecules around these exotic places would be a clue to the origin of life on Earth. These molecules could be trapped inside the ice layer of meteorites which could then bombard to the proto-earth like system for their further evolution. The problem of Origin of life is a long standing puzzle and formation of amino acids in the laboratory by well known work of Miller (1953) ushered

Figure 1: Cartoon diagram of the chemical process

Figure 2: Cross sectional view of an Interstellar grain mantle

Back to Contents

Back to Contents 15

Volume -5, Issue-4, Oct 2015a new direction of research in this area. Recent millimeter and infrared observations along the comets like Hale-Bopp provide a strong correlation between the abundances of some species with that observed along hot cores and corinos. This suggests that at least some of the volatile ices observed in star forming regions are incorporated unaltered into icy solar system bodies. Complex organic species have been noticed from the sample returned from the Stardust mission. Murchison, Orgueil and Tagish Lake meteorites are found to be rich in organic materials.

Further Reading/References:

1. Belloche, A., Menten, K. M., Comito, C., Muller, H. S. P., Schilke, P., et al. 2008, Astron. Astrophys. 482, 179

2. Chakrabarti, S. K., Majumdar, L., Das, A., Chakrabra-ti, S., 2015, Astrophysics and Space Science, 357, 90

3. Das, A., Chakrabarti, S. K., 2011, MNRAS, 418, 5454. Das, A., Majumdar, L., Chakrabarti, S. K., Saha, R.,

Chakrabarti, S., 2013, MNRAS, 433, 3152 5. Das, A., Majumdar, L., Sahu, D., Gorai, P., Sivara-

man, B., Chakrabarti, S. K., 2015, ApJ, 808, 216. Herbst, E., 2005, ESASP, 577, 2057. Herbst, E., van Dishoeck, E. F., 2009, Annu. Rev. As-

tro. Astrophys. 47, 4278. Hollis, J. M., Lovas, F. J., Jewell, P. R., Coudert, L.

H., 2002. ApJ. Lett., 571, L599. Kuan, Y. J., Charnley, S. B., Huang, H. C., Tseng, W.

L., Kisiel, Z., 2003. ApJ, 593, 84810. Puzzarini, C., Stanton, J. F., & Gauss, J., 2010, Inter-

national Reviews in Physical Chemistry, 29:2, 273-367

11. Snyder, L. E., Lovas, F. J., Hollis, J. M., Friedel, D. N., Jewell, P. R., et al. 2005, ApJ, 619, 914

12. https://www.csp.res.in/ICSP-WEB/Docs/Thesis/ank-an_thesis.pdf

13. https://www.astro.uni-koeln.de/cdms/molecules14. http://astroconcepts.obspm.fr/

Ankan DasIndian Centre for Space Physics

43 Chalantika, Garia Station Road, Kolkata

E-mail: [email protected]@gmail.com

Contact: +91-(0)-9830469158

Multi-Application Solar Telescope (MAST) at Udaipur Solar Observatory of PRL

The Multi-Application Solar Telescope (MAST) has re-cently been operationalized at the Udaipur Solar Observa-tory (USO) . MAST has many novel features which make it a unique modern solar telescope. As the name suggests, the telescope is designed to address several solar physics problems that remain unsolved.

Although the field of astronomy has been revolutionized by space-based observations and solar astronomy is no exception, however, in the case of the Sun, ground-based observations continue to complement the space observa-tions. The main advantage being that they allow studies of long-term variation of the Sun and physical mechanisms operating inside the Sun. Ground -based telescopes are also flexible in terms of instrumentation and modifications with time. Keeping in view of easy access, and convenient plan-ning of solar observations from the ground, the scientists of USO worked out a proposal to build a ground-based solar telescope that would be capable of addressing many key unsolved questions.

One of the primary goal was to observe the solar magnetic fields at the smallest possible scales. The existing theories suggest that the process of destruction of magnetic field occurs at small-scales; the flow patterns within sunspots and active regions show distinct properties indicative of fragmentary nature of sunspot magnetic field, in particular, in the chromospheric layers above the sunspots and pores.

Further the evolution of sunspots can be understood either as manifestation of different cross-sections of an emerg-ing flux rope or as the coalescence of a large number of small magnetic elements. Direct measurement of vector magnetic fields in an evolving sunspot alongwith the ve-locity fields can provide clues to distinguish between the opposing sunspot models. To address this crucial question, near-simultaneous vector magnetic field measurements in the photosphere and chromosphere was a key objective of the MAST.

Coronal mass ejections or CMEs are known to originate from non-potential magnetic active regions. Distinct prop-erties of the source active regions promise a scheme to categorise their non-potentiality and hence, the kinematics of the CMEs ensuing from these regions. Combining in-formation on both photospheric and chromospheric layers, can also help us to develop predictive tools to forewarn the occurrence of geo-effective CMEs and therefore the space weather.

To address the above scientific problems, a scientific proposal was laid out to make sensitive magnetic field

Back to Contents

16


Back to Contents 16


measurements with a large aperture telescope at USO by Prof. Venkatkrishnan(Principal Investigator) and the MAST team. The proposal emphasized exploiting the high angular studies from a good observing site such as Udaipur, situated on a geographically advantageous location. The proposal also outlined the scientific goals ranging on spatial scales of active region size (~300 arc-sec) to the fine –scale structure (~0.5 arc-sec).

To fulfil the above objectives, the specifications of the MAST telescope were defined by the USO scientists, based on which it was finally built by Advanced Mechanical and Optical Systems (AMOS) in Liege, Belgium (Denis et al. 2008, 2009). Different back-end instruments for MAST have been built in-house at USO and are being integrated with the telescope presently.

MAST is an off-axis Gregorian telescope with a clear ap-erture of 50 cm, installed on an alt-azimuth mount on the island in the Lake Fatehsagar in Udaipur, Rajasthan (Figures 1 & 2). One of the key objectives of MAST is to study solar activity in high resolution and to measure the magnetic field in photosphere and chromosphere, almost simultaneously.

MAST also has a low-order adaptive optics system to com-pensate for the atmospheric seeing effects. The telescope is housed in a unique fully collapsible dome made of tensile

Figure 1: The housing and the dome (left) for MAST on the island observatory in the lake Fatehsagar of Udaipur

Figure 2: The optical design of the MAST telescope showing different optical components.

Back to Contents

17


Back to Contents 17


fabric. MAST has salient features like a field de-rotator to compensate the image rotation and a guider to track the Sun continuously with high precision (~0.01 arc-sec/min). It also has a wave front sensor for correcting optical misalignments caused due to temperature variations (Mathew et al. 2009).

The MAST telescope consists of 3 main components namely the tube, the fork and the ground interface structure (GIS). The main tube is a stiff central structure and is unconven-

Figure 3: The mechanical structure of the telescope show-ing the tube, the fork and the coude train

Figure 4: MAST pointing towards the Sun as the sun sets. The rear side of the primary mirror is seen here. The black plate with a circular opening is the sun-shield.

tional due to the off–axis optical design of the telescope. It is designed to hold the primary mirror of 50 cm in the central part, the secondary unit comprising of a hexapod, its support and cooling system and tertiary mirror (Figure 3). The fork provides mechanical connection between the azimuth bearing and the two altitude supports. The GIS is a steel welded stiff structure meant to provide connection between the azimuth assembly and the telescope pier to ensure a strong grip of the telescope with the ground rock. GIS supports the derotator system, field rotation mirror, and the wavefront sensor unit.

Owing to large diurnal temperature variations in Udai-pur, which affects the ‘seeing’, the thermal design of the telescope was a key issue and proved to be challenging. Thermal design of MAST is aimed at reducing the effects of solar flux falling on its opto-mechanical components in order to minimise the differential expansion. The tubes and the fork are shaded from the sun’s illumination by an upper sunshield system, shown in Figure 4. The sunshield is a mechanical structure ending in a flat top plate, with two holes one for the primary mirror and the other for the guider. The sunshield moves synchronously with the main telescope (Figure 4).

In order to minimise the temperature difference between the ambient medium and the main mirror, so as to reduce the seeing effects, the primary mirror is thermally controlled

Figure 5: The primary mirror design is such that the temperature is maintained within 1oC of the ambient me-dium. The rear part of M1 shows the pipes through which compressed air flows at a desired temperature.

Back to Contents

18


Back to Contents 18


by flushing air at controlled temperature with a speed of 1.5 m/s. The primary mirror surface is always maintained within ± 1oC of the ambient temperature (Figure 5).The MAST telescope was built in several parts at the AT-MOS factory in Belgium. The components were shipped to India in several boxes which were then transported across the Fatehsagar lake on a pontoon to the island which is about 700 m from the shore with the help of a crane( Figure 6). It was a logistic challenge to lift the heaviest box which weighed ~ 4.5 tonnes. A strut structure was erected on the island for lifting the boxes from the pontoon to the building top by a gantry crane.

After the transportation of all the components, the mechani-cal structure i.e. the GIS, the main tube and the fork, were assembled and integrated. The electrical hardware to sup-port the movement of the telescope was connected. In the next step, thermal system was set-up. After the complete integration of mechanical, electrical and thermal systems of the telescope, the main task was the installation and in-tegration of all the mirrors, mainly the primary mirror and the optical alignment of the whole telescope.

For a perfect optical alignment, the 50 cm mirror which is the main light feed for the telescope is held in a cell. It is controlled by 3 screws that allow the alignment of the cell with respect to the tube structure. The mirror is supported by different kind of fixtures along different directions (axial, radial and tangential) to ensure that its surface accuracy remains intact from the mechanical and thermal loads while telescope is in operation (Figure 7).The primary mirror is an off-axis parabola with a surface accuracy of around l/50.

A preliminary alignment of all the mirrors with respect to the telescope and optic axes was done on-site using a the-odolite. Telescope wave-front quality was tested by using a 45 cm flat and a Zygo interferometer in auto-collimation

Figure 6: Transportation of MAST telescope components in several boxes from the shore to the island in Lake Fateh-sagar on a pontoon built in-house (left image). The gantry crane erected to lift the components from the pontoon to place in the MAST building, is seen in operation.

mode. Secondary hexapod parameters were then adjusted to minimize the errors in the optical alignment of primary and secondary. The rms wave front was found to vary be-tween λ/12 - λ/14. After the completion of installation and alignment, MAST was finally accepted by a committee of experts and was operationalised on June 16, 2015.

The potential of MAST has been realised with the de-velopment of specialised back-end instruments, namely a Narrow–band Imager (Bayanna et al. 2014) to record simultaneous images of the photosphere and chromosphere, a Polarimeter to measure the magnetic fields in sunspots and an Adaptive Optics system (Sridharan et al. 2005) for image stabilisation and to achieve diffraction-limited performance. Several test images have been obtained us-ing MAST. Images of a 3 arc-min circular field-of-view of the Sun taken by a G-band 1nm filter (for photosphere) and 0.05 nm Halle Ha filter (for chromosphere) are shown in Figure 8.

Regular observations of solar photosphere and chromo-sphere are planned to begin from October 2015, after the end of the monsoon season. The evaluation and test obser-vations using the polarimeter and adaptive optics system

Figure 7: Primary mirror M1 being installed at the island site by the optics engineer of AMOS.

Back to Contents

19


Back to Contents

with the MAST telescope are expected to be carried out in the next few months. With the commissioning of MAST, dedicated to high resolution observations of sun, we expect to unravel the outstanding questions in solar physics which will provide a better understanding of solar activity and space weather.

Further reading/References:1. Mathew, S. K.: 2009, in S.V. Berdyugina, S.K., Nagendra,

R. Ramelli (ed.) Solar Polarization, 5: 405, 4612. Raja Bayanna et al., 2014 Solar Physics, Volume 289, Issue

10, pp.4007-40193. Sridharan et al., 2005, Bull. Astron. Soc. India, 33, 414.4. Denis et al., 2008, Proc. SPIE7012, id. 701235.5. Denis et al., 2010, Proc. SPIE7733, id. 773335.

Figure 8: Images of a 3 arc-min circular field-of-view of the Sun taken by a G-band 1nm filter (for photosphere) and 0.05 nm Halle H-alpha filter(for chromosphere) are shown on the left and right, respectively.

The telescope was formally inaugurated on August 4, 2015. On this occasion, Prof. U R. Rao, Chairman, Council of Management of PRL, Prof. Utpal Sarkar, Director PRL and Prof. J. N. Goswami, former director, PRL & Prof. P. Venkatakrishan, former Head, USO addressed the gathering. MAST is now set to take regular solar observations.

Nandita Srivastava E-mail: [email protected]: +91-0294-2457211

Shibu K. Mathew E-mail: [email protected]

Contact: +91-0294-2457212

& MAST TeamUdaipur Solar Observatory, PRL, Udaipur, Rajasthan

20


Back to Contents 20


Volume -5, Issue-4, Oct 2015Emergence of statistical behavior in many

particle mechanical systems:Boltzmann’s ideas on macroscopic irreversibilityAbstract

An attempt is made to de-mystify the apparent paradox be-tween microscopic time reversibility and macroscopic time irreversibility. It is our common experience that a hot cup of coffee cools down to room temperature and it never auto-matically becomes hot (unless we put that in a microwave oven for heating or on gas stove etc). There are numerous such examples. This “one sidedness” of physical processes (like cooling of hot cup) is in apparent contradiction with the time reversibility of the dynamical equations of motion (classical or quantum). The process of automatic heating of a cold cup is perfectly possible from the perspective of dy-namical equations. Ludwig Boltzmann explained this “one sidedness” of physical processes starting from dynamical equations (the famous H-theorem). A criticism was raised by Boltzmann’s contemporaries. The origin of this criticism lies in the very philosophy of “mechanism” that was very prevalent in the 19th century. Everyone wanted to understand physical phenomena through Newtonian mechanics (even J. C. Maxwell devised a mechanical mechanism using gears to explain the electromagnetic field!). The central issue was how can one obtain this “one sidedness” (time irreversibil-ity) if the underlying dynamical laws are time reversible. This article is an attempt to de-mystify this ̀ `paradox’’ from a simple and practical point of view.

1.The “paradox”: Microscopic reversibility and macro-scopic irreversibility

“Directionality” or time asymmetry of macroscopic phe-nomena: There are numerous daily life examples which have “directionality” of time. From our sense perceptions these occur from past to future or in the direction of increasing time. Consider an example of a hot cup of tea placed on a table in a room (figure 1). With time, both tea and cup cool down to room temperature. The cooling requires transfer of heat from hotter tea to colder ambient air. As is well known, at the microscopic level, the colder air molecules (with lesser kinetic energy) collide continuously with the hotter outer surface of the cup thereby taking the energy from the vibrating molecules at the surface of the cup. The result of these collisions is to reduce the kinetic energy of molecules in tea and to enhance that of air molecules. Also at the surface a lot of activity happens in which hotter water molecules in tea evaporate from the surface and the colder ones in air condense. This process of evaporation and condensation leads to the lowering of the kinetic energy of tea molecules with an end result in which average kinetic energy of tea molecules equals that

of air molecules and the system acquires thermodynamic equilibrium [1].

Thus, from the point of view of first law of thermodynamics (conservation of energy), spontaneous heating of a room temperature tea is perfectly possible in which energy is transferred from air to tea. But then why do we never observe this reverse process? One can consider another example. Consider a gas enclosed in one of the compart-ments of a box (figure 2). When the partition is removed gas expands and fills the whole box. It is never observed that the gas automatically re-occupies the original half at any later time although in the dynamical equations of motion of the gas molecules there is nothing that prohibits this reverse process. Again, the reverse process is perfectly in accord with the first law of thermodynamics and is in accord with the laws of dynamics. The laws of dynamics or Newton’s equations of motion are time symmetric i.e., if at a given instant, velocities of all the molecules are exactly reversed and there is no external influence, the system (gas molecules in a box (figure 2)) will re-trace its microscopic thus ``macroscopic’’ trajectory re-filling the first half again.

The simplest reason why this never happens in practice (although perfectly possible in theory) is that there is ``no superhuman being out there’’ that can exactly reverse the velocity vector of all the molecules at a same instant of time. Even if, say, some hypothetical clever experimentalist does this, the reverse trajectories of molecules will not be perfect in the sense that very quickly external influences will totally change the course of all the molecules as no system in nature can ever be ideally isolated (Force exerted by the planet Jupiter on a gas molecule (say Nitrogen mol-

Figure 1: Hot tea cup

Figure 2: Gas in one of the compartments of a box

Back to Contents

21


Back to Contents 21


21

Volume -5, Issue-4, Oct 2015Volume -5, Issue-4, Oct 2015ecule) in a box/container on earth is roughly 10-32 Newtons which sufficient to impart an acceleration of 10-6m/sec2 to the molecule. Under this acceleration, path of the molecule can deviate by ~1 micro-meter in one second!). Thus, in practice, the question of incompatibility of mi-croscopic time reversibility and macroscopic irreversibility is not relevant. The question becomes relevant when one tries to explain this irreversibility theoretically that is with a mathematical model. And Boltzmann with a nice mathematical model was able to explain this macroscopic irreversibility with an implicit assumption which, initially, he himself did not recognize.

2. Resolution of the paradox2.1 Phase space arguments

One can understand the compatibility of microscopic reversibility with macroscopic irreversibility by first recognizing the important role played by the theory of probability when one considers relevant observables that are not much dependent upon the microscopic dynamics [2]. For example, density at a given point in fluid does not depend on how a given molecule is moving about. It is just the average number of molecules in a given volume. Thus observables are highly coarse-grained with respect to microscopic details. Secondly, randomness automatically results when one considers the fact that no system is ide-ally isolated and motion of any molecule becomes random very quickly due to multitude of forces that it experiences. One can appreciate “directionality” of physical processes by considering the following simple example.

Let us consider again a box with a molecule or particle in it and imagine a fictitious partition in the box. Since the particle is under the action of multitude of random forces, on a time scale much greater than some characteristic time scale of random forces, one has to use probabilistic considerations:1.Probability for the particle to be on left side =1/22.Probability for two particles to be on the same side = 1/22 3.Probability for N particles to be on the same side = (1/2N) << 1 for large NThus for large N it is very unlikely that all the particles or molecules spontaneously accumulate in one compart-ment of the box. The behaviour of systems with only few particles is radically different from those containing very large number (an Avogadro number in ordinary cases) of particles.

There is another nice example, due to T. D. Lee1. that can be quoted here. We present an equivalent of it.

Consider the following two cases. In case 1, let us consider that 1000 cars start from Vikramnagar (a place in

Ahmedabad) at time t=0 (Figure 3). Drivers take random turns and they drive for one hour. But most importantly drivers remember the turns taken. At the end of one hour, they reverse their cars and follow the same path that they followed in the forward journey (a right turn at a junction (x) on the forward journey would be a left turn in the back-ward journey, on the same junction). Thus after two hours they all will reach Vikramnagar again. This is equivalent to the microscopic reversibility of the dynamics.

Now consider case 2: Again 1000 cars start from Vikram-nagar at t=0. This time, however, drivers do not remember the turns taken. They drive for one hour and at the end of it they reverse their cars. Now they take random turns again, as they don’t remember their past trajectories. Thus after two hours (starting from t=0) all of them end up at differ-ent locations in the city. Their locations will be randomly distributed all over the city. This example clearly shows that randomness is the root cause of irreversibility although dynamics is completely reversible. Similarly in each colli-sion molecules in a gas suffer randomness and Boltzmann captured it with his famous ansatz (assumption). It will be explained in the next section

1 Author thanks his colleague Namit Mahajan for bringing this example to author’s notice.

The above qualitative considerations can be made quanti-tative. For this, one has to consider the concepts of phase space and microstates. If we have N molecules (point like with no internal degrees-of-freedom) in a box of volume

Figure 3: Map of Ahmedabad.

Back to Contents

22


Back to Contents 22


Volume -5, Issue-4, Oct 2015V, then there are total 6N degrees-of-freedom [3 position (x) and 3 for momentum (p) for each molecule]. The dynamical state of the whole system can be represented by a point in an extended space of 6N dimensions (called the phase space Γ). The point in the phase space is called a microstate. As the molecules move about under mutual and external interactions the phase point also moves and traverses a trajectory called the phase trajectory. Consider now an ensemble of such systems (with the same number of particles in the same volume, and with same ambient tem-perature and pressure). Now in the phase space there will be a “swarm” of phase points (the total number of phase points will be equal to the total number of the members in the ensemble). In this language one recognizes that it is not that every microscopic state at the initial time of an ensemble of systems will evolve in accord with experience (macroscopic irreversibility), but only a great “majority” of them. The “majority” becomes so overwhelming for macroscopic systems that irreversible behaviour becomes a certainty. Thus macroscopic irreversibility emerges (1) when the number of constituents (atoms/molecules) be-comes very large, (2) the observables are coarse-grained, and (3) for such coarse-grained observables dominant role is not played by the dynamics but by the probabilistic laws. As explained above the origin of probabilistic laws is at the heart the fact that no system is ideally isolated and the motion of a molecule becomes random due complex external influences.

Boltzmann quantitatively defined these considerations by invoking the concept of entropy. One defines the system at macroscopic level by few parameters: energy (E), vol-ume (V) and the number of particles in the system (N). This is called the macrostate M of the system. Clearly a very large number of microstates (defined by a point in phase Γ) corresponds to the macrostate M (for example the molecules in the ink droplet can have many configura-tions “Komplexions” as said by Boltzmann)). Define ΓM as the region of phase space containing all microstates (for specific E, V, and N) called compatible microstates. Define |ΓM| =∫ ∏Ni=1dridpi, as the volume of phase space containing all compatible microstates, as a measure of the number of the microstates.

Above considerations lead Boltzmann to propose SB(X) = log|ΓM(X)|called the Boltzmann entropy, which always increases for irreversible processes, as |ΓM| increases due to above considerations. The important point made by him is the identification of this entropy (at equilibrium) with the thermodynamic entropy introduced by Clausius, thus providing the microscopic foundation of thermodynamics. Thus in an irreversible process both entropies thermody-namic and Boltzmann increase. But there is an essential difference. The Boltzmann entropy can be defined for non-equilibrium processes whereas thermodynamic one can only be defined for equilibrium (quasi-static) processes

(see for details [3]). Thus, the macroscopic irreversibility is essentially captured by the Boltzmann entropy [4].

2.2 Kinetic method

One can understand irreversibility from Boltzmann’s kinet-ic method [5]. This method utilizes the fact that no system is ideally isolated and external forces quickly randomize the molecular motion. The dynamically developed correlations quickly vanish: a fact called molecular chaos (originally ``hypothesis of molecular chaos’’ or “Stosszzahl Ansatz”). To understand this consider Boltzmann Kinetic equation for distribution function ƒ(r,v,t) in µ-space (6-dimensions; 3 for position and 3 for momenta) of a molecule. In simple terms the Boltzmann equation depicts the time evolution of the distribution function. It involves two terms, one is called the drift term which arises due to external forces, and the second is called the collision term which captures molecular collisions. For a detailed account consult [5]. Boltzmann defines the H function as H(t)= ∫dr∫dvƒlogƒ. He proves from his equation that (dH/dt ≤ 0), further H is constant if ƒ’ƒ’1 = ƒƒ1 and the distribution function is given by the Maxwell-Boltzmann distribution.

In solving his equation he used his famous assumption “Stosszzahl Ansatz” in which the two particle distribution function in the collision term is written as a product of the single particle distribution functions: ƒ2 (r, v1, r, v2, t) = ƒ1(r, v1, t) ƒ1(r, v2, t). The dynamical correlations, devel-oped via collision process which conserves momentum and energy, are contained in the two particle distribution function (and higher order functions). Writing two particle distribution function as a product of single particle distribu-tion functions essentially removes correlations! Although Boltzmann’s assumption conserve energy but momentum is randomized. This is analogous to drivers forgetting the turns taken (the case 2 of our previously mentioned example). We can now easily see the justification of the assumption made. As mentioned before, “randomness automatically results when one considers the fact that no system is ideally isolated and motion of any molecule becomes random very quickly due to multitude of forces that it experiences” [6]. Thus, the natural randomness in realistic physical systems is captured by the mathemati-cal assumption of Boltzmann, the Stosszzahl Ansatz or assumption. In view of the great success that Boltzmann equation enjoys the assumption of “Stosszzahl Ansatz” has posterior justification too.

3. The origin of the cosmological arrow of time

We perceive time as flowing from past to future. The subtlety of the concept of time is so deceptive that we take it granted and given, independent of the material bodies. But if we approach the notion of time from the thermody-namical perspective it reveals its true nature. To be specific,

Back to Contents

23


Back to Contents 23


Volume -5, Issue-4, Oct 2015consider the Hubble law of the expansion of the universe in which galaxies are all moving away from each other. We perceive the motion of galaxies as they move away from each other with respect to the “time”. Who did define this “time”? The very notion of time that we perceive emerges from our experience with material bodies. And as we have seen that there is one- sidedness to the physical processes (reconsider our previous example of cooling of a cup of tea, or, the irreversible increase of the entropy). This one-sidedness is at the foundation of the very concept of time. This permanent feature (one-sidedness of physical processes) is deep seated in human psychology that is why the subtlety of the concept of time is so deceptive that we take it given. The above argument can be illustrated by the following case. We know that our universe is expanding and in the past it started from a point (the big bang). The initial state of the universe was of the lowest entropy and ever since it is continuously increasing—in accord with the laws of thermodynamics. Thus, the thermodynamical arrow of time (one sidedness of physical processes due to the law of increase of entropy) is at the foundation of our concept of time

4. Summary

It is not difficult to see how macroscopic irreversibil-ity emerges even though the fundamental equations that govern the dynamics of constituents (molecules/atoms) obey time reversibility. The simplest reason why this never happens in practice (although perfectly possible in theory) is that

(1) There is “no superhuman being out there’’ that can exactly reverse the velocity vector of all the molecules at a same instant of time. Even if, say, by some clever means the velocity vectors are reversed, the reverse trajectories of molecules will not be perfect in the sense that very quickly external influences will totally change the course of all the molecules as no system in nature can ever be ideally isolated.

(2) Macroscopic systems involve very large number of constituents, and observables are very coarse with respect to the constituents. For example, size of a hydrodynamical unit cell (say 1 mm3) is very large as compared to the size of the atom/molecule (sub-nanometers) and time scale on which density fluctuates in that unit cell is much greater than typical molecular time scale (like time between two successive collisions. In such cases probabilistic laws become certainties for all practical purposes.

When one theoretically (i.e., using a mathematical model) derives irreversibility from reversible microscopic dynam-ics, one must invoke some “randomness’’ assumption. Boltzmann’s “Stosszzahl Ansatz” is a salient example.

Further Reading:

1. R. Feynman, R. B. Leighton, M. Sands, The Feyn-man Lectures on Physics, Vol. 1, Addison-Wesley, Reading, Mass.(1963).

2. R. P. Feynman, The Character of Physical Law}, MIT Press, Cambridge, Mass. (1967).

3. S. Goldstein and J. L. Lebowitz, On the Boltzmann Entropy of Nonequilibrium Systems, Physica D, 193, 53 (2004).

4. J. L. Lebowitz, (1) Macroscopic Laws and Micro-scopic Dynamics, Time’sArrow and Boltzmann’s En-tropy, Physica A 194, 1-97 (1993); (2) Boltzmann’s Entropy and Time’s Arrow, Physics Today, 46, 32-38 (1993); (3) Microscopic Origins of Irreversible Mac-roscopic Behavior, Physica A, 263, 516-527, (1999).

5. C. Cercignani, Ludwig Boltzmann, the man who trusted atoms, Oxford University Press, Oxford (1998).

6. A. Ya. Khinchin, Mathematical foundations of statis-tical mechanics, Dover Publications; reprint edition (1949).

Navinder SinghPhysical Research Laboratory

E-mail: [email protected] Contact: +91-(079)-2631 4457

Back to Contents

24


Back to Contents 24


24


mISSION STORy - NEw HORIzONS NASA’s New Horizons mission was set on a voyage to explore the distant ‘dwaft planet with a satellite– Pluto and Charon’ system and most primordial Kuiper Belt Objects (KBO) at the verge of our solar system. Follow-ing its long voyage, New Horizons marks the first recon-naissance of Pluto system and KBO. Pluto System and KBOs are termed as “Third Zone” in the solar system as their properties are different from the inner rocky planets and outer gaseous planets. New horizons aims to provide clues about the atmosphere, surface and interiors of these mysterious objects. Mission Profile:New Horizons mission was launched onboard Atlas V-551 vehicle on Jan. 19, 2006. With a primary emission of flyby study of Pluto and its moons, the spacecraft also witnessed close encounters with other objects en route its long jour-ney. On June 13, 2006, New horizons tracked asteroid 2002 JF56 at a flyby distance of nearly 102,000 km to find out its colour, shape and size. New Horizons used gravity assist by Jupiter, about 23 million kilometers, to reduce the total trip time to Pluto by few years. This also gave the spacecraft an opportunity to carry out a number of studies of the Jupiter system. These include jovian atmospheric and magnetospheric studies, dust sampling and so on. Several investigations targeting Jupiter’s moons were also carried out by the spacecraft. After Jupiter’s gravity assist, New Horizons went into hibernation on June 27, 2007. On Oct. 16, 2010, the spacecraft reached half way mark of its journey. A series of annual checkouts and trajectory correc-tion maneuvers were carried out in due course of time till Dec. 6, 2014, when the spacecraft came out of hibernation and began Pluto encounter phase. On July 14, 2015, the spacecraft had its closest approach to Pluto. The mission is currently in departure phase-2. If extended, the mission would aim at further exploring the mesmerizing KBOs.

Spacecraft and Payloads:The New Horizon spacecraft is a 0.7m x 2.1m x 2.7m structure with a 2.1m wide dish antenna and weighs around nearly 478 kg which includes nearly 77 kg of scientific payload. The spacecraft is powered through a single RTG (Radioisotope Thermoelectric Generator) and utilises hydrazine-fueled thrusters for propulsion. The spacecraft carried a suite of scientific instruments to probe the at-omsphere and the surface of the planet. The instruments suite include visible and infrared (IR) spectral mapping, ultraviolet (UV) spectroscopy, imaging, radio science, and in situ plasma sensors.

Ralph is, a Multispectral Visible Imaging Camera and an Infrared compositional mapping spectrometer and provides color images, surface composition and thermal maps.

Alice is a sensitive Ultraviolet imaging spectrometer de-signed to investigate the structure and composition of the dynamic atmosphere of Pluto, and also peep atmospheres around Charon and KBOs. REX (Radio Science EXperiment), an integrated part of New Horizons telecommunication system functions as a passive radiometer and primarily aims at measuring the atmospheric composition and temperature. LORRI (Long Range Reconnaissance Imager) is a pan-chromatic high magnification Telescopic imager aimed at obtaining high resolution images particularly at long dis-tance encounters. LORRI is also expected to provide, Pluto’s far side maps and high resolution geologic data of surface.SWAP (Solar Wind Around Pluto) is a Solar wind and plasma spectrometer aimed at studying solar wind in-teractions with Pluto. SWAP measurements will also provide clues about atmospheric “escape rate” of Pluto.PEPSSI (Pluto Energetic Particle Spectrometer Science Investigation) is the most compact Energetic particle spectrometer that measures the composition and den-sity of plasma (ions) escaping from Pluto’s atmosphere. VBSDC (Venetia Burney Student Dust Counter), a student built dust counter which aims at counting and measuring the sizes of dust particles encountered by New Horizons spacecraft during its entire journey.New Horizons, after its distant trek and successful, Pluto reconnaissance providing us some intriguing facts about the dwarf planet, is now heading for unravelling the mys-teries of other KBOs.Sources: http://www.nasa.gov/sites/default/files/atoms/files/nh-fact-sheet-2015_1.pdf; http://www.nasa.gov/pdf/139889main_PressKit12_Kit12_05.pdf http://www.nasa.gov/pdf/168024main_011607_Jupi-terPressKit.pdf

Back to Contents

Back to Contents 25


25

provide several opportunities of observing Jupiter’s Moon, Europa. The prime aim of the mission is to look for any primitive life that exists on the Icy Moon.

InSight undergoes crucial testsThe upcoming Mars Interior probe InSight is under-going crucial tests towards its preparation for 2016 launch. During July 2015, the lander has undergone a vibration test. It is already known that the lander was subjected to Space Simulation tests during May, 2015.

Opportunity in its 7th Mars WinterOne of the twin Mars Rovers, Opportunity, is now proceeding through its 7th winter on Martian Surface. After diminished activity due to solar conjunction, opportunity resumed operations on 27 June 2015. Opportunity will now concentrate on a new study area near “Marathon Valley” for its further investigations.

MRO completes a decade since launchNASAs Mars Reconnaissance Orbiter (MRO) has completed a decade in Aug. 2015 since its launch to the red planet on Aug. 12, 2015. Since inception, MRO has been providing intriguing results and also assisting mission planning and operations for various Mars Missions. MRO is also expected to support 2016 InSight landing on Mars.

Latest high resolution images of Pluto releasedSeveral high resolution images of Pluto clicked by New Horizons mission were recently released. These images show up a variety of surface features indi-cating diverse landforms and presence of complex processes.

KBO target for New Horizons selectedAfter Pluto reconnaissance, the next target for New Horizons has been selected. The new target is a Kuiper Belt Object (KBO) known as 2014 MU69.

Akatsuki passes through closest point to the SunJAXAs Venus Orbiter passed through perihelion point on Aug. 30, 2015. It is for the ninth time Akatsuki has passed perihelion since its launch. Orbit control maneuver was performed in July for re-injecting Akatsuki into Venus Orbit.

mISSION upDATES (Source: Websites of various space agencies, press releases and published articles)

ASTROSAT launched successfullyThe long awaited India’s Multi Wavelength Space Ob-servatory, ASTROSAT, has been successfully launched on board PSLV-C30 on Sept. 28, 2015. After launch, ASTROSAT was placed into a 644.6 x 651.5 km orbit with 6o inclination. In its heaviest ‘XL’ version, PSLV-C30 has also launched six other foreign satellites along with ASTROSAT. All major astronomy institutions, universities and two institutes from Canada and the UK have supported ISRO in realising the mission.

MOM celebrates anniversaryIndia’s Mars Orbiter Mission (MOM) has now com-pleted one year orbiting the red planet, Mars. On this occasion, Mars Atlas containing a compilation of images acquired by Mars Colour Camera and results obtained by other payloads.

GSAT-6 launched successfully by GSLVGSLV carrying its third indigenously developed Cryo-genic Upper Stage (CUS) has successfully launched Communication Satellite GSAT-6 on Aug. 27, 2015. This success has paved another step forward towards achieving capabilities of launching heavier satellites for future inter-planetary missions.

CubeSats to search for Ice on the MoonRecently NASA has selected Lunar IceCube, a public-private partnership mission to scout for Ice on the Moon. Orbiting in a highly inclined elliptical orbit, Lunar IceCube, is a 6U CubeSat mission that will search for water in its various forms using its on board miniaturised instrument, Broadband InfraRed Compact High Resolution Explorer Spectrometer (BIRCHES).

Curiosity on additional task, track SunspotsApart from being busy analysing martian surface, curiosity intermittently shifts its concentration to look at the face of the sun for monitoring sunspots. This provides an opportunity to look at the opposite side of the sun with respect to the one facing Earth. A series of images depicting the sunspots and solar eruptions have been released recently by NASA.

NASA Europa Mission on the goScientists and Engineers working towards NASA’s 2020 Europa mission have met for the first time in Aug. 2015. While orbiting Jupiter, the mission would

Back to Contents

Back to Contents 26


EvENTS

“mARS ORBITER mISSION (mOm) DATA ANALySIS wORkSHOp”On completion of nearly one year, since Indian Space Research Organisation (ISRO) became the first space agency to reach Mars orbit in its first attempt, PLANEX, PRL Ahmedabad organized a two-day workshop during 4-5 September 2015 to discuss on the utility of the datasets acquired by Mars Orbiter Mission (MOM). The prime objectives of this workshop were to (i) discuss the MOM science objectives and first results, (ii) explore the potential scientific areas from discussion of results from analysis of datasets from other missions, and (iii) evaluate the potential science objectives for a future Mars mission and necessary payloads for driving the Martian science ahead. This workshop was third in the series of workshops organized for improving our preparedness for delivering meaningful scientific information from analysis of datasets acquired by MOM. Invitation for attending and submitting abstracts to this workshop was sent to

all interested and motivated students, engineers, scientists and academicians across the nation for ensuring dense ex-change of opinions among participants and experts of different scientific fields. Such an effort has gathered nearly 50 participants from different ISRO centers, institutes/universities and re-search organisations in the workshop. It is worth mentioning here that such a workshop has not only provided a platform where participants from dif-ferent field of expertise can discuss and learn but also churned up ignited minds to explore the new scientific challenges for a future mission to Mars.

Dr. D. Banerjee, Co-ordinator PLANEX, welcomed the participants and gave an overview of the important scientific aspects while briefing upon some of the important areas in Martian science that demands detailed exploration utilizing datasets acquired in future. In addition, he discussed the ExoMars Trace Gas Orbiter (TGO) mission objectives and onboard in-struments planned to be launched in early 2016 by European Space Agency and the Russian Federal Space Agency. Subsequent to this, Prof. S.V.S. Murty delivered the welcome address, wherein he has compared the differ-ent objectives of the first two MOM related workshops with the objectives of this workshop. He recommended that the principal investigators (PI) of the instruments onboard MOM should come forward in sharing the acquired datasets and suggested that the datas-ets should be released immediately to avoid further delay in interpretation of interesting science aspects that MOM instruments may drill out in near future. He encouraged the participants to collaborate with the PI’s for getting access to the acquired datasets and expressed his excitement towards listening to the first cut results from MOM.

In total, there were five sessions in the workshop; out of which the first four sessions were conducted during the first day itself and the fifth session was conducted during the second day. The first session of the workshop comprised of presentations from science and engineering teams of the Mars Exospheric Neutral Composition Analyser (MENCA) and Ly-man Alpha Photometer (LAP) instruments onboard MOM. In both these presentations, in addition to discussions over instrument operation modes, calibration issues, data quality and data dissemination, the first cut results obtained from the analysis of acquired datasets were displayed. The par-ticipants raised several queries regarding the interaction of MOM instru-ments with the comet Siding Spring (C/2013 A1) during its Mars flyby.

Back to Contents

Back to Contents 27


27

The second session of the workshop dealt with generation and archive of MOM science data products and discussions over methodologies adopted for necessary geometric and radiometric processing. The presentations in this session highlighted upon the hard work and efforts put together in ensuring that the MOM datasets are easily acces-sible to the users and free from artifacts before it is released for public usage. Additionally, the outreach activities for enabling students to acquire hands on experience with the datasets and the “Announcement and Opportunities (A&O)” for requesting access to MOM datasets were discussed. Several interesting images of Mars and its Moons (Phobos and Deimos) acquired by the Mars Color Camera (MCC; one of the instruments onboard MOM) and the generated 3D models for selected areas of Mars were displayed for introducing interested users to the potential of MCC images in exploration of Mars. Further, the importance of Planetary Data System (PDS) and utility of data archive was discussed.

The third session of the work-shop comprised of presentations from researchers analysing datasets from spacecrafts and lander/rover missions sent prior to MOM to Mars. Several interesting aspects related to Martian geology, atmosphere and potential ter-restrial analogues were discussed in this session. The first presentation was made by Dr. V.J. Rajesh, wherein he has highlighted on the potential of paleo-lacustrine depositional setting in Warkalli Formation, Kerala as a Martian analogue for realizing and understanding processes pertaining to hydrous environment of Mars. In his second pre-sentation, he discussed the preliminary insights from their analysis of MRO CRISM datasets of a portion in Valles Marineris on Mars to emphasize on the processes that led to emplacement of certain hydrous minerals in stratigraphic layers. Following this, Dr. S. Rastogi briefed upon the use of atmospheric models to derive the atmospheric gaseous constituents and discussed the significant issues that had influenced detection of methane on Mars. He has showed that it might be due to the dominant CO2 feature in the Martian atmosphere that completely overwhelms the spectral signature of methane and underlined the need for an atmospheric model that may help remove the CO2 dominance and enable accurate detection of methane in Martian atmosphere, if at all it is present. Later, Dr. K.N. Kusuma and Mr. R. K. Sinha, in their respective presentations, displayed certain geomorphic evidences extracted from the analysis of high-resolution remote sensing datasets of Martian surface for extending implications to the aqueous and glacial history of Mars. Subsequent to the tea break in this session, a novel attempt in which for the first time, use of Mars Science Lab (MSL) Curiosity rover data has been employed to estimate the local scale thermal diversity across the various Martian sols traversed by the rover has been presented by Mr. Subhadyouti Bose. He discussed the implica-tions of their estimates of thermal inertia for Gale crater on Mars in the presentation. In the last presentation of this session, Dr. Vijayan discussed the recent geomorphic observations and interpretations carried out for constraining the origin of multi layered ejecta (MLE) craters. He has indicated that the permanent cryosphere in Martian subsurface might have contributed significantly in emplacement of fluidized ejecta around MLE craters in Arabia Terra region.

The fourth session has included presentations of scientific results in form of posters by young and motivated researchers from PLANEX, PRL. The young research-ers utilised this session to gain experience towards learning of presentation skills and adopting methods to explain their key findings in a focused manner while discussing with the participants and experts in the workshop. Several important findings related to glacial, geochemical, thermophysical, aeolian, impact cratering and subsurface properties of Mars were presented and discussed. This session gathered plenty of suggestions and recommendations by ex-perts of respective fields that had great implication on improvement of the quality of results presented.

EvENTS

Back to Contents

28


Back to Contents

The second day of the workshop was relatively more exciting wherein the prime focus was to explore the scientific objectives and necessary payloads for a future Mars mission. Several aspects related to dust, ice, mineralogy, plasma and neutral dynamics, thermal evolution, atmosphere, subsurface, and soft X-ray and gamma ray spectroscopy of Mars were discussed in this session. This session has given a preliminary vision to the important scientific areas demanding detailed exploration in future. Initially, in this session, Dr. Varun Sheel gave a brief description of the dust in the lower atmosphere of Mars, which included the dust storm variability, dust abundance and vertical distri-bution, detached dust layers and their occurrence and effects of the ionosphere. In addition, he has discussed on the implications of dust-ion interactions for providing a base for using data from Thermal Imaging Sensor (TIS; one of

the instruments onboard MOM) for monitoring the variability and characteristics of dust storms. Mr. S. Panini subsequently discussed the science potentials for soft X-ray spectroscopy at Mars and presented the status of development of the X-ray telescope for a future mission to Mars. Further, Dr. N. Srivastava put forward the justification for need of an IR spectrometer with improved spatial resolution than what was in CRISM and OMEGA spectrometers sent earlier to Mars. He has concisely provided a brief summary of the status of infrared spectroscopy and discussed certain scientific findings that were essential in understanding geochemical evolution of Mars. The importance of accurate estimation and characterization of dust, ice and water vapor in the Martian atmosphere was later discussed

by Mr. B. Jaiswal. He has indicated in his presentation that their prime aim is to perform simultaneous measure-ment of water vapor in the limb view and train themselves to estimate the accurate concentrations of water vapor in the atmosphere. Following this, Dr. S. Sahijpal discussed the early thermal evolution and differentiation of Mars in form of sophisticated models wherein he simulated the core-mantle-crust differentiation scenario by considering the upward extrusion of 26Al upon 20% partial melting of silicate. Dr. S Sarkhel subsequently discussed investigation of meteoric metals in the Martian atmosphere using airglow emissions. A brief description on the exploration of plasma and neutral dynamics on Mars using the radar sounder onboard Mars Express was presented by Dr. D. Chakrabarty.

Following the morning session, the need for subsurface exploration of Martian outpost (Phobos and Deimos) was briefed to the participants during presentation made by Dr. B Sivaraman for understanding the chemical com-position through a planned impact experiment triggering molecular ejecta in a future Mars mission. Subsequently, Mr. S. K. Goyal proposed an HPGe detector based gamma ray spectrometer for a future Mars mission for map-ping naturally radioactive elements and other elements on the Martian surface and Dr. J Pabari proposed MODEX for future Mars mission to understand the origin and implications of dust in the Martian atmosphere. In addition, Mr. K. Durga Prasad demonstrated the potential of a multi tier wireless sensor network proposed for a future Mars mission for exploration of hydrothermal targets on Mars. Finally, Dr. S. Vijayan, in this line of proposing potential instruments for a future Mars mission, presented on the imperative need of shallow radar and a stereo camera for exploration of near subsurface (top few meters) and imaging low-relief targets on Mars. He has also taken over the discussions to propose radar for exploration of Venus, wherein, apart from radar there are no other instruments that can penetrate the dense and tenuous atmosphere of Venus and acquire information about its surface and subsurface.

In the concluding session, Prof. N. Bhandari recommended that round table conference amongst the planetary scientists and the PI groups should be ventured in future. In addition, he emphasized that there is an urgent need for pooling of the data for access to public usage. Dr. Shiv Mohan expressed his views regarding the two-fold improvement in the quality of scientific results and presentations made during the workshop. Dr. S. Rastogi requested the workshop co-ordinator to increase the participation of institutes/universities in analysis of Mars Orbiter Mission (MOM) datasets. Mr. Ramakant Mahajan further suggested to publish the abstract volume in a form of workshop proceedings for proper citation of the interesting scientific results presented during the two-day workshop. He also expressed his views on the participation and opportunities given to younger researchers to present their research work in this workshop. Finally, Dr. D. Banerjee in his concluding note thanked all the participants and experts for successful conduct of this workshop.

EvENTS

Back to Contents 29


gROup pHOTO

my ASSOCIATION wITH pLANEx

PLANEX is one of the leading research groups in India that is dedicated to planetary science research and explora-tion. My journey with planetary sciences started when I joined PLANEX as MTech project trainee in July 2013 and that was my first step into the world of planets. I started working on the assessment of scattering mechanism associated with the craters having deposits of water ice on Moon’s poles under the guidance of Dr. Shiv Mo-han and Prof S. V. S. Murty. I was very fortunate and am thankful to both of them for truly guiding me on the way to become a good researcher by teaching me the value of science and analyzing critically my work. After that, I attended the 14th PLANEX Workshop on “Instrumentation for Planetary Exploration” at D. D. Univer-sity, Nadiad, Gujarat, in January 2014 and joined PLANEX as a project associate in June 2014. As a project as-sociate, I worked on the glacial features of the mid-latitudes of Mars using microwave dataset (i.e. SHARAD).

I am thankful to PLANEX for giving me many opportunities to attend various symposiums/workshops/con-ferences which gave me another chance to meet and interact with the elite scientists and researchers from all around the world and hope this becomes one of the great inspirations to achieve even greater heights.

Among many special qualities of PLANEX, one is it’s regular and systematic seminars every Friday, which not only inspires and encourages us but also gives us an opportunity to understand the other topics of planetary exploration. I also had the honour to be associated with the PLANEX Newsletter as a member of the editorial board. I express my gratitude towards the whole team of PLANEX who has supported and encouraged me through-out my stay. I wish PLANEX all the very best and success in all of its future endeavors and hope it continues to encourage, nurture and educate numerous new seeds like me. Best Wishes!

Ms. Santosh Choudhary Ex Project Associate, PLANEX E-mail: [email protected] Phone no: - +91 - 8128177009

Back to Contents

30


Back to Contents

ANNOuNCEmENTS AND OppORTuNITIES

» “47th Lunar and Planetary Science Conference (LPSC)” will take place at The Woodlands Waterway Marriott Hotel and Convention Center, Houston, Texas, between Mar. 21-25, 2016. The deadline for the submission of abstracts is Jan. 12, 2016. The deadline for submissions for a special session is 2nd Oct., 2015.

For more details, visit:- http://www.hou.usra.edu/meetings/lpsc2016/

» “ The 2nd Conference on Astrophysics and Space Science (APSS 2016)” will be held during Feb. 28 - Mar. 1, 2016 in Beijing, China. The deadline for submission of abstracts is up to Oct. 14, 2015.

For more details, visit:- http://www.engii.org/ws2016/Home.aspx?id=686

» “From Giotto to Rosetta” 50th ESLAB Symposium” is supposed to be held in Leiden, The Netherlands, between Mar. 14-18, 2016. The deadline for submission of abstracts is Dec.1, 2015.

For more details, visit:- http://www.congrexprojects.com/2016-events/16a07/introduction

» “Protoplanetary Discussions” will be held from Mar. 7 - 11, 2016 at the John McIntyre Conference Cen-tre, Edinburgh, UK. The last date for abstract submission is Nov.20, 2015.

For more details, visit:- http://www-star.st-and.ac.uk/ppdiscs/index.html

» “Water in the Universe: From Clouds to Oceans” is supposed to be held during Apr. 12-15, 2016, in ESA/ESTEC, Noordwijk, The Netherlands. The deadline for the submission of abstracts is Dec. 11, 2015.

For more details, visit:- http://www.congrexprojects.com/2016-events/16a06

» “Sixth International Conference on Mars Polar Science and Exploration” will take place in the Uni-versity of Iceland, Reykjavik, Iceland, during Sep. 5- 9, 2016. The deadline for submission of Indication of Interest is May, 6, 2016.

For more details, visit:- http://www.hou.usra.edu/meetings/marspolar2016/

» “Enceladus And The Icy Moons Of Saturn” will take place in Boulder, Colorado, USA during Jul. 26 to 29, 2016.

For more details, visit:- http://www.hou.usra.edu/meetings/enceladus2016/

» “ International Symposium And Workshop On Astrochemistry “ will be held at Campinas, Sao Paulo, Brazil between 3rd and 8th July, 2016. The deadline for abstract submission is 15th March, 2016.

For more details and abstract submission guidelines, please visit:- http://www1.univap.br/gaa/iswa/

Name ExoWorlds - Help to decide the names of planets orbiting other stars,

http://nameexoworlds.iau.org

National Space Science Symposium - NSSS 2016

http://spl.gov.in/NSSS2016/index.html

31


Back to Contents

LIST OF REvIEwER’S (vOLumE-v)

The editors acknowledge the following reviewers for their valuable contribution in maintaining the quality and presentation of the contents published in Volume 5 of PLANEX Newsletter.

• A.K. Singal, Physical Research Laboratory, Ahmedabad• D. Chakrabarty, Physical Research Laboratory, Ahmedabad• D. Banerjee, Physical Research Laboratory, Ahmedabad• E. Etim, Indian Institute of Science, Bangalore• K. Acharyya, S.N. Bose National Centre for Basic Sciences, Kolkata• K. Durga Prasad, Physical Research Laboratory, Ahmedabad• K. Niranjan, Andhra University, Visakhapatnam• N. Bhandari, PRL, Physical Research Laboratory, Ahmedabad• N. Mahajan, Physical Research Laboratory, Ahmedabad• N. Srivastava, PRL, Physical Research Laboratory, Ahmedabad• P. Senthilkumar, National Geophysical Research Institute, Hyderabad• P. Appala Naidu, RGUKT, Hyderabad• R. K. Sinha, Physical Research Laboratory, Ahmedabad• S. Phani Rajasekhar, Space Applications Centre, Ahmedabad• S. Vadavale, Physical Research Laboratory, Ahmedabad • S. V. S. Murty, Physical Research Laboratory, Ahmedabad• S. Naik, Physical Research Laboratory, Ahmedabad• S.S. Mamatha, National Institute of Oceanography, Goa• V. K. Rai, Physical Research Laboratory, Ahmedabad• S. Vijayan, Physical Research Laboratory, Ahmedabad

AwARDS & HONOuRS

Prof. J.N. Goswami, Former Director, PRL has been conferred with the ISRO Outstanding Achievement Award 2012 towards his significant contribution to Chandrayaan Mission

Prof. J. S. Ray of PRL has been awarded the Shanti Swarup Bhatnagar (SSB) Prize for the year 2015 in Earth, Atmosphere, Ocean and Planetary Sciences for his outstanding contributions related to the study of stable isotope fractionation, involving the origin and evolution of mantle-derived magmas

32


Back to Contents


ContactPlanetary Sciences and Exploration Programme (PLANEX)

Physical Research Laboratory (Thaltej Campus)(A Unit of Dept. of Space, Govt. of India)Navrangapura, AHMEDABAD – 380 009

GUJARATINDIA

Tel: +91 – (0) 79 – 2631 4416FAX: +91 – (0) 79 – 2631 4407E-mail: [email protected];

url: http://www.prl.res.in/~planex/planexnews

ASTROnomy SATellite (ASTROSAT)From optical to hard X-rays, ASTROSAT is a multi-wavelength space observatory conceived and realised in our country for all of us who care to look up the skies. It will be placed in a Low Earth Orbit (LEO) with an altitude of 650 km and inclination of 6°, an ideal orbit for astrophysical observations due to very low and stable background, from where it will perform observations of various exotic astrophysical objects for over five years.

Some of the most interesting objects that Astrosat will study include astrophysical black holes (both versions stellar mass and super-massive black holes), neutron stars, pulsar, supernova remnants, hot stars, star clusters, galaxy clusters etc. The objects, such as black hole or neutron star in binary system provides the only opportunity to address some of the most fundamental questions of modern physics such as how accurate our understanding of theory of gravity under extremely large gravitational fields of black holes and how matter behaves under extremely large densities of neutron stars. Astrosat will provide one the most comprehensive suit of instruments available on any single platform to address these and many more such fundamental questions. There are five major scientific payloads along with a charged particle monitor that will monitor the radiation environment

1. Large Area X ray Proportional Counters (LAXPC): consists of three large area proportional counter detectors in the energy range 3-100 keV 2. Soft X ray telescope (SXT): consists of a grazing incidence Wolter type 1 X ray telescope with a X-ray CCD at the focal plane and operates in the 0.3- 8 keV energy range.3. Cadmiun Zinc Telluride (CZT) Imager: consists of 64 CZT detectors arranged in four quadrants and operates in the 15 to 100 keV energy range. There is a coded mask for imaging as well.4. Ultraviolet Imaging Telescope (UVIT): consists of two telescopes in the optical, NUV and FUV range. 5. Scanning Sky Monitor (SSM): consists of three proportional counters in the 2-10 keV energy range along with coded masks to detect transient X ray events. SSM continuously scans the sky on a rotating platform.

First four are co-aligned payloads provided detailed pointed observations of variety of celestial sources in optical, UV, soft X-rays and hard X-rays. The fifth payload, SSM, will continuously monitor the sky in X rays. The X-ray sky is highly variable with almost all known sources showing intensity variations over various time scales ranging from minutes to months, some times completely disappearing and new sources appearing in the sky. Thus SSM will play a very important role of keeping a watch on the state of X-ray sky by scanning it twice a day and will provide an alert when an event is encountered.

First year of Astrosat is reserved for the instruments performance verification and calibration (first 6 months) and initial scientific observations by the instrument teams (next 6 months). From second year onwards, it will be a proposal driven mission where any astronomer can propose observation. The data from all scientific observations by Astrosat will eventually be made public after a brief lock-in period.

Art i s t ’s impress ion o f an X-ray binary system (Image credit: NASA)

ASTROSAT ( Image credi t : ISRO)

Back to Contents

Documents

Planetary Sciences and Exploration Programmerajiv/planexnews/oldPlanexpdf...11 Volume -5, Issue-4, Oct 2015 c to otets Volume -5, Issue-4, Oct 2014 EDITOR’S DESk Dear Readers This