Dawn (Spacecraft)

Dawn (spacecraft)

Dawn is a space probe launched by NASA in 2007 tostudy the two most massive protoplanets of the asteroidbelt: Vesta and the dwarf planet Ceres.[6] Dawn has beentaking high-resolution images of Ceres since December1, 2014,[5][7] and entered orbit around Ceres on March 6,2015.[8][9]

Dawn was the first spacecraft to visit Vesta, entering or-bit on July 16, 2011, and successfully completed its 14-month Vesta survey mission in late 2012.[10][11] Dawn isthe first spacecraft to visit Ceres, to orbit a dwarf planetand to orbit two separate extraterrestrial bodies.[8]

The mission is managed by NASAs Jet Propulsion Labo-ratory, with major components contributed by Europeanpartners from the Netherlands, Italy and Germany. It isthe first NASA exploratory mission to use ion propulsionto enter orbits; previous multi-target missions using con-ventional drives, such as the Voyager program, were re-stricted to flybys.[2]

1 Project history

1.1 Initial cancellations

The status of the Dawn mission changed several times.The project was cancelled in December 2003,[12] and thenreinstated in February 2004. In October 2005, work onDawn was placed in stand down mode, and in Jan-uary 2006, the mission was discussed in the press as in-definitely postponed, even though NASA had made nonew announcements regarding its status.[13] On March 2,2006, Dawn was again cancelled by NASA.[14]

1.2 Reinstatement

The spacecrafts manufacturer, Orbital Sciences Corpo-ration, appealed NASAs decision, offering to build thespacecraft at cost, forgoing any profit in order to gainexperience in a new market field. NASA then put thecancellation under review,[15] and on March 27, 2006, itwas announced that the mission would not be cancelledafter all.[16][17] In the last week of September 2006, theDawn missions instrument payload integration reachedfull functionality. Although originally projected to costUS$373 million, cost overruns inflated the final cost ofthe mission to US$446 million in 2007.[18] The Dawnmission team is led by Christopher T. Russell.

2 Scientific background

True-to-scale comparison of Vesta, Ceres, and Earths moon

The Dawn mission was designed to study two large bodiesin the asteroid belt in order to answer questions about theformation of the Solar System, as well as to test the feasi-bility of its ion drive. Ceres and Vesta were chosen as twocontrasting protoplanets, the first one apparently wet(i.e. icy and cold) and the other dry (i.e. rocky), whoseaccretion was terminated by the formation of Jupiter. Thetwo bodies provide a bridge in scientific understandingbetween the formation of rocky planets and the icy bodiesof the Solar System, and under what conditions a rockyplanet can hold water.[19]

The International Astronomical Union (IAU) adopted anew definition of planet on August 24, 2006, which intro-duced the term "dwarf planet" for ellipsoidal worlds thatwere too small to qualify for planetary status by clearingtheir orbital neighborhood of other orbiting matter. If itsucceeds, Dawn will be the first mission to study a dwarfplanet, arriving at Ceres a few months before the arrivalof the New Horizons probe at Pluto in July 2015.Ceres is a dwarf planet whose mass comprises about one-third of the total mass of the bodies in the asteroid belt,and whose spectral characteristics suggest a compositionsimilar to that of a water-rich carbonaceous chondrite.[20]Vesta, a smaller, water-poor achondritic asteroid, has ex-perienced significant heating and differentiation. It showssigns of a metallic core, a Mars-like density and lunar-likebasaltic flows.[21]

Available evidence indicates that both bodies formed veryearly in the history of the Solar System, thereby retaininga record of events and processes from the time of the for-

1

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2 3 OBJECTIVES

Dawn image of Ceres from 46,000 km, 19 February 2015

mation of the terrestrial planets. Radionuclide dating ofpieces of meteorites thought to come from Vesta suggeststhat Vesta differentiated quickly, in three million years orless. Thermal evolution studies suggest that Ceres musthave formed some time later, more than three millionyears after the formation of CAIs (the oldest known ob-jects of Solar System origin).[21]

Moreover, Vesta appears to be the source of many smallerobjects in the Solar System. Most (but not all) V-typenear-Earth asteroids, and some outer main-belt asteroids,have spectra similar to Vesta, and are thus known asvestoids. Five percent of the meteoritic samples foundon Earth, the howarditeeucritediogenite (HED) mete-orites, are thought to be the result of a collision or colli-sions with Vesta.It is thought that Ceres may have a differentiatedinterior;[22] its oblateness appears too small for an un-differentiated body, which indicates that it consists of arocky core overlain with an icy mantle.[22] There is a largecollection of potential samples from Vesta accessible toscientists, in the form of over 1,400 HED meteorites,[23]giving insight into Vestan geologic history and structure.Vesta is thought to consist of a metallic ironnickel core,an overlying rocky olivine mantle and crust.[24][25][26]

3 Objectives

The Dawn missions goal is to characterize the conditionsand processes of the Solar System's earliest eon by inves-tigating in detail two of the largest protoplanets remain-ing intact since their formation.[27] The primary questionthat the mission addresses is the role of size and waterin determining the evolution of the planets.[27] Ceres andVesta are highly suitable bodies with which to address thisquestion, as they are two of the most massive of the pro-

A Dawn image of Vesta from orbit, taken on July 17, 2011

Dawn ' s approximate flight trajectory

toplanets. Ceres is geologically very primitive and icy,while Vesta is evolved and rocky. Their contrasting char-acteristics are thought to have resulted from them formingin two different regions of the early Solar System.[27]

There are three principal scientific drivers for the mission.First, the Dawn mission can capture the earliest momentsin the origin of the Solar System, granting an insight intothe conditions under which these objects formed. Sec-ond, Dawn determines the nature of the building blocksfrom which the terrestrial planets formed, improving sci-entific understanding of this formation. Finally, it con-trasts the formation and evolution of two small plan-ets that followed very different evolutionary paths, al-lowing scientists to determine what factors control thatevolution.[27]

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4.4 Payload 3

4 Specifications

4.1 Dimensions

With its solar array in the retracted launch position, theDawn spacecraft is 2.36 meters (7.7 ft) long. With its so-lar arrays fully extended, Dawn is 19.7 m (65 ft) long.[28]Total area of solar arrays is 36.4 m2 (392 sq ft).[29]

4.2 Propulsion system

Dawn ' s solar array at full extension

The Dawn spacecraft is propelled by three xenon ionthrusters that inherited NSTAR engineering technol-ogy from the Deep Space 1 spacecraft.[30] They have aspecific impulse of 3,100 s and produce a thrust of 90mN.[31] The whole spacecraft, including the ion propul-sion thrusters, is powered by a 10 kW (at 1 au) triple-junction gallium arsenide photovoltaic solar array manu-factured by Dutch Space.[32][33] To get to Vesta, Dawnwas allocated 275 kg (606 lb) of xenon, with another110 kg (243 lb) to reach Ceres,[34] out of a total capacityof 425 kg (937 pounds) of on-board propellant.[35] Withthe propellant it carries, Dawn can perform a velocitychange of more than 10 km/s over the course of itsmission, far more than any previous spacecraft achievedwith onboard propellant after separation from its launchrocket.[34] Dawn is NASAs first purely exploratory mis-sion to use ion propulsion engines.[36] The spacecraft alsohas twelve 0.9N hydrazine thrusters for attitude control,which can assist in orbital insertion.[37]

4.3 Microchip

Dawn carries a memory chip bearing the names of morethan 360,000 space enthusiasts.[38] The names were sub-mitted online as part of a public outreach effort betweenSeptember 2005 and November 4, 2006.[39] The mi-crochip, which is about the size of a United States nickelcoin, was installed on May 17, 2007, above the space-crafts forward ion thruster, underneath its high-gain an-tenna.[40] More than one microchip was made, with a

back-up copy put on display at the 2007 Open Houseevent at the Jet Propulsion Laboratory in Pasadena, Cal-ifornia.

4.4 Payload

Dawn prior to encapsulation at its launch pad on July 1, 2007

NASAs Jet Propulsion Laboratory provided overall plan-ning and management of the mission, the flight sys-tem and scientific payload development, and providedthe Ion Propulsion System. Orbital Sciences Corpora-tion provided the spacecraft, which constituted the com-panys first interplanetary mission. The Max PlanckInstitute for Solar System Research and the GermanAerospace Center (DLR) provided the framing cam-eras, the Italian Space Agency provided the mappingspectrometer, and the Los Alamos National Laboratoryprovided the gamma ray and neutron spectrometer.[2]

Framing camera (FC) The framing camerauses 20 mm aperture, f/7.9 refractive optical sys-tem with a focal length of 150 mm.[41][42] A frame-transfer charge-coupled device (CCD), a Thom-son TH7888A,[42] at the focal plane has 1024 1024 sensitive 93-rad pixels, yielding a 5.5 x 5.5field of view. An 8-position filter wheel permitspanchromatic (clear filter) and spectrally selectiveimaging (7 narrow band filters). The broadest fil-ter allows imaging at wavelengths ranging from 400

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4 5 MISSION SUMMARY

to 1050 nm. In addition, the framing camera willacquire images for optical navigation while in thevicinities of Vesta and Ceres. The FC computer isa custom radiation-hardened Xilinx system with aLEON2 core and 8 GiB of memory.[42] The camerawill offer resolutions of 17 m/pixel for Vesta and 66m/pixel for Ceres.[42] Because the framing camera isvital for both science and navigation, the payload hastwo identical and physically separate cameras (FC1& FC2) for redundancy, each with its own optics,electronics, and structure.[2][43]

Diagram showing the location of various key components on theDawn spacecraft bus

Visible and infrared spectrometer (VIR) Thisinstrument is a modification of the visible and in-frared thermal-imaging spectrometer used on theRosetta and Venus Express spacecraft. It also drawsits heritage from the Saturn orbiter Cassinis visibleand infrared mapping spectrometer. The spectrom-eters VIR spectral frames are 256 (spatial) 432(spectral), and the slit length is 64 mrad. The map-ping spectrometer incorporates two channels, bothfed by a single grating. A CCD yields frames from0.25 to 1.0 m, while an array of HgCdTe photodi-odes cooled to about 70K spans the spectrum from0.95 to 5.0 m.[2][44]

Gamma Ray and Neutron Detector (GRaND) This instrument is based on similar instrumentsflown on the Lunar Prospector and Mars Odysseyspace missions. This instrument includes 21 sensorswith a very wide field of view.[41] It will be used tomeasure the abundances of the major rock-formingelements (oxygen, magnesium, aluminium, silicon,calcium, titanium, and iron) on Vesta and Ceres, aswell as potassium, thorium, uranium, and water (in-ferred from hydrogen content).[45][46][47][48][49][50]

A magnetometer and laser altimeter were considered forthe mission, but were not ultimately flown.[51]

5 Mission summary

5.1 Launch preparations

On April 10, 2007, the spacecraft arrived at the As-trotech Space Operations subsidiary of SPACEHAB,Inc. in Titusville, Florida, where it was prepared forlaunch.[52][53] The launch was originally scheduled forJune 20, but was delayed until June 30 due to delayswith part deliveries.[54] A broken crane at the launch pad,used to raise the solid rocket boosters, further delayed thelaunch for a week, until July 7; prior to this, on June 15,the second stage was successfully hoisted into position.[55]A mishap at the Astrotech Space Operations facility, in-volving slight damage to one of the solar arrays, did nothave an effect on the launch date; however, bad weathercaused the launch to slip to July 8. Range tracking prob-lems then delayed the launch to July 9, and then July 15.Launch planning was then suspended in order to avoidconflicts with the Phoenix mission to Mars, which wassuccessfully launched on August 4.

5.2 Launch

Dawn launching on a Delta II rocket from Cape Canaveral AirForce Station Space Launch Complex 17 on September 27, 2007

The launch of Dawn was rescheduled for September 26,2007,[56][57][58] then September 27, due to bad weather

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5.4 Vesta approach 5

delaying fueling of the second stage, the same prob-lem that delayed the July 7 launch attempt. The launchwindow extended from 07:2007:49 EDT (11:2011:49GMT).[59] During the final built-in hold at T4 minutes,a ship entered the exclusion area offshore, the strip ofocean where the rocket boosters were likely to fall afterseparation. After commanding the ship to leave the area,the launch was required to wait for the end of a colli-sion avoidance window with the International Space Sta-tion.[60] Dawn finally launched from pad 17-B at the CapeCanaveral Air Force Station on a Delta 7925-H rocket[61]at 07:34 EDT,[62][63][64] reaching escape velocity with thehelp of a spin-stabilized solid-fueled third stage.[65][66]Thereafter, Dawns ion thrusters took over.

5.3 Transit (Earth to Vesta)

After initial checkout, during which the ion thrusters ac-cumulated more than 11 days of thrust, Dawn began long-term cruise propulsion on December 17, 2007.[67] On Oc-tober 31, 2008, Dawn completed its first thrusting phaseto send it on to Mars for a gravity assist flyby in February2009. During this first interplanetary cruise phase, Dawnspent 270 days, or 85% of this phase, using its thrusters.It expended less than 72 kilograms of xenon propellantfor a total change in velocity of 1.81 kilometers per sec-ond. On November 20, 2008, Dawn performed its firsttrajectory correction maneuver (TCM1), firing its num-ber 1 thruster for 2 hours, 11 minutes.

Greyscale NIR image of Mars (northwest Tempe Terra), taken byDawn during its 2009 flyby

Dawn made its closest approach (549 km) to Marson February 17, 2009 during a successful gravityassist.[68][69] On this day, the spacecraft placed itself insafe mode, resulting in some data acquisition loss. Thespacecraft was reported to be back in full operation twodays later, with no impact on the subsequent mission iden-

tified. The root cause of the event was reported to be asoftware programming error.[70]

To cruise from Earth to its targets, Dawn traveled in anelongated outward spiral trajectory. NASA posts andcontinually updates the current location and status ofDawn online.[71] The actual Vesta chronology and esti-mated Ceres chronology are as follows:[1]

September 27, 2007: launch

February 17, 2009: Mars gravity assist

July 16, 2011: Vesta arrival and capture

August 1131, 2011: Vesta survey orbit

September 29, 2011 November 2, 2011: Vestafirst high altitude orbit

December 12, 2011 May 1, 2012: Vesta low alti-tude orbit

June 15, 2012 July 25, 2012: Vesta second highaltitude orbit

September 5, 2012: Vesta departure

March 6, 2015: Ceres arrival

Early 2016: End of primary Ceres operations

5.4 Vesta approach

As Dawn approached Vesta, the Framing Camera instru-ment took progressively higher-resolution images, whichwere published online and at news conferences by NASAand MPI.

Vesta from 265,000 km, June 14, 2011

Vesta from 152,000 km, June 24, 2011

Vesta from 100,000 km, July 1, 2011

Vesta from 41,000 km, July 9, 2011

On May 3, 2011, Dawn acquired its first targeting image,1,200,000 km from Vesta, and began its approach phaseto the asteroid.[72] On June 12, Dawns speed relative toVesta was slowed in preparation for its orbital insertion34 days later.[73][74]

Dawn was scheduled to be inserted into orbit at 05:00UTC on July 16 after a period of thrusting with its ionengines. Because its antenna was pointed away from theEarth during thrusting, scientists were not able to imme-diately confirm whether or not Dawn successfully madethe maneuver. The spacecraft would then reorient itself,and was scheduled to check in at 06:30 UTC on July17.[75] NASA later confirmed that it received telemetryfrom Dawn indicating that the spacecraft successfully en-tered orbit around Vesta.[76] The exact time of insertion

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6 5 MISSION SUMMARY

could not be confirmed, since it depended on Vestas massdistribution, which was not precisely known and at thattime had only been estimated.[77]

5.5 Vesta orbit

After being captured by Vestas gravity and entering itsorbit on July 16, 2011,[78] Dawn moved to a lower, closerorbit by running its xenon-ion engine using solar power.On August 2, it paused its spiralling approach to en-ter a 69-hour survey orbit at an altitude of 2,750 km.It assumed a 12.3-hour high-altitude mapping orbit at680 km on September 27, and finally entered a 4.3-hour low-altitude mapping orbit at 210 km on December8.[79][80][81]

Image of Vesta from 16,000 km, July 17, 2011

Image from 10,500 km, July 18, 2011



In May 2012, NASA released the preliminary results ofDawn ' s study of Vesta, including estimates of the sizeof Vestas metal-rich core, which is theorized to be 220km across. NASA scientists furthermore stated that theythink that Vesta is the last of its kind the only remain-ing example of the large planetoids that came togetherto form the rocky planets during the formation of theSolar System.[78][82][83] In October 2012, NASA statedthat data from Dawn had revealed the origin of anoma-lous dark spots and streaks on Vestas surface, which werelikely deposited by ancient asteroid impacts.[84][85][86] InDecember 2012, it was reported that Dawn had ob-served gullies on the surface of Vesta that were inter-preted to have been eroded by transiently flowing liquidwater.[87][88] More details about the Dawn missions sci-entific discoveries at Vesta are included on the Vesta page.Dawn was originally scheduled to depart Vesta and beginits two and a half year journey to Ceres on August 26,2012.[11] However, a problem with one of the spacecraftsreaction wheels forced Dawn to delay its departure fromVestas gravity until September 5, 2012.[10][89][90][91][92]

Central Mound at the South Pole on the asteroidVesta on August 12, 2011

The snowman shaped craters on Vesta

Craters and ridges of Vesta

5.5.1 Results

5.6 Transit (Vesta to Ceres)

During its time in orbit around Vesta the probe experi-enced failures of reaction wheels. Investigators will mod-

ify their activities upon arrival at Ceres for close rangegeographical survey mapping. The Dawn team will ori-ent the probe by what they have stated is a hybridmode. This mode will utilize both reaction wheels andion thrusters. Engineers have determined that the hybridmode will conserve fuel. On November 13, 2013, duringthe transit, in a test preparation, Dawn engineers com-pleted a 27-hour-long series of exercises of said hybridmode.[97]

On September 11, 2014, Dawn's ion thrusting unexpect-edly halted and the probe began operating in a triggeredsafe mode. To avoid a lapse in propulsion, the missionteam hastily exchanged the active ion engine and electri-cal controller with another. The team stated that they hada plan in place to revive this disabled component later in2014. The controller in the ion propulsion system mayhave been damaged by a high-energy particle of radia-tion. Upon exiting the safe mode on September 15, theprobe resumed normal ion thrusting.[98]

Further, the Dawn investigators also found that they couldnot aim the main communications antenna towards Earth.Another antenna of weaker capacity was instead retasked.To correct the problem the probes computer was resetand the aiming mechanism of the main antenna was re-stored.

5.7 Ceres approach

Dawn began photographing an extended disk of Ceres onDecember 1, 2014,[7] with images of partial rotations onJanuary 13 and 25, 2015 released as animations. Imagestaken from Dawn of Ceres after January 26 exceed theresolution of the Hubble Space Telescope,[99] while im-ages taken of Pluto by New Horizons will exceed the res-olution of the Hubble telescope by approximately May 5,2015.[100]

Progression of images of Ceres by Dawn betweenJanuary and February 2015

From 147,000 miles (237,000 kilometers) away onJanuary 25, 2015

From 90,000 miles (145,000 kilometers) away onFebruary 4, 2015



Because of the failure of two reaction wheels, Dawn willmake fewer camera observations of Ceres during its ap-proach phase than it did during its Vesta approach. Cam-era observations require turning the spacecraft, whichconsumes precious hydrazine fuel. Seven optical naviga-tion photo sessions (OpNav 17, on January 13 and 25,

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7

February 3 and 25, March 1, and April 10 and 15) andtwo full rotation observation sessions (RC12, on Febru-ary 12 and 19) are planned before full observation beginswith orbital capture. The gap in March and early Aprilis when Ceres appears too close to the sun from Dawn ' svantage point to take pictures safely.[101]

Dawn entered Ceres orbit on March 6, 2015,[5] fourmonths prior to the arrival of New Horizons at Pluto;Dawn is thus the first mission to study a dwarf planet atclose range.[102][103]

5.8 Ceres orbit

Dawn ' s mission profile calls for it to enter polar orbitaround Ceres at an initial altitude of 13,500 km for a firstfull characterization (RC3). One RC3 orbit will take 15days, during which Dawn will alternate taking picturesand sensor measurements and then relaying the resultingdata back to Earth.[105] Dawn will then spiral down toa survey orbit at an altitude of 4,430 km. This phasewill last for 22 days, and is designed to obtain a globalview of Ceres with Dawn ' s framing camera, and globalmaps with the visible and infrared mapping spectrome-ter (VIR). Dawn will then spiral down to an altitude of1,480 km, where in August 2015 it will begin a two-month phase known as the high-altitude mapping orbit.During this phase, Dawn will continue to acquire near-global maps with the VIR and framing camera at higherresolution than in the survey phase. It will also image instereo to resolve the surface in 3D. After spiralling downfor another two months, Dawn will begin its closest or-bit around Ceres in late November 2015, at a distance ofabout 375 km. This orbit is designed to acquire data forthree months with Dawn's gamma-ray and neutron detec-tor (GRaND) and gravity investigation.[102]

5.9 Mission conclusion

It was initially hoped that after the primary mission, aflyby of the remaining protoplanet in the asteroid belt,Pallas, might be possible when it crosses the ecliptic in2018. (Because of the high inclination of the Palladianorbit, only a quick flyby would have been possible.) How-ever, with two of Dawns reaction wheels out of commis-sion, the remainder of Dawns hydrazine fuel will need tobe expended to orient the craft in low Cererian orbit.[106]The supply of hydrazine will dictate the length of the pri-mary mission; it will not be possible for Dawn to leaveCeres. Dawn will become a long-term satellite of Cereswhen the hydrazine fuel is exhausted, with orbital stabil-ity on a time scale of centuries.[107]

6 See also

Other asteroid missions

Chang'e 2 4179 Toutatis flyby

Galileo probe 951 Gaspra and 243 Ida flybys

Hayabusa 25143 Itokawa rendezvous and samplereturn

Near Earth Asteroid Rendezvous (NEAR) 253Mathilde flyby, orbited 433 Eros from 20002001

Rosetta 2867 teins and 21 Lutetia flyby, is orbit-ing 67P/ChuryumovGerasimenko

Other related articles

List of asteroids visited by spacecraft

2007 in spaceflight

2011 in spaceflight

2015 in spaceflight

7 References[1] GSpace Topics: Dawn. Retrieved November 9, 2013.

[2] Rayman, Marc; Fraschetti, Raymond, Russell (April 5,2006). Dawn: A mission in development for explorationof main belt asteroids Vesta and Ceres. Acta Astronau-tica 58 (11): 605616. Bibcode:2006AcAau..58..605R.doi:10.1016/j.actaastro.2006.01.014. Retrieved April14, 2011.

[3] Dawn Spacecraft Successfully Launched. NASA.September 27, 2007. Retrieved November 9, 2013

[4] NASAs Dawn Spacecraft Begins Science Orbits ofVesta. NASA. August 1, 2011. Retrieved August 6,2011.

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[87] Scully, J. E. C. et.al. (2014). Sub-Curvilinear GulliesInterpreted As Evidence For Transient Water Flow OnVesta. 45th Lunar and Planetary Science Conference.Universities Space Research Association. Retrieved Au-gust 7, 2014.

[88] Dawn probe spies possible water-cut gullies on Vesta.BBC. December 6, 2012. Retrieved December 8, 2012.

[89] Dawn departs Vesta to become first asteroid hopper.New Scientist. September 6, 2012. Retrieved November9, 2013.

[90] Dawn Engineers Assess Reaction Wheel. NASA/JPL.August 18, 2012. Retrieved January 22, 2015.

[91] "'Dawn has departed the giant asteroid Vesta'".NASA/JPL. September 5, 2012.

[92] Staff, Space.com. NASAs Dawn Spacecraft Says Good-bye to Giant Asteroid Vesta. Yahoo.com. RetrievedSeptember 6, 2012.

[93] Williams, D. A.; Yingst, R. A.; Garry, W. B. (December2014). Introduction: The geologic mapping of Vesta.Icarus 244: 112. doi:10.1016/j.icarus.2014.03.001.

[94] Scully, J. E. C.; Yin, A.; Russell, C. T.; Buczkowski, D. L.;Williams, D. A.; Blewett, D. T.; Ruesch, O.; Hiesinger,H.; Le Corre, L.; Mercer, C.; Yingst, R. A.; Garry, W.

B.; Jaumann, R.; Roatsch, T.; Preusker, F.; Gaskell, R.W.; Schrder, S. E.; Ammannito, E.; Pieters, C. M.; Ray-mond, C. A. (December 2014). Geomorphology andstructural geology of Saturnalia Fossae and adjacent struc-tures in the northern hemisphere of Vesta. Icarus 244:2340. doi:10.1016/j.icarus.2014.01.013.

[95] Schfer, M.; Nathues, A.; Williams, D. A.; Mittle-fehldt, D. W.; Le Corre, L.; Buczkowski, D. L.; Kneissl,T.; Thangjam, G. S.; Hoffmann, M.; Schmedemann,N.; Schfer, T.; Scully, J. E. C.; Li, J. Y.; Reddy,V.; Garry, W. B.; Krohn, K.; Yingst, R. A.; Gaskell,R. W.; Russell, C. T. (December 2014). Imprint ofthe Rheasilvia impact on Vesta Geologic mapping ofquadrangles Gegania and Lucaria. Icarus 244: 6073.doi:10.1016/j.icarus.2014.06.026.

[96] Kneissl, T.; Schmedemann, N.; Reddy, V.; Williams, D.A.; Walter, S. H. G.; Neesemann, A.; Michael, G. G.; Jau-mann, R.; Krohn, K.; Preusker, F.; Roatsch, T.; Le Corre,L.; Nathues, A.; Hoffmann, M.; Schfer, M.; Buczkowski,D.; Garry, W. B.; Yingst, R. A.; Mest, S. C.; Russell, C.T.; Raymond, C. A. (December 2014). Morphology andformation ages of mid-sized post-Rheasilvia craters Ge-ology of quadrangle Tuccia, Vesta. Icarus 244: 133157.doi:10.1016/j.icarus.2014.02.012.

[97] JPL Dawn Fills out its Ceres Dance Card jpl.nasa.gov

[98] Dawn Operating Normally After Safe Mode Triggeredjpl.nasa.gov

[99] Dawn Journal October 31. NASA. October 31, 2014.Retrieved January 18, 2015.

[100] New Horizons Mission Timeline. JHUAPL.edu. Re-trieved January 18, 2015.

[101] Dawn Journal January 29. NASA. January 29, 2015.Retrieved February 13, 2015.

[102] NASAs Dawn Fills out its Ceres Dance Card. NASA.December 3, 2013. Retrieved December 8, 2013.

[103] McCord, Thomas B.; Castillo-Rogez, Julie; Rivkin, Andy(2011). The Dawn Mission to Minor Planets 4 Vesta and1 Ceres - Ceres: Its Origin, Evolution and Structure andDawns Potential Contribution. p. 63. doi:10.1007/978-1-4614-4903-4_5. ISBN 978-1-4614-4902-7.

[104] Dawn Journal February 25. NASA. February 25, 2015.Retrieved March 1, 2015.

[105] Dawn Journal February 28. NASA. February 28, 2014.Retrieved February 13, 2015.

[106] Mid-continent Research for Education and Learning:McREL. Dawn Mission: Mission > Dawn Journal:November 30, 2013. nasa.gov.

[107] Dawn spacecraft gets an eyeful of dwarf planet Ceres.BBC. January 19, 2015. Retrieved January 20, 2015.

http://www.dailymail.co.uk/sciencetech/article-2144652/Asteroid-Vesta-Nasas-Dawn-probe-reveals-huge-rippled-asteroid-like-small-planet.html?ito=feeds-newsxmlhttp://www.dailymail.co.uk/sciencetech/article-2144652/Asteroid-Vesta-Nasas-Dawn-probe-reveals-huge-rippled-asteroid-like-small-planet.html?ito=feeds-newsxmlhttps://en.wikipedia.org/wiki/Daily_Mailhttp://www.sciencedirect.com/science/article/pii/S0019103512003302http://www.sciencedirect.com/science/article/pii/S0019103512003302https://en.wikipedia.org/wiki/Icarus_(journal)https://en.wikipedia.org/wiki/Bibcodehttp://adsabs.harvard.edu/abs/2012Icar..221..544Rhttps://en.wikipedia.org/wiki/Digital_object_identifierhttps://dx.doi.org/10.1016%252Fj.icarus.2012.08.011http://www.nature.com/nature/journal/v491/n7422/abs/nature11561.htmlhttp://www.nature.com/nature/journal/v491/n7422/abs/nature11561.htmlhttps://en.wikipedia.org/wiki/Nature_(journal)https://en.wikipedia.org/wiki/Digital_object_identifierhttps://dx.doi.org/10.1038%252Fnature11561https://en.wikipedia.org/wiki/PubMed_Identifierhttps://www.ncbi.nlm.nih.gov/pubmed/23128228http://www.latinospost.com/articles/6285/20121031/nasas-dawn-spacecraft-probes-proto-planet-vesta.htmhttp://www.latinospost.com/articles/6285/20121031/nasas-dawn-spacecraft-probes-proto-planet-vesta.htmhttp://www.latinospost.com/articles/6285/20121031/nasas-dawn-spacecraft-probes-proto-planet-vesta.htmhttp://www.hou.usra.edu/meetings/lpsc2014/pdf/1796.pdfhttp://www.hou.usra.edu/meetings/lpsc2014/pdf/1796.pdfhttp://www.hou.usra.edu/meetings/lpsc2014/pdf/1796.pdfhttp://www.bbc.co.uk/news/science-environment-20582704http://www.newscientist.com/blogs/shortsharpscience/2012/09/asteroid-hopping-spacecraft-ma.htmlhttps://en.wikipedia.org/wiki/New_Scientisthttp://dawn.jpl.nasa.gov/feature_stories/engineers_assess_reaction_wheel.asphttp://dawn.jpl.nasa.gov/feature_stories/dawn_departs_vesta.asphttp://news.yahoo.com/nasas-dawn-spacecraft-says-goodbye-giant-asteroid-vesta-205041936.htmlhttp://news.yahoo.com/nasas-dawn-spacecraft-says-goodbye-giant-asteroid-vesta-205041936.htmlhttps://en.wikipedia.org/wiki/Digital_object_identifierhttps://dx.doi.org/10.1016%252Fj.icarus.2014.03.001https://en.wikipedia.org/wiki/Digital_object_identifierhttps://dx.doi.org/10.1016%252Fj.icarus.2014.01.013https://en.wikipedia.org/wiki/Digital_object_identifierhttps://dx.doi.org/10.1016%252Fj.icarus.2014.06.026https://en.wikipedia.org/wiki/Digital_object_identifierhttps://dx.doi.org/10.1016%252Fj.icarus.2014.02.012http://dawn.jpl.nasa.gov/feature_stories/Dawn_Fills_Out_Ceres_Dance_Card.asphttp://dawn.jpl.nasa.gov/feature_stories/Dawn_operated_normally.asphttp://dawnblog.jpl.nasa.gov/2014/10/31/dawn-journal-october-31/#sthash.OPRlufJs.dpufhttp://pluto.jhuapl.edu/mission/mission_timeline.phphttp://dawnblog.jpl.nasa.gov/2015/01/29/dawn-journal-january-29/http://www.jpl.nasa.gov/news/news.php?release=2013-347http://link.springer.com/chapter/10.1007/978-1-4614-4903-4_5http://link.springer.com/chapter/10.1007/978-1-4614-4903-4_5http://link.springer.com/chapter/10.1007/978-1-4614-4903-4_5https://en.wikipedia.org/wiki/Digital_object_identifierhttps://dx.doi.org/10.1007%252F978-1-4614-4903-4_5https://dx.doi.org/10.1007%252F978-1-4614-4903-4_5https://en.wikipedia.org/wiki/International_Standard_Book_Numberhttps://en.wikipedia.org/wiki/Special:BookSources/978-1-4614-4902-7http://dawnblog.jpl.nasa.gov/2015/02/25/dawn-journal-february-25/#tablehttp://dawnblog.jpl.nasa.gov/2014/02/28/dawn-journal-february-28-2014/http://dawn.jpl.nasa.gov/mission/journal_11_30_13.asp#reactionwheelshttp://dawn.jpl.nasa.gov/mission/journal_11_30_13.asp#reactionwheelshttp://www.bbc.com/news/science-environment-30888818

11

8 External links Dawn mission home page at JPL

Dawn mission home page at NASA

Visible and Infrared Spectrometer Instrument atINAF (Istituto Nazionale di Astrofisica)

Dawn Framing Camera at Max Planck Institute forSolar System Research

Gamma Ray and Neutron Spectrometer for Dawn,short paper on the instrument, from 37th Lunar andPlanetary Science Conference

http://dawndata.igpp.ucla.edu Download Dawndata here

Dawn in the clean room, June 20, 2007

http://dawn.jpl.nasa.gov/http://www.nasa.gov/mission_pages/dawn/main/index.htmlhttp://www.ifsi-roma.inaf.it/vir/https://en.wikipedia.org/wiki/Istituto_Nazionale_di_Astrofisicahttp://www.dawn.mps.mpg.de/index.php?id=21&L=1https://en.wikipedia.org/wiki/Max_Planck_Institute_for_Solar_System_Researchhttps://en.wikipedia.org/wiki/Max_Planck_Institute_for_Solar_System_Researchhttp://www.lpi.usra.edu/meetings/lpsc2006/pdf/2231.pdfhttp://dawndata.igpp.ucla.edu/http://nasatech.net/ntDawnCeres_PAGE.html

12 9 TEXT AND IMAGE SOURCES, CONTRIBUTORS, AND LICENSES

9 Text and image sources, contributors, and licenses

9.1 Text Dawn (spacecraft) Source: http://en.wikipedia.org/wiki/Dawn%20(spacecraft)?oldid=650431874 Contributors: Bryan Derksen, Rmher-

men, Patrick, Ixfd64, Cyde, Stan Shebs, Darkwind, Conti, Stone, Tpbradbury, Tempshill, Wernher, Nickshanks, Chrisjj, Northgrove, Rob-bot, Ppe42, Wjhonson, PedroPVZ, Rursus, Craig Butz, Awolf002, Curps, JamesHoadley, Ryjaz, Niteowlneils, Patteroast, Yath, The SingingBadger, Piotrus, Eregli bob, Kaldari, Hellisp, Willhsmit, N328KF, O'Dea, Jkl, Brianhe, Vsmith, ArnoldReinhold, YUL89YYZ, Moo-chocoogle, Bender235, RJHall, Huntster, Kwamikagami, PatrikR, Supersexyspacemonkey, Hektor, Miranche, Andrew Gray, VladimirKo-rablin, Aranae, Gene Nygaard, YixilTesiphon, Adrian.benko, Kenyon, Dismas, Oleg Alexandrov, Japanese Searobin, Pcd72, Amara, Ben-hocking, E. Brown, Benbest, Lincher, Bricktop, Duncan.france, Emerson7, Drbogdan, Rjwilmsi, Jivecat, Mike s, Ligulem, Schumin-Web, Kolbasz, Mirecki, Chobot, Ravenswing, YurikBot, Epolk, Shawn81, RadioFan, Hydrargyrum, Centurion328, Gaius Cornelius, Cam-bridgeBayWeather, Lavenderbunny, Ergzay, Lexicon, Ravedave, Gadget850, Bota47, Barrymyles, Yabbadab, Ephemeral life, Georgewil-liamherbert, Miraculouschaos, Aremisasling, Silverhorse, Chaos syndrome, Knotnic, Mike Selinker, Arthur Rubin, Reyk, Hurricane De-von, Afrigeri, Ilmari Karonen, GrinBot, Tirronan, SmackBot, Cdogsimmons, Nickst, Alsandro, Commander Keane bot, Skizzik, MarcKupper, Chris the speller, Hibernian, Sangrolu, CSWarren, Arsonal, Modest Genius, WDGraham, Writtenright, NickDupree, MJCde-troit, Andy120290, Nakon, IntrplnetSarah, MatthewBChambers, Vina-iwbot, NeilFraser, John, Shirifan, JorisvS, PowerCS, Ckatz, StikE-manon, Rock4arolla, Vedexent, MarkHardaker, Novangelis, Michaelbusch, Clarityfiend, Craigboy, Broberds, George100, VoxLuna, Drini-bot, ThreeBlindMice, N2e, Badseed, Necessary Evil, Cydebot, Gogo Dodo, Quibik, Ssilvers, Mtpaley, Tewapack, Thijs!bot, Davidelit,Paulus Hook, PJtP, Dfrg.msc, Dawkeye, Dawnseeker2000, Oreo Priest, Ricnun, Dbrodbeck, Smcmanus, TuvicBot, HolyT, NapoliRoma,CosineKitty, Something14, Arch dude, Jespley, Magioladitis, WolfmanSF, Bongwarrior, Tachypaidia, Tomhannen, Gg3369, Soulbot,Shythylacine, Cardamon, BatteryIncluded, JefeMixtli, Lunsford2000, Afterthewar, NatureA16, Neonblak, Keith D, AlexiusHoratius,CASfan, Dmosher, Lilac Soul, J.delanoy, Mange01, Cocoaguy, Derlay, Rod57, LordAnubisBOT, Xdado, AndrewMcinally, Nwbeeson,Ohms law, Ljgua124, Potatoswatter, Pablogm, JohnBlackburne, Nburden, Sdsds, TXiKiBoT, XavierGreen, Vovven, Lucamauri, BotKung,Synthebot, Djmckee1, Truthanado, SieBot, ToePeu.bot, JayJayEss, Jerryobject, Murlough23, RSStockdale, Joldy, Sean.hoyland, Gw-pray, Shrewpelt, Martarius, ClueBot, Trojancowboy, CarolSpears, Wwheaton, Solar-Wind, Kukuciao6, Frenchbreadpizza, Kukuciao7,Noca2plus, Njardarlogar, Chaosdruid, Jonverve, HumphreyW, DumZiBoT, Local hero, BodhisattvaBot, Little Mountain 5, Airplaneman,CrackDragon, Kbdankbot, Addbot, Mortense, Roentgenium111, DOI bot, Fluffernutter, OliverTwisted, AndersBot, Maddox1, Samat-Bot, Lightbot, Gail, Carlesrc, Luckas-bot, Yobot, Aldebaran66, Crispmuncher, Anypodetos, Tempodivalse, AnomieBOT, Thuvan Dihn,Rubinbot, Xosema, Fordcat, Jo3sampl, Hunnjazal, Citation bot, Astor14, Xqbot, A aniq22, Suntanman, RibotBOT, Lee6597, Pikarl,GreekAlexander, Fotaun, Io Herodotus, Kr2009, Cmdred, Cannolis, 117Avenue, Citation bot 1, JKDw, Abductive, Jonesey95, MastiBot,Jedi94, Treaclecustard, Dinamik-bot, RjwilmsiBot, EmausBot, K6ka, Cashewntt, Cogiati, Josve05a, Dondervogel 2, H3llBot, GianniG46,Sandwirt, Brandmeister, Hang Li Po, DinoSlider, EvenGreenerFish, SkywalkerPL, ChiZeroOne, ClueBot NG, Michaelmas1957, Xession,Pinoyaussie, Lanthanum-138, Cntras, Parcly Taxel, Widr, Helpful Pixie Bot, Bobherry, Bibcode Bot, Cgruda, BG19bot, Daboll, SirKe-plan, Cusop Dingle, Trevayne08, Vesna Wylde, Zedshort, Hamish59, EricEnfermero, BattyBot, Ronin712, Fennfoot, Oranjblud, YFdyh-bot, Dexbot, Kulpreet33, Mogism, Lumpman23, Rfassbind, Epicgenius, PhantomTech, Jakec, Evensteven, MKUV, Anythingcouldhappen,Monkbot, Nlunning, Dawnatvesta, Epicchanger360, JezGrove, Jmt42, Jie Wu, Tetra quark, Wik20150113, K scheik, LL221W, Nocturnt,Raparla.Eakanath, Chesare222862, Pewd!epie and Anonymous: 156

9.2 Images File:4_Vesta_1_Ceres_Moon_at_20_km_per_px.png Source: http://upload.wikimedia.org/wikipedia/commons/f/fe/4_Vesta_1_

Ceres_Moon_at_20_km_per_px.png License: Public domain Contributors: enWiki Original artist: NASA, composition by Urhixidur File:Artist{}s_Concept_of_the_InSight_Lander.jpg Source: http://upload.wikimedia.org/wikipedia/commons/4/42/Artist%27s_

Concept_of_the_InSight_Lander.jpg License: Public domain Contributors: http://insight.jpl.nasa.gov/multimedia/ (direct link) Originalartist: NASA/JPL

File:Collision_d'une_comte.jpg Source: http://upload.wikimedia.org/wikipedia/commons/e/ef/Collision_d%27une_com%C3%A8te.jpg License: Public domain Contributors: ? Original artist: Nasa

File:Commons-logo.svg Source: http://upload.wikimedia.org/wikipedia/en/4/4a/Commons-logo.svg License: ? Contributors: ? Originalartist: ?

File:Dawn_-_Sonda.jpg Source: http://upload.wikimedia.org/wikipedia/commons/b/bc/Dawn_-_Sonda.jpg License: Public domainContributors: ? Original artist: ?

File:Dawn_Flight_Configuration_2.jpg Source: http://upload.wikimedia.org/wikipedia/commons/b/ba/Dawn_Flight_Configuration_2.jpg License: Public domain Contributors: ? Original artist: ?

File:Dawn_at_Launch_Pad.jpg Source: http://upload.wikimedia.org/wikipedia/commons/9/95/Dawn_at_Launch_Pad.jpg License:Public domain Contributors: http://mediaarchive.ksc.nasa.gov/detail.cfm?mediaid=32660 Original artist: NASA/Amanda Diller

File:Dawn_ignition.jpg Source: http://upload.wikimedia.org/wikipedia/commons/c/c2/Dawn_ignition.jpg License: Public domain Con-tributors: http://mediaarchive.ksc.nasa.gov/detail.cfm?mediaid=33580 Original artist: Photo credit: NASA/Tony Gray & Robert Murray

File:Dawn_logo.jpg Source: http://upload.wikimedia.org/wikipedia/commons/6/63/Dawn_logo.jpg License: Public domain Contributors:http://mediaarchive.ksc.nasa.gov/detail.cfm?mediaid=33416 Original artist: Unknown

File:Dawn_solar_panel.jpg Source: http://upload.wikimedia.org/wikipedia/commons/b/b7/Dawn_solar_panel.jpg License: Public do-main Contributors: http://mediaarchive.ksc.nasa.gov/detail.cfm?mediaid=32158 Original artist: NASA/George Shelton

File:Dawn_trajectory_as_of_September_2009.png Source: http://upload.wikimedia.org/wikipedia/commons/c/cb/Dawn_trajectory_as_of_September_2009.png License: Public domain Contributors: http://www.planetary.org/image/dawn_trajectory_20090900.png Orig-inal artist: NASA / JPL / courtesy Marc Rayman

File:Folder_Hexagonal_Icon.svg Source: http://upload.wikimedia.org/wikipedia/en/4/48/Folder_Hexagonal_Icon.svg License: Cc-by-sa-3.0 Contributors: ? Original artist: ?

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9.3 Content license 13

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File:NASA_logo.svg Source: http://upload.wikimedia.org/wikipedia/commons/e/e5/NASA_logo.svg License: Public domain Contribu-tors: Converted from Encapsulated PostScript at http://grcpublishing.grc.nasa.gov/IMAGES/Insig-cl.eps Original artist: National Aero-nautics and Space Administration

File:PIA18788-VestaAsteroid-GeologicMap-DawnMission-20141117.jpg Source: http://upload.wikimedia.org/wikipedia/commons/1/1b/PIA18788-VestaAsteroid-GeologicMap-DawnMission-20141117.jpg License: Public domain Contributors:http://photojournal.jpl.nasa.gov/jpeg/PIA18788.jpg Original artist: NASA/JPL-Caltech/ASU

File:PIA18920-Ceres-DwarfPlanet-20150219.jpg Source: http://upload.wikimedia.org/wikipedia/commons/b/be/PIA18920-Ceres-DwarfPlanet-20150219.jpg License: Public domain Contributors: http://www.jpl.nasa.gov/spaceimages/images/largesize/PIA18920_hires.jpg Original artist: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

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Project historyInitial cancellationsReinstatement

Scientific backgroundObjectivesSpecificationsDimensionsPropulsion systemMicrochipPayload

Mission summaryLaunch preparationsLaunchTransit (Earth to Vesta)Vesta approachVesta orbitResults

Transit (Vesta to Ceres)Ceres approachCeres orbitMission conclusion

See alsoReferencesExternal linksText and image sources, contributors, and licensesTextImagesContent license

Documents

Dawn (Spacecraft)