AURA 2 Sep 2004. Context National Academy’s Decadal Review recommended a ‘large synoptic survey telescope’ (LSST) 6m class aperture –dedicated wide-field

AURA 2 Sep 2004AURA 2 Sep 2004


ContextContext

National Academy’s Decadal Review recommended a ‘large synoptic survey telescope’ (LSST)• 6m class aperture

– dedicated wide-field optical imager– all-sky survey to enable multiple science goals– applications from solar system to cosmology– strategic emphasis in NEO threat

LSST is assumed to accept natural seeing• for many applications the figure of merit is then simply the

etendue: A • an alternative to a single 6m telescope is an array of smaller

telescopes with the same total area A• many pros and cons, the major advantages are:

– single: no duplication of detectors, can go fainter faster– distributed: cheaper, faster to build, more flexible


Pan-STARRS Design PhilosophyPan-STARRS Design Philosophy

Given the following constraints:• Construction time ~ 1 year per meter aperture• Telescope cost rises faster than D2

• Pixel size limited to >10m, desire 0.3” pixels requires a focal length of <8m

• Optical design for a large becomes very expensive for fast f-ratios

• Costs of CCD detectors have been falling– (O)MEGACAMs: ~$8-10M for ~3x108 pixel or ~2-3c/pixel– Today it is possible to do a factor of 10 better

We believe it is cheaper and better to build an a survey instrument from an array of telescopes and detectors.


Pan-STARRS in a NutshellPan-STARRS in a Nutshell

Telescopes• Four 1.8m R-C + corrector• 7 square degree FOV• Sited on Mauna Kea or Haleakala

Operation mode:• Broad band optical imaging • Four telescopes view the same field

to detect transient or moving objects and build up a deep image of the sky

Partners:• IfA: science, detectors, pipelines• MHPCC: production DP,

infrastructure• SAIC: databases and mass storage

systems• MIT-Lincoln Lab: detectors

Detector and controllers• 109 0.3” pixels per camera• Image motion compensation• 512 channel controller• 2 second readout• 4e- read-noise

Data-Processing System• Multicolor summed images• Difference images for detection

of moving and variable objects• Catalogs of static, moving,

transient objects Science:

• “Killer Asteroids” (PHAs)• Huge range of other science

topics – presently imagination limited


Pu`u Poliahu

UH 0.6-m

UH 0.6-m

UH 2.2-m


UKIRT

CFHT


Science OverviewScience Overview

Time domain astronomy• Transient objects• Moving objects• Variable objects

Static sky science• Enabled by stacking

repeated scans to form a collection of ultra-deep static sky images

Observing Programs

Science Programs

Very extensive overlaps between observational requirements of science programs!


Pan-STARRS SurveysPan-STARRS Surveys

Solar System (Ecliptic Plane) – used primarily to satisfy the observing requirements imposed by the PHO, NEO, MBA, KBO and other SS programs.

3 – used primarily to satisfy the observing requirements of the WL, LSN census, and EG object detection & classification programs; primary cadence drivers are the LSN census (and other proper motion studies)

Medium-Deep – the SNe, LSS, and the EG object detection & classification programs; primary cadence driver being SNe

Ultra-Deep – EG object detection & classification and, to some extent, SNe programs

Object Variability/Auxiliary – mostly user-defined supporting programs such as stellar variability and the search for extra-solar planets


Design Reference MissionDesign Reference Mission

Mode PSY Area Cad. w g r i z y

SSNEO

1.1d 0.2b

7000 h/d/m27.3 300

SSKBO

1.0d 0.2b

3 hdmy26.3 60

Var.0.8d 0.8b

133 4 min29.222000

28.67400

28.54400

24.94400

3 1.3d 2.5b

3 14d25.9 30

25.6 30

25.4 60

23.9 20

22.3 30

Med. Deep

0.6d 0.9b

1200 4d27.1 271

27.0 460

27.31200

25.01900

24.0 600

Ultra Deep

0.5d 0.7b

28 4d29.110000

29.018000

28.06300

27.06700

26.026000

5-5- limit (AB) limit (AB)

Total int. (min)Total int. (min)


Science with Pan-STARRSScience with Pan-STARRS

Moving Object Science• NEO – Near Earth Object threat• OSS/MBO – Main Belt and Other Solar System science• KBO – Kuiper Belt Objects• SOL – Solar Neighborhood (parallaxes and proper motions)

Static and Invariable Object Science• WL – Weak Lensing• LSS – Large Scale Structure• LSB – Low Surface Brightness and dwarf galaxies• SPH – Spheroid formation• EGGS – Extragalactic and Galactic Stellar science

Transient and Variable Object Science• AGN – Active Galactic Nuclei• SNE – Supernovae• GRB – Gamma Ray Bursts and afterglows• EXO – Exoplanets (from occulation)• YSO – Young Stellar Objects• VAR – Variability Science (especially stars)

TGBN (Things that go Bump in the Night)


Near Earth AsteroidsNear Earth Asteroids

Local

Regional

Global108 Mton105

103

102

100m 1km 10km2x105 5x108 year

SizeTime Interval

Energy


Damage vs SizeDamage vs Size


Risk Reduction vs TimeRisk Reduction vs Time

(200m)(200m)

(50m)(50m)

(500m)(500m)

(1000m)(1000m)

PSPSLINEARLINEAR

LSSTLSST


Inner Solar System ScienceInner Solar System Science

~107 asteroids• Families• Orbit parameter

space structure

~104 NEOs• Phase-space

distribution• Hazardous

asteroids

Comets


Outer Solar System ScienceOuter Solar System Science

Kuiper Belt Objects• Orbital distribution• Formation and

evolution Trans-Neptunian

Objects Interlopers on

hyperbolic orbits


Stars and the GalaxyStars and the Galaxy

Parallax survey• Complete stellar census to 100pc

Proper motions• Formation history

Other goals:• Stellar variability• Low mass stars• Extra-solar planets


Moving ObjectsMoving Objects

KBO – 20,000 KBOs over 10 years; all sky, unbiased.• ~100 in binary pairs

OSS – many more asteroids and comets (~20x)• 5x106 million main belt, 105 Jupiter Trojans, etc.

SOL – parallaxes to ~100pc in 10 years• Best substellar IMF available (better than UKIDSS)• 10-100x more brown dwarfs than SDSS or 2MASS

EGGS – proper motions of most stars in the Milky Way• Accuracy of 2.5 km/s at 1kpc.


Cosmology – Weak LensingCosmology – Weak Lensing

Total mass power spectrum P(k) to large scales

• Test of inflation theory• Evolution of P(k)

Higher order statistics• Gravitational instability

theory Cluster mass function Cosmology

• Cosmological parameters• Geometric tests• World model


Static and Invariable ObjectsStatic and Invariable Objects

WL – Weak lensing over 1000 sq deg.• Large-scale structure of mass on large scales (wide

area) and small scales (high density of objects) as a function of redshift, evolution of mass clustering.

• Mass profiles of galaxies SPH, LSB, AGN – Evolution of galaxies

• Pan-STARRS will survey 4x the area of SDSS, will have the same photometric accuracy but 3-4 mag fainter, good sensitivity at 1um (y band).

• Reionization, metal formation, spheroid formation, AGN activity, galaxy merging, and cluster formation.


Cosmology – SupernovaeCosmology – Supernovae

Hubble diagram• Dark energy equation

of state w(z)• Cosmological

parameters Supernova physics Star formation history


Transient and Variable ObjectsTransient and Variable Objects

SNE – 10,000’s of SNIa to z=1• Measure time (redshift) evolution of dark energy

AGN – Dropouts to z=7, variability identification• Reionization, metals, spheroid formation, nature of

radio sources, stellar disruptions, etc. GRB – Optical counterparts (~100 per year)

• Possibly V~8 declining to V~20 in one day EXO – Occultations of stars by planets

• Pan-STARRS is sensitive to Jupiters around sub-solar mass stars or Earths around brown dwarfs.

VAR – Stellar variability• White dwarfs, binaries, Cepheids, Miras, RR Lyrae,

microlensing, supergiants, etc, etc.


TGBNTGBN

The Pan-STARRS survey is 10-20 times SDSS, Megacam survey, Vista, etc. in extent, but…

We are repeating it 30 – 500 times! We will be the first to have extensive time domain

information, designed with useful and interesting cadences, well controlled selection and systematics, and huge samples.

There is a high likelihood for unanticipated discoveries• Unexpected variable objects• Extremely rare objects• Very large scale patterns


Data VolumeData Volume

Expect 700 images = 6 Tb per night raw; 3 Tb per night = 1 Pb per year reduced!

We have to be prepared not to “save the bits” We must create a reliable enough pipeline that we tap

all the science we want as the data flow through, and then throw the bits on the floor. (This has never been achieved before.)


Image Processing PipelineImage Processing Pipeline

Phase 1 Detector

Calibration (Calibration

and Instrument CorrectionProcesses)

Phase 2 Map and

Warp to Sky(Image

Manipulation Processes)

Phase 3 Create Sky

Image (Image

CombinationProcesses)

Inte

rfac

e 1

Inte

rfac

e 2

Inte

rfac

e 3

Inte

rfac

e 4

Inte

rfac

e 5

Data Storage

Data Storage

Data Storage

Telescope Cameras

ScienceClients

Phase 6ScienceClient

Interfaces

TCS andEnvironmentMonitoring

Phase 4 Augmented

Image Processing

Data Storage

Inte

rfac

e 7

Chip Level Chip Level Telescope and System Level

Inte

rfac

e 6

Phase 5 Science Client

Product Generation

Data Storage

Data Storage

System Level System Level System LevelImage Capture

Scheduler

Phase 0

Internal Product

Generation

Internal Product

Generation

Mission Planning…pre-staging of each night’s scheduling and supporting data…TBD

NB: specifics have changed!


Confusing IssuesConfusing Issues

LSST should not be discussed as an either – or competitor to Pan-STARRS; Pan-STARRS will exist before LSST begins construction. Therefore:

• Astro-photo precursor survey will have been done,• A robust data pipeline will have been shaken down,• 50% of 300m PHAs will have been discovered, etc, etc.

What etendue is really needed? • Etendue is A those last two factors are important!• SDSS at A CFHT at 10, Suprime at 13 cannot

approach LSST science because of limited and/or• Pan-STARRS at A is designed to have superb

and and the software and scheduling to maintain LSST science.

• Pan-STARRS will improve on the present state of the art (SDSS, upcoming synoptic surveys) by at least an order of magnitude in science productivity.


Design Reference MissionDesign Reference Mission

Mode PSY Area Cad. w g r i z y

SSNEO

1.1d 0.2b

7000 h/d/m27.3 300

SSKBO

1.0d 0.2b

3 hdmy26.3 60

Var.0.8d 0.8b

133 4 min29.222000

28.67400

28.54400

24.94400

3 1.3d 2.5b

3 14d25.9 30

25.6 30

25.4 60

23.9 20

22.3 30

Med. Deep

0.6d 0.9b

1200 4d27.1 271

27.0 460

27.31200

25.01900

24.0 600

Ultra Deep

0.5d 0.7b

28 4d29.110000

29.018000

28.06300

27.06700

26.026000

5-5- limit (AB) limit (AB)

Total int. (min)Total int. (min)


Final Data ProductsFinal Data Products

Sky, the wallpaper: • 10 Tpix x 6 colors x N versions

Sky, the movie:• 10 Tpix x 6 colors x 50 epochs

Sky, the database:• 2x1010 objects (x 6 colors x 20-60 epochs)

– Photometry to < 0.01 mag, astrometry to < 50 mas– Photometric redshifts of most of these objects

• 109 proper motions (complete over 3)• 108 variable stars and AGN• 107 asteroids (104 NEO/PHA)• 107 transients (SN, GRB, etc.)• 3x105 stars within 100 pc (with good parallax)

Documents

AURA 2 Sep 2004. Context National Academy’s Decadal Review recommended a ‘large synoptic survey telescope’ (LSST) 6m class aperture –dedicated wide-field