Transcript Document

AURA 2 Sep 2004
Context
 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
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for many applications the figure of merit is then simply the
etendue: A W  / dW
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
AURA 2 Sep 2004
Pan-STARRS Design Philosophy
 Given the following constraints:
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Construction time ~ 1 year per meter aperture
Telescope cost rises faster than D2
Pixel size limited to >10mm, desire 0.3” pixels requires a focal
length of <8m
Optical design for a large W 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.
AURA 2 Sep 2004
Pan-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
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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
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UH 0.6-m
Pu`u Poliahu
UH 2.2-m
UH 0.6-m
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CFHT
UKIRT
AURA 2 Sep 2004
Science Overview
 Time domain astronomy
• Transient objects
• Moving objects
• Variable objects
 Static sky science
 Very extensive
overlaps between
observational
requirements of
science programs!
• Enabled by stacking
repeated scans to form a
collection of ultra-deep static
sky images
AURA 2 Sep 2004
Pan-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
AURA 2 Sep 2004
Design Reference Mission
Mode
PSY
Area
Cad.
SS
1.1d
0.2b
7000
h/d/m
1.0d
0.2b
3
hdmy
Var.
0.8d
0.8b
133
4 min
3
1.3d
2.5b
3
14d
Med.
Deep
0.6d
0.9b
1200
4d
Ultra
Deep
0.5d
0.7b
28
4d
NEO
SS
KBO
w
g
r
i
27.3
z
300
5- limit (AB)
26.3
Total int. (min)
y
60
29.2
28.6
28.5
24.9
22000
7400
4400
4400
25.9
25.6
25.4
23.9
22.3
30
30
60
20
30
27.1
27.0
27.3
25.0
24.0
271
460
1200
1900
600
29.1
29.0
28.0
27.0
26.0
10000
18000
6300
6700
26000
AURA 2 Sep 2004
Science with Pan-STARRS
 Moving Object Science
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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
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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
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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)
AURA 2 Sep 2004
Near Earth Asteroids
Size 100m
Time Interval 103
Energy 102
1km
2x105
105
10km
5x108 year
108 Mton
Global
Regional
Local
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Damage vs Size
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Risk Reduction vs Time
(1000m)
(500m)
(200m)
PS
LSST
(50m)
AURA 2 Sep 2004
Inner Solar System Science
 ~107 asteroids
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Families
Orbit parameter
space structure
 ~104 NEOs
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Phase-space
distribution
Hazardous
asteroids
 Comets
AURA 2 Sep 2004
Outer Solar System Science
 Kuiper Belt Objects
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Orbital distribution
Formation and
evolution
 Trans-Neptunian
Objects
 Interlopers on
hyperbolic orbits
AURA 2 Sep 2004
Stars and the Galaxy
 Parallax survey
• Complete stellar census to 100pc
 Proper motions
• Formation history
 Other goals:
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Stellar variability
Low mass stars
Extra-solar planets
AURA 2 Sep 2004
Moving 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.
AURA 2 Sep 2004
Cosmology – 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
AURA 2 Sep 2004
Static 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.
AURA 2 Sep 2004
Cosmology – Supernovae
 Hubble diagram
• Dark energy equation
of state w(z)
• Cosmological
parameters
 Supernova physics
 Star formation history
AURA 2 Sep 2004
Transient 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 subsolar mass stars or Earths around brown dwarfs.
 VAR – Stellar variability
• White dwarfs, binaries, Cepheids, Miras, RR Lyrae,
microlensing, supergiants, etc, etc.
AURA 2 Sep 2004
TGBN
 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
AURA 2 Sep 2004
Data 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.)
AURA 2 Sep 2004
Image Processing Pipeline
Chip Level
Image Capture
Phase 0
Telescope
Cameras
Chip Level
Telescope and
System Level
System Level
System Level
System Level
Phase 6
Science
Client
Interfaces
Phase 1
Detector
Calibration
(Calibration
and
Instrument
Correction
Processes)
Phase 2
Map and
Warp to Sky
(Image
Manipulation
Processes)
Phase 3
Create Sky
Image
(Image
Combination
Processes)
Phase 4
Augmented
Image
Processing
Phase 5
Science
Client
Product
Generation
Data
Storage
Data
Storage
Data
Storage
Data
Storage
Data
Storage
Science
Clients
Interface 7
Internal
Product
Generation
Data
Storage
Interface 6
Interface 5
Interface 4
Internal
Product
Generation
Interface 3
Interface 1
TCS and
Environment
Monitoring
Interface 2
Scheduler
NB: specifics have changed!
Mission Planning…pre-staging of each night’s scheduling and supporting data…TBD
AURA 2 Sep 2004
Confusing 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 W  / dW: those last two factors are important!
• SDSS at A W =7.5, CFHT at 10, Suprime at 13 cannot
approach LSST science because of limited  and/or dW.
• Pan-STARRS at A W = 50 is designed to have superb  and
dW 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.
AURA 2 Sep 2004
Design Reference Mission
Mode
PSY
Area
Cad.
SS
1.1d
0.2b
7000
h/d/m
1.0d
0.2b
3
hdmy
Var.
0.8d
0.8b
133
4 min
3
1.3d
2.5b
3
14d
Med.
Deep
0.6d
0.9b
1200
4d
Ultra
Deep
0.5d
0.7b
28
4d
NEO
SS
KBO
w
g
r
i
27.3
z
300
5- limit (AB)
26.3
Total int. (min)
y
60
29.2
28.6
28.5
24.9
22000
7400
4400
4400
25.9
25.6
25.4
23.9
22.3
30
30
60
20
30
27.1
27.0
27.3
25.0
24.0
271
460
1200
1900
600
29.1
29.0
28.0
27.0
26.0
10000
18000
6300
6700
26000
AURA 2 Sep 2004
Final 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)
AURA 2 Sep 2004