LSST Science Requirements Review Working Group 1: Astrometry

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LSST Science Requirements ReviewWorking Group 1
Astrometry

• Chuck Claver
• Dave Monet
• Imants Platais
• Zeljko Ivezic
• Kem Cook

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Primary Science Astrometric Drivers

• Structure and Accretion History of the Galaxy
• Census and 3D Solar Neighborhood Map to R500pc

Supporting Documents Towards a Design Reference
Mission for the LSST (sec. 6 and references
therein) Strauss Science Working Group for LSST
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Review of Current Requirements
Current requirements are insufficient, additional
entries are needed
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Structure Accretion History of the Galaxy

• Stellar Dynamics in the Halo from Proper Motion
• Tracing the Luminous Dark Halo
• Shape, Cutoffs (shells)
• Test infall theories
• Co-moving streams
• Current Requirements sufficient for Vtan170kms
  at 100kpc

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Solar Neighborhood to R200pc

• Parallax Survey
• 10 errors at limiting distance
• At 200pc ?5mas ?0.5masAt 500pc ?2mas ?0.2mas
  (H burning limit for single exposure)
• Final measurement error scales as 1/vN
• N120-150 vN 11-12
• Single exposure requirement for
  local(r1-2arcminutes) precision 5mas at
  optimal S/NGoal 2mas at optimal S/N
• Is this reasonable?

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Subaru Tests (AAS Poster)
10sec
30sec
Very Close to goal!
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Revised Requirements

• Astrometric Precision Requirement (Goal)
• Local 5mas (2-3mas) over arcminute scales
• Global 30mas (10mas) limited by atmospheric
  noise
• Astrometric Accuracy
• Global 30mas (15-20maswrt HCRF e.g. UCAC)
• Proper motion (10yr)
• 1mas (0.5mas)

10sec
30sec
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Revised Requirements

• 22) Transfer Standards to Astrometric System
• Need for NDbandpass for transfer of bright
  standard system to LSST limit?Only if no other
  means is available. It is a very inefficient use
  of LSST.
• Should this be a funded activity during
  construction so? Puts calibration system in
  place at start of science ops.

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New Requirements

• Technical
• Camera Rotation ?90 Degrees need to calibrate
  skew in astrometric solutions.
• FPA Calibration
• Pixel axis orthoganality 3" (1") within FPA raft
• FPR global calibration fields
• Deep to mR25 of full FOV (9.6sq. Deg.)
• Derive supper plate solutions for proper
  stacking

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New Requirements

• Catalogs are a requirement for astrometric as
  well as other LSST Science 4 levels (D. Monet)
• Pointing
• Initial catalog to initiate on observation at a
  given pointing
• Guide star selection, wavefront sensing, bright
  object avoidance etc..
• Contamination
• Initial catalog to support reduction algorithms
• Contains known artifacts and defects as seen at
  the FPA
• Glints, reflections etc (uses pointing catalog
  as input)
• Stacking
• Needed at 1st light to support image differencing
  and stacking
• DCR corrected images transformed to standard grid
• Static Object
• Detection (x, y, flux, shape) ? objects (RA, DEC,
  mag., Type)
• 1-3 needed at first light

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Work Status

• Studies underway
• Precision limits vs exposure time and airmass
• CTIO/Subaru data analyzed
• KPNO Data taken, reduced, analysis in process
• Remaining Questions
• Wavelength and brightness dependencies
• Cadence requirement in 1st year
• Science Support for Revision of Proper Motion
  Requirement