Pan-STARRSobservational requirements

specification

Outline

• Benchmark design specs– Telescopes– Detectors– Pipeline– Data products– Precision goals

• Specification of observational requirements– Format for input to science DWG

Pan-STARRS in a Nutshell• Who?

– IfA - detectors, pipelines, science, site; MHPCC - data processing; SAIC - massive databases; Lincoln Lab - detectors

• What?– Dedicated wide field optical survey A=54 m2 deg2

– “pilot project” for LSST• How?

– Funded by AFRL– 1st year (design development) funded - 2nd year

funding in place - total system cost ~$40M• When?

– To be operational in 2006

Telescope specs

• 4 x 1.8-2m RC + WF corrector• 7 sq deg FOV• F/4 or ~m/arcsec• A = 4 x 13.5-15 m2 deg2

– MEGACAM, SUPRIMECAM ~ 8 m2 deg2

• Filters: BVRIZ, R+V (U?)• Dedicated follow up telescope?

Detectors• Array of arrays

– 4 x (8 x 8) x (8 x 8) x (512 x 512) = 4 x 1Bn pixels

• OTCCD• 0”.3 pixels -> 12m pitch• ~2s read out• ~3e read noise

– 2read = 0.1 2

sky @ t ~ 15 s (V+R)

The Orthogonal Transfer Array (OTA)

• A new paradigm in large imagers

OTCCD pixelstructure

Basic OTCCD cellOTA:

8x8 array of OTCCDs

OTCCD Array

Electronics – Signal Chain• SDSU dual channel video

board– 2 channels– 150 kpixel/sec– CDS, 16 bit ADC– 15 W power

• Analog Devices 9826– 3 channels (RGB)– 15 Mpixel/sec– CDS, 16 bit ADC– 250 mW power

Operation mode options

• Simultaneous– 4 telescopes observe the same field– 7 sq deg => ~ 6000 sq deg / night @ 30s

integration• Independent

– 28 sq deg– Poorer rejection of cosmic ray and other

backgrounds

The pipeline• Image acquisition• Flat fielding/sky subtraction/photo

calibration• Registration• Warping to sky coordinates

– 0”.15-0”.2 sampling• Stacking/cosmic ray rejection• Convolution with PSF (rotated)• Differencing• Accumulation

Data products

• Cumulative sky images (BVRIZ…)– 0”.15-0”.2 sampling– Catalogs

• Difference images– High resolution real-time stream– Lossy compressed -> archive– Transient catalogs

• Point source ML fits etc

Precision goals

• Photometry– ~1% absolute– Better relative

• Astrometry– Statistical: ~ 0”.07 (FWHM/0”.6)(5/SN)

• Floor at ~0”.003– Systematics: < 0”.10

• Coherent over ~10 arcmin

Performance summary

• Sensitivity (assuming 0.6” seeing)– T(R=24) = 58s– T(V=24.4) = 67s– T(R+V) = 31s

• 30s exposure -> 6000 sq deg / night• Sky noise

– 7e/s/pixel from sky (R+V)– Read noise ~2-3e is negligible for t >~ 20s

• Astrometry– Sigma=0”.07 (FWHM/0”.6) / (SN/5)– Systematics limited by atmosphere

Observational Requirements Specification

• Fundamental parameters– Sky coverage – Depth/integration time tint

– Repeat visit cadence requirements (if any)– Filter requirements

• Other requirements– Need for follow up?– Need for archival image data?– Time criticality?– Simultaneous multi-passband imaging?

Inputs to science design working group:

• Science case:– Science objectives– Why will this be interesting in 2006-2010?

• Requirements for optimal performance– I.e. what if Pan-STARRS were used exclusively for this

task• Minimum requirements

– Filters, integration times, follow up needs etc.• External requirements (if any)