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Astronomy & Astrophysics Decadal Survey Large Synoptic Survey Telescope (LSST)

Astronomy & Astrophysics Decadal Survey Large Synoptic Survey Telescope (LSST). 6-8m equivalent aperture 3 degree Field of View (FOV) 1-3 Gpixel detector ($30-100M at present costs) Data pipeline, data mining, “National Virtual Observatory” (NVO). The Panoramic Optical Imager.

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Astronomy & Astrophysics Decadal Survey Large Synoptic Survey Telescope (LSST)

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  1. Astronomy & Astrophysics Decadal Survey Large Synoptic Survey Telescope (LSST) • 6-8m equivalent aperture • 3 degree Field of View (FOV) • 1-3 Gpixel detector ($30-100M at present costs) • Data pipeline, data mining, “National Virtual Observatory” (NVO) The Panoramic Optical Imager http://poi.ifa.hawaii.edu

  2. Science Goals – NEOs • Near Earth (“killer”) asteroids 1907 1908 • Requires whole sky survey, good PSF, <10 sec readout

  3. Science Goals – SNIa • Supernovae – The Future of the Universe – is it dominated by dark energy?

  4. Science Goals – SNIa • Supernovae – What is the dark energy, and the future of physics • What are the relative roles of • Dark matter • Dark energy (“Quintessence”) • What is the dark energy equation of state? • Need ~300 SNIa at z~0.7 (Z band ~23 mag) • red response and PSF essential!

  5. Science Goals – PN • From the Main Sequence to the White Dwarfs  will the Sun make a planetary nebula? • It will, but only if white dwarf remnant has >0.55 solar masses • We don’t know what sort of white dwarf the sun will make • clusters, like M67, fill blanks in our knowledge • need to survey lots of sky (~1 degree) for very faint white dwarfs (V ~ 26) • Need good PSF to separate galaxies from stars

  6. Many Other Science Goals • Near Earth Objects • Space junk / fast objects • Trans-Neptunian objects / Asteroid belt • Variability / microlensing / transients • Proper motions / binaries / parallax • High-z supernovae (z~0.4, z~0.8, z~1.2) • Strong lensing • Weak lensing • Star properties / galactic structure • Galaxy evolution / formation • Large-scale structure / clusters • z > 6 (first light in the universe) • Rare unknown objects

  7. Traditional Mosaic Imagers • Too expensive • Too slow • Poor red response • Figure of merit: AW e M = 2 dq • Collecting area A may be fixed, but we can improve all three other factors

  8. Targeted Detector Enhancements • Cost • Current mosaics ~0.5 ¢ / pixel CCD only 2-3 ¢ / pixel, with electronics, shutter, filter • Speed • Current mosaics have 30 –100 sec readout • NEO searches call for <20 sec exposures • Red response • Current mosaics 25% QE at Z band, poor fringing • Image motion compensation • Only slow (~1 Hz) telescope guiding, but atmospheric image motion and telescope shake at 10-20 Hz

  9. Our Proposed Solution Bring state of the art and system approach to bear • Detector • Bring yield to >50%; currently ~25% • Extend red sensitivity by 3x • Add image motion compensation  improve PSF by 20% • CCD Packaging -- make it efficient for 100's of detectors • Cryostat -- make it efficient for 100's of detectors • Electronics -- design a cheap, scalable module • Computers -- 1GHz Linux PC per 8K x 8K imager is enough • Software -- pay attention to scalability and efficiency

  10. The Orthogonal Transfer Array (OTA) – A New Technology CCD Imager • A new paradigm in large imagers OTCCD pixel structure OTA: 8x8 array of OTCCDs Basic OTCCD cell

  11. Components of an OTA • Bond to carrying wafer • Flip over • Thin backside • AR coat Output lines One 512x512 CCD One 4K x 4K monolithic OTA Clock, bias, address lines

  12. DetectorDetails – Overview Each CCD cell of a 4Kx4K OTA • Independent 512x512 CCD • Individual or collective addressing • 1 arcmin field of view • Dead cells excised, yield >50% • Bad columns confined to cells • Cells with bright stars for guiding • 8 output channels per OTA • Fast readout (8 amps, 2 sec) • Disadvantage -- 0.1 mm gaps, but gaps and dead cells are dithered out anyway 5cm 12 um pixels

  13. Detector Details – CCD Output • Wrap output amplifier and JFET follower around under serial register. • Run clock, bias, and address lines between cells. • Limit to ~100 micron gap between cells • Good metrology over entire OTA

  14. Detector Details – Clock and Analog Signals and Cell Addressing Clocks and biases to OTA cells 8 channels of output from OTA

  15. DetectorDetails – Enhanced Red • 45um high-resistivity Si • extended red response • very low fringing

  16. DetectorDetails – Orthogonal Transfer • Orthogonal Transfer • remove image motion • high speed (few usec) Normal guiding (0.73”) OT tracking (0.50”)

  17. Detector Details – Image Motion Compensation • “Rubber” focal plane permits low order “AO” over degrees • Every 30 msec collect guide star info (Guide stars are plentiful for WIYN) • Compute a “displacement surface” for all cells • Perform OT shifts of all cells • Removes image motion from atmosphere and telescope shake on arbitrarily large angular scale • Improvement in PSF (20-30%) is very significant • Exposure time to a given S/N decreases by 30-40%

  18. Package andDemonstration Camera (QUOTA) • 4-side buttable package with multilayer ceramic substrate • Flexprint to hermetic or through wall • Cryocooled bars • Four OTAs = QUOTA (8K x 8K = 15 x 15 arcmin)

  19. 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

  20. Electronics – Computer Communications • Four OTA served by an Interface Unit and Gbit fiber • Decodes computer commands • Synchronizes readout • Formats data for computer transmission • 64 Mpixel = 128 Mb

  21. Electronics – Block Diagram • Scalable system architecture QUOTA

  22. Acquisition Software Tasks • Observation shift and guide loop

  23. Reduction Software Tasks • Read out science arrays; organize data • Flat fielding: OT shifting integrates over many pixels • Adding dithered images • Determine offsets (Continuous? Piecewise constant?) • Remove bad data (dead cells, gaps, etc) • Remove cosmic rays • Combine (Remap? Piecewise constant? Integer pixel?) • Ideally want many dithers but only one final image

  24. The WIYN One Degree Imager (ODI) • PI-driven science for WIY (U. Wisconsin, Indiana U., Yale) and the US community (via NOAO) • Pathfinder for LSST detector and data pipeline • Why WIYN? • Excellent “seeing”; median ~ 0.7” • 1 degree FOV, inherent to telescope • Hydra spectrograph – 1 degree FOV • US access NGC 7620 in R, I Seeing = 0.38” Sky Survey

  25. WIYN One Degree Imager • Instrumentation goal for WIYN • 64 OTAs = ODI (32K x 32K = 1 x 1 deg) • QUOTA does the R&D, different funding for large cryostat, additional devices, filters, shutter, etc. • Deployment in 2005 16”

  26. The OTA Team • CCD Design and Fabrication: Barry Burke (Lincoln Labs), John Tonry (IFA) – CCDs for 20+ years, inventors of OTCCD • Project management: George Jacoby (WIYN) – 20+ years of instrumentation at NOAO, Director of WIYN Observatory • Package and Cryostat design: Gerry Luppino (IFA) – 8K, 12K CCD mosaics for CFHT, UH • Electronics, device testing: Barry Starr (NOAO) – 12K at CFHT • Optics, filter, shutter, commissioning: Chuck Claver (NOAO) – WIYN optics, AO, George Jacoby (WIYN) • Software: John Tonry (IFA)

  27. Experience • OTCCD camera used at MDM (Tonry, Burke, Schechter 1997) • Extensive modelling of image motion compensation (Kaiser, Tonry, Luppino 2000)

  28. Experience • OTCCD camera used at MDM (Tonry, Burke, Schechter 1997) • Extensive modelling of image motion compensation (Kaiser, Tonry, Luppino 2000) • OPTIC camera nearing completion (two 2K x 4K OTCCDs)

  29. Timeline to Deployment

  30. Budget • QUOTA (Quad OTA Camera)  ~$700K + Detectors ($750K) • 2 ¢ / pixel (but large R&D costs) • ODI (WIYN One Degree Imager)  additional $3.7M • 0.4 ¢ / pixel (includes corrector, shutter, and filters) • Additional funding now would allow • Multiple foundry runs to reduce risk, produce more devices • Additional engineering for improved hardware and software design, earlier and more reliable implementation • On-chip shuttering • Integrated CMOS ASICs for focal plane controllers (read out NxN CCDs of OTA instead of N)

  31. Budget Details: ODI • Total -- $3.7M • Detectors (2 add’l foundry runs) $1000K • Hardware Design $ 300K • Dewar plus cooling system $ 300K • Shutter plus BVRIZ filters $ 400K • Software Design $ 200K • Acquisition computers/software $1000K • Optical corrector for WIYN $ 500K

  32. Summary • QUOTA: 8K 4” 16” • ODI: 32K (~$4M) • LSST: 48K

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