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Destiny, The Dark Energy Space Telescope

Destiny, The Dark Energy Space Telescope. DESTINY Fact Sheet. 1.65m telescope at L2 32 H2RG FPAs: 0.15” pixels FOV: 0.18° x 0.72° SN1a survey over > 3° 2 NIR imaging 0.85 m < l 1.7 m “objective Prism” with l/  l ~ 75. A Brief History of Destiny.

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Destiny, The Dark Energy Space Telescope

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  1. Destiny, The Dark Energy Space Telescope ISWG - December 7, 2009

  2. DESTINY Fact Sheet • 1.65m telescope at L2 • 32 H2RG FPAs: 0.15” pixels • FOV: 0.18° x 0.72° • SN1a survey over > 3°2 • NIR imaging 0.85 m < l1.7 m • “objective Prism” with l/l~ 75 ISWG - December 7, 2009

  3. A Brief History of Destiny • Astronomical community recognizes the potential of dark energy space probes. • NASA & DOE propose a generic Joint Dark Energy Mission • Initial Destiny concept for JDEM proposed in 2003. Wins initial concept study. GFSC, LMCO, & LANL partners. • NASA creates general “Beyond Einstein” program for astrophysical missions: Con-X, LISA, CMB probes, etc. Includes JDEM . • Destiny wins 1 of 3 JDEM concept studies in 2006. NRC BEPAC recommends JDEM for first BE start in 2007. • Development continued to September 2008. ISWG - December 7, 2009

  4. DESTINY Philosophy • In 2003, SN Ia was the favored DE methodology - DETF identified NIR observations of SN Ia as the sole “space unique” methodology. • Do only in space what must be done in space - ground observations for low-redshift. • Use the minimal instrument required. • Variable DE EOS  observing over 0 < z < 1.7 • Stage IV errors  Sample ~ 3000+ SN Ia. • 5 day cadence  3 deg survey area for 2 year mission. • S/N requirements  A product (detectors vs. Primary) • All spectra all the time. Complete spectro- photometric time series on all SN events. One data set provides photometry, classification, redshifts, time decay, extinction, etc. • Highly automated survey - no time critical operations. ISWG - December 7, 2009

  5. Supernovae ISWG - December 7, 2009

  6. Why go to high redshifts? Dark energy can be detected at low redshift, but precise constraints on the DE Eos requires measurements over both the acceleration and deceleration epochs. Ground Space ISWG - December 7, 2009

  7. NIR available only in space Crucial near-infrared observations are impossible from the ground for the required photometric accuracy • Sky is very bright in NIR: >100x brighter than in visible • Sky is not transparent in NIR: absorption due to water is very strong and extremely variable Data from Gemini Observatory & ATRAN: Lord (1992) ISWG - December 7, 2009

  8. Riess et al. (2004) obtain ACS grism spectra of z ~ 1.3 SN Ia ISWG - December 7, 2009

  9. ACS Grism Images of SN2002FW (z = 1.30) Riess et al. (2004) ISWG - December 7, 2009

  10. Supernova Observations • Filter: locate SN & host galaxy • Dispersed mode: spectral time series • Difference & extract SN spectrophotometry ISWG - December 7, 2009

  11. Supernovae Survey Schema Survey area is a contiguous Mosaic of Destiny FOVs. Orientation rolls by 90º every 3 months. Dithering will fill in chip gaps and ensure Nyquist sampling. ISWG - December 7, 2009

  12. Triprism for nearly constant dispersion ISWG - December 7, 2009

  13. Sn Photometric Calibration • Obtain high fidelity external and internal flats in ground tests. • Monitor with internal flats on orbit, plus field stars. • Absolute photometric calibration with DA white Dwarfs. • Sn spectra isolated with differencing. Ad hoc spectral flat extracted from data cube of monochromatic flats. ISWG - December 7, 2009

  14. On-orbit calibration system (from Jason Budinoff) Diffuser Fold Mirror Integrating Sphere Monochromator Baffle Box 500 mm Light Pipe Shutter F/8 Light Pipe Diffuser Mechanism Diffuser Mirror ISWG - December 7, 2009

  15. Supernova Survey • Present day & ongoing surveys find hundreds • Destiny will find >3000 SN in 2 yrs. • Most at z~1; requires 3.2 deg2 survey area ISWG - December 7, 2009

  16. Focal Plane Layout • Science FPAs: HAWAII-2RG 2k x 2k arrays, 4 x 8 mosaic =128M pixels • Guide FPAs:2k x 2k arrays, 2 x 2 sparse mosaic (dichroic overlay) ISWG - December 7, 2009

  17. Observatory Instrument Radiators Outer Baffle Assembly • Lockheed Spacecraft bus • Goodrich Optical Telescope Assembly • GSFC Science Instrument, Teledyne FPA • GSFC Instrument Outer Baffle Destiny Observatory Spacecraft Bus Fixed Solar Array Goodrich OTA GSFC Science Instrument Telescope Optical Bench 1.65m primary mirror Destiny OTA + Science Instrument Destiny Optics ISWG - December 7, 2009

  18. Optical layout Telescope Bench Tertiary Instrument Bench Central “Shark Mouth” Baffle Fold2 Cell Filter/Prism Wheel Interface Deck Internal Thermal Enclosure Secondary Mirror Guider FPA Primary Mirror Science FPA Monochrometer ISWG - December 7, 2009

  19. Destiny, The Dark Energy Space Telescope ISWG - December 7, 2009

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