ISWG - December 7, Destiny, The Dark Energy Space Telescope

ISWG - December 7, 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 <  1.7  m “objective Prism” with  ~ 75

ISWG - December 7, 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 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 NRC BEPAC recommends JDEM for first BE start in Development continued to September 2008.

ISWG - December 7, 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 ~ 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, Supernovae

ISWG - December 7, 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. SpaceGround

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

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

ISWG - December 7, Supernova Observations 1. Filter: locate SN & host galaxy 2. Dispersed mode: spectral time series 3. Difference & extract SN spectrophotometry

ISWG - December 7, 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, Triprism for nearly constant dispersion

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

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

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

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

ISWG - December 7, Destiny, The Dark Energy Space Telescope