برنامه تحقیق و توسعه برای آزمایش انرژی تاریک SNAP

The SNAP mission includes two surveys to study dark energy. In the deep survey, we detect more than 2000 matched Type Ia supernovae within a 7.5 deg2 field, with redshifts covering the range z=0.1–1.7. This uniform and high-quality set of “standard candles” will provide the most precise mapping of the expansion of the universe through the magnitude-redshift relation (Hubble diagram) ever constructed. The SNAP wide survey maps 1000 deg2/year in nine passbands to 28th magnitude. A weak-lensing study of the wide survey data traces the growth of structure and provides completely independent constraints on dark energy parameters. SNAP utilizes a 2 m class rigid light-weight telescope with a three-mirror anastigmatic design for a large, diffraction-limited field of view. The telescope feeds an instrumented ∼0.7 deg2 focal plane with ∼600 million pixels sensitive to wavelengths from 400 to 1700 nm. Full-depletion, high-purity silicon CCDs detect visible wavelengths, and 1700 nm cutoff HgCdTe detector arrays detect the near-IR. Passive cooling of the focal plane, fixed solar panels, fixed filters, and fixed antenna for telemetry simplify the mission. Room temperature operation of the telescope facilitates preflight testing. The satellite is placed in orbit about the second Earth–Sun Lagrange point (L2).

The SuperNova/Acceleration Probe (SNAP) is a proposed space-based experiment designed to measure the expansion history of the Universe, motivated by the discovery that the expansion is accelerating [1]. It will measure dark energy and its time variation by mapping the distance-redshift relation of Type Ia supernovae, and by mapping the distribution of matter and energy using gravitational weak lensing. A 2-m three-mirror anastigmat wide-field telescope feeds a focal plane consisting of a 0.7 deg2 imager tiled with equal areas of visible and near-infrared sensors, and a high-efficiency, low-dispersion integral field spectrograph. The instrumentation suite provides simultaneous discovery, classification, and light-curve measurements for many supernovae and targets individual objects for detailed spectral characterization. The SNAP mission will obtain high signal-to-noise calibrated light curves and spectra for over 2000 Type Ia supernovae at redshifts between z=0.1 and 1.7 from a deep survey of 7.5 deg2. The wide-area weak gravitational lensing survey will survey 1000 deg2/year in nine filters. The weak lensing survey benefits from a stable, high-resolution point spread function, and absence of atmospheric distortions. To facilitate thermal management of the observatory and instruments, and reduce stray light from the Earth's limb, the satellite is placed in orbit about the second Earth–Sun Lagrange point (L2) using a Delta IV or equivalent launch vehicle.