The NISAR Science Payload consists of an L-band SAR instrument (L-SAR) and an S-band SAR instrument (S-SAR) each with their own feed sharing a single 12m reflector. The instrument design, based on “SweepSAR” architecture for wide-swath coverage, is a multi-beam polarimetric system employing on-board time-to-angle digital beam forming to each of the receive channels. The instrument exhibits a few “features” that are not present in the conventional SAR system that utilizes a rectangular phased-array antenna and electronically steering the antenna beam in “ScanSAR” operation mode. The most prominent feature is the large reflector-feed antenna, whose geometry is more susceptible to the on-orbit thermal environment. When the geometry gets changed thermally, the mechanical boresight will be perturbed, and the antenna patterns will be distorted. For NISAR science objectives, the instrument can be used as a repeat-pass interferometer with polarimetric capability; Science imposed a set of “Performance” requirements and a set of “Pointing” requirements on L-SAR and these two sets are inter-related. The large reflector-feed antenna cannot be tested with the instrument in a deployed configuration and is the driver of several test-as-you-fly exceptions. To verify that the system is meeting project requirements before launch and to understand what’s expected once on-orbit, a set of inter-related system models were developed and used to evaluate L-SAR’s sensitivity when the radar antenna is subject to on-orbit thermal environment influences affecting pointing and performance. The results from these models run as a whole, portends what to expect during the mission and the results also are used to certify L2 requirements.
UV-SCOPE is a mission concept to determine the causes of atmospheric mass loss in exoplanets, investigate the mechanisms driving aerosol formation in hot Jupiters, and study the influence of the stellar environment on atmospheric evolution and habitability. As part of these investigations, the mission will generate a broad-purpose legacy database of time-domain ultraviolet (UV) spectra for nearly 200 stars and planets. The observatory consists of a 60 cm, f/10 telescope paired to a long-slit spectrograph, yielding simultaneous, almost continuous coverage between 1203 Å and 4000 Å, with resolutions ranging from 6000 to 240. The efficient instrument provides throughputs < 4% (far-UV; FUV) and < 15% (near-UV; NUV), comparable to HST/COS and much better than HST/STIS, over the same spectral range. A key design feature is the LiF prism, which serves as a dispersive element and provides high throughput even after accounting for radiation degradation. The use of two delta-doped Electron-Multiplying CCD detectors with UV-optimized, single-layer anti-reflection coatings provides high quantum efficiency and low detector noise. From the Earth-Sun second Lagrangian point, UV-SCOPE will continuously observe planetary transits and stellar variability in the full FUV-to-NUV range, with negligible astrophysical background. All these features make UV-SCOPE the ideal instrument to study exoplanetary atmospheres and the impact of host stars on their planets. UV-SCOPE was proposed to NASA as a Medium Explorer (MidEx) mission for the 2021 Announcement of Opportunity. If approved, the observatory will be developed over a 5-year period. Its primary science mission takes 34 months to complete. The spacecraft carries enough fuel for 6 years of operations.
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