The Bragg Crystal Spectrometer (BCS) is one of the instruments which makes up the scientific payload &the SOLAR-A mission. The spectrometer employs four bent germanium crystals, views the whole Sun and observes the resonance line complexes of H-like FexxvI and He-like Fexxv, CaxIx, and S xv in four narrow wavelength ranges with a resolving power ()o/A,t) of between 3000 and 6000. The spectrometer has approaching ten times better sensitivity than that of previous instruments thus permitting a time resolution of better than 1 s to be achieved. The principal aim is the measurement of the properties of the 10 to 50 million K plasma created in solar flares with special emphasis on the heating and dynamics of the plasma during the impulsive phase, This paper summarizes the scientific objectives of the BCS and describes the design, characteristics, and performance of the spectrometers.
We describe the two 140-mm-aperture simulated blackbody sources used for the on-board calibration of the Along Track Scanning Radiometer, a spaceborne thermal infrared instrument for the accurate remote sensing of sea surface temperature, in operation since 1991. The design of these spaceborne sources, which operate at ≈ -10 °C and ≈ +30 °C, allows them to meet their unprecedented accuracy goal, namely a 3σ uncertainty in their brightness temperature of <0.1 K for the whole mission. This performance is empirically demonstrated in the laboratory and in flight by long-term temperature readout tests, temperature uniformity measurements, and direct emissivity measurements.
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