SEOCS. Sun-Earth Observatory and Climatology Satellite, phase A study: Scanning radiometer feasibility

The feasibility of a scanning radiometer to be used on SEOCS was studied. The scanning radiometer is a radiation budget instrument with 50 km spatial resolution at nadir and a radiometric accuracy of approximately 0.5 %. The radiometer will measure reflected and emitted energy from every spot on earth at varying look angles. It will thus provide the data to determine the total outgoing flux from the earth and its spectral distribution. The SEOCS spacecraft employs spacecraft yawing (rotation around the nadir line) to maintain the solar panels oriented towards the sun. A strong preference was therefore presented for a radiometer design that would be insensitive to a slow yaw motion of the satellite. The design concept selected as the baseline is a rotating instrument. It employs 8 cm Ritchey-Chretien optics and a simple object plane stepping mirror. Spectral separation is performed by means of a reflecting chopper and 2 sets of narrow detectors from which the signal is integrated up over a 50 km distance in the scan direction.