SeaStar was a spacecraft, developed by Orbital Sciences Corporation, to deliver daily, worldwide, high precision, moderate resolution, multispectral visible observations of ocean radiance for research in biogeochemical processes, climate change, and oceanography. A near noon sun-synchronous orbit was flown for optimum illumination of the lighted hemisphere. Data were taken from a single ocean color scanner on-board the satellite (SeaWiFS - Sea-viewing Wide Field-of-View Sensor). The SeaStar spacecraft was launched into low Earth orbit via a Pegasus launch vehicle which was flown under the wing of a modified Lockheed L-1011 aircraft. The spacecraft had an on-board hydrazine propulsion system which was used to raise the satellite to its final 705 km circular, noon, sun-synchronous orbit. Final orbit was achieved 20 days after launch. The spacecraft was three-axis stabilized by an Attitude Control System (ACS) which consisted of orthogonal magnetic torque rods for roll and yaw control and two momentum wheels for pitch stabilization. ACS sensors included redundant sun sensors, horizon sensors, and magnetometers. The propulsion system consisted of a reaction control subsystem for third stage stabilization and a hydrazine propulsion subsystem for raising the space- craft to its operational orbit and for orbit stabilization. Local high resolution (1 km) data (LAC) were delivered by direct broadcast at L-Band to regional scientific centers nationwide. Reduced resolution (4 km) data (GAC and selected LAC) were directly broadcast at S-band to smaller research centers and ships at sea. All reduced resolution data and selected full resolution data were recorded on board and transmitted to GSFC via daily dump at S-Band or via the Tracking and Data Relay Satellite System (TDRSS). A minimum three year mission life was expected.
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