scope:

Abstract:

Past analyses of electronic, mechanical, and optical hardware performance have sometimes focused on steady state characteristics to the exclusion of known transients. As indicated in the Wide-Field Infrared Explorer (WIRE) mission loss scenario, spacecraft venting configurations designed for steady state flow rates may experience large unexpected blow-down impulses, or even nominal cryogen flows sufficient to cause mission loss or degradation. Secondly, the inability of the WIRE spacecraft to counteract accelerated venting rates suggests a marginal attitude control system authority. Third, the unavailability of definitive cryostat temperature data during the anomalous venting period hampered early, real-time identification of the root problem (premature cover deployment). Consider all venting mission sequences, plus the possibility of unplanned worst-case venting scenarios, in the spacecraft system design. Design the thrust neutralizing capability of the attitude control system to encompass transient venting-induced torque. Ensure that the electronics monitoring spacecraft health supply data during critical operational sequences.