baalke@mars.jpl.nasa.gov (Ron Baalke) (02/08/91)
MAGELLAN STATUS REPORT February 7, 1991 The Magellan spacecraft is performing as expected. All STARCALS (star calibrations) and DESATS (desaturations) of the past 24 hours were successful. The spacecraft is now in its 958th mapping orbit and the radar system performance is nominal. Temperatures of spacecraft subsystems continue to be the focus of mission controllers. The geometry of Magellan's orbit about Venus and its position relative to the sun during mapping and playback were expected to produce higher temperatures during the this part of the prime mission and extending into the extended mission cycle. Anticipating these higher temperatures, two strategies were developed. One strategy, called "Flip Flop," controls the temperatures by turning the opposite side of the spacecraft to the sun during the second playback period. The timing of the mapping pass and playback periods would be unchanged. The disadvantage of this approach is that spacecraft parts would be subjected to more thermal cycles. If used, the Flip Flop strategy would be implemented starting with the April 9 command load, and continuing until April 30, then switching to the second strategy. The second strategy, called "Two Hide," controls spacecraft temperatures by including two periods in each orbit when the equipment bays would "hide" in the shade of the High Gain Antenna. This strategy would require a shortening of the mapping pass and playback periods similar to the strategy during occulted mapping. This strategy would be used from the April 30 command load until the July 23 load. Using both strategies is a severe challenge to the sequence planners since command sequences are started at least six weeks before the date of the command upload. At the Spacecraft Technical Interchange Meeting in Denver last week, predicted spacecraft temperatures for this transition period were presented, and the pros and cons of the two strategies discussed. Based on this discussion, the Mission Director, Jim Scott, decided to stay with the nominal mapping sequence thru April 16, then go directly to the "Two Hide" strategy for the mapping loads for the next 14 weeks. ___ _____ ___ /_ /| /____/ \ /_ /| Ron Baalke | baalke@mars.jpl.nasa.gov | | | | __ \ /| | | | Jet Propulsion Lab | ___| | | | |__) |/ | | |___ M/S 301-355 | It's 10PM, do you know /___| | | | ___/ | |/__ /| Pasadena, CA 91109 | where your spacecraft is? |_____|/ |_|/ |_____|/ | We do!