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OFJ Field Journal from Lou D'Amario - 11/27/95

As we get closer and closer to arrival day and the Jupiter Orbit Insertion burn, there are an increasing number of meetings to go to. Today I attended two meetings. One was a meeting of the members of the Navigation Team who are responsible for figuring out the strategy to use for working on OTM-1 (Orbit Trim Maneuver #1 -- notice how we are changing the jargon here from "Trajectory Change Maneuver" to "Orbit Trim Maneuver," now that the spacecraft will be in orbit around Jupiter, and not just on its way to Jupiter).

OTM-1 is performed one day after the large JOI (Jupiter Orbit Insertion) maneuver. OTM-1 mainly corrects errors resulting from either (1) an Io flyby altitude that is above or below the target value (1000 kilometers) and/or (2) a JOI velocity change that is larger (overburn) or smaller (underburn) than the value we want (644.4 meters per second). The strategy for OTM-1 has just recently become very complicated because we now know it is possible to make OTM- 1 much smaller (and hence use less propellant) by changing the date of the first satellite encounter in the orbital tour, called the "Ganymede 1" flyby.

Today's other meeting was with representatives from the DSN (Deep Space Network) Team. We were looking at how to model the JOI burn in the DSN computers to guarantee continuous, or nearly-continuous, tracking of Galileo by the DSN antennas during the JOI burn. The better that the DSN understands how the orbiter's trajectory will change during the burn, the better able it will be to keep tracking the spacecraft.

 
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