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Dawn Science Operations Planning Gets Underway

Carol A. Raymond
Dawn Deputy Principal Investigator, JPL

A meeting of the Dawn Science team was held January 11-12, 2005 at UCLA to kick-off the science operations planning activities. A Science Plan is under development that will define time-ordered activity listings describing what we know at this point about how we will operate the spacecraft at each of the target bodies, Vesta and Ceres, as well as during cruise and the Mars Gravity Assist [MGA] flyby. The activities are organized by sub-phases of the encounters, which are summarized in Table 1

The draft Science Plan will be reviewed at the next Science Team meeting held on April 23-24 in Vienna preceding the EGU meeting. Plans will then be finalized and the Initial Science Plan will be delivered in June. The plan will be updated beginning one year before arrival at each of the bodies, culminating in updated plan deliveries six months before each arrival.

The Dawn Science Center [DSC] at UCLA will collect and integrate sequence inputs from the instruments and facilitate the review of the spacecraft sequences by the Science Team. DSC is rapidly developing functionality to support the science operations. The DSC will participate in the first instrument commanding thread test that will occur in April. End-to-end information system tests, mission scenarios tests, and operational readiness tests will occur between August 2005 and March 2006 to test and validate all the functions and interfaces used in the operations. These tests are driven by the Science Plan to establish the ‘test-as-you-fly’ framework.

The mission design team is currently studying options for harvesting unused mass and power margins to lengthen the duration of the science orbits at both bodies. It is likely that we will be able to arrive earlier to Vesta, and stay at least one month longer at both Vesta and Ceres. The Science Team is considering how to use additional time that becomes available as we become more certain of the actual flight system mass, and the system performance in flight. The team is also looking at whether we can skip the Mars Gravity Assist and go directly to Vesta, as was originally planned. That decision will be made by June of 2005. A non-MGA mission will shave one-year off the trip time to Vesta and much of that extra time can be used to collect more science data. We are considering options that lengthen the number of days in each orbit sub-phase, with the majority of the time devoted to the Low-Altitude Mapping Orbit [LAMO]. The other major trade being considered is lowering the altitude of LAMO to increase the resolution of the gamma ray and neutron spectroscopy, as well as the gravity field determination. High-resolution spectra and images will also be collected in LAMO, but the global imaging campaigns will be at higher altitudes.