Operational Pre -Planning for Intensive Science Periods: the New Horizons Jupiter Flyby

The New Horizons spacecraft launched January 19th 2006 on a mission to flyby Pluto in July of 2015. The trajectory of the spacecraft includes a Jupiter Gravity Assist, with Jupiter closest approach on February 28, 2007. Jupiter was observed with the payload instrument suite for a five-month period starting in January of 2007. The Jupiter Encounter Science Team developed an ambitious plan for Jupiter. Most observations were intricate, finely timed, and command-intensive. The command loads for the flyby period were expected to be large, complex, and delicate. The nominal operational command load build process would not be sufficient to support planning the science for the Jupiter flyby, so a pre-planning phase was instituted to develop critical command sequences well in advance of the nominal schedule; this was termed Phase A. The four-month period from October 2006 through January 2007 was allocated to Jupiter Encounter Phase A command load development for the critical science period, identified as the 80 days from January 1 through mid-March, 2007. The work was scheduled to put each of the six command loads through three complete build cycles. The repeated build cycles allowed the science sequencers to check, correct and refine the timing of the observations, the timing between observations, the spacecraft pointing when observing Jupiter and its moons, etc. The four months allocated to Phase A development proved to be insufficient, and observations had to be pulled from the Far Encounter period to free up resources to concentrate on the Near Encounter. The load containing Near Encounter and closest approach stressed the system in several ways: a piece of ground software had to be fixed to manage the large volume of commanding, and the load itself had to be split into 4 parts to fit into the command storage space in the C&DH. The Jupiter Encounter Phase A development effort was arduous, but necessary to carry out the science plan for the Jupiter flyby. The New Horizons Mission Operations team has concluded that the extra time that Phase A provides for developing, reviewing, and updating the command sequences is well worth the resource commitment for ensuring success and reducing risk. The Phase A method is being implemented as a standard practice for the New Horizons Pluto flyby, other critical spacecraft events. The MESSENGER mission operations team has also adopted the Phase A method for the Mercury flybys.