By Yanhua Anderson, MIRO Operations Engineer
Although it is perhaps less well known outside the project, Rosetta Science Operations is absolutely critical to the success of the mission. Its task is to run the scientific payload of the spacecraft, and to manage the flow of information from the science teams to science planning to command sequences to spacecraft and back.
Each science team is responsible for the operation of their individual instrument. However, like any other planetary mission, Rosetta has several highly constrained resources that require the science inputs from all 11 instruments to be pre-planned and coordinated like a symphony concert, to optimize the science output.
For Rosetta, the constraints include how much data can be radioed back to Earth (downlink rates are typically on the order of kilobits per second), how much power is used (the solar panels right now could power about 10, 100W light bulbs), and the spacecraft pointing direction (it can only point in one direction at a time).
ESA’s European Space Astronomy Center in Madrid, Spain, manages the planning and coordination of the inputs from the instrument teams.
Typically science plans are chopped into 4 week-long periods, and we go through a cycle of making long, medium, and short term plans. Long term planning starts 20-16 weeks in advance of the plan’s first execution time. It establishes the baseline science plan, we negotiate which instrument gets to observe at which time, solve data volume oversubscriptions, and make sure we don't use more power than we have. This work is done by the Rosetta Science Working Team, which consists of principal investigators and co-investigators of the instruments, science operations engineers, the spacecraft operations team, and project management.
Medium term planning starts 12-4 weeks ahead of the plan execution time, with goals to define the specific pointing strategy and the detailed payload operations. At this stage, we identify and resolve any flight rule violations, which would be things like pointing certain instruments too close to the Sun, or trying to make the spacecraft swing around faster than it can.
Short-term planning is done one week in advance. During this period scientists and engineers fine-tune the timelines of operations, the amount of data each instrument produces, and any other instrument-specific commands. The final product of the science planning cycle is a week-long integrated, conflict-free, and constraint-checked command sequence from all instrument teams. At this point, the product is ready to be uplinked to the spacecraft for execution.
During the science operations process, the scientists and engineers get a lot of help from a set of standardized tools provided by the European Space Agency (ESA). A key tool is called MAPPS - Mission Analysis and Payload Planning System. MAPPS can not only display the timeline of a plan, it also can show the trajectory and attitude of the spacecraft in a 3D visualization. It also warns us if we try to do something that is against our flight rules.