Day to Day Operations
One of the most challenging aspects of Cluster is the launch and control of four identical spacecraft. The day-to-day operation of the spacecraft is carried out by the European Space Operations Centre (ESOC) in Darmstadt, Germany. The main control room at ESOC was used during the launch and early orbit phases of the mission, with teams of operators working around the clock. About two weeks after the second Cluster launch, mission operations was switched to a smaller, dedicated control room.
ESOC is responsible for:
Spacecraft telemetry, command and tracking are handled primarily by the ESA ground station in Villafranca, Spain, with supplementary support from NASA's Deep Space Network. In the critical early stages between launch and final orbit insertion, additional ground stations in Kourou (French Guiana), Perth (Australia) and Kiruna (Sweden) were used.
During the two-year mission, signals to and from the spacecraft are routed through the Operations Control Centre at ESOC. The centre controls the spacecraft and their payloads, and carries out all activities related to mission planning and scheduling. Normal ESOC operations are interrupted every six months to conduct orbit manoeuvres. Controllers adjust the separation distances between the four spacecraft in order to allow the study of different scientific phenomena.
One of the main factors influencing data acquisition and spacecraft control is the limited time available for ground contact with the spacecraft. On average they are visible for about 10 hours per day from the Villafranca ground station. However, since there are four Cluster spacecraft, the time available to acquire data from each one is only around two and a half hours per day.
The Joint Science Operations Centre (JSOC) at Rutherford Appleton Laboratory in the UK co-ordinates the science operations. Its main task is to merge all commands coming from the 11 instrument teams into an overall command schedule, which is then be sent through ESOC to the 44 spacecraft instruments. JSOC also collects and processes the data needed to plan these instrument operations and monitors the performance of the individual instruments.
The vast amount of scientific information sent back by the four spacecraft is handled by the Cluster Science Data System (CSDS). This comprises eight national data centres - six in Europe, one in the USA and one in China. The CSDS supports scientific data processing and distribution activities. Raw data from the spacecraft is distributed on CD-ROM to scientists around the world.