Mission Phases

The Cluster mission can be divided into three main phases:

• The Launch and Early Orbit Phase/Transfer Orbit Phase
  This includes launch activities, first acquisition of the spacecraft signals, orbital manoeuvres and delivery of the four spacecraft into the desired mission orbits
• The Commissioning and Verification Phase
  Preparations in readiness for the start of the science mission. This lasted about ten weeks. During this time, the spacecraft subsystems and 44 science instruments were switched on, checked and calibrated to verify their in-orbit performance
• The Mission Operations Phase
  Includes all of the routine operations in support of spacecraft and payload activities and scientific data acquisition during the two year long primary mission. The normal routine is interrupted once every six months by orbit manoeuvres which adjust the separation distances between the four spacecraft so that scientists can study different phenomena in near-Earth space

Science Operations

The sheer volume of scientific data expected during the mission - about one gigabyte per day over a two year period - requires new handling procedures. This vast amount of information returned by the four spacecraft is dealt with by the Cluster Science Data System (CSDS). This comprises eight national data centres - six in Europe, one in the USA and one in China.

Flow Diagram of the CSDS

The Cluster Science Data System supports scientific mission planning; preparation of requests for sending up instrument commands to the satellites; data processing and distribution activities.

The CSDS Web sites include a 3D display which shows the position and configuration of the four spacecraft in relation to the various scientific regions of interest. Data is exchanged between ESOC, the national data centres and the scientific investigators via the public Internet. This enables scientists to access new data which is only a few hours old.