09 Aug 2000

About three hours after launch, when the pair of Cluster spacecraft had successfully separated from the Fregat upper stage, the mini-camera transmitted back to Earth a series of 27 colour images taken 3 seconds apart.

The star of the 1½ minute VMC image sequence was the lower Cluster spacecraft (FM 8 - Tango), which was imaged spinning against the background of the blue and white Earth and the black void of deep space. Since the spacecraft carrying the camera was also spinning slowly, the Earth appears to rotate around the sky.

The Cluster team were delighted with the results of their experiment, since the exact field of view in the images depended on the orientation of the spacecraft at the time of separation, and the camera's exposure setting was estimated from simulations in the laboratory.

The images were downlinked to the ground after communication with the spacecraft was established from Kiruna ground station in Sweden, then processed at the European Space Research and Technology Centre (ESTEC) in The Netherlands.

The VMC is a late add-on camera on board the Cluster quartet. Each spacecraft carries 11 identical scientific instruments to detect and measure charged particles and electromagnetic phenomena. However, since plasma, electric fields and magnetic waves are usually invisible at optical wavelengths, a camera was in the first instance not included in this impressive instrument package.