Rumba and Tango in orbit. Photo: ESA

Following the successful launch of the second pair of four ESA Cluster satellites on August 9th, Rumba and Tango are heading towards their final operational orbits. The first step in this celestial dance was to increase the spin rate of both spacecraft from 5 to 13.7 revolutions per minute and then modify their attitude in preparation for the first apogee raising manoeuvre. This took place out of ground station coverage at 0853 GMT on August 10 for Tango and at 1359 GMT for Rumba.

Telemetry subsequently received at Kiruna (Sweden) and Villafranca (Spain) showed that both spacecraft had reached their correct orbits, with a perigee of around 239 km and an apogee of 23,199 km.

The next step in the sequence of four apogee raising manoeuvres was successfully accomplished this morning. A burn of the spacecraft main engine took place at 0340 GMT for Rumba and at 0458 GMT for Tango, with ground station coverage only at the beginning of the manoeuvre. As a result, the spacecraft orbits were elongated still further, with a perigee of about 240 km and apogees of about 33,000 km and 34,000 km.

"Everything is exactly as we want it to be at this stage," said Cluster operations manager Manfred Warhaut at the European Space Operations Centre in Darmstadt.

In order to bring the spacecraft to their operational orbits, another two apogee raising manoeuvres was scheduled for early this morning (August 12) and afternoon. A much longer engine burn to alter their orbital inclination from 64.8 degrees to 90 degrees will take place on 13 August.

The space quartet should be complete on August 15 when Rumba and Tango join their two companions (Salsa and Samba).