Final boom deployment clears the way for Cluster commissioning
16 November 2000Events have moved quickly over the past week as the Cluster mission has passed a series of significant landmarks.
Yesterday, the final boom deployment on the Cluster quartet was successfully completed when all four wire antennae on the Tango spacecraft were fully extended to a length of 44 m. This brought to an end a remarkable two-month-long sequence which involved 64 separate operations to unravel 16 booms (a record) and deploy around 700 m of wire (also a mission record).
The successful conclusion of this complex process was due to the tremendous dedication and hard work of the scientists and the mission operations team in the control room at the European Space Operations Centre (ESOC) in Darmstadt, Germany.
"Every step was a critical operation," said Silvano Manganelli, the ESOC engineer in charge of the 16 boom deployments. "Our first activity was to fire small pyro devices to open the doors on the booms. This was very stressful, since there was nothing we could do if this went wrong. All 16 devices worked perfectly - an excellent achievement."
"We also had to be very careful that there was no large asymmetry of the booms as they were released on opposite sides of the spacecraft," he added. "Otherwise, there would have been problems for the experiments and the spacecraft dynamics. This procedure has been done on a single spacecraft before, but never on four identical spacecraft in such quick succession."
One further complication was the need to increase the spin rate of each satellite in order to deploy the last 1½ m of wire. This final piece of very thin cable, to which the wave experiment's probe was attached, was released by relying upon centrifugal force to "throw" the wire outwards.
"My colleagues from the flight dynamics department monitored this manoeuvre very closely, and did a remarkable job," said Mr. Manganelli. "In each case they were able to predict the effects of the deployment and then calculate the manoeuvres needed to bring the spin rate back to within a few hundredths of a revolution per minute of the nominal value."
Now that they are all fully deployed from the spinning satellites, the booms will sweep out a giant circle in the electrified gas (plasma) around each spacecraft and provide a flood of data for the five instruments within the Wave Experiment Consortium (WEC) on each Cluster satellite.
"My colleagues and I want to thank everyone at ESOC, particularly Silvano, for all their hard work," said a delighted Per-Arne Lindqvist, Chairman of the WEC. "We really appreciate the support given to us during this long deployment campaign."
The team who designed. constructed and tested these boom units include scientists and engineers from Berkeley, Oulu, Uppsala, Oslo and Friedrichshaven.