have taken their first major steps toward data collection. Over the last two weeks, European scientists have begun deployment of mission-critical booms -- long tether-like wires that will help the spacecraft gather information about the Earths magnetosphere. Full deployment of the satellites 16 booms will continue through the next five weeks.
"This is a major step toward the start of our unique scientific program," said Philippe Escoubet, Cluster project scientist.
Salsa and Rumba, two of the four Cluster satellites, were the first to begin the boom-releasing process. Last week, covers that were protecting their booms were released, and the booms were allowed to creep out of their individual spacecraft at a snails pace of 0.4 inch (1 centimeter) per second.
Though theyre creeping along, the booms are actually being "whipped" out of their spinning satellites by a combination of centrifugal force and remote mechanical maneuvering. "Its rather like reeling out a fishing line," said Escoubet. "The centrifugal force generated as the spacecraft rotates causes the wires to slowly extend outward, away from the spacecrafts main body."
Each of the booms consists of 135 feet of wire and a small information-collecting instrument at each end. "The idea is to have four booms on each spacecraft separated by 90 degrees," said Michael Fehringer, deputy project scientist for Cluster. This configuration, said Fehringer, allows for the highest and best information relay back to Earth.
The two main Cluster instruments that will specifically use information gathered by the wire booms are the Electric Field and Wave (EFW) instrument and the Waves of High frequency and Sounder for Probing of Electron density by Relaxation (WHISPER) instrument. Together, these will measure the density of electric fields and charges near Earth.
So far, ESA officials have reported that the boom deployment has been running smoothly. But even if a small problem should arise with one of the booms, scientists wont have to worry much. Though the configuration of four booms per spacecraft is preferred because it means the best resolution and the best data possible, each spacecraft only needs one pair to successfully collect magnetosphere data.
Though officials admit that the Cluster boom deployment is going rather slowly, scientists and engineers say this was planned. In fact, the inching along of the booms is preferable to a quick maneuver because it allows scientists to make sure all systems are working properly. In about two weeks, the booms for Salsa and Rumba should be completely deployed. And in October, deployment of eight more booms those of Tango and Samba will begin.
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