Europe's Cluster mission is back in the fold after controllers fixed a glitch that would have seriously curtailed its ability to do science.
Cluster is comprised of four identical satellites that have been studying Earth's space environment and its interaction with the solar wind since 2000. They pirouette around each other as they orbit Earth, and data from all four are key to mapping out the space environment in 3D.
Each craft carries 11 sensors, of which five make up the Wave Experiment Consortium. It was these five on satellite 3 (dubbed Samba) that failed to respond in March to ground commands. Several weeks of intense work involving scientists, controllers, and the spacecraft manufacturers traced the problem to the simultaneous locking of all five power switches on the instruments—an eventuality that designers had thought too unlikely to consider.
The team resorted to what it called a "dirty hack," a nonstandard procedure that was impossible to test beforehand. During a tense day last month in the control room at the European Space Agency's space operations center in Darmstadt, Germany, controllers sent up a series of commands that flipped each of the power switches back on.
All instruments are now working normally, and team members are trying to make sure that something similar doesn't happen again.