Scientists Pull the Plug on Herschel

Herschel, the the most powerful infrared telescope every flown in space, was officially turned off June 17 after four years of research into the dark, cold recesses of the cosmos.

First to cover and bridge the entire range from far-infrared to submillimeter wavelengths, the satellite blew through the last of its helium coolant necessary for maintaining the its instruments on April 29. At that point, engineers at the European Space Agency's (ESA) European Space Operations Centre seized the rare opportunity to conduct a series of technology tests on the device that remained fully functional although no longer capable of scientific observation.

"Normally, our top goal is to maximize scientific return, and we never do anything that might interrupt observations or put the satellite at risk," Micha Schmidt, Herschel's Spacecraft Operations Manager at ESOC, said in a press release. "But the end of science meant we had a sophisticated spacecraft at our disposal on which we could conduct technical testing and validate techniques, software and the functionality of systems that are going to be reused on future spacecraft. This was a major bonus for us."

As an example, Schmidt explained that they were asked to perform a series of reaction wheel tests as well as validation using Herschel's Visual Monitoring Camera. According to Paolo Ferri, ESA's Head of Mission Operations, such experiments are designed to "increase the robustness and flexibility of future missions operations."

Among the last steps taken by mission operators was to ensure the satellite was completely disposed of fuel and in a safe disposal orbit around the Sun. Once in place and fully exhausted, scientists proceeded to send the final command via ESA's deep space antenna at New Norcia, Australia.

Almost one and a half times bigger than the Hubble Space Telescope, the spacecraft carried three advanced science instruments -- two cameras and a very high-resolution spectrometer -- it used to collect almost 20 times more light than any previous infrared space telescope. In so doing, Herschel gave and continues to give scientists a better understanding of the origin and evolution of stars and galaxies in the wealth of information it collected, much of which researchers have only begun to dissect.