Team members shut down the Cosmic Hot Interstellar Plasma Spectrometer satellite (CHIPSat), NASA's only university-class Explorer spacecraft, on April 11th. Mark Hurwitz, the mission's principal investigator, said scientists turned the satellite off due to a lack of funds.

"Typically, missions just kept getting extended, but we're now reaching the end of diminishing returns on some of these small satellites," said Patrick Crouse, project manager of space science mission operations at Goddard Space Flight Center, in a prepared statement. CHIPSat marks the third time NASA has pulled the plug on a functioning satellite since last fall.

CHIPSat photo

CHIPSat in the lab. The black rectangles are solar cells, and the apertures for studying the ISM are just below the disk in front.

University of California, Berkeley

The University of California, Berkeley, Space Sciences Laboratory (SSL) designed CHIPSat to look for extreme ultraviolet (EUV) emissions from the hot interstellar gas theorists believe permeates the solar neighborhood. The mission was five years old.

CHIPSat spent the last 10 years in an uncertain battle. NASA first funded the mission in 1998, yet the satellite faced various transportation hurdles before its launch in 2003. The U.S. government refused the planned Russian rocket ride due to a policy prohibiting the launch of government-funded satellites on foreign vehicles, and the satellite's Plan B (a seat on a GPS) fell through in 1999. It finally reached Earth orbit on a Delta rocket four years later.

Once in space, the satellite never detected the EUV emissions Hurwitz hoped to find. He later concluded that the local interstellar medium glows 30 times fainter in EUV than expected. CHIPSat's results could suggest either that the interstellar gas is a different temperature than previously thought, or that astronomers have yet to figure out exactly what comprises the matter between the stars.

Attempting to put to good use the working equipment and the team's leftover funds, SSL pointed CHIPSat at the Sun to study solar EUV emissions. They observed radiation from the Sun's chromosphere and corona as well as the chemical processes provoked by solar EUV radiation in the Earth's upper atmosphere.

NASA already has satellites studying the Sun's UV emissions, though, and the agency ultimately denied two new SSL proposals to conduct more detailed data analysis. So ended CHIPSat's contribution to our knowledge of the Sun's atmospheric temperature distribution.

CHIPSat is not quite dead: SSL and NASA can wake the satellite up should they ever need to use it. For now, though, the Agency has concluded that the mission's output is not worth its cost.

"It is sad and liberating," says Hurwitz, who has moved on to teaching high-school physics. "It's been lucky that the project has gone on as long as it has, and it has been very cool."


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