In Homer's Odyssey, Odysseus (known as Ulysses to the Greeks) made it safely home after 10 years of wandering. His namesake, the Ulysses probe that has studied the solar environment for more than 17 years, lasted longer. But it's not coming home.
Researchers say the probe, originally launched from a space shuttle in in 1990, is nearing the end of its life, after outlasting its expected mission duration by more than four times.
A joint NASA-European Space Agency mission, it was the first probe to be launched into a polar solar orbit, studying the environment above and below the solar poles, and the effect of the star on the space around it. Its six-year solar orbit takes it as far as Jupiter and back again.
But it's cold out there.
In order to operate, Ulysses has to stay above 2 degrees Celsius (about
35.6 degrees Fahrenheit), or its fuel will freeze. Until now, that hasn't been a problem, since heaters powered by the decay of a radioactive isotope have kept it relatively warm.
That power supply is now failing, however. It no longer has enough power to run the heaters, the scientific instruments and its transmitter simultaneously.
In an attempt to lengthen the probe's life, researchers turned off the transmitter, hoping to free up power for the heater and science tasks, and restart the transmitter when Ulysses returned to warmer climes. But in a test of this in January, the transmitter couldn't be restarted.
That means that large quantities of data can no longer be sent back to
Earth, and that the probe will probably freeze, blocking its fuel lines, over the next few months. They'll be operating it for the next few weeks, trying to get a few more bits of data out. But for most practical purposes, Ulysses' mission is over.
Ulysses mission coming to a natural end [ESA press release]
(Image: Artist's rendition of the Ulysses probe in space. Credit: ESA)
