A joint mission between ESA and NASA, Ulysses was launched by space shuttle in 1990 in the first mission to study the environment of space above and below the poles of the Sun.

The probe is on a huge, six-year orbit of the Sun that takes it out as far as the orbit of Jupiter.

A radioactive isotope provides Ulysses with power for communications and scientific equipment and for onboard heaters to warm its hydrazine fuel, which freezes when the temperature falls below minus two degrees Celsius (28.4 degrees Fahrenheit).

But the isotope source is running low, and the craft can no longer send back large quantities of data, nor can it ward off the deep chill of space.

As a result, the fuel lines will freeze up in the next month or two, leaving Ulysses unmanoeuverable and doomed to encircle the Sun for aeons.

"Ulysses is a terrific old workhorse. It has produced great science and lasted much longer than we ever thought it would," said Richard Marsden, the project's chief scientist and mission manage.

The team plan to continue operating the spacecraft for as long as they can before the curtain comes down, some time in the next month or two, ESA said in a press release.

"The reams of data Ulysses has returned have forever changed the way scientists view the Sun and its effect on the space surrounding it," the agency said.

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