Goodbye to an Unsung Hero…

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This is the story of a spacecraft that most of us had never heard of before.

The unsung hero is Ulysses, a solar space probe that is loyally and silently doing its job out in space, for over 17 years!  And it was designed only to last 5 years.  After almost 2 decades in space, its radioactive power source has finally decayed to a point where it can no longer support all its instruments.  Ulysses is succumbing to its harsh environment and is likely to finish sometime in the next month or two.

The most interesting aspect of this spacecraft was its solar polar orbit; meaning its orbit is perpendicular to the orbit of the planets so that it could look straight down onto the Sun’s pole, something that we had never seen before.  To reach such high solar latitudes, Ulysses was launched toward Jupiter so that Jupiter’s large gravitational field would accelerate Ulysses out of the ecliptic plane to high latitudes.

Ulysses is in a six-year orbit around the Sun. Its long path through space carries it out to Jupiter’s orbit and back again.  Ulysses is equipped with instruments to characterize fields, particles, and dust, to study the Sun’s environment and understand how it works.

However, this is all going to end soon… as Ulysses is receding from the Sun out to Jupiter’s orbit, the spacecraft is getting colder and colder.  With its power source dying, it is unable to heat up and prevent its hydrazine fuel from freezing in the fuel lines.  Hydrazine fuel is critical for Ulysses to maneuver to point its antenna toward Earth.


Ulysses is a joint mission between ESA and NASA.  It was launched in 1990 from a space shuttle and was the first mission to study the environment of space above and below the poles of the Sun.  The reams of data Ulysses has returned have forever changed the way scientists view the Sun and its effect on the space surrounding it.

Source: ESA News


~ by thChieh on March 6, 2008.

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