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This will be very brief as (a) I’m not a solar astronomer so (b) I don’t really know very much about this spacecraft, but as one of the longest running space missions I think we should mark its passing. The Ulysses satellite was launched on 6th October 1990 and has been observing the solar environment at all latitudes ever since – a remarkable 18 years, 9 months (and this is without any servicing or repair visits, unlike the equally long-lasting Hubble Space Telescope). Today at around 2100 GMT the final command – to turn off its transmitter – will be sent and the mission will be officially over.
Ulysses was the first solar satellite to have a polar orbit (i.e. unlike the Earth, which stays in the region of the Sun’s equator, it passed over its poles), meaning that it could map previously unexplored regions of the heliosphere. There’s a good movie of its orbit here. In total it orbited the Sun three times, meaning it managed a total of six polar passes.
The mission has already lasted four times as long as originally predicted but the weakening power supply, combining with diminishing scientific returns means that sadly its time is now up.