Ulysses’ Farewell

The European Space Agency (ESA) and NASA have shut down Ulysses, one of the longest serving solar orbiters in history. Ulysses was the pioneer spacecraft to chart the space area above and below the poles of the Sun. Clocking in over 18 years, Ulysses’ transmitter was switched off upon receipt of the final command from Earth on the 30th of June, 2009. The final communication started at 17:35 CEST and ran until 22:20 CEST, when radio transmission was programmed to ‘monitor only’ mode.
 Ulysses was launched by Space Shuttle Discovery in October 1990. It headed out to Jupiter, arriving in February 1992 for the gravity-assist maneuver that swung the craft into its unique solar orbit. It orbited the Sun three times and performed six polar passes (Credit: C. Carreau, ESA)
Ulysses was launched by Space Shuttle
Discovery in October 1990. It headed
out to Jupiter, arriving in February 1992 for
the gravity-assist maneuver that swung the
craft into its unique solar orbit. It orbited the
Sun three times and performed six
polar passes (Credit: C. Carreau, ESA)

The spacecraft surveyed the sun’s environment in the four dimensions of space and time and presented ground breaking results. The data provided by Ulysses proved that the Sun’s magnetic field is conducted through the Solar System by a more complex way than previously thought. It was found that particles ejected from the lower latitudes of the Sun can ascent to high latitudes and vice versa. These dangerous particles could even reach other planets, which is not good news for astronauts and satellites that could be affected by them.

“Ulysses has taught us far more than we ever expected about the Sun and the way it interacts with the space surrounding it,” said Richard Marsden, ESA’s Ulysses Project Scientist and Mission Manager. ESA and NASA came up with a joint decision to end the mission last year due to the weakening of Ulysses and frozen fuel lines. However, the satellite persevered and was shut down only a year later.

The scientists working on Ulysses found that by burning the thrusters every two hours, warm fuel would circulate around the frozen fuel lines, keeping the spacecraft functioning. This workaround allowed for Ulysses’ extended time in space.

 Ulysses’s orbit is an ellipse with the Sun at one focus (heliocentric), and is inclined 80° with respect to the Sun’s equator (polar). The orbital period is 6.2 years. Maximum distance from the Sun (aphelion) is reached at about 810 million km and minimum distance is at about 200 million km (Credit: C. Carreau, ESA)
Ulysses’s orbit is an ellipse with the
Sun at one focus (heliocentric), and is
inclined 80° with respect to the Sun’s
equator (polar). The orbital period is
6.2 years. Maximum distance from the
Sun (aphelion) is reached at about 810
million km and minimum distance is at about
200 million km (Credit: C. Carreau, ESA)

Another reason that contributed to the shut down of Ulysses was the increase in demands associated with the 70 meter-diameter Deep Space Network ground stations used to maintain operation with the spacecraft. Furthermore, since Ulysses has traveled further from Earth, the data bit rate during communications has reduced to a level at which the input energy outweighs the resultant output.

“We expected the spacecraft to cease functioning much earlier. Its longevity is a tribute to Ulysses’s builders and the people involved in operations over the years,” says Paolo Ferri, Head of the Solar and Planetary Missions Division at ESA’s European Space Operations Centre in Darmstadt, Germany. As of the shut down, Ulysses has become a man-made ‘comet’ that will continue to orbit the Sun.

TFOT has previously written about other NASA satellites such as the Kepler Telescope, which will look for Earth-sized planets, which orbit stars at distances where temperatures permit liquid water to endure on their surface – a region often referred to as the “habitable” zone. You can also check out our article on space garbage, which is exactly what Ulysses has become and IBEX, another NASA program that collects data on solar wind.

Additional information on Ulysses can be obtained at NASA’s website and ESA’s website.