Ulysses operations

The mission

Ulysses's instruments studied the solar wind that streams non-stop from the Sun and produces a huge bubble in space called the heliosphere. Ulysses provided the first-ever map of the heliosphere from the equator to the poles.

The mission was a cooperative programme between ESA and NASA. The science instruments for Ulysses were provided by US and European science teams. The spacecraft was built for ESA by Germany's Dornier Systems. NASA provided the Space Shuttle Discovery for launch, the upper stages and the radioisotope thermoelectric generator, which was built by General Electric Co. Ulysses tracking and data reception were provided by NASA's Deep Space Network, which is operated by the Jet Propulsion Laboratory (JPL); spacecraft operations and data analysis were performed at JPL by a joint ESA/JPL team.

The Ulysses Mission Support Area (MSA) was located at JPL, Pasadena, California.

After over 18 years in space and defying several earlier expectations of its demise due to a weakened power supply, Ulysses conducted its final communication pass with a ground station on 30 June 2009, starting at 17:35 CEST via DSS-63 (NASA's 70-m station at Madrid). The final command switched the satellite's radio communications into 'monitor only' mode. No further contact with Ulysses is planned.

The Flight Control Team

The joint ESA-NASA Mission Operations Team (MOT) works at JPL. The Flight Control Team is provided by ESA, and comprises 11 engineers, headed by Nigel Angold, the Mission Operations Manager, and Fernando Castro, the Spacecraft Operations Manager.

The Ground Operations Team is provided by NASA, and comprises five engineers headed by the Ground Operations Manager, Bruce Brymer. Additional support from JPL resources is provided by experts for navigation and other technical functions.

Mission operations overview

Ulysses was scheduled for launch onboard a space shuttle in May 1986, and was shipped to NASA's Kennedy Space Center (KSC) in January 1986.

On 28 January 1986, the Space Shuttle Challenger disaster put an immediate stop to all Shuttle launches and therefore the Ulysses Mission; the spacecraft had to be dismantled and shipped back to Europe. After shuttle operations were restarted in 1989, Ulysses was launched successfully on 6 October 1990 from KSC's Pad 39.

Launch and transfer to solar orbit

The spacecraft was successfully deployed from the Space Shuttle Discovery into low earth orbit, and was then boosted by two solid-fuel motor upper stages, the Inertial Upper Stage (IUS) and Payload Assist Module (PAM-S), into an outbound trajectory for Jupiter. Earth departure speed was 15.3 kilometres per second, one of the fastest ever and surpassed only by NASA's New Horizons mission, at 16 km/s, in January 2006.

It arrived at Jupiter in February 1992, and the effect of the giant planet's gravity assist was to swing Ulysses out of the ecliptic plane and into its unique Sun-polar orbit.

The first south solar pole pass ended in November 1994, and the spacecraft swung up to complete its first north polar pass in September 1995.

Routine phase

The spacecraft has now completed 2-1/2 solar orbits, and will start the third north polar pass in November 2007, reaching maximum north solar latitude (79.8°) on 14 January 2008 and ending in March 2008.

In 2007, a typical spacecraft-to-Earth distance was 284,948,700 km (1.905 AU), on 20 May 2007, the closest approach to Earth occurred on 26 August 2007, at approximately 62,200 km (0.42 AU), and the closest approach to Mars came on 20 July 2007, at approximately 133,700 km (0.89 AU).

End of mission

The mission had been predicted to end in July 2008, when the satellite's weakened power supply was expected to fall below the minimum required to keep fuel lines from freezing, without which Ulysses would be uncontrollable. At that time, the ESA/NASA operations team planned to continue operating the spacecraft in a reduced capacity for a few more weeks.

However, through smart engineering and realtime innovation, controllers determined they could keep the lines from freezing by briefly firing the thrusters every few hours. In fact, Ulysses continued gathering valuable scientific data throughout 2008 and into the first half of 2009. However, with higher priority missions requiring access to NASA's Deep Space network, and with the overall science data return falling, a joint decision by ESA and NASA was taken to end the mission on 30 June 2009.

The ground stations
NASA DSN, New Norcia DSA 1

Routine telecommanding and data download for Ulysses are provided by NASA's Deep Space Network (DSN) using antennas located at Madrid (Spain), Canberra (Australia) and Goldstone (California); DSN antennas range in size from 26 to 70 metres.

In addition, ESA's deep-space antenna DSA 1, in New Norcia (Australia), the ESTRACK station in Kourou and non-DSN NASA stations are used, as well as other agencies' stations including the German Aerospace Center's Weilheim station and Chile's Santiago station.

Ulysses downloads data primarily using X-band wavelengths via the on-board High Gain Antenna. Ulysses occasionally uses an S-band downlink in addition to the prime X-band downlink; this extra signal is used to gather radio science data. In radio science, scientists learn about any matter (typically, dust, plasma and other particles) through which radio waves transmitted from the spacecraft must pass by studying how the originally transmitted signal is affected by the matter.

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