Ulysses Jupiter Encounter Approaches

Press Release From: European Space Agency
Posted: Tuesday, January 27, 2004

image Mission Status

The spacecraft and all scientific instruments are in good health. Preparations are underway for the Jupiter Distant Encounter campaign that will take place between the end of January and mid-March 2004.

During this 50-day period, 24-hour per day real-time coverage by the Deep Space Network has been scheduled to allow the on-board tape recorders to be switched off. This in turn will permit the majority of the scientific payload to be operated continuously, without the need for power sharing. "Closest approach" to Jupiter occurs on 4 February, at a distance of 1684 Jupiter radii (~0.8 AU or 120 million km) from the planet.

On 1 February, Ulysses will be at a radial distance of 5.3 AU from the Sun, and will cross the heliographic equator heading south on 20 February.

Operations and Archive

All science operations during the reporting period have been nominal.

Science Highlights

Even though the sunspot maximum of the current solar cycle (23) occurred in mid-2000, the Sun recently underwent a major surge in activity starting at the end of October. As noted in the report to SPC in February 2003, strong outbursts in the form of solar flares and coronal mass ejections (CMEs) are often seen during the declining phase of a solar cycle. The recent activity, however, was unusual both in its intensity, and its relative lateness. The largest solar flare of the series, rated at X28, occurred on 4 November while the responsible active region was on the Sun's west limb, rotating off the visible disk.

Although quite far from the Sun (5.3 AU), Ulysses was well placed to observe the effects of this violent outburst, being more or less in the "line of fire". Analysis of data from the event is still underway, but indications are that the fast CME that was associated with the X28 flare swept over Ulysses, driving a significant interplanetary shock wave. Impressive enhancements in the flux of energetic particles, modulated by the passage of CME-related solar wind transients - and the passage of high-speed solar wind streams originating in a large, persistent, trans-equatorial coronal hole - were seen at Ulysses throughout the period of increased activity. The study of the precise mechanisms whereby solar energetic particles are distributed throughout large volumes of the heliosphere, and under which conditions efficient re-acceleration of these particles occurs, remains an important area of research using data from Ulysses. This unusual solar activity period appears to have been the Sun's final outburst before settling into a more stable configuration leading to the next solar minimum.

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