Ulysses Jupiter Encounter Approaches

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.