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- FACT SHEET February 1992
-
- ULYSSES
-
- The Ulysses spacecraft, an international project to
- study the poles of the sun and interstellar space above and below
- the poles, has reached Jupiter, where it will use the planet's
- gravity to swing out of the ecliptic plane and onward to the
- poles of the sun.
- The mission, managed jointly by NASA's Jet Propulsion
- Laboratory and the European Space Agency, is designed to study
- three major topics in solar physics: the sun, the solar wind and
- interstellar space. The instruments of Ulysses will study those
- phenomena at nearly all solar latitudes, but the most important
- work will be at high solar latitudes, near the polar regions of
- the sun that have never been reached by spacecraft.
- Until l984, when it was renamed for the Greek
- adventurer in Homer's epic poem, the project was called the
- International Solar Polar Mission.
- Ulysses is a 370-kilogram (8l4-pound) spacecraft that
- will be sent into an orbit at right angles to the solar system's
- ecliptic plane using a gravity-assist on Feb. 8, 1992 from
- Jupiter. (The ecliptic is the plane in which the Earth orbits
- the sun.) The orbit will allow Ulysses to examine, for the first
- time, the regions of the sun's north and south poles.
- Scientific data returned by Ulysses are expected to aid
- scientists in their studies of the sun and of space beyond the
- solar system. All spacecraft that have studied the sun have done
- 1
- so in or near the ecliptic plane. But the sun's magnetic
- and electric fields and the solar wind have a strong influence on
- interplanetary space in that region. Because of the structure
- and shape of the sun's magnetic field, scientists expect to see
- very different phenomena, both outbound from the sun and inbound
- from interstellar space, in the polar regions.
- Besides examining the sun's polar regions, the
- instruments on Ulysses will study other phenomena from the Milky
- Way galaxy and beyond.
- Scientists have studied the sun for centuries, but they
- know little about matter reaching the solar system from nearby
- stars. That is because particles entering the region dominated
- by the sun's magnetic field from beyond the solar system are
- greatly changed by the magnetic field itself and by collisions
- with particles flowing from the sun.
- No spacecraft has left the solar system to make direct
- measurements of the interstellar medium above and below the sun.
- NASA launched Ulysses on Oct. 6, 1990 from the space
- shuttle Discovery. No launch vehicle has enough energy to lift
- the spacecraft directly from Earth over the sun's poles, so
- Ulysses was sent to Jupiter atop a two-stage Inertial Upper Stage
- rocket and a PAM-S. (Before the Challenger accident in January
- l986, Ulysses had been set for launch from the shuttle on a
- Centaur G-prime.)
- Sixteen months and 920 million kilometers (575 million
- miles) after launch, Ulysses is approaching Jupiter at about 30
- degrees north latitude. At closest approach, Jupiter's gravity
- will change Ulysses' trajectory so that, when the spacecraft
-
- leaves Jupiter, it will be climbing out of the ecliptic plane and
- heading for the sun's southern pole.
- The first high latitude solar pass will begin when
- Ulysses reaches 70 degrees south solar latitude in June l994.
- Ulysses will spend about four months above that latitude, about
- 2.2 astronomical units from the sun. (An astronomical unit is
- about l50 million kilometers or 93 million miles, the average
- distance between the sun and the Earth.)
- The sun's gravity will bend Ulysses' trajectory.
- Ulysses will cross the sun's equator in February l995 and then
- continue toward the north pole.
- During its second polar passage, Ulysses will spend four
- months at latitudes greater than 70 degrees. The northern polar
- pass will begin in June l995.
- The mission will be completed in October l995.
- Ulysses' scientific payload is composed of nine
- instruments. The spacecraft radio will also be used to conduct a
- pair of experiments in addition to its communications function.
- * A pair of magnetometers will measure magnetic fields
- in space. The objective is to measure changes in the
- interplanetary magnetic field at different heliographic
- latitudes. Dr. Andre Balogh of Imperial College London is the
- principal investigator and has provided a scalar magnetometer.
- Dr. Edward J. Smith of JPL has provided a vector helium
- magnetometer.
- * A solar-wind plasma experiment will study protons,
- electrons and heavy ions in the solar wind and their dependence
- on distance from the sun and heliospheric latitude. Dr. SamuelJ. Bame of Los Alamos National Laboratory is principal
- investigator.
- * A solar-wind ion-composition spectrometer will study
- the elemental and ionic-charge composition, and the mean
- temperatures and mean speeds of all solar-wind ions from hydrogen
- to iron. Measurements will reveal conditions and processes in
- the region of the sun's corona where the solar wind is
- accelerated, as well as plasma interactions in the solar wind.
- George Gloeckler of the University of Maryland and Johannes Geiss
- of the University of Bern, Switzerland, are co-principal
- investigators.
- * An energetic-particle composition experiment will
- measure intensities and energies of interplanetary ions to
- resolve their masses and to observe helium penetrating the
- heliosphere from interstellar space. Erhardt Keppler of the Max
- Planck Institut für Aeronomie in Germany is principal
- investigator.
- * A low-energy charged-particle detector will measure
- elemental abundances of interplanetary ions and electrons. The
- full name of the instrument is the Heliosphere Instrument for
- Spectral, Composition and Anisotropy at Low Energies (HI-SCALE).
- Louis J. Lanzerotti of Bell Laboratories, New Jersey, is
- principal investigator.
- * A cosmic-ray and solar-particle instrument will
- resolve outstanding problems in solar, interplanetary and cosmic-
- ray physics for which observations far out of the ecliptic plane
- are required. Dr. John A. Simpson of the Univeristy of Chicago
- is principal investigator.
-
- * A unified radio and plasma-wave experiment will
- determine direction and polarization of distant radio sources,
- charged particles in solar wind that emit bursts of radio noise
- and can be tracked as they travel outward through the
- heliosphere. The instrument will also study waves in clouds of
- ionized particles in the solar wind as they move past the
- spacecraft. Dr. Robert G. Stone of Goddard Space Flight Center
- is principal investigator.
- * A solar-flare X-ray and cosmic gamma-ray burst
- experiment will measure electrons in solar flares and determine
- the direction of gamma-ray bursts from the galaxy whose sources
- are unknown. Kevin Hurley of the University of California,
- Berkeley, and Michael Sommer of the Max Planck Institut für
- Extraterrestrische Physik, Germany, are co-principal
- investigators.
- * A cosmic-dust experiment will provide direct
- observations of particulate matter and its interaction with solar
- radiation as a function of ecliptic latitude. Dr. Eberhard Gruen
- of the Max Planck Institut für Kernphysik, Germany, is principal
- investigator.
- * A coronal-sounding experiment will use the Ulysses
- radio to measure density, turbulence and velocity of the plasma
- in the sun's corona. The measurements are made when the
- spacecraft is nearly behind the sun as viewed from Earth. Dr.
- Hans Volland of Bonn University, Germany, is principal
- investigator.
- * A gravity-wave search will also be conducted by the
- radio. By analyzing the radio signal from the spacecraft whenthe Earth is between the sun and Ulysses, scientists can measure
- tiny movements of the spacecraft. Those motions could reveal the
- presence of passing gravity waves. Dr. Bruno Bertotti of the
- University of Pavia, Italy, is principal investigator.
- The science instruments for Ulysses were provided by
- the science teams, both U.S. and European. The spacecraft was
- built by Dornier Systems of Germany, for ESA, which is
- responsible for on-orbit operations. NASA provided the space
- shuttle Discovery and the IUS and PAM-S upper stages and the
- radioisotope thermoelectric generator, which was built for the
- U.S. Department of Energy by the General Electric Co.
- Jet Propulsion Laboratory manages the U.S. portion of
- the mission for NASA's Office of Space Science and Applications.
- Ulysses is being tracked and data gathered by NASA's Deep Space
- Network, which is operated by JPL. Spacecraft operations and
- data analysis are being performed at JPL by a joint ESA/JPL team.
- Willis Meeks of JPL is the U.S. project manager. Dr.
- Edward J. Smith of JPL is the U.S. project scientist. The
- program manager is James Willett of NASA Headquarters and the
- program scientist is Dr. W. Vernon Jones, also of NASA
- Headquarters. The European Space Agency's project manager is
- Derek Eaton and the ESA project scientist is Dr. Klaus-Peter
- Wenzel.
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- 2/1/92 dea JPL-PIO
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- MISSION TIMELINE
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- EVENT DATE
-
- Launch Oct. 6, l990
- Upper stage deployment and firing Day l
- Ulysses checkout Days 2-9
- Jupiter encounter Feb. 8, l992
- First solar polar passage (max. lat.) June l994
- Cross solar equator February l995
- Second solar polar passage (max. lat.) June l995
- End of mission Oct. l, l995
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- (Distance are from the center of the planet.)
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