CCSD3ZF0000100000001NJPL3IF0PDSX00000001 PDS_VERSION_ID = PDS3 LABEL_REVISION_NOTE = "J. MAFI (PPI), 1998-05-18" RECORD_TYPE = STREAM OBJECT = MISSION MISSION_NAME = "ULYSSES" OBJECT = MISSION_INFORMATION MISSION_START_DATE = 1990-10-06 MISSION_STOP_DATE = 2001-12-31 MISSION_ALIAS_NAME = "INTERNATIONAL SOLAR POLAR MISSION" MISSION_DESC = " Mission Overview ================ 1. Introduction --------------- Launched in October 1990, Ulysses was an exploratory mission carried out jointly by ESA and NASA and had as its primary objective the study of the inner heliosphere in three dimensions. The importance of such a mission was recognized even at the dawn of the space era (e.g., [SIMPSONETAL1959]), since it was generally accepted that the conditions found in the narrow band of heliographic latitudes available to observers in the ecliptic plane were not representative of the global structure of the inner heliosphere. Nevertheless, prior to Ulysses, attempts to understand the basic physical processes occurring within this environment had, by necessity, been based for the most part on observations made in or near the ecliptic plane. The Ulysses mission provided, for the first time, comprehensive in-situ measurements of the heliospheric particles and fields at distances from 1 to 5 AU from the Sun, and at essentially all solar latitudes. Within the framework of the Ulysses project, ESA was responsible for the operation of the European-built spacecraft, while NASA provided the launch, the spacecraft's radioisotope thermoelectric power source, and was responsible for acquisition of data using the Deep Space Network of tracking stations. The scientific payload comprising nine hardware investigations was provided by international teams of scientists from Europe and the United States. The mission provided results addressing many aspects of solar and heliospheric science. In addition to numerous individual publications, as of 1996 seven collections of papers had appeared as special issues or sections of journals, each one focusing on a specific part of the mission ([GRLV19N121992], [SCIENCEV257N50761992], [JGRV98NA121993], [PSSV41N11/121993], [SSRV72N1/21995], [SCIENCEV268N52131995], [GRLV22N231995]). 2. General aspects of the mission --------------------------------- Following launch by the Space Shuttle, a combined IUS/PAM-S upper-stage was used to inject Ulysses into a direct Earth/Jupiter transfer orbit. A gravity-assist maneuver at Jupiter in February 1992 placed the spacecraft in its final Sun-centered out-of-ecliptic orbit, with a perihelion distance of 1.3 AU and an aphelion of 5.4 AU. The orbital period was 6.2 years. Ulysses' unique trajectory took the spacecraft literally into the uncharted third dimension of the heliosphere. Throughout the first six years of the mission, all spacecraft systems and the nine sets of instruments that make up the scientific payload continued to function well. The prime mission, covering the period from launch up to the end of September 1995, included two polar passes, which are defined to be the parts of the trajectory when the spacecraft was above 70 degrees heliographic latitude in either hemisphere. The first polar pass (over the south solar pole) commenced on 26 June 1994 and ended on 5 November, the second pass (north) occurred one year later (19 June - 29 September), making a total of 234 days (corresponding to approximately 9 solar rotations) above 70 degrees latitude. The maximum heliographic latitude reached by Ulysses was the same in both hemispheres, namely 80.2 degrees. Based on the scientific success of the mission in the first solar orbit, and the excellent health of the spacecraft and its payload, both ESA and NASA undertook to continue operating the spacecraft for a second orbit of the Sun. Constituting what was essentially a new mission, the so-called Second Solar Orbit would bring Ulysses back over the solar poles in 2000 and 2001. In contrast to the high-latitude phase of the prime mission, which took place under quiet solar conditions, the second set of polar passes occurred close to solar maximum. 3. Scientific investigations ---------------------------- One of the major strengths of the mission was the breadth of its scientific investigations. Phenomena that were studied by Ulysses include the solar wind, the heliospheric magnetic field, solar radio bursts and plasma waves, solar and interplanetary energetic particles, galactic cosmic rays, interstellar neutral gas, cosmic dust, solar X-rays and gamma-ray bursts. The prime goal of all of these studies was to characterize the heliographic latitude dependence of the physical parameters involved. In addition, however, Ulysses' unique interplanetary orbit was highly suitable for carrying out measurements that are difficult to perform from the relative proximity of the Earth's orbit to the Sun. An important example of such measurements was the detection of interstellar pick-up ions (atoms of interstellar gas that have become singly ionized). Other investigations carried out by Ulysses included detailed interplanetary-physics studies during the in-ecliptic Earth-Jupiter phase, measurements in the Jovian magnetosphere during the Jupiter encounter, and radio-science investigations of the Suns corona and the Io Plasma Torus using the spacecraft and ground telecommunication systems. 4. Scientific highlights ------------------------ Summaries of the key findings from the southern polar pass and pole-to-pole transit have been reported elsewhere (e.g. [SMITH&MARSDEN1995], [MARSDEN&SMITH1996A], [MARSDEN&SMITH1996B]). The papers in [A&AV316N21996], in addition to addressing new aspects of the data obtained during these periods, also focus on the results from the first northern polar pass. Of particular interest in this context are the north-south asymmetries reported by various authors. (The preceding text has been adapted from [MARSDENETAL1996]) Mission Phases ============== Launch ------ The spacecraft was launched on Oct. 6, 1990 by the shuttle Discovery with two upper stages. To reach high solar latitudes, the spacecraft was aimed close to Jupiter so that Jupiter's large gravitational field would accelerate Ulysses out of the ecliptic plane to high latitudes; no man-made launch vehicle could by itself provide the needed velocity for Ulysses to achieve high latitudes. Spacecraft ID : ULY Mission Phase Start Time : 1990-10-06 Mission Phase Stop Time : 1990-12-03 Spacecraft Operations Type : LAUNCH/CHECK-OUT Earth-Jupiter Cruise -------------------- Spacecraft ID : ULY Mission Phase Start Time : 1990-12-04 Mission Phase Stop Time : 1992-01-24 Spacecraft Operations Type : CRUISE Jupiter Encounter ----------------- Ulysses arrived at Jupiter 16 months after departing from Earth, having traveled nearly 1 billion kilometers in the ecliptic. Closest approach to the planet occurred at 12:02 UT on 8 February, 1992. The inbound trajectory was rather similar to those of the four spacecraft which flew past Jupiter previously: Pioneer 10, 11 (1972, 1973) and Voyager 1, 2 (1979). In contrast to these missions, however, Ulysses reached high latitudes (40 deg. north of Jupiter's equator) near closest approach. A unique aspect of the Ulysses flight path was the outbound passage through the hitherto unexplored dusk sector (18:00 hours local time) of the magnetosphere, this time at high southern latitudes. Another unique aspect of the flyby was the penetration of the Io Plasma Torus (IPT), a few hours after closest approach, in a basically north-south direction which contrasted with the nearly equatorial Voyager 1 traversal. In addition to this direct penetration, the spacecraft radio signal passed through the IPT for a significant length of time making it possible to probe the electron density distribution in the Torus. Spacecraft ID : ULY Target Name : JUPITER Mission Phase Start Time : 1992-01-25 Mission Phase Stop Time : 1992-02-17 Spacecraft Operations Type : FLYBY Sequence of Events during the Ulysses Jupiter Flyby. Event Time Distance (Day/Hour/Min) (Rj) ------------------------------------------------------------- Bow Shock Crossing (In) 033/17:33 113 Magnetopause Crossings (In) 033/21:30-035/04:00 110-87 Magnetodisc/Plasmadisc 036/06:30-037/22:00 67-36 Crossings High Latitude Polar Cap 038/22:30 15 (or possibly Cusp) 039/06:30 8.7 Closest Approach 039/12:02 6.31 Observations of Io Plasma 039/13:00-18:00 6.4-9.0 Torus Observation of Field Aligned 041/01:00-043/13:00 35-82 Currents, Electron and Ion Streaming Magnetopause Crossings (Out) 043/13:57-045/21:40 83-124 Bow Shock Crossings (Out) 045/00:37-047/07:52 109-149 (The description of the Ulysses Jupiter Encounter was excerpted from [MARSDEN&WENZEL1992]) First Solar Orbit ----------------- The launch energy provided by the space shuttle and three powerful upper stage rockets, combined with the gravity assist maneuver at Jupiter, placed the Ulysses spacecraft in a Sun-centered, elliptical orbit inclined at 80 degrees with respect to the Sun's equator. Important design requirements for the mission were to maximize the time spent at high solar latitudes and to achieve the highest possible latitude. Owing to the relative positions of the Earth, Sun and Jupiter at the time of the planetary swing-by, a south-going out-of- ecliptic trajectory best met these requirements. (The description of the Ulysses First Solar Orbit was excerpted from [MARSDEN1995A]) Spacecraft ID : ULY Target Name : HELIOSPHERE Mission Phase Start Time : 1992-02-18 Mission Phase Stop Time : 1995-09-30 Spacecraft Operations Type : ORBITER First Polar Pass ---------------- On 26 June 1994, 28 months after leaving Jupiter, Ulysses began its passage over the Sun's southern polar cap. The Ulysses polar passes are defined to be the segments of the trajectory corresponding to solar latitudes greater than or equal to 70 degrees in either hemisphere. The south polar pass lasted 132 days, equivalent to 5 solar rotations. During this time, the distance from the spacecraft to the Sun decreased from 2.8 AU to 1.9 AU (1 AU = 150 million km). The spacecraft reached its most southerly point, 80.2 degrees south of the solar equator, on 13 September 1994, at a distance of 2.3 AU from the Sun. (The description of the Ulysses First Polar Pass was excerpted from [MARSDEN1995A]) Polar Pass (latitude > 70 S) : 1994-06-26 to 1994-11-05 Max. Latitude (80.2 S) : 1994-09-13 Second Polar Pass ----------------- On 30 September, five years after launch, Ulysses completed the first phase of its exploratory mission to study the Sun's environment from the perspective of a solar polar orbit. Between 19 June and 29 September, one year after its south polar pass, the spacecraft flew over the Sun's northern polar regions, reaching a maximum latitude of 80.2 degrees north of the equator on 31 July. (The description of the Ulysses Second Polar Pass was adapted from [MARSDEN1995B]) Polar Pass (latitude > 70 N) : 1995-06-19 to 1995-09-29 Max. Latitude (80.2 N) : 1995-07-31 Second Solar Orbit ------------------ With the spacecraft and its scientific payload in excellent condition, Ulysses embarked on its second orbit of the Sun. The ultimate goal of this phase of the mission is the study of the Sun's polar regions under conditions of high solar activity, culminating in polar passes in 2000 and 2001 (south polar pass: Sep 2000 to Jan 2001; north polar pass: Sep to Dec 2001). Much before this, however, with Ulysses descending slowly in latitude after the northern polar pass, there is an opportunity to make coordinated observations with ESA's SOHO spacecraft, which carries an extensive complement of experiments dedicated to studying the Sun's corona and the solar wind. The period around aphelion (1997-98) will also be of great interest. During this interval Ulysses will spend many months close to the ecliptic at almost constant radial distance (~ 5 AU) from the Sun, enabling the temporal evolution of many interplanetary phenomena to be studied free of concern about spatial variations. Measurements of interstellar pick-up ions (atoms of interstellar gas that have become singly ionized) will also benefit from the 'dwell' at moderately large heliocentric distance, since many species are unable to reach the inner solar system. Ulysses' out-of-ecliptic orbit has a period of 6.2 years, corresponding to approximately half a solar cycle. As noted above, a consequence of this is that the high-latitude passes of the second solar orbit will occur close to the maximum of solar cycle 23. The conditions in the polar regions are expected to be dramatically different from those encountered during the prime mission. In particular, the rather simple configuration of the corona found at solar minimum, with large coronal holes over the polar caps, will have been replaced by a much more complex arrangement, probably including high-latitude streamers. Transient events (solar flares, coronal mass ejections, etc.) related to the increase in solar activity will dominate, greatly disturbing the underlying structure of the solar wind and influencing the transport of cosmic rays and energetic solar particles. (The description of the Ulysses Second Solar Orbit was adapted from [MARSDEN1995B]) Spacecraft ID : ULY Target Name : HELIOSPHERE Mission Phase Start Time : 1995-10-01 Mission Phase Stop Time : 2001-12-31 Spacecraft Operations Type : ORBITER Perihelion : 2001-05-26 Third Polar Pass ---------------- Polar Pass (latitude > 70 S) : 2000-09-08 to 2001-01-16 Max. Latitude (80.2 S) : 2000-11-27 Fourth Polar Pass ----------------- Polar Pass (latitude > 70 N) : 2001-09-03 to 2001-12-12 Max. Latitude (80.2 N) : 2001-10-13 " MISSION_OBJECTIVES_SUMMARY = " Mission Objectives Overview =========================== The primary mission of the Ulysses spacecraft was to characterize the heliosphere as a function of solar latitude. The heliosphere is the vast region of interplanetary space occupied by the Sun's atmosphere and dominated by the outflow of the solar wind. The periods of primary scientific interest are when Ulysses was at or higher than 70 degrees latitude at both the Sun's south and north poles. On 26 June 1994, Ulysses reached 70 degrees south. There it began a four-month observation from high latitudes of the complex forces at work in the Sun's outer atmosphere -- the corona. Scientists have long studied the Sun from Earth using Earth- based sensors. More recently, solar studies have been conducted from spaceborne platforms; however, these investigations have been mostly from the ecliptic plane (the plane in which most of the planets travel around the Sun) and no previous spacecraft have reached solar latitudes higher than 32 degrees. Now that Ulysses high latitude data is available, scientists from the joint National Aeronautics and Space Administration (NASA)-European Space Agency (ESA) mission are obtaining new and better understanding of the processes going on at high solar latitudes. Scientists have long been aware of differences between the polar regions of the Sun and lower latitudes. Sunspots are only seen at lower latitudes, and photographs of the solar corona take during solar eclipses often showed dark regions over the poles. The solar corona consists of hot gasses (over 1,000,000 degrees); at this temperature the gravitational field of the Sun can not prevent escape of coronal gas as the solar wind. However, the Sun has a global magnetic field. Many of the solar magnetic field lines that leave the solar surface return to the surface, but some of the field lines, particularly those over the poles, extend deep into interplanetary space. The solar wind expands into interplanetary space along these field lines, and the regions (known as coronal holes) of the corona from which the hot gas escapes are dark because of the low gas density. The properties of the Sun's polar magnetic field are poorly understood, and it has an important influence on the escape of the solar wind. The complex processes that heat and accelerate the solar wind are not well understood, and Ulysses observations over the poles should provide important new information on how the solar wind expands from the Sun that will aid scientists in understanding these processes. The magnetic field also exerts a crucial influence on matter arriving near the Sun from the Milky Way galaxy and from the nearby interstellar medium. Incoming cosmic rays are subjected to forces exerted by the magnetic field. The structure of the Sun's magnetic field is thought to favor entry of cosmic rays by way of the Sun's polar regions. Scientists hope that Ulysses can shed some light on the extent to which the galactic cosmic rays observed at Earth use this route and on the ways in which their properties are modified as a result. Scientists also hope to gain more knowledge of the intensity and properties of the cosmic rays far from the Sun. Jupiter Encounter ----------------- The primary aim of the flyby was to place the spacecraft in its final heliocentric out-of-ecliptic orbit with a minimum of risk to the onboard systems and scientific payload. Scientific investigations at Jupiter are a secondary objective of the mission. Nevertheless, the opportunity to study Jupiter's magnetosphere was exploited to the greatest extent possible. Jupiter is a strongly magnetized, rapidly rotating planet. Its magnetosphere is the largest object in the solar system, a fact reflected in the long interval of 12 days from 2 to 14 February (days 033 to 045 of 1992) that it took for Ulysses to travel through it. The large Galilean satellites are embedded within the magnetosphere and Io is known to be a prolific source of ions and neutral particles. Ions, predominantly of sulfur and oxygen, are distributed around the orbit of Io to form a large torus. Electrons and ions from Io, Jupiter's ionosphere and the solar wind are all present and are transported throughout the magnetosphere. A substantial fraction of these particles are accelerated to extremely high energies to form intense radiation belts. Upstream of the magnetosphere, in the free-streaming solar wind, a detached bow shock forms which slows the solar wind and allows it to be deflected around the magnetosphere. A wide variety of complex physical phenomena are available for study. (Description of the Jupiter Encounter Mission Objectives adapted from [MARSDEN&WENZEL1992])" END_OBJECT = MISSION_INFORMATION OBJECT = MISSION_HOST INSTRUMENT_HOST_ID = ULY OBJECT = MISSION_TARGET TARGET_NAME = SUN END_OBJECT = MISSION_TARGET OBJECT = MISSION_TARGET TARGET_NAME = JUPITER END_OBJECT = MISSION_TARGET END_OBJECT = MISSION_HOST OBJECT = MISSION_REFERENCE_INFORMATION REFERENCE_KEY_ID = "A&AV316N21996" END_OBJECT = MISSION_REFERENCE_INFORMATION OBJECT = MISSION_REFERENCE_INFORMATION REFERENCE_KEY_ID = "BALOGHETAL1995" END_OBJECT = MISSION_REFERENCE_INFORMATION OBJECT = MISSION_REFERENCE_INFORMATION REFERENCE_KEY_ID = "BARROWETAL1996" END_OBJECT = MISSION_REFERENCE_INFORMATION OBJECT = MISSION_REFERENCE_INFORMATION REFERENCE_KEY_ID = "BOTHMERETAL1996" END_OBJECT = MISSION_REFERENCE_INFORMATION OBJECT = MISSION_REFERENCE_INFORMATION REFERENCE_KEY_ID = "FERRANDOETAL1996" END_OBJECT = MISSION_REFERENCE_INFORMATION OBJECT = MISSION_REFERENCE_INFORMATION REFERENCE_KEY_ID = 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