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The solar wind plasma experiment aboard the Ulysses spacecraft, including separate ion and electron instruments, measured the plasma properties of the Jovian magnetosheath during the February 1992 encounter with Jupiter. Seven separate magnetosheath intervals were observed, as well as four bow shock crossings and numerous encounters with the magnetopause and its boundary layer.
The primary goal of the Ulysses mission is the exploration of the polar regions of the heliosphere.
Several parameters measured by Ulysses as it traveled southward to heliographic latitudes of -50° are presented and analyzed. Three topics of scientific importance are investigated: (1) latitude gradient; (2) extent of agreement between observed and Parker spiral angles near -50°; (3) field variances and their interpretation.
Data obtained by the Ulysses magnetometer and solar wind analyzer have been combined to study the properties of such magnetic holes in the solar wind between 1 AU and 5.4 AU and to 23° south latitude.
Describes the solar wind plasma experiment on the Ulysses spacecraft over the solar range of 1.15 to 5.40 AU between Nov. 18, 1990 and May 5, 1992.
In may, 1993, the heliopheric current sheet (HCS) ceased to be seen by the Ulysses spacecraft at a heliocentric latitude of ~30degrees S and distance of 4.7 AU. The disapearance of the HCS coincided with the solar wind speed remaining >560km/s and with the disappearance of one of four interaction regions previously seen on each solar rotation.
The rate of occurrence of interplanetary discontinuities (ROID) is examined using Ulysses magnetic field and plasma data from 1 to 5 AU radial distance from the Sun and at high heliospheric latitudes. It is found that there are two regions in interplanetary space where the ROID is high: in stream-stream interaction regions and in Alfven wave trains.
Observations by the Ulysses SWOOPS plasma experiment are used to investigate spatial and temporal gradients during the mission, with emphasis on more recent high latitude opbservations including the recent South Pole to North Pole passage during solar minimum.
Two invariants associated with the parker model of the solar wind involved the radial, BR, and azimuthal, BT, components of the heliospheric magnetic field. These invariants have been investigated using Ulysses data obtained at high latitudes in both the north and south solar hemispheres.
Current design tools for digital circuits and systems are not well-integrated among the behavioral, gate, and transistor levels of design. Ulysses is a prototype software system that consists of a description language, a description compiler, and a simulator that make no distinction among these levels. The language is uniform over the entire range of logical descriptions, the description is hierarchical with no fundamental restrictions on depth or mixing of levels, and the simulator is fully integrated with the description. The structure of the language, compiler, and simulator are described in terms of their relationships to the abstractions of physical systems that are made in order to create logical descriptions and models of behavior.
Using photospheric magnetic field observations obtained at the Stanford Wilcox Solar Observatory, results from a potential field model for the present solar cycle are given, and qualitative predictions of the IMF that Ulysses may encounter are presented. Results indicate that the IMF consists of large regions of opposite polarity separated by a neutral sheet (NS) (extended to at least 50 deg) and a four-sector structure near solar minimum (produced by small quadripolar NS warps). The latitudinal extent of the NS increases following minimum and the structure near maximum includes multiple NSs, while a simplified IMF is found during the declining phase.
The management of the Ulysses project, a probe which will fly a solar polar orbit, is described. The 5-yr mission will feature a flyby of Jupiter to deflect the spacecraft into a high-inclination orbit. Data on the solar corona, solar wind, the sun-wind interface, the heliospheric magnetic field, solar and nonsolar cosmic rays, etc., will be gathered as a function of the solar latitude. NASA will track and control the probe with the Deep Space Network. JPL provides project management for NASA while the Directorate of Scientific Programs performs ESA management functions. The DOE will provide a radioisotope thermoelectric generator while NASA and ESA each supply half the scientific payload. A NASA-ESA Joint Working Group meets about twice per year to monitor the project and discuss the technical and scientific requirements. Safety issues and measures which are being addressed due to the presence of the Pu-238 heat source for the RTG are discussed.
A procedure for the generation and reduction of the radiometric data known as REGRES is described. The software is implemented on a HP-1000F computer and was tested on REGRES data relative to the Voyager I spacecraft. The REGRES data are a current output of NASA's Orbit Determination Program. The software package was developed in view of the data analysis of the gravitational wave experiment planned for the European spacecraft Ulysses.
The Ulysses mission will, for the first time, explore the heliosphere within a few astronomical units of the sun over the full range of heliographic latitudes, thereby providing the first characterization of the uncharted third dimension. Highly sophisticated scientific instrumentation carried on board the spacecraft is designed to measure the properties of the solar wind, the sun/wind interface, the heliospheric magnetic field, solar radio bursts and plasma waves, solar X-rays, solar and galactic cosmic rays, and interplanetary/interstellar neutral gas and dust. This collaborative ESA/NASA mission, scheduled for launch in October 1990, will use a Jupiter gravity-assist to achieve a trajectory extending to high solar latitudes /1,2/.
This Draft Environmental Impact Statement (DEIS) addresses the environmental impacts which may be caused by the preparation and operation of the Ulysses spacecraft, including its planned launch on the Space Transportation System (STS) Shuttle and the alternative of canceling further work on the mission. The launch configuration will use the STS/Inertial Upper Stage (IUS)/Payload Assist Module-Special(PAM-S) combination. The Tier 1 EIS included a delay alternative which considered the Titan 4 launch vehicle as an alternative booster stage for launch in 1991 or later. However, the U.S. Air Force, which procures the Titan 4 for NASA, could not provide a Titan 4 vehicle for the 1991 launch opportunity because of high priority Department of Defense requirements. The only expected environmental effects of the proposed action are associated with normal Shuttle launch operations. These impacts are limited largely to the near-field at the launch pad, except for temporary stratospheric ozone effects during launch and occasional sonic boom effects near the landing site. These effects have been judged insufficient to preclude Shuttle launches. In the event of (1) an accident during launch, or (2) reentry of the spacecraft from earth orbit, there are potential adverse health and environmental effects associated with the possible release of plutonium dioxide from the spacecraft's radioisotope thermoelectric generators (RTG). The potential effects considered in this EIS include risks of air and water quality impacts, local land area contamination, adverse health and safety impacts, the disturbance of biotic resources, impacts on wetland areas or areas containing historical sites, and socioeconomic impacts. Intensive analysis of the possible accidents associated with the proposed action are underway and preliminary results indicate small health or environmental risks. The results of a Final Safety Analysis Report will be available for inclusion into the final EIS.
The delay of the Ulysses launch from May 1986 to October 1990, because of the Challenger disaster, has altered both the constraints under which the mission must be designed and the timing of several mission critical events. Safety and launch reliability concerns from the Shuttle have increased the effective launch window to durations greater than one hour. Fortuitously high declinations of the launch asymptote (DLA), of the order of the launch site latitude, ameliorate the impact of the new constraints on the launch window. Target overlays in the first hour of the launch window provide higher departure energies that improve mission performance and avoid a science schedule conflict at second opposition near the time of closest Jupiter approach. The mission design starts with the maximum earth departure energy that the upper stage can deliver within the launch constraints. The Jupiter arrival asymptotes are chosen from the optimal point of mission performance in the mission space defined in the Jupiter B-plane by contours mapped by the science and spacecraft constraints. More than half the orbital energy of the earth-to-Jupiter transfer orbit is lost in the Jupiter flyby, and the Jupiter gravitational assist rotates the orbit plane out of the ecliptic to an inclination of about 80 degrees.
Cooperation between ESA and NASA is discussed, noting that the Memorandum of Understanding lays the framework for this relationship, defining the responsibilities of ESA and NASA and providing for appointment of leadership and managers for the project. Members of NASA's Jet Propulsion Laboratory and ESA's ESTEC staff have been appointed to leadership positions within the project and ultimate control of the project rests with the Joint Working Group consisting of two project managers and two project scientists, equally representing both organizations. Coordination of time scales and overall mission design is discussed, including launch cooperation, public relations, and funding of scientific investigations such as Ulysses. Practical difficulties of managing an international project are discussed such as differing documentation requirements and communication techniques, and assurance of equality on projects.
The baseline Ulysses spacecraft control and monitoring system (SCMS) concepts and the converted SCMS, residing on a DEC/VAX 8350 hardware, are considered. The main functions of the system include monitoring and displaying spacecraft telemetry, preparing spacecraft commands, producing hard copies of experimental data, and archiving spacecraft telemetry. The SCMS system comprises over 20 subsystems ranging from low-level utility routines to the major monitoring and control software. These in total consist of approximately 55,000 lines of FORTRAN source code and 100 VMS command files. The SCMS major software facilities are described, including database files, telemetry processing, telecommanding, archiving of data, and display of telemetry.