On June 30, the satellite filled with 20 year old technology will go silent as it continues to orbit the sun. Ulysses and all its scientific instruments will be abandoned. One reason for the termination of the mission is that the communications bit rate has decreased, and other demands for the Deep Space Network stations have increased. The amount of scientific data being sent to Earth has decreased to a point where the cost is outweighing the usefulness of the information.
ESA (European Space Agency) is an international organization with 18 Member States, with programs designed to find out more about Earth, its immediate space environment, our solar system, the universe, and to develop satellite-based technologies. With NASA, (National Aeronautics and Space Administration) in the US they put the Ulysses project together.
More than 120 scientists from around the world were involved in investigations of every type. (Each data gathering effort has its own acronym.) There are three sets of charged-particle detectors to quantify ion and electron fluxes over a wide range of energies and for many ion species. They are: COSPIN–Cosmic Ray and Solar Particle Investigation, EPAC–Energetic Particle Investigation, and HI-SCALE–Heliosphere Instrument for Spectra, Composition & Anisotropy at Low Energies. which is designed to obtain measurements of interplanetary ions and electrons The ions and electrons are detected by five separate solid-state detector telescopes oriented to give essentially complete pitch-angle coverage from the spinning spacecraft. The launch of Ulysses in October 1990 occurred during the peak of solar activity in solar cycle 22.
HISCALE made significant contributions to science during this interval and during the prime polar passes. One of the objectives of HISCALE is the “application of the new knowledge gained from Ulysses investigations of the global dynamics and structure of the heliosphere to attain a better understanding of the influence of solar activity on the terrestrial environment and its technological systems”.
Many other instruments gathered important data as well. The Vector Helium Magnetometer / Flux Gate – FHM/FGM are two magnetometers for magnetic field investigation carried out in the United Kingdom. Other instruments are: SWOOPS – Solar Wind Plasma Investigation out of San Antonio Texas, SWICS – Solar Wind Ion Composition Experiment, URAP – Unified Radio & Plasma Wave instrument from Greenbelt Maryland, GAS – Interstellar Neutral Gas Experiment to provide sky maps of interstellar helium, GRB – Gamma Ray Burst Experiment, and my favorite, DUST – Cosmic Dust Experiment being conducted from Germany.
Radio-science experiments were making use of the spacecraft’s radio communication link in specific periods: .SCE – Coronal Sounding Experiment and GWE – Gravitational Wave Experiment conducted in Italy.
The Ulysses spacecraft in launch configuration, shows the locations of the various instruments. Experiment electronics and spacecraft subsystems are enclosed in the main body, with external antennas for communications. A set of eight CD-ROMS are available through ESA which contain the data that Ulysses collected during its long journey around our solar system.
The technology on board Ulysses continues to work perfectly according to EADS Astrium, however the power supply, the RTG, Radioisotope Thermoelectric Generator, has reached its end. Paolo Ferri, Head of the Solar & Planetary Missions Division at ESA’s European Space Operations Centre, Darmstadt, Germany sadly said: “Although it is always hard to take the decision to terminate a mission, we have to accept that the satellite is running out of resources and a controlled switch-off is the best ending.”
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