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Launch date: 06-Oct-1990 11:47 UT
Mission end: 30-Jun-2009
Launch vehicle: Space Shuttle Discovery STS-41
Launch mass: 367 kg
Mission phase: Archive
Orbit: Ulysses is in a 6.2 year heliocentric orbit inclined at 80° to the solar equator.
Achievements: Ulysses has conducted the first-ever survey of the Sun's environment in space from the equator to the poles, and over a wide range of solar activity conditions. Key results to date include the first detailed measurements of the solar wind from the Sun's polar regions at solar minimum and solar maximum, the discovery that the magnetic flux leaving the Sun is the same at all latitudes, the discovery of energetic particle "reservoirs" surrounding the Sun, the discovery of interstellar dust in the solar system, and the first direct measurements of interstellar helium atoms in the solar system.

The joint ESA-NASA Ulysses deep-space mission was designed to study the heliosphere - the region of space influenced by the Sun and its magnetic field. The primary scientific goal was to make the first-ever measurements of the unexplored region of space above the Sun's poles. Other areas of investigation include determination of the global properties and behaviour of the solar wind, the study of energetic particles of solar and interplanetary origin, measurement of the magnetic field of the Sun and the heliosphere, study of galactic cosmic rays, investigation of how the heliosphere interacts with interstellar space, and participation in a programme to identify the origin of gamma-ray bursts. On 10 June 2009, Ulysses became the longest running ESA-operated spacecraft overtaking IUE's record of 6822 days (18 years 246 days).

Mission Objectives

  • Determine the global, three-dimensional properties of the heliospheric magnetic field and the solar wind
  • Study the origin of the solar wind by measuring its composition at different heliographic latitudes
  • Learn more about waves and shocks in the solar wind by sampling conditions that are different from those available near the ecliptic
  • Learn more about the processes affecting the motion of galactic and anomalous cosmic rays
  • Learn more about the origin of galactic cosmic rays by measuring their isotopic composition
  • Study the energization and motion of energetic particles of solar and interplanetary origin by observing their properties at low and high latitudes
  • Learn more about the local interstellar space by measuring directly the neutral helium atoms that enter the heliosphere, as well as inferring its properties from measurements of interstellar pick-up ions
  • Improve our understanding of interplanetary and interstellar dust
  • Search for gamma-ray burst sources and, together with observations from other spacecraft, help to identify them with known celestial objects

Mission Name

Ulysses was named after the hero of Greek legend. Like its mythical namesake, Ulysses has ventured into unexplored territory - charting the unknown reaches of space above and below the poles of the Sun.


The overall design of the Ulysses spacecraft is dictated by the large distances from the Earth and the Sun at which the spacecraft has to operate (up to 950 million km from Earth, 800 million km from the Sun).

Mass at launch 366.7 kg
Dimensions Length × Width × Height = 3.2m × 3.3m × 2.1m
Launch 6 October 1990, 11:47:15 UTC
Kennedy Space Centre, Florida, United States
Launcher Discovery (OV-103), flight STS-41 (36)
Power generation Radio-isotope thermoelectric generator (RTG)
Payload 9 sets of instruments; in-situ particles and fields observations; gamma-ray burst detection


Magnetometer (VHM/FGM) To determine the features and gradients of the magnetic field, as well as the heliolatitude dependence of interplanetary phenomena so far only observed near the ecliptic plane.
Solar Wind Plasma Experiment (SWOOPS) To characterise the bulk flow and internal state conditions of the interplanetary plasma in three dimensions on the way out to Jupiter. Observations will continue over the full range of heliocentric distances and heliographic latitudes reached by the probe after its encounter with Jupiter and consequent deflection out of the ecliptic plane.
Solar Wind Ion Composition Instrument (SWICS) To determine uniquely the elemental and ionic-charge composition, and the temperatures and mean speeds of all major solar-wind ions, from H through Fe, at solar wind speeds ranging from 175 kms-1 (protons) to 1280 kms-1 (Fe8+).
Unified Radio and Plasma Wave Instrument (URAP) To determine the direction, angular size, and polarization of radio sources for remote sensing of the heliosphere and the Jovian magnetosphere. Detailed study of local wave phenomena, which determine the transport coefficients of the ambient plasma.
Energetic Particle Instrument (EPAC) To measure the fluxes, angular distributions, energy spectra, and composition of ions in the energy range from 300 keV/nucleon to 25 MeV/nucleon.
Interstellar Neutral-Gas Experiment (GAS) To measure in-situ the properties (density, bulk velocity relative to the solar system, and temperature) of the local interstellar gas, represented by neutral helium penetrating the heliosphere.
Low-Energy Ion and Electron Experiment (HISCALE) To make measurements of interplanetary ions and electrons throughout the entire mission.
Cosmic Ray and Solar Particle Instrument (COSPIN) To measure the three-dimensional anisotropies of protons and helium at low energies.
Solar X-ray and Cosmic Gamma-Ray Burst Instrument (GRB) To study of gamma-ray bursts, also to study soft gamma repeaters and solar flares.
Dust Experiment (DUST) To provide direct observations of dust grains with masses between 10-16 g and 10-6 g in interplanetary space, to investigate their physical and dynamical properties as functions of heliocentric distance and ecliptic latitude.
Coronal-Sounding Experiment (SCE) To derive the plasma parameters of the solar atmosphere using established coronal-sounding techniques.
Gravitational Wave Experiment (GWE) To detect gravitational waves in the low frequency band.


Ulysses is in an elliptical heliocentric orbit inclined at 80° to the solar equator. Aphelion is reached at about 5.4 AU, perihelion at 1.3 AU.

During its 17 years if operations Ulysses completed three orbits of the Sun thus performing 6 polar passes:

  • South pole: June-November 1994, September 2000-January 2001, November 2006-April 2007;
  • North pole: June-September 1995, August-December 2001, November 2007-March 2008.

Operations Centre

A joint ESA-NASA team, located at the Jet Propulsion Laboratory, Pasadena, has overseen spacecraft operations and data management.

Last Update: 1 September 2019
28-May-2024 10:34 UT

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