# Ulysses

> NASA robotic space probe that studied the Sun

**Wikidata**: [Q156081](https://www.wikidata.org/wiki/Q156081)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Ulysses_(spacecraft))  
**Source**: https://4ort.xyz/entity/ulysses-q156081

## Summary
Ulysses was a robotic space probe designed to study the Sun from a unique orbit passing over its poles. A joint mission of the European Space Agency (ESA) and the National Aeronautics and Space Administration (NASA), it was launched in 1990 and operated until 2009. The spacecraft used a gravity-assist maneuver at Jupiter to leave the ecliptic plane and achieve its unprecedented polar trajectory.

## Key Facts
- **Mission Type:** Robotic space probe, artificial satellite of the Sun
- **Primary Subject:** The Sun
- **Launch Date:** October 6, 1990, at 11:47:16 UTC
- **Mission End Date:** June 30, 2009
- **Operators:** Jet Propulsion Laboratory (JPL), European Space Operations Centre (ESOC), European Space Research and Technology Centre (ESTEC)
- **Funders:** European Space Agency (ESA), National Aeronautics and Space Administration (NASA)
- **Launch Mass:** 371 kg
- **Launch Vehicle:** Space Shuttle Discovery (STS-41)
- **Power Source:** Radioisotope thermoelectric generator (RTG)
- **Orbital Period:** 2264.26 days (approx. 6.2 years)

## FAQs
### Q: What was the purpose of the Ulysses mission?
A: The primary purpose of the Ulysses mission was to study the Sun's environment, including the solar wind, magnetic field, and cosmic rays, from a unique high-inclination orbit that passed over the Sun's poles.

### Q: Who built and operated the Ulysses spacecraft?
A: Ulysses was a joint mission between NASA and the European Space Agency (ESA). The spacecraft was built by Dornier, while operations were managed jointly by NASA's Jet Propulsion Laboratory and ESA's European Space Operations Centre.

### Q: How did Ulysses get into a polar orbit around the Sun?
A: To achieve its unique polar orbit, Ulysses performed a gravity-assist maneuver at Jupiter. On February 8, 1992, the spacecraft flew by the giant planet, using its immense gravity to be flung out of the ecliptic plane (the plane in which planets orbit) and into its final trajectory over the Sun's poles.

### Q: When did the Ulysses mission end?
A: The Ulysses mission officially ended on June 30, 2009, after more than 18 years of operation.

## Why It Matters
Ulysses was significant because it was the first and only spacecraft to study the Sun from a polar orbit. All planets and most spacecraft orbit the Sun in a relatively flat plane called the ecliptic. By leaving this plane, Ulysses provided a unique three-dimensional perspective of the heliosphere—the vast bubble of plasma and magnetic fields generated by the Sun.

This unique vantage point allowed scientists to make the first-ever direct measurements of the solar wind and magnetic field over the Sun's poles, revealing that the solar wind flows much faster there than at the equator. It fundamentally changed our understanding of the Sun's influence on the surrounding space. The mission's long duration, spanning nearly two full 11-year solar cycles, also provided invaluable data on how the Sun's activity changes over time. Ulysses's findings were crucial for space weather forecasting and for understanding the environment that future interplanetary missions will travel through.

## Notable For
- **First Polar Orbit of the Sun:** Ulysses was the first spacecraft to ever fly over the Sun's north and south poles, providing a unique three-dimensional view of the heliosphere.
- **Jupiter Gravity Assist:** The mission pioneered the use of a Jupiter gravity assist to achieve an out-of-ecliptic trajectory, a complex maneuver that flung the probe into its final polar orbit.
- **International Collaboration:** It was a landmark joint project between the European Space Agency (ESA) and NASA, demonstrating successful long-term international cooperation in space exploration.
- **Mission Longevity:** The spacecraft operated for over 18 years, from its launch in 1990 until its retirement in 2009, far exceeding its planned mission duration and covering nearly two complete solar cycles.

## Body
### ### Mission and Operations
Ulysses was a joint robotic space mission funded and operated by the National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA). Originally known as the International Solar Polar Mission (ISPM), the project was approved in 1976. Operational control was shared between NASA's Jet Propulsion Laboratory (JPL) and ESA's European Space Operations Centre (ESOC) and European Space Research and Technology Centre (ESTEC). The mission's orbital activity around the sun began on February 24, 1992, and concluded with the spacecraft's retirement on June 30, 2009.

### ### Spacecraft and Systems
The Ulysses spacecraft was manufactured by the German company Dornier. It had a launch mass of 371 kilograms. The probe was not powered by solar panels but by a single General Electric GPHS-RTG (Radioisotope Thermoelectric Generator), which provided approximately 285 watts of power at the beginning of the mission. The RTG was fueled by plutonium-238 supplied by the United States Department of Energy.

### ### Launch and Trajectory
Ulysses was launched on October 6, 1990, from Kennedy Space Center Launch Complex 39B. It was carried into Earth orbit aboard the Space Shuttle Discovery on mission STS-41.
- **Deployment:** After deployment from the shuttle, a two-stage solid rocket combination, an Inertial Upper Stage (IUS) and a PAM-S (Payload Assist Module), fired to send Ulysses on its trajectory toward Jupiter.
- **Jupiter Gravity Assist:** On February 8, 1992, Ulysses flew by Jupiter. This maneuver used the planet's gravity to redirect the spacecraft out of the ecliptic plane and into its final, highly inclined solar orbit.
- **Heliocentric Orbit:** The final orbit around the Sun had the following characteristics:
    - **Parent Body:** Sun
    - **Orbital Inclination:** 79.11 degrees
    - **Orbital Period:** 2264.26 days
    - **Apoapsis (farthest point):** 5.40 Astronomical Units (AU)
    - **Periapsis (closest point):** 1.35 Astronomical Units (AU)
    - **Eccentricity:** 0.60262

### ### Identifiers
- **COSPAR ID:** 1990-090B
- **NSSDCA ID:** 1990-090B
- **SCN:** 20842
- **NAIF ID:** -55

## References

1. [Source](https://www.esa.int/Science_Exploration/Space_Science/Ulysses_overview)
2. [Source](https://www2.jpl.nasa.gov/galileo/messenger/oldmess/RTGs.html)
3. Jonathan's Space Report
4. [Source](https://nssdc.gsfc.nasa.gov/nmc/spacecraft/displayTrajectory.action?id=1990-090B)
5. [Source](https://www.eoportal.org/satellite-missions/ulysses#spacecraft)
6. Freebase Data Dumps. 2013
7. [Source](https://www.esa.int/Enabling_Support/Operations/Ulysses_12_extra_months_of_valuable_science)
8. [Source](https://www.cosmos.esa.int/web/ulysses/jupiter-flyby)
9. [Source](https://sci.esa.int/web/ulysses/-/47369-fact-sheet)
10. [Source](https://space.skyrocket.de/doc_sdat/ulysses.htm)
11. [Source](https://space.skyrocket.de/doc_stage/ius.htm)
12. [Source](https://space.skyrocket.de/doc_stage/pam-d.htm)
13. [Source](https://solarsystem.nasa.gov/missions/ulysses/in-depth/)
14. [Source](https://naif.jpl.nasa.gov/pub/naif/toolkit_docs/C/req/naif_ids.html)