# Galileo

> NASA robotic space probe that studied the Jupiter system, as well as asteroids Gaspra and Ida

**Wikidata**: [Q105425030](https://www.wikidata.org/wiki/Q105425030)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Galileo_(spacecraft))  
**Source**: https://4ort.xyz/entity/galileo

## Summary  
Galileo was a NASA robotic planetary probe launched in 1989 that became the first spacecraft to orbit Jupiter, study its system in detail, and deploy an atmospheric probe into the planet’s atmosphere. It also performed historic fly‑bys of the asteroids Gaspra and Ida, returning the first close‑up images of these bodies.

## Key Facts  
- **Launch date:** 18 October 1989 (16:53:40 UTC) from Kennedy Space Center Launch Complex 39B aboard Space Shuttle *Atlantis* (STS‑34).  
- **Mission type:** Planetary probe and orbiter (part of the Galileo mission).  
- **Launch mass:** 2 223 kg (launch weight); dry mass 1 298 kg.  
- **Dimensions:** Height 6.15 m; equipped with a 2‑meter high‑gain antenna that failed to fully deploy in flight.  
- **Power system:** Two radioisotope thermoelectric generators (RTGs) plus a 400 N S‑400 bipropellant thruster (MM‑Böhm) using monomethylhydrazine and dinitrogen tetroxide.  
- **Operator & manufacturer:** Operated by NASA’s Jet Propulsion Laboratory (JPL); spacecraft built by JPL, propulsion by Messerschmitt‑Bölkow‑Blohm, power system by General Electric.  
- **Key mission events:**  
  - Gravity‑assist fly‑bys of Venus (Feb 1990) and Earth (Dec 1990, Dec 1992).  
  - Asteroid fly‑bys: 951 Gaspra (29 Oct 1991) and 243 Ida (28 Aug 1993).  
  - Jupiter orbit insertion (8 Dec 1995, 00:27 UTC).  
  - Completed 35 Jupiter orbits before atmospheric entry (21 Sep 2003, 18:57 UTC).  
- **Scientific payload:** Included the Jupiter Atmospheric Probe and a suite of instruments for imaging, magnetometry, plasma, and atmospheric analysis.  
- **Identifiers:** COSPAR 1989‑084B; NAIF ‑77; Wikidata Q? (linked via Wikipedia title “Galileo (spacecraft)”).  

## FAQs  
### Q: What was the primary goal of the Galileo mission?  
A: Galileo was designed to study Jupiter’s atmosphere, magnetic field, moons, and rings, and to conduct the first close‑up investigations of the asteroids Gaspra and Ida.  

### Q: How did Galileo reach Jupiter?  
A: After launch, Galileo used a series of gravity‑assist maneuvers at Venus and Earth to gain speed, followed by a long cruise phase that culminated in Jupiter orbit insertion on 8 December 1995.  

### Q: What happened to Galileo at the end of its mission?  
A: To avoid contaminating Jupiter’s moons, Galileo was deliberately sent into Jupiter’s atmosphere, where it burned up on 21 September 2003.  

### Q: Why did Galileo’s high‑gain antenna not fully deploy?  
A: A mechanical failure prevented full deployment; the spacecraft nevertheless completed its mission using a low‑gain antenna for communications.  

### Q: Which organizations built and operated Galileo?  
A: The spacecraft was built by NASA’s Jet Propulsion Laboratory, with propulsion supplied by Messerschmitt‑Bölkow‑Blohm and power by General Electric; JPL also served as the mission operator.  

## Why It Matters  
Galileo transformed our understanding of the outer Solar System. By becoming the first spacecraft to orbit Jupiter, it provided unprecedented data on the planet’s complex magnetosphere, intense radiation belts, and dynamic atmosphere. Its atmospheric probe delivered the first direct measurements of Jupiter’s pressure, temperature, and composition below the cloud tops, revealing a deep, layered structure and unexpected chemical abundances. The mission’s fly‑bys of Gaspra and Ida yielded the first high‑resolution images of asteroids, showing surface geology and confirming the existence of a small moon (Dactyl) around Ida, which reshaped theories of asteroid formation. Technologically, Galileo pioneered the use of radioisotope thermoelectric generators for deep‑space missions beyond Mars and demonstrated the effectiveness of multiple gravity‑assist trajectories for reaching distant planets. The mission’s legacy continues in subsequent Jupiter explorers, such as Juno, and informs the design of future outer‑planet probes.  

## Notable For  
- **First Jupiter orbiter:** First spacecraft to enter orbit around the gas giant.  
- **First atmospheric probe:** First probe to descend through Jupiter’s atmosphere, delivering in‑situ measurements.  
- **Asteroid firsts:** First close‑up imaging of asteroids Gaspra and Ida, and discovery of Ida’s moon Dactyl.  
- **Gravity‑assist trajectory:** First mission to use a sequence of Venus and Earth fly‑bys to reach Jupiter.  
- **Power innovation:** First deep‑space mission to rely on dual RTGs for long‑duration operations beyond Mars.  

## Body  

### Overview  
Galileo was a NASA planetary probe launched on 18 Oct 1989 aboard Space Shuttle *Atlantis* (STS‑34). It formed the centerpiece of the Galileo mission, aimed at a comprehensive study of the Jovian system and nearby asteroids.  

### Mission Timeline  
- **1989‑10‑18:** Launch from KSC LC‑39B; deployment of Jupiter Atmospheric Probe in low Earth orbit.  
- **1990‑02‑10:** Venus gravity‑assist (≈ 16 000 km perigee).  
- **1990‑12‑08 & 1992‑12‑08:** Earth gravity‑assist passes (≈ 1 000 km and 300 km perigee).  
- **1991‑10‑29:** Fly‑by of asteroid 951 Gaspra (≈ 1 600 km distance).  
- **1993‑08‑28:** Fly‑by of asteroid 243 Ida (≈ 2 400 km distance).  
- **1995‑12‑08:** Jupiter orbit insertion (00:27 UTC).  
- **1995‑2003:** Completed 35 Jupiter orbits, conducting extensive remote sensing.  
- **2003‑09‑21:** Atmospheric entry and mission termination (18:57 UTC).  

### Spacecraft Design  
- **Structure:** 6.15 m tall, mass 2 223 kg at launch.  
- **Antenna:** 2 m high‑gain dish intended for high‑rate data; failed to fully deploy, requiring reliance on a low‑gain antenna.  
- **Power:** Two RTGs supplied continuous electrical power; supplemented by an S‑400 bipropellant thruster for trajectory corrections.  
- **Propulsion:** S‑400 engine (400 N thrust) using monomethylhydrazine and dinitrogen tetroxide, built by Messerschmitt‑Bölkow‑Blohm.  
- **Instrumentation:** Included the Jupiter Atmospheric Probe, imaging systems, magnetometers, plasma detectors, and spectrometers (specific instrument list not detailed in source).  

### Scientific Achievements  
- **Jupiter Atmosphere:** Direct measurements of temperature, pressure, composition, and cloud structure down to ~ 22 bar.  
- **Magnetosphere:** Mapping of Jupiter’s powerful magnetic field and radiation belts.  
- **Moons:** Detailed observations of Io’s volcanism, Europa’s icy surface, Ganymede’s magnetic field, and Callisto’s geology.  
- **Asteroids:** First high‑resolution images of Gaspra and Ida; discovery of Ida’s moon Dactyl, confirming binary asteroid systems.  

### End of Mission  
To prevent possible biological contamination of Europa, the spacecraft was deliberately deorbited into Jupiter’s atmosphere, where it burned up on 21 Sep 2003.  

## Schema Markup  
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## References

1. [Source](https://www.jpl.nasa.gov/news/press_kits/gllarpk.pdf)
2. [Source](http://astro.if.ufrgs.br/solar/galfs.htm)
3. [Source](http://www.resa.net/nasa/engineer.htm)
4. Jonathan's Space Report
5. [Source](https://space.skyrocket.de/doc_sdat/galileo.htm)
6. [Source](https://solarsystem.nasa.gov/missions/galileo-probe/in-depth/)
7. [Source](http://www.astronautix.com/g/galileoprobe.html)
8. Freebase Data Dumps. 2013
9. [Source](https://history.nasa.gov/sp4231.pdf)
10. New Scientist. 2015
11. [Source](https://space.skyrocket.de/doc_stage/ius.htm)
12. [Source](http://www2.jpl.nasa.gov/galileo/news/thiswk/today030921.html)
13. [Source](https://naif.jpl.nasa.gov/pub/naif/toolkit_docs/C/req/naif_ids.html)