# Kepler Space Telescope

> defunct NASA space telescope

**Wikidata**: [Q47272](https://www.wikidata.org/wiki/Q47272)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Kepler_space_telescope)  
**Source**: https://4ort.xyz/entity/kepler-space-telescope

## Summary
Kepler Space Telescope was a NASA space telescope designed to discover Earth-size planets orbiting other stars. Launched in 2009, it operated for nearly 10 years before running out of fuel and being retired in 2018.

## Key Facts
- Launched on March 7, 2009, aboard a Delta II rocket from Cape Canaveral Space Launch Complex 17B
- Mass: 1,052.4 kg (launch weight), 1,040.7 kg (dry weight), with 478 kg payload and 11.7 kg of hydrazine fuel
- Dimensions: 4.7 meters long, 2.7 meters in diameter
- Operated in a heliocentric orbit with a period of 372.57 days
- Designed for 3.5 years but exceeded expectations, operating for 9.69 years
- Discovered over 2,600 confirmed exoplanets during its mission
- Retired on November 15, 2018, after depleting its hydrazine fuel
- Part of NASA's Discovery Program (mission #10)
- Operated by NASA and the Laboratory for Atmospheric and Space Physics

## FAQs
### Q: What was the primary mission of the Kepler Space Telescope?
A: Kepler's primary mission was to survey a portion of our region of the Milky Way galaxy to discover Earth-size and smaller planets in or near the habitable zone and determine how many of the billions of stars in our galaxy have such planets.

### Q: How did Kepler detect planets?
A: Kepler used the transit method, measuring tiny dips in a star's brightness when a planet passed in front of it. This allowed scientists to determine the planet's size and orbital period.

### Q: Why did the Kepler mission end?
A: The Kepler mission ended because the spacecraft ran out of hydrazine fuel needed to maintain its orientation and point at target stars. NASA officially retired Kepler on November 15, 2018.

## Why It Matters
Kepler Space Telescope fundamentally transformed our understanding of the universe and our place in it. Before Kepler, astronomers had confirmed fewer than 350 exoplanets, most of which were gas giants similar to Jupiter. Kepler's data revealed that planets are incredibly common throughout the galaxy, with small, rocky planets like Earth being particularly abundant. The mission discovered that approximately 20-25% of stars have small planets in their habitable zones, suggesting billions of potentially habitable worlds in our galaxy alone. This revolutionized the field of exoplanet research and provided crucial data for future missions searching for signs of life beyond Earth. Kepler's legacy continues to influence astronomy, planetary science, and our philosophical understanding of humanity's place in the cosmos.

## Notable For
- Discovered over 2,600 confirmed exoplanets, revolutionizing our understanding of planetary systems
- First space telescope capable of detecting Earth-size planets in habitable zones
- Operated more than 2.5 times longer than its planned mission duration
- Provided the first statistical census of exoplanets in our galaxy
- K2 mission extension repurposed the telescope after reaction wheel failures

## Body
### Technical Specifications
Kepler Space Telescope featured a 0.95-meter aperture photometer with a 105-square-degree field of view. The spacecraft was powered by a photovoltaic system generating 1,100 watts and included lithium-ion batteries for eclipse operations. Its primary mirror was 1.4 meters in diameter, making it the largest mirror launched outside Earth's orbit at the time.

### Mission Timeline
The telescope launched on March 7, 2009, at 03:49:57 UTC and achieved service entry on May 13, 2009, at 00:01 UTC. The primary mission lasted until 2013 when two of four reaction wheels failed, preventing precise pointing. NASA developed the K2 "Second Light" mission using solar pressure for stabilization, extending operations until October 30, 2018, when fuel depletion was detected.

### Scientific Achievements
Kepler's data revealed that planets are ubiquitous in our galaxy, with small, rocky planets being more common than gas giants. The mission discovered the first Earth-size planets in habitable zones, multi-planet systems, and planets orbiting binary stars. Its observations showed that our solar system is not unique, with many planetary systems having architectures vastly different from our own.

### Orbital Characteristics
Kepler operated in an Earth-trailing heliocentric orbit with a semi-major axis of 1.0133 AU and an orbital period of 372.57 days. The orbit had a low inclination of 0.44765 degrees and a small eccentricity of 0.036095, placing it in a stable position that avoided Earth's shadow while maintaining thermal stability.

### Legacy and Impact
Kepler's discoveries have guided the design of subsequent exoplanet missions, including TESS and the James Webb Space Telescope. The mission demonstrated that Earth-like planets are common in the galaxy, fundamentally changing our understanding of planetary formation and the potential for life elsewhere. Kepler's data archive continues to yield new discoveries as scientists develop new analysis techniques and combine Kepler data with other observations.

## References

1. [Source](https://space.skyrocket.de/doc_sdat/kepler.htm)
2. Jonathan's Space Report
3. [Source](https://ssd.jpl.nasa.gov/horizons.cgi?find_body=1&body_group=mb&sstr=-227)
4. [Source](https://www.jpl.nasa.gov/news/press_kits/Kepler-presskit-2-19-smfile.pdf)
5. Freebase Data Dumps. 2013
6. [Source](https://www.ball.com/getattachment/bb8c3c95-42b2-4ce0-8aa7-c6f766fa0fa8/D1920_BCP_SC_3.pdf)
7. [Source](https://www.nasa.gov/mission_pages/kepler/news/keplerm-20090514.html)
8. [Source](https://www.nasaspaceflight.com/2018/10/kepler-retired-after-running-out-of-fuel/)
9. [Source](https://www.jpl.nasa.gov/news/kepler-telescope-bids-goodnight-with-final-commands)
10. BBC Things
11. [Source](https://naif.jpl.nasa.gov/pub/naif/toolkit_docs/C/req/naif_ids.html)