# CHEOPS

> 2019 European space telescope

**Wikidata**: [Q376628](https://www.wikidata.org/wiki/Q376628)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/CHEOPS)  
**Source**: https://4ort.xyz/entity/cheops

## Summary
CHEOPS (CHaracterising ExOPlanet Satellite) is a European space telescope launched in 2019 to study the size, mass, and density of exoplanets. It is part of the European Space Agency's (ESA) Cosmic Vision program and operates in a Sun-synchronous orbit. The mission focuses on characterizing planets orbiting nearby bright stars to better understand planetary formation and evolution.

## Key Facts
- **Launch Date**: December 18, 2019, at 08:54 UTC.
- **Operator**: Swiss Space Office, with ESA oversight.
- **Primary Instrument**: A photometer designed to measure exoplanet sizes with high precision.
- **Orbit**: Sun-synchronous orbit with an altitude of approximately 715 km (apoapsis) and 712 km (periapsis), inclined at 92.8 degrees.
- **Mass**: 273 kg at launch, with a payload weight of 58 kg.
- **Manufacturer**: Airbus Defence and Space.
- **Launch Vehicle**: Soyuz-2.1a rocket (serial number R15000-008), launched from the Ensemble de Lancement Soyouz in Kourou.
- **Mission Duration**: Planned for at least 3.5 years.
- **Website**: Available in English, German, and French (cheops.unibe.ch).

## FAQs
### Q: What is the main purpose of the CHEOPS mission?
A: CHEOPS measures the radius of exoplanets to determine their density, helping scientists distinguish between rocky, gaseous, or icy worlds and understand their formation processes.

### Q: Who built and operates CHEOPS?
A: The satellite was manufactured by Airbus Defence and Space and is operated by the Swiss Space Office, with the European Space Agency (ESA) leading the mission.

### Q: What type of orbit does CHEOPS use?
A: It operates in a Sun-synchronous orbit at an altitude of ~715 km, ensuring consistent lighting conditions for observations.

## Why It Matters
CHEOPS plays a critical role in exoplanet science by bridging the gap between exoplanet detection and detailed atmospheric studies. By precisely measuring the size of exoplanets, it helps identify which planets are terrestrial or gas giants, guiding follow-up observations by larger telescopes like the James Webb Space Telescope. As part of ESA’s Cosmic Vision program, CHEOPS advances our understanding of planetary systems beyond the Solar System, addressing fundamental questions about how planets form and evolve. Its data supports statistical studies of exoplanet populations, refining models of planetary structure and migration.

## Notable For
- First ESA mission dedicated to exoplanet characterization.
- Uses a high-precision photometer to detect minute changes in star brightness during exoplanet transits.
- Operates in a thermally stable Sun-synchronous orbit to minimize measurement errors.
- International collaboration involving over 10 European nations and led by Switzerland.
- Designed for flexibility, allowing observations of targets selected by the broader scientific community.

## Body
### Mission Overview
CHEOPS launched on December 18, 2019, aboard a Soyuz-2.1a rocket from the Guiana Space Centre. The mission is led by the University of Bern, Switzerland, with ESA oversight. Its primary goal is to determine the radius of exoplanets with 10% precision, enabling the calculation of planetary density when combined with mass data from radial velocity measurements.

### Technical Specifications
- **Spacecraft Bus**: S450 Optical platform.
- **Power**: 64 W nominal output.
- **Launch Mass**: 273 kg (including 58 kg payload).
- **Scientific Instrument**: A Ritchey-Chrétien telescope with a 32 cm aperture, feeding a single photometer operating in visible light (400–900 nm).

### Launch and Orbit
- **Launch Contractor**: Arianespace.
- **Space Tug**: Fregat-M (serial 133-12).
- **Orbital Parameters**: 715 km apoapsis, 712 km periapsis, 92.8° inclination.
- **Orbit Type**: Sun-synchronous, ensuring dawn-dusk orbits for stable thermal conditions.

### Scientific Contributions
CHEOPS observes known exoplanet-hosting stars, monitoring brightness dips during planetary transits. Its data helps:
- Distinguish between rocky, icy, and gaseous planets.
- Study planetary atmospheres and internal structures.
- Test theories of planet formation and migration.
- Identify targets for future spectroscopic analysis by missions like JWST and Ariel.

### Ground Segment
- **Mission Control**: Swiss Space Office (Bern, Switzerland).
- **Data Processing**: University of Geneva, with open access to the scientific community.
- **Observing Strategy**: Targets selected through a competitive proposal process, with 20% of observation time allocated to Belgian scientists in exchange for instrument contributions.

## References

1. [Source](https://space.skyrocket.de/doc_sdat/cheops.htm)
2. Jonathan's Space Report
3. Freebase Data Dumps. 2013
4. [Source](https://space.skyrocket.de/doc_stage/fregat.htm)
5. BBC Things