# Yohkoh Gamma and X-ray solar satellite

> Solar observatory spacecraft

**Wikidata**: [Q586893](https://www.wikidata.org/wiki/Q586893)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Yohkoh)  
**Source**: https://4ort.xyz/entity/yohkoh-gamma-and-x-ray-solar-satellite

## Summary
Yohkoh is a Japanese solar observatory spacecraft and space telescope designed to observe the Sun in X-ray and gamma-ray wavelengths. Operated by the Institute of Space and Astronautical Science (ISAS), it was launched in 1991 to study high-energy solar phenomena and remained in orbit for over 14 years.

## Key Facts
- **Classifications:** Artificial satellite and space telescope.
- **Operator:** Institute of Space and Astronautical Science (ISAS), Japan.
- **Launch Date:** August 30, 1991.
- **Launch Vehicle:** M-3S2 Japanese carrier rocket.
- **Launch Site:** Uchinoura Space Center.
- **Mass:** 390 kilograms.
- **Mission End:** Orbit decay occurred on September 12, 2005.
- **Identification Codes:** COSPAR ID 1991-062A, NSSDCA ID 1991-062A, and NAIF ID -164.
- **Former Names:** Originally designated as Solar-A or 第14号科学衛星SOLAR-A.

## FAQs
### Q: What was the primary mission of the Yohkoh satellite?
A: Yohkoh was a dedicated solar observatory used as a space telescope to monitor the Sun. It focused on capturing high-energy solar activity through X-ray and gamma-ray instrumentation that cannot be used from the Earth's surface.

### Q: Who was responsible for the Yohkoh mission?
A: The mission was operated by the Institute of Space and Astronautical Science (ISAS), a Japanese national research institute. The spacecraft was launched using a Japanese M-3S2 carrier rocket from the Uchinoura Space Center.

### Q: How long did Yohkoh remain operational in space?
A: Yohkoh was launched on August 30, 1991, and stayed in orbit for approximately 14 years. Its mission officially concluded when its orbit decayed on September 12, 2005.

## Why It Matters
Yohkoh represents a significant milestone in Japanese space exploration and solar science. As a dedicated solar observatory, it provided a platform for high-energy observations of the Sun that are impossible to conduct from the Earth's surface due to atmospheric interference. Operated by the Institute of Space and Astronautical Science (ISAS), the mission demonstrated Japan's capability to design, launch, and maintain complex space telescopes for long-duration scientific research.

The satellite's focus on X-ray and gamma-ray emissions allowed researchers to study solar flares and other high-energy solar activities with high precision. By operating for over a decade, Yohkoh captured data across a significant portion of the solar cycle, contributing to a deeper understanding of solar physics. Its launch using the M-3S2 rocket from the Uchinoura Space Center also highlighted the integration of domestic Japanese launch technology with advanced scientific instrumentation. The mission's longevity, lasting from 1991 until its decay in 2005, provided a continuous stream of data that has been cataloged by major international space databases, ensuring its contributions remain accessible to the global scientific community.

## Notable For
- **Scientific Designation:** It was Japan's 14th scientific satellite, originally known as Solar-A before being renamed Yohkoh (Sunbeam).
- **Longevity:** Maintained an active presence in orbit for 14 years, providing long-term data on solar cycles.
- **High-Energy Observation:** Specialized in X-ray and gamma-ray solar observation, filling a critical gap in Earth-based astronomy.
- **International Recognition:** Documented extensively in global scientific databases including the NSSDCA, NAIF, and the Encyclopædia Britannica.

## Body

### Mission Overview
Yohkoh was a solar observatory spacecraft designed to function as a space telescope. Before its successful deployment, the project was designated as Solar-A. Its primary purpose was the observation of distant space objects, specifically focusing on the Sun's high-energy emissions.

### Launch and Technical Specifications
The spacecraft was launched on August 30, 1991, from the Uchinoura Space Center in Japan. It was carried into orbit by the M-3S2, a Japanese carrier rocket. The satellite was relatively compact, with a total mass of 390 kilograms. 

### Operations and Management
The mission was managed and operated by the Institute of Space and Astronautical Science (ISAS). ISAS is a Japanese national research institute with roots dating back to 1955. Under their management, Yohkoh was assigned several international tracking identifiers:
- **COSPAR ID:** 1991-062A
- **NSSDCA ID:** 1991-062A
- **NAIF ID:** -164
- **Satellite Catalog Number (SCN):** 21694

### Mission Conclusion
Yohkoh provided scientific data for over a decade. The mission reached its final conclusion when the spacecraft experienced orbit decay on September 12, 2005. Its legacy is preserved through extensive documentation in academic sources and official space agency archives, including both English and Japanese mission websites maintained by ISAS/JAXA.

## References

1. Jonathan's Space Report
2. [Source](https://www.isas.jaxa.jp/en/missions/spacecraft/past/yohkoh.html)
3. [Source](http://ylstone.physics.montana.edu/ylegacy/about_yohkoh.html)
4. Freebase Data Dumps. 2013