# Hisaki

> decommissioned Japanese ultraviolet astronomy satellite

**Wikidata**: [Q3459972](https://www.wikidata.org/wiki/Q3459972)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Hisaki_(satellite))  
**Source**: https://4ort.xyz/entity/hisaki

## Summary
Hisaki was a Japanese ultraviolet astronomy satellite operated by JAXA, launched in 2013 to study the dynamics of planetary exospheres. It was decommissioned in December 2023 after a decade-long mission. The satellite used advanced ultraviolet spectroscopy to observe planets and moons in the solar system.

## Key Facts
- **Launch Date**: September 14, 2013, at 05:00:00 UTC from Uchinoura Space Center.
- **Operator**: Japan Aerospace Exploration Agency (JAXA).
- **Manufacturer**: NEC Corporation.
- **Mission End**: Decommissioned on December 8, 2023.
- **Instrument**: Extreme Ultraviolet Spectroscope for Exospheric Dynamics (EXCEED).
- **Launch Vehicle**: Epsilon rocket (E-1 configuration).
- **Mass**: 348 kg (launch weight).
- **Power Source**: 2 spacecraft solar arrays.
- **Preceded By**: None; **Followed By**: Arase satellite.
- **NAIF ID**: -750 (NASA identification).

## FAQs
### Q: What was the primary mission of the Hisaki satellite?
A: Hisaki studied the exospheres of planets and moons in the solar system using ultraviolet spectroscopy, focusing on atmospheric dynamics and interactions with solar wind.

### Q: Why was Hisaki decommissioned in 2023?
A: The satellite was retired after completing its extended mission objectives, with operational limitations likely contributing to the decision.

### Q: What made Hisaki unique compared to other astronomy satellites?
A: It was the first satellite launched on Japan’s Epsilon rocket and specialized in extreme ultraviolet observations of planetary exospheres.

## Why It Matters
Hisaki played a critical role in advancing understanding of planetary atmospheres, particularly Jupiter’s magnetosphere and the escape of atmospheric particles from planets like Mars. Its observations provided insights into how solar wind shapes planetary environments, contributing to comparative planetology. As Japan’s first ultraviolet-dedicated space telescope, it demonstrated technological capabilities in low-cost, focused missions. The data from Hisaki supported international research collaborations, influencing subsequent missions like Arase and helping scientists model atmospheric loss processes.

## Notable For
- First payload launched on Japan’s Epsilon rocket (2013).
- Conducted the first long-term ultraviolet monitoring of Jupiter’s magnetosphere.
- Operated far beyond its planned 1-year mission, lasting over 10 years.
- Utilized the NEXTAR spacecraft bus designed for low-cost missions.
- Collaborated with ground-based observatories for coordinated observations.

## Body
### Launch and Deployment
- **Rocket**: Epsilon (E-1 configuration), launched from Uchinoura Space Center.
- **Cost**: Part of JAXA’s low-cost mission initiative, leveraging the Epsilon rocket’s cost-effective design.

### Mission Objectives
- **Primary Goal**: Study the exospheres of planets and moons using extreme ultraviolet spectroscopy.
- **Targets**: Jupiter, Saturn, Mars, and comets.
- **Key Discoveries**: Documented atmospheric escape from Mars and dynamic changes in Jupiter’s magnetosphere.

### Instrumentation
- **EXCEED Spectrometer**: Focused on extreme ultraviolet wavelengths (55–135 nm).
- **Spectral Resolution**: High-resolution measurements of atmospheric emissions.

### Decommissioning
- **Retirement Date**: December 8, 2023.
- **Reason**: Completion of mission objectives and degradation of operational capabilities over time.

### Legacy
- **Data Archive**: Over 10 years of ultraviolet spectral data publicly available for scientific research.
- **Successor**: Arase satellite (launched 2016), focusing on Earth’s Van Allen belts.

## Schema Markup
```json
{
  "@context": "https://schema.org",
  "@type": "Satellite",
  "name": "Hisaki",
  "description": "Decommissioned Japanese ultraviolet astronomy satellite",
  "url": "https://www.isas.jaxa.jp/home/sprint-a/index_en.html",
  "sameAs": [
    "https://www.wikidata.org/wiki/Q15241312",
    "https://en.wikipedia.org/wiki/Hisaki_(satellite)"
  ],
  "manufacturer": "NEC",
  "operator": "Japan Aerospace Exploration Agency",
  "launchDate": "2013-09-14",
  "mass": "348 kg",
  "rocket": "Epsilon"
}

## References

1. [Source](https://space.skyrocket.de/doc_sdat/sprint-a.htm)
2. [Source](https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=2013-049A)
3. Jonathan's Space Report
4. Freebase Data Dumps. 2013
5. [Source](https://www.isas.jaxa.jp/home/sprint-a/index_en.html#section04)
6. [Source](https://naif.jpl.nasa.gov/pub/naif/toolkit_docs/C/req/naif_ids.html)