# Hitomi

> failed Japanese X-ray astronomy satellite

**Wikidata**: [Q298048](https://www.wikidata.org/wiki/Q298048)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Hitomi_(satellite))  
**Source**: https://4ort.xyz/entity/hitomi

## Summary
Hitomi was a Japanese X-ray astronomy satellite that failed shortly after its launch in 2016. Developed by the Japan Aerospace Exploration Agency (JAXA) and operated in collaboration with NASA's Goddard Space Flight Center, it was designed to study high-energy phenomena in the universe but disintegrated in March 2016 due to a structural failure. Despite its brief operational period, Hitomi provided valuable scientific data during its short lifespan.

## Key Facts
- **Launch Date**: February 17, 2016, at 08:45 UTC aboard an H-IIA rocket (serial number H-IIA-30) from Yoshinobu Launch Complex Pad 1.
- **Failure Date**: March 26, 2016, at 01:42 UTC due to a chain of events triggered by a computer error, leading to structural break-up.
- **Mass**: 2,700 kilograms.
- **Operators**: Institute of Space and Astronautical Science (ISAS) and NASA's Goddard Space Flight Center.
- **Mission Objective**: To observe X-ray emissions from black holes, supernovae, and galaxy clusters using advanced spectrometers and imagers.
- **COSPAR ID**: 2016-012A.
- **Replacement Mission**: Succeeded by the X-ray Imaging and Spectroscopy Mission (XRISM), launched in 2023.

## FAQs
### Q: Why did the Hitomi satellite fail?
A: Hitomi disintegrated on March 26, 2016, after a computer error caused its solar panels to detach, leading to structural failure. The incident occurred while the satellite was attempting to recover from a chain of command errors.

### Q: What was Hitomi's primary scientific goal?
A: Hitomi aimed to study high-energy astrophysical phenomena, such as black holes and supernova remnants, using its advanced X-ray spectrometers and imagers to capture high-resolution data.

### Q: Who operated the Hitomi mission?
A: The mission was operated jointly by the Institute of Space and Astronautical Science (ISAS) in Japan and NASA's Goddard Space Flight Center in the United States.

## Why It Matters
Hitomi represented a significant advancement in X-ray astronomy, equipped with cutting-edge instruments like the Soft X-ray Spectrometer (SXS), which offered unprecedented energy resolution. Its failure was a major setback for the global astrophysics community, as it deprived scientists of a powerful tool for studying cosmic phenomena. However, the mission demonstrated the potential of international collaboration in space research and informed the development of subsequent missions, including XRISM. Hitomi's partial data return also contributed to scientific insights, such as observations of the Perseus Cluster, highlighting the importance of high-resolution X-ray spectroscopy in understanding the universe.

## Notable For
- **Advanced Instrumentation**: Carried the Soft X-ray Spectrometer (SXS), a revolutionary cryogenically cooled detector.
- **International Collaboration**: Joint project between JAXA, NASA, and European institutions.
- **High-Resolution Imaging**: Designed to capture detailed X-ray spectra of celestial objects.
- **Predecessor to XRISM**: Its legacy directly influenced the design and goals of the X-ray Imaging and Spectroscopy Mission.

## Body

### Mission Overview
Hitomi, also known as ASTRO-H, was launched on February 17, 2016, to study X-ray emissions from high-energy astrophysical sources. The satellite carried four main instruments: the Soft X-ray Spectrometer (SXS), the Soft X-ray Imager (SXI), the Hard X-ray Imager (HXI), and the Soft Gamma-ray Detector (SGD). These tools were designed to observe black holes, neutron stars, and galaxy clusters.

### Launch and Failure
- **Launch Vehicle**: H-IIA rocket (Flight H-IIA-30) from Tanegashima Space Center.
- **Failure Timeline**: 
  - March 25, 2016: Communication errors led to uncontrolled rotation.
  - March 26, 2016: Structural failure at 01:42 UTC resulted in disintegration.
- **Investigation**: JAXA attributed the failure to a software error that caused the satellite to lose stability, leading to the detachment of its solar paddles and eventual break-up.

### Instrumentation
- **Soft X-ray Spectrometer (SXS)**: A microcalorimeter with energy resolution 30 times sharper than previous instruments.
- **Hard X-ray Imager (HXI)**: Detected high-energy X-rays using silicon detectors and scintillators.
- **Weight**: Total mass of 2,700 kg, with instruments contributing to its scientific payload.

### Legacy
Despite its brief operational period, Hitomi collected 1,500 hours of scientific data, including observations of the Perseus Cluster. Its failure prompted improvements in spacecraft redundancy and error handling, influencing the design of XRISM. The mission underscored the challenges of space-based X-ray astronomy and the importance of international cooperation in high-energy astrophysics.

## References

1. [Source](https://www.isas.jaxa.jp/en/missions/spacecraft/past/hitomi.html)
2. Jonathan's Space Report
3. [Source](https://spacenews.com/u-s-air-force-no-evidence-malfunctioning-japanese-satellite-was-hit-by-debris/)
4. [Source](https://spaceflightnow.com/2016/04/18/spinning-japanese-astronomy-satellite-may-be-beyond-saving/)
5. Freebase Data Dumps. 2013
6. [Source](https://global.jaxa.jp/press/2016/04/files/20160428_hitomi.pdf)