# SDS-4

> Japanese small satellite

**Wikidata**: [Q5977509](https://www.wikidata.org/wiki/Q5977509)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/SDS-4)  
**Source**: https://4ort.xyz/entity/sds-4

## Summary
SDS-4 (Small Demonstration Satellite 4) is a 50 kg Japanese microsatellite operated by the Japan Aerospace Exploration Agency (JAXA). Launched in 2012, it served as a technology demonstration spacecraft in Sun-synchronous orbit before its retirement in 2021.

## Key Facts
- **Full Name:** Small Demonstration Satellite 4
- **Operator:** Japan Aerospace Exploration Agency (JAXA)
- **Launch Date:** May 17, 2012 (16:39 UTC)
- **Launch Vehicle:** H-IIA (specifically the H-IIA-21 variant)
- **Mass:** 50 kilograms
- **Orbit:** Sun-synchronous orbit
- **Launch Site:** Yoshinobu Launch Complex Launch Pad 1
- **Service Retirement:** June 2021
- **Satellite Catalog Number (SCN):** 38339
- **COSPAR ID:** 2012-025C

## FAQs
### Q: What was the primary purpose of SDS-4?
A: SDS-4 was a Japanese microsatellite designed as a spacecraft for technology demonstration. It was part of a series of small satellites used to test and validate space-based systems in a Sun-synchronous orbit.

### Q: Which organization managed SDS-4?
A: The satellite was originally operated by the Japan Aerospace Exploration Agency (JAXA). However, in 2019, the spacecraft was transferred to the SKY Perfect JSAT Corporation.

### Q: How was SDS-4 launched into space?
A: SDS-4 was launched on May 17, 2012, using an H-IIA-21 expendable medium-lift launch vehicle. The launch took place from Launch Pad 1 at the Yoshinobu Launch Complex.

## Why It Matters
SDS-4 represents a significant milestone in Japan's development of miniaturized satellite technology. As a microsatellite weighing only 50 kg, it demonstrated JAXA's ability to deploy highly functional, small-scale spacecraft that are more cost-effective than traditional large-scale satellites. Its mission highlights the utility of the H-IIA launch vehicle in delivering secondary payloads into precise Sun-synchronous orbits, which are critical for consistent Earth observation and environmental monitoring.

The satellite's operational history is also notable for its transition from a government-led research project to a commercial asset. The transfer of SDS-4 to the SKY Perfect JSAT Corporation in 2019 illustrates a successful model for extending the life of orbital assets through public-private cooperation. By remaining operational for nine years—from its 2012 launch until its retirement in 2021—SDS-4 proved the durability and long-term viability of microsatellite platforms in the harsh environment of space. This longevity provides essential data for future small satellite missions and contributes to the growing field of miniaturized space systems.

## Notable For
- **Microsatellite Classification:** Distinguished by its small form factor and a mass of exactly 50 kilograms.
- **Operational Longevity:** Maintained active service in orbit for nine years, exceeding many typical expectations for small demonstration craft.
- **Organizational Transfer:** Notable for its 2019 transfer from the Japanese national space agency (JAXA) to a private entity, SKY Perfect JSAT Corporation.
- **Launch Platform:** Successfully deployed via the H-IIA-21, a key Japanese medium-lift launch vehicle.

## Body

### Mission and Classification
SDS-4, an acronym for Small Demonstration Satellite 4, is a Japanese spacecraft categorized as a microsatellite. Microsatellites are miniaturized artificial satellites that generally weigh between 100 and 200 kg; SDS-4 sits at the lower end of this scale with a mass of 50 kg. It was developed to function as a vehicle for testing space technologies.

### Technical Identifiers
The satellite is tracked globally under several identification systems:
- **SCN:** 38339
- **COSPAR ID:** 2012-025C
- **NSSDCA ID:** 2012-025C
- **Wolfram Language Code:** Entity["Satellite", "38339"]

### Launch and Orbital Parameters
SDS-4 was launched on May 17, 2012, at 16:39. The mission utilized the H-IIA-21 launch vehicle, an expendable medium-lift rocket. The launch originated from the Yoshinobu Launch Complex Launch Pad 1 in Japan. Upon reaching space, the satellite was placed into a Sun-synchronous orbit, a specific type of polar orbit that allows the satellite to pass over any given point of the Earth's surface at the same local solar time.

### Operational History and Retirement
The spacecraft's lifecycle included three major milestones:
- **Launch:** May 17, 2012.
- **Transfer:** In 2019, the satellite was transferred from JAXA to the SKY Perfect JSAT Corporation.
- **Retirement:** The satellite officially reached service retirement in June 2021.

## References

1. Jonathan's Space Report
2. Freebase Data Dumps. 2013