Also on September 27, at 08:20 UTC, a Chinese Long March 3B launched from the Xichang Satellite Launch Center.

Few details about this launch were released officially as of press time. We do know that the rocket launched successfully and that the satellite made it to the correct orbit. Xinhua reported that “during the rocket flight, the satellite operating conditions were abnormal, and the specific reasons are being further analyzed and investigated.”

In the press release of the launch, the spacecraft onboard was called Shiyan 10. Shiyan means “experiment” or “test” in Chinese, and this series of satellites is thought to typically have a military mission.

First a quick refresher on what geostationary and geosynchronous mean and then we’ll talk about the mysterious satellite. These are two similar-sounding terms that mean slightly different things, but the difference is important.

A geostationary orbit matches a planet’s rotation and is parallel to the equator. This means that a satellite remains fixed over one spot. Communication satellites like Direct TV use this kind of orbit.

A geosynchronous orbit matches a planet’s rotation but is not parallel to the equator. A satellite in this orbit would not remain over one spot because it is not at the equator. Japan operates a constellation of navigation satellites called QZSS, or Quasi Zenith Satellite System, in an inclined geosynchronous orbit because the country is too far north for satellites in geostationary orbit to cover it.

Shiyan 10’s orbit is unusual, at least for this series of satellites. According to tracking data from the Space Force’s 18th Space Control Squadron, it was launched into a 177-kilometer by 40,104-kilometer orbit inclined 51.06 degrees to the equator, which is an inclined geosynchronous transfer orbit. All other Shiyan series satellites have launched into a more conventional geostationary transfer orbit like a satellite launched on a Falcon 9, for example. If Shiyan 10 hadn’t failed after launch, it likely would have circularized in this 51-degree orbit and begun its mission.

More Information

Xinhua News Agency release (Chinese)

TJS 2, 5, 6 info page (Gunter’s Space Page)

TJS 1, 4 info page (Gunter’s Space Page)

Quasi Zenith Satellite System info page (Gunter’s Space Page)