Issue 46

Shiyan-10 Reaches Molniya Orbit

15 Apr 2022: China's classified Shiyan (SY)-10 satellite has been tracked operating in a specialized orbit, six months after an anomaly during launch appeared to leave it stranded in an initial transfer orbit. SY-10 is now in a “Molniya” orbit according to tracking data from the U.S. Space Force’s 18th Space Control Sq…

15 Apr 2022: China’s classified Shiyan (SY)-10 satellite has been tracked operating in a specialized orbit, six months after an anomaly during launch appeared to leave it stranded in an initial transfer orbit. SY-10 is now in a “Molniya” orbit according to tracking data from the U.S. Space Force’s 18th Space Control Squadron (SPCS). Related: the 18 SPCS is now the 18th Space Defense Squadron.

– SY-10 launched in Sep 2021 with an initial orbit of 177 x 40104 km x 51.0°.

– Chinese media reported that the launch proceeded normally, but the satellite operating conditions were abnormal.

– In Oct, Chinese satellite operators raised the satellite’s perigee to 1106 x 40092 km x 51.1°.

– At that time CASC announced the mission was a “success.” The announcement was deleted minutes after being posted.

– On 28 Feb SY-10 was still in that orbit and no US tracking updates until the end of Mar.

– In late-Mar, SY-10’s orbit was updated to a 1853 x 38878 km x 63.6° orbit.

– On 7 Apr SY-10 tweaked its orbit to 1484 x 38877 km x 63.6° with a period of 11h 58m, or half a sidereal day – the true Molniya orbit.

– Plane changes are exceptionally expensive in fuel expenditure. To alter SJ-10 12.5° (from 51.1° to 63.6°) required ~ 400 m/s of Δv.

– Chinese space operators likely conducted several small burns at apogee (when the spacecraft is at its lowest velocity) over the course of several orbits. Each burn put the satellite closer to the desired inclination and reduced the mass of the vehicle – allowing each sequential maneuver to be more efficient (the same fuel achieves more inclination change with the lower mass).

– The altitude changes could have been combined with plane change maneuvers or completed after the plane change. A combined plane change is more fuel efficient than conducting separate maneuvers.

– The 63° is ‘special’, as the Earth’s flattening locks in the latitude of perigee.

– Molniya orbits are traditionally used for Missile Warning, Communications to northern latitudes and Signals Intelligence.

– SY-10 is China’s first satellite to use this orbit and its overall mission remains unknown.

– There is no open source reporting to indicate China originally intended the SY-10 to use the Molniya orbit, or if the launch anomaly made Molniya the best option to salvage the mission.

– China operates its China Remote Sensing Satellite North Polar Ground Station, which is located in Kiruna, northern Sweden, which would be visible to Shiyan-10 for long periods near its apogee.

Special thanks to the Integrity ISR Space team for their assistance with fuel cost calculations!

SY-10 Molniya Orbit.

SY-10 Ground Track.