On 2013 February 4, Dr. Vasiliy Yurasov and Dr. Andrey Nazarenko, working with the Institute for Precision Instrument Engineering (IPIE) in Moscow, reported to CSSI a significant change in the orbit for their BLITS satellite. BLITS is tracked to high precision by the International Laser Ranging Service (ILRS), and IPIE had detected a sudden decrease of 120 m in the semi-major axis of its orbit and a change in its spin velocity and attitude. Prior to the event, BLITS had a spin axis perpendicular to the orbit plane and had a stable spin period of 5.6 sec.
Drs. Yurasov and Nazarenko’s analysis, based on optical and photometric analysis (since they are no longer able to perform laser tracking), estimated that the change occurred on 2013 January 22 at approximately 0757 UTC. They requested help in determining whether these changes might have been the result of a collision with another object in orbit. They were also able to determine a new spin period of 2.1 sec.
Starting from the hypothesis that an object capable of causing this change in the orbit of the 7.53-kg BLITS satellite might be large enough to be tracked by the US Space Surveillance Network, CSSI reviewed the SOCRATES archives to determine whether there were any close approaches around the reported time. Using the SOCRATES archive generated 2013 January 22 at 0308 UTC, CSSI discovered that only one close approach occurred for BLITS:
NORAD Catalog Number: 30670
Min Range: 3.109 km
Relative Velocity: 9.676 km/s
TCA: 2013 Jan 22 07:56:51.629
Although the predicted distance would seem to preclude a collision, the fact that the close approach occurred within 10 seconds of the estimated change in orbit made it appear likely that this piece of FENGYUN 1C debris actually collided with BLITS.
Using the reported change in the semi-major axis of the BLITS orbit, it is possible to calculate the change in velocity imparted by the collision (about 62 mm/s) and the corresponding change in momentum for the 7.53-kg BLITS. From that, with an in-track relative velocity of -6.273 km/s, the mass of 30670 would have to be at least 0.075 g to have imparted the necessary change in momentum in a completely elastic collision.
CSSI is continuing to work with Drs. Yurasov and Nazarenko to further assess the circumstances of this likely collision.
The Joint Space Operations Center (JSpOC) released the first TLE for debris associated with BLITS (NORAD Catalog Number 39119) via the Space Track web site on 2013 March 3, further confirming CSSI’s analysis.