A little over two years ago, China conducted the now notorious direct ascent ASAT shot on the Fengyun-1 satellite which was in a polar orbit.Â We’ve commented extensively at the time and a year hence on the issues raised by this shot.Â So where do we stand just past the second anniversary?Â Well, like rabbits, the debris field is growing:
The NASA report said that two years after China used a ground-based missile to destroy the retired ChineseÂ Fengyun-1C weather satellite in an 800-kilometer orbit, SSN is tracking nearly 2,800 pieces of debris measuring at least 5 centimeters in diameter. “The estimated population of debris larger than 1 centimeter is greater than 150,000,” NASA said. “The Fengyun-1C debris cloud easily constitutes the largest collection of fragments in Earth orbit.” (space.com)
What brought our attention to this latest state of affairs was a report of another satellite potentially in trouble – this time a Soviet-era test platform based on a RORSAT (radar ocean-reconnaissance satellite), powered by a prototype reactor (Topaz) that used pressurized sodium-potassium as a coolant for the reactor.Â The reactor was necessary to generate the high-power required by the satellite for the ocean-surveillance mission.Â Placed in a polar orbit between 774 and 803 km, the Plasma-A satellite acted as a test bed not only for the functionality of the Topaz-reactor, but taking advantage of the power generated by the reactor, also tested electrostatic maneuvering engines composed of six SPT-70 Stationary Plasma Thrusters, ion orientation and stabilization engines, solar sensors, magnetic momentum compensators and multi-channel wave devices (one of the ancillary missions was to map out the Earth’s magnetosphere for a magnetic-based navigation system). (Gunter’s space page).Â Specifically what appears to have happened was what NASA is calling a “fragmentation event” that occurred 4 July 2008 while the satellite was in at 800 km altitude, releasing up to 30 small pieces of debris, conjectured to be metal spheres extruded from a conjectured leak in the reactor’s coolant system.Â Of note – the satellite is slated to eventually re-enter the atmosphere sometime around mid-century and is supposed to burn up well high in the upper atmosphere.Â Unlike the RORSATs which separated into two parts upon termination of mission, one being the reactor body which was moved to a higher orbit, Kosmos-1818/Plasma-A remained a single object.
A couple of theories are making the round as to what caused the event — one being that the plumbing for the metal coolant became thermal stressed from its prolonged exposure on-orbit,weakened and cracked releasing the liquid metal which promptly froze.Â Another, with some traction, is that the release was the result of a collision with debris.Â Where the debris came from is another issue — in its present orbit there is debris from older RORSATs that have leaked or otherwise left debris behind.Â In fact, the present orbit transits some of the highest debris-laden areas – including the growing debris field from the Chinese ASAT, and serves to highlight – again, the growing issue of on-orbit debris.
Orbital debris – the gift that keeps on giving…