A collision of two satellites on 10 February was the first between two intact spacecraft travelling at orbital velocity, and produced debris that poses a potential risk to Earth observation satellites, according to NASA.

A non-operational Russian Cosmos 2251 communications satellite collided with one belonging to US-based mobile satellite service company Iridium. Each satellite was travelling at a velocity of at least 28,200km/h (17,500mph). The collision took place over Siberia, at an altitude of 790km (490 miles).

Debris from the destroyed satellites - which is estimated by the US Strategic Command to comprise more than 500 pieces - has "slightly elevated" the risk to the International Space Station, says NASA. However, the risk remains "very small" and "within acceptable limits". NASA adds that the manoeuvring capability of the ISS allows it to perform collision avoidance.

However, other satellites appear to be at greater risk. Orbiting at an altitude of 705km, NASA's Earth observation satellites are "among the closest to the collision altitude" and hence are "of highest concern", it says. According to a NASA internal email, "the collision could begin to be a problem for Earth-observing satellites".

Iridium expects a "very limited" disruption to its voice and data services, in the form of "brief, occasional outages". It says it will move one of its in-orbit spares to permanently replace the lost satellite within 30 days.

Source: Flight International