Artist’s impression of Nasa’s Timed satellite in orbit. Image: Nasa

The US department of defence is monitoring a close pass between Nasa’s Thermosphere Ionosphere Mesosphere Energetics and Dynamics Mission (Timed) spacecraft and the Russian Cosmos 2221 satellite, Nasa said on Wednesday.

Although the spacecraft are expected to miss each other, a collision could result in significant debris, the US space agency said, adding that it was continuing to monitor the situation with the department of defence. The statement did not say how close the spacecraft would come to each other.

The two satellites, which cannot manoeuvre, are expected to make their closest pass about 1.30am US Eastern (8.30am SAST) on 28 February, at an altitude of about 600km, Nasa said.