Space is 200km lower than expected

Currently, the ionosphere - a layer of charged particles that envelopes the planet - is at an altitude of about 420km, some 200km lower than expected.

The behaviour of the ionosphere is important because disturbances in its structure can upset satellite communications and radar.

The C/NOFS satellite's data will be used to try to forecast such problems.

"C/NOFS is focusing on one small aspect of 'space weather' which is the impact of the upper atmosphere - a region called the ionosphere - on radiowaves that try to get from satellites down to the ground," said Don Hunton, the technical manager on the satellite programme at the US Air Force Research Laboratory.

"Sometimes the ionosphere interrupts satellite communications and sometimes it doesn't, and we're trying to understand how to forecast, or predict ahead of time, when those problems are going to arise," he told BBC News.