Radio limb sounding: a technique for measuring global profiles of free electrons in the ionosphere

A technique is proposed to measure the electron density profile of the ionosphere between 100 and 800 km using a microwave frequency receiver on board a conventional Earth Observations Satellite and a series of transmitters on micro satellites in appropriate orbits. A pair of pulsed frequencies will enable the relative signal delay to be determined and hence the total electron content between the two devices. The vertical profiles of N along the satellite track can be retrieved using a modified form of tomography. Regular global coverage from a single experiment over several years would provide a unique data set for comparison with models of the ionosphere, and also its interaction with the neutral atmosohere and its response to changes in solar activity.