Aspects of remote detection of ionospheric disturbances caused by spacecraft engine exhaust jets

Since 2007, we have carried out active space experiments using the `Progress´ transport spacecraft (TSC) and the Irkutsk Incoherent Scatter Radar (IISR). Engine burns of orbital maneuvering subsystem were a source of ionospheric disturbances at a height of 340 km. The amount of used fuel varied from 2 to 11 kg. The flow directions relative to IISR and amount of injected exhaust products varied from flyby to flyby. The flows directed to IISR were almost parallel to the geomagnetic field line. In these cases, the observed effects were most pronounced. The electron density depletion reached 20-40%. According to our estimations, life-time of the ionospheric `hole´ was about 10-15 minutes. The experiment sessions in 2011-2013 showed rather weak effects of engine exhaust jet on ionospheric plasma. The difference between electron density profiles obtained before and after burning does not exceed statistical uncertainty, and the engine exhaust jet effect is undistinguishable. The most important factor affecting the `Radar-Progress´ experiment is the TSC `Progress´ orbit altitude.