Detection of, and communication with space vehicles during atmospheric entry, problems in simulation

In considering the problem of communicating with outer space and detection of spacecraft from the ground, one usually has to worry about only the propagation characteristics of electromagnetic waves of vacuum wavelength falling within either one of the two well known "atmospheric windows," namely; (1) the "optical window" extending from about 0.3 microns to a few microns, and (2) the "RF window" extending from a few millimeters to about 30 meters in the wavelength scale. However, during entry (or reentry) of a spacecraft into the earth's atmosphere, there exists two physical phenomena which tend to complicate the communication problem on the one hand, and to simplify the detection problem on the other hand.