From AMS Glossary
In radar, the time after the transmission of a pulse for the receiver to regain its full sensitivity.
Ordinarily the receiver is turned off during pulse transmission to protect it from the strong transmitted signal and is turned back on as soon as the transmitter is turned off. The recovery time is the transient time during which full receiver sensitivity is restored. Because the receiver is not operating at its full sensitivity at times shorter than the recovery time, quantitative reflectivity measurements at close ranges are difficult or impossible. Through the use of fast switches, recovery times may be in the order of a fraction of a microsecond, so that the minimum range for quantitative measurements can be as small as a few tens of meters.