QET meaning in Radio Science ?

In computing, phoning home is a term often used to refer to the behavior of security systems that report network location, username, or other such data to another computer.

Phoning home may be useful for the proprietor in tracking a missing or stolen computer. This type of phoning home is frequently used on mobile computers at corporations. It typically involves a software agent which is difficult to detect or remove. However, there are malicious types of phoning homes such as surreptitious communication between applications or hardware installed at end-user sites and their manufacturers or developers. The traffic may be encrypted to make it difficult or impractical for the end-user to determine what data are being transmitted.

The Stuxnet attack on Iran's nuclear facilities was facilitated by phone home technology as reported by The New York Times.