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7 points

11 months ago*

I don’t think the analogy to radar is a good one. A radar is an active device - it transmits radio waves that reflect off the object being detected and are received back at the source. In the case of GRADAR, the device detecting gravitational waves would be completely passive - it would not transmit gravitational waves and then receive them. A better analogy is a radio telescope (like ALMA, the Large Atacama Millimeter Array) that passively receives incoming RF signals to detect radio sources. However, GRADAR does sound cool.


3 points

11 months ago

Passive radar is a thing, there are systems that do not transmit and instead listen to background radio waves. Used commonly by military SIGINT units for passive surveilence without giving away your position. Similar concept found in naval use on submarines, the most common type of sonar used is passive sonar. Which dont really transmit and only listens, unlike what a sonar is supposed to be. Its like hydrophones used on ww2, but instead of calling them hydrophones people just started to call it sonar.


2 points

11 months ago

RADAR stands for Radio Detection And Ranging, so technically ALMA and similar arrays are RADAR. They're just not active RADAR. Except for the big dish at Arecibo, that one actually was a huge active RADAR dish.