3 ms·
Replying to myself here, but three things: 1) the receiver arrays are about 50x 6m diameter (3m radius) antennas (https://www.seti.org/projects/ata/ https://ww
by GlibMonkeyDeath 2mo ago
Replying to myself here, but three things:
1) the receiver arrays are about 50x 6m diameter (3m radius) antennas (https://www.seti.org/projects/ata/ https://www.seti.org/projects/ata/) So that helps about 7x.
2) The 2e15 W/10 MJ/pulse has to be all the radars summed together already, so that is all the power available.
Take these two points together, the single photon detection limit is indeed about 200 ly.
Third: if we assume a 1 Hz detection bandwidth, I get ~200 photons/s for the CMB @ 3 GHz. I can't find the original paper (just the abstract) so they must assume 100-200 s integration time or so to get to an SNR of 1. So 200 ly is on the very edge of possibility - the example curves were calculated for 10x closer (~30 ly), as I would expect. Still, a lot further than a fractional light year!
- M95D 2mo agoConsider military radars, Cernobyl woodpecker [1]. [1] https://en.wikipedia.org/wiki/Duga_radar https://en.wikipedia.org/wiki/Duga_radar
- GlibMonkeyDeath 2mo agoI am learning a lot about radar :) This radar is using 1 MJ, 3 millisecond pulses at ~3-30 MHz (not ~5 ns pulses at ~3 GHz), so peak power is a far cry from the 2e15 W in the article (~3e8 W.) That's why I think the 2e15 W in the article has to be peak power of all radars summed together. The average power used by all human activity is something like 20 TW (20e12 W, https://ourworldindata.org/energy-production-consumption https://ourworldindata.org/energy-production-consumption)