#100 November 1996
Section 18.104.22.168.100.of the Artemis Data Book
REMOTE MAPING OF LUNAR LAVATUBES: Teleo-Spelunking on the Moon
[Reprint of MMM #44, April '91, page 6]
To provide deep radar imaging, the antenna diameter must be four times the radar wavelength being used. To penetrate deeply enough we'd need a wavelength of 5-20 meters, meaning an antenna 20-80 meters across! That's a lot of mass to put into orbit along with the ancillary equipment.
Billings suggests a way out. Readings from a number of smaller antennas in an interferometer array can substitute, synthesizing an image. It will be tricky to do this in orbit, and an intercontinental interferometer is an option. Using a 7-meter wavelength, you'd have a 250 meter resolution and a penetration of 70 meters, good enough to detect a convincing sample, given that many tubes are likely to be larger than this.
However, a considerable amount of power will be needed if the signal returning to Earth is to be detectable. Computer algorithms needed to sift signal from noise are getting better. Nor need the search extend beyond a few months, so maybe the expense wouldn't be out of line with the rewards. TB
[Ed.: 1) Would it be practical to intercept the signal in lunar orbit where it would be stronger? 2) Would Earth-based searches be limited to central nearside? 3) We could use the same instrumentation package to search for tubes on Mars, Mercury, Venus, Io, and Vesta; worlds with shield volcanoes and lava sheets.]
Contents of this issue of Moon Miners' Manifesto