In message , Ray Tomes
writes
First some background and then a question or two.


Has any observation been made below 10^6 Hz of the general
background spectrum?

[[Mod. note -- I think very little radio astronomy of any kind has been
done at such low frequencies. Indeed, I'm not even sure if the Earth's
ionosphere is even transparent at 1 MHz frequencies; if not, the
observations would have to be done from space. Try searching on the
ADS or scholar.google.com for 'low frequency radio astronomy'. -- jt]]

The Voyager planetary radio astronomy experiment apparently covered the
range 1.2 kHz to 1.228 MHz
http://www.igpp.ucla.edu/pds2/VG_1601/DOCUMENT/PRA/PRAINST.HTM.
I see Bill Keel has noted the Radio Astronomy Explorers and absorption
in the ISM; I'll just comment that the absorption is mentioned in Arthur
Clarke's novel Imperial Earth, where this LF astronomy plays a
significant role.
--
mail to jsilverlight AT merseia DOT fsnet DOT co DOT uk is welcome.