dietz@cs.rochester.edu (Paul Dietz) (08/12/89)
In article <14531@bfmny0.UUCP> tneff@bfmny0.UUCP (Tom Neff) writes: >The re-entry ionization blackout has more to do with the severity of >radio noise from the fireball than it does with who's listening, I >thought. There have been "light" distruptions in the past, I recall, >but I don't know what the common denominator is. If TDRSS somehow does >it, I'd like to know how. Any plasma has a frequency, called the plasma frequency, at which the electrons & ions in the plasma can oscillate against one another. This frequency is a function of electron density and temperature. I had always thought (I could be wrong) that the blackout on reentry was due to the use of RF frequencies below the reentry plasma's frequency, so the radiation could not penetrate (just as shortwaves are reflected from the ionosphere, or light from a metal). Perhaps the TDRSS lets them use higher frequency microwaves, above the reentry plasma's frequency? Paul F. Dietz dietz@cs.rochester.edu
smb@ulysses.homer.nj.att.com (Steven M. Bellovin) (08/12/89)
If you want some gross speculation, the plasma generated by the shuttle re-entries does not cover the top surfaces. Thus, it's not so much TDRSS that helps as the presence of a receiver above the plasma ball.
tneff@bfmny0.UUCP (Tom Neff) (08/14/89)
My thanks to Peter and Paul [where's Mary?!] for the TDRS/plasma/blackout explanations. The physics sounds a bit strange (why does it matter which side of the transmitter the plasma ball is on?) and I'm not sure how TDRS picks up an omni at that distance, but as long as it works... -- "We walked on the moon -- (( Tom Neff you be polite" )) tneff@bfmny0.UU.NET