Tracking an desending spacecraft from space?

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Christopher - 17 Jul 2003 11:11 GMT

I know that the plasma halo cause by atmospheric friction cuts out
radio contact from a returning space craft i.e. the Shuttle, Apollo
Comand module, Gemini/Mercury/Suyous capsule..., but does it also
block out radar waves/transmission, as radar like radio is just
electromagnetic energy but at a different wave length?

i.e. NASA and the Russian space agency knew which trajectory they
would be returning, but could they be able to track the desent during
the radio 'blackout' phase if they didn't know which desent path the
craft was taking. In other words does a dense ionised layer around
the craft block radar signals?

Christopher
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Gordon D. Pusch - 17 Jul 2003 20:32 GMT

> I know that the plasma halo cause by atmospheric friction cuts out
> radio contact from a returning space craft i.e. the Shuttle, Apollo
[quoted text clipped - 7 lines]
> craft was taking. In other words does a dense ionised layer around
> the craft block radar signals?

The plasma "blocks" radio transmission because it is quite a good
REFLECTOR at radio and radar wavelengths --- so far from being
"invisible," the plasma trail sticks out on radar like a sore thumb!

(A rather eerie image I remember from the Columbia disaster was the
loop of the Texas NEXRAD composite, clearly showing the plasma trail
left by the orbiter drifting eastward with the upper atmospheric wind,
long after the orbiter had disintegrated...)

-- Gordon D. Pusch

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Jorge R. Frank - 18 Jul 2003 13:56 GMT

> I know that the plasma halo cause by atmospheric friction cuts out
> radio contact from a returning space craft i.e. the Shuttle, Apollo
> Comand module, Gemini/Mercury/Suyous capsule...,

It only blocks comm in the downward direction (spacecraft-to-ground). The
shuttle can communicate fine during entry by relaying through TDRSS. STS-
107 had intermittent comm dropouts, possibly due to vaporized aluminum from
the left wing getting into the plasma "tail".

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Space Forum / Space Flight / July 2003

Tracking an desending spacecraft from space?