Re: What's slowing down the two Voyagers?
From: Jonathan Silverlight (jsilverlight_at_spam.merseia.fsnet.co.uk.invalid)
Date: 07/12/04
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Date: Mon, 12 Jul 2004 18:38:02 +0100
In message <ROhHMBAXQ57AFwxi@econym.demon.co.uk>, Mike Williams
<nospam@econym.demon.co.uk> writes
>Wasn't it dave schneider who wrote:
>>henry@spsystems.net (Henry Spencer) wrote in message
>>news:<Hzrzu9.318@spsystems.
>>net>...
>>> In article <2jttleF15bjesU1@uni-berlin.de>,
>>> Benign Vanilla <BVremove@tibetanbeefgarden.com> wrote:
>>> >> Even the biggest dish antennas are nearing the limits of picking up
>>> >> Voyager's weak and distant signal...
>>> >
>>> >I wonder why we would not launch some intermediate satellites to act as
>>> >repeaters. Seems they could be light, fast and cheap and extend the life of
>>> >these other missions.
>>> >What are the complexities?
>>>
>>> Mostly, that the idea doesn't work very well. The problem is that a relay
>>> satellite halfway to (say) Voyager 1 will be hearing a signal only four
>>> times as strong as what Earth is hearing... and the antennas and receivers
>>> on Earth are much more than four times as good as the ones on a cheap,
>>> lightweight relay satellite.
>>
>>At what point would it be worth it to add a long leg to the net of
>>earth-based dishes by placing a dish at, say, a Lagrangre point?
>>
>>I don't think this would pay much in terms of making the effective
>>antenna any larger than building another eb dish, and synchronizing
>>things would probably be a bit fussy.
>>
>>My take is that the advantage would be that this antenna would be
>>available for long stretches because diurnal pointing issues wouldn't
>>be involved. There would be occultations occuring slightly later or
>>slightly before the eb antennas experience them.
>>
>>In fact, this sort of application would probably only happen if there
>>was another reason to populate that position and the dish could be
>>piggybacked on that for relatively low cost.
>
>Well, yes. A modest sized dish at a Lagrange Point would be wonderful
>for radio astronomy, because the resolution increases with the size of
>the baseline. At present the synthetic apertures we can construct are
>limited to the size of the Earth. Placing an antenna at a Lagrange point
>increases the baseline by a factor of 30.
>
Presumably we're talking about the Earth-Moon Lagrange point. I know
dishes have been placed in Earth orbit for VLBI, but aren't you going to
have problems with the fact that your Lagrange dish is in some horrible
looping orbit around its nominal location? The O'Neill colony fans have
done work on this.
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