Henry Spencer wrote:
>
> On Sun, 28 Jul 2002, Alex Fraser wrote:
> >
> > You of course would need to have
> > antennas all the way around the planet as it seems to spin on a daily basis.
>
> Continuous coverage is nice, but for a brief asteroid encounter, you can
> plan the encounter so it's within view of your main ground station.
In fact, enough flash memory to hold a hundred or so megapixel 24-bit
images need cost only a few hundred dollars and weigh under 100 grams --
so you time your encounter when you can (with short notice, you'll have
to take what you can get) and download the images when your antenna can
see the spacecraft. Also lets you avoid the mass and reliability issues
of a movable antenna; you aim the entire spacecraft for imaging, and
then reorient for data transfer. You'll only need to download once in
any case, since the encounter for a flyby of a NEO will be a one shot
opportunity. And don't bother with solar panels; you can do what you
need with lithium polymer batteries charged on the ground, and they
don't care where the camera or antenna are pointed.
BTW, this kind of flyby would be a great simulator of the ability to
deflect an asteroid in the time between discovery and impact -- a
capability mankind very strongly needs to develop.
Oh, BTW, there's now a VGA digital camera the size of a credit card, and
about three times as thick; megapixel class cameras, OTS for under $500,
could be stripped of case and flash (but autofocus left in place) and
come in close to 50 grams without battery. It may be possible to reduce
both price and weight starting from commercially made boards and
building up instead of stripping down from a finished consumer product.
--
Love wealth above life itself, and starve in splendor.
-- Elvish proverb
Donald Qualls, aka The Silent Observer NAR # 70141-SR Insured
Rocket Pages http://silent1.home.netcom.com/launches.htm
Telescope Pages http://silent1.home.netcom.com/astronomy.htm
Lathe Pages http://silent1.home.netcom.com/HomebuiltLathe.htm
Opinions expressed are my own -- take them for what they're worth
and don't expect them to be perfect.
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