[ExI] Arkyd

Alfio Puglisi alfio.puglisi at gmail.com
Tue Jun 4 18:56:54 UTC 2013

On Tue, Jun 4, 2013 at 7:41 PM, Kelly Anderson <kellycoinguy at gmail.com>wrote:

> On Sun, Jun 2, 2013 at 1:26 PM, Alfio Puglisi <alfio.puglisi at gmail.com>wrote:
>> I agree it's most likely a PR move. By the way, I am a little surprised
>> by how small the Arkyd telescope really is. A diameter of 20 cm? I had
>> previously read most of Planetary Resources' web site, but the size of the
>> Arkyd had escaped me for some reason. Being so small, it will have a
>> resolving power of about 1 arcsecond - about the same as you can get on the
>> ground ! Basically, you don't need to send such a telescope in orbit,
>> except maybe to gain some wavelength coverage. But for the same $1M, you
>> could buy hundreds of commercially available 20cm telescopes. So yes, it's
>> PR and PR only. Maybe it's useful as a training system to remotely operate
>> stuff in orbit. Whatever, I'm a bit disappointed.
> But being in space, you don't get the diffraction of the atmosphere...
> Shouldn't a 20cm space telescope be able to see much more than one on the
> ground?

No, not really. The atmosphere will smear a point-like source into a blob
about 1 arcsecond wide, or maybe half of that in a really good site. A 20
cm telescope can't resolve anything smaller than 1 arcsec, so it won't gain
any resolution in going out in space. Since resolution scales linearly with
the telescope diameter, a bigger one would gain a lot (the Hubble space
telescope is only 2.4 meters, which counts as "small" in modern astronomy,
but up to recent times it was the sharpest eye on the sky).
Compared to a ground-based 20cm telescope, the Arkyd will gain a factor of
about 4 in efficiency, because you can observe for 24 hours instead of 8
and the weather is always good, plus a factor of nearly two in sensitivity
because the atmosphere does scatter some light away, and some UV
wavelengths that the atmosphere blocks.

Besides, this is all about involving schools and other organizations in
> science. Just for that reason, I think it's a great idea. Science has a bad
> reputation among too many people.

I agree it's a good idea from this angle, it's just that I see it as a side
show compared to the main one.


> -Kelly
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