Newsgroups: sci.space.history
From: henry@spsystems.net (Henry Spencer)
Subject: Re: Apollo 11 Photos-From above
Date: Tue, 23 Jan 2001 22:19:44 GMT

In article <94knu0$8qp6$1@newssvr06-en0.news.prodigy.com>,
Steve Jahn <f15eagle@prodigy.net> wrote:
>Does anyone know if there have been photos taken from Earth based or
>Satelite base cameras that have photographed the landing site recently. With
>the power of cameras and lenses increasing daily, I would think this would
>be very easy to accomplish.

Fundamental physics and the wave nature of light severely limit what can
be done.  To a crude first approximation, the diffraction limit on optical
resolution is distance times wavelength divided by optics diameter; no
amount of cleverness will get you past this.

To get, say, 1m resolution (enough to see the overall shape of the LM and
maybe the rover, and make out things like the ALSEP instruments as dots)
from 400,000km away using light wavelengths around 500nm, you inherently
and inescapably need optics circa 200m across.

While there are people looking at building really enormous telescopes, and
others experimenting with combining multiple telescopes in the same way
the radio astronomers do, neither approach has produced any operational
hardware yet.

The *only* way to get useful images of the Apollo landing sites is to
take several zeros off that distance.  There have been only three lunar
orbiters in the last thirty-ish years, and two of them had no optical
instruments at all.  The third (Clementine) had only very small optics,
and some awkward constraints on how its highest-resolution camera was
used, and got no striking images of the landing sites.  (Note that Mars
Global Surveyor has not succeeded in resolving any of the Mars landers,
even as dots, despite several attempts... and its camera is much bigger
than the ones on Clementine.)
--
When failure is not an option, success  |  Henry Spencer   henry@spsystems.net
can get expensive.   -- Peter Stibrany  |      (aka henry@zoo.toronto.edu)