[amsat-bb] Re: On the possibility of imaging AO-40

Fri Oct 16 04:56:56 PDT 2009


Getting an image is clearly possible, but only if you can get a certain
agency known by its initials to do it.  Recall that Skylab, circa 1973, took
some damage on launch.  Some amazing pictures were provided by said agency,
among others, to assess what was needed for repair.  Now imagine 35 years
later.  However, that is not going to happen, and in any case, there is
little to be gained, though of course we are all curious.


-----Original Message-----
From: amsat-bb-bounces at amsat.org [mailto:amsat-bb-bounces at amsat.org] On
Behalf Of Tim - N3TL
Sent: 15 October, 2009 07:58
To: k6hx at arrl.net; amsat-bb at amsat.org
Subject: [amsat-bb] Re: On the possibility of imaging AO-40 with earth

Please see Page 19 of the May-June 2008 issue of The AMSAT Journal. 

Patrick Seitzer, WA4DSR, provided a photo of AO-40 taken by the University
of Michigan's Curtis-Schmidt Telescope at Cerro Tololo Inter-American
Observatory in Chile. Following is information from a University of Michigan
Web page about the telescope:

"The Curtis-Schmidt telescope is a 0.61 meter aperture f/3.5 Schmidt
telescope located at the Cerro Tololo Inter-American Observatory, about 500
km north of Santiago, Chile. This telescope was originally installed at the
University of Michigan's Portage Lake Observatory in 1950, and moved to the
much clearer skies of north central Chile in 1966. 
It is named for Heber D. Curtis, Director of the University of Michigan
Observatories from 1930 until 1942. 
The telescope is dedicated to optical studies of artificial space debris for
NASA's Orbital Debris Program Office at the Johnson Space Center. Projects
include optical surveys for debris and follow-up observations to determine
orbits and photometric properties of recently discovered debris."
If you find the Journal photo, you'll see a field with dozens of blurred
stars and one sharp litttle white dot, which is AO-40.  I believe it's safe
to say that obtaining an image with the detail necessary to try assess
damage is impossible.
73 to all,

Tim - N3TL

From: Mark VandeWettering <kf6kyi at gmail.com>
To: amsat-bb at amsat.org
Sent: Thursday, October 15, 2009 2:57:40 AM
Subject: [amsat-bb] On the possibility of imaging AO-40 with earth bound

> Has there been any serious attempt to take a photograph of the damaged
> bird using ground based optical telescopes while it is in sunlight ?

It's not going to work.  AO-40 just isn't big enough.  For fun,
let's worth through
some of the details.

> With modern telescopes such as
> or similiar and a modern digital camera and a known RA/DEC co-ordinate
> of the satellite at any point in its orbit, it should be possible get
> a fairly decent picture of what is still up there...

> Note RA / DEC are astronomy co-ordinates which should be able to be
> calculated from AZ/EL or TLE, but I may not be able to do it myself.

> We don't need to track it, but just to image it in several consecutive
> frames. From:

Table 1. Nominal Orbit Parameters for AO-40
Orbit Parameter Value
Semimajor Axis (km) 36,245
Perigee Height (km) 1,042
Apogee Height (km) 58,691
Eccentricity 0.797
Inclination (deg) 6.04
Period (hours) 19.1

Let's look at a couple of potential telescopes.  The short tube
refractor that you linked to has an 80 mm (roughly 3 inch) aperature.
According to the Rayleigh criterion, that scope should be able to
resolve angles as small as about 1.5 arc seconds.    At perigee, the
resolving power is 1042000 * tan(1.5 arc seconds), or about 7.5 meters
(or 25 feet).    To increase the resolution by a factor of 2, you need
to to double the  aperature.  To get resolutions down to 1/2 a foot,
you need an aperature 50x larger, or 150 inches.

This doesn't take into account any effects of atmosphere either.
it's actually fairly rare to get sub arcsecond resolution from any
earthbound telescope without using adaptive optics..  This limits the
practicality of high resolution imaging.

Impressive photos of the space shuttle, ISS and HST have been taken
using amateur equipment, but these objects are both closer and an
order of magnitude larger than AO-40.  While we might be able to
measure spin rate and the like by measuring the brightness curve,
actual imaging of the satellite isn't likely.

73 Mark K6HX
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