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Re: [APML] OT: Satellite orbital taxonomy
depending on orbit height, that glass is gong to be trashed pretty quickly from on orbit debris or in higher orbits from various particles from solar wind to just small debris in the universe.
>>> rybskip@idcnet.com 5/24/02 2:39:11 AM >>>
Dear All,
Matt was spot-on concerning the stealth technology. And he was almost
entirely right about the IR luminosity. Why?
The satellite hid behind a large sheet of very clean, seamless, flat
glass. It would not have been antireflection-coated, otherwise it would
not have served its primary purpose of hiding the satellite from pulsed
radar from below. Under specific Sun-plate-Earth geometry, the Sun would
be reflected toward the observer from the entire sheet of glass: it was
visible to the unaided eye when glinting.
The satellite system was hot in the IR because it had a finite
temperature and radiated in all directions, including through the glass.
Any dust or other material attached to the front surface (facing
Earth) would be illuminated by the Sun and would be clearly visible at some
level to Earth-bound observers (as it was to me, though it took a 2.7 meter
telescope and a pulse-counting, panoramic detector to do it).
Paul
>At 11:57 PM 5/23/2002 -0400, Matt BenDaniel wrote:
>>At 11:19 PM 5/23/2002 -0400, Matt BenDaniel wrote:
>>>At 08:38 PM 5/23/2002 -0500, Paul M. Rybski wrote:
>>>> If you wanted to look down on an enemy's installations 24/7 but
>>>>didn't want him to successfully detect you by diffuse reflection off of
>>>>satellite surfaces or by Kelvin retroreflection off of your solid state
>>>>detectors when he painted you with a pulsed laser and looked for
>>>>reflections synchronously at the time of the expected return pulse,
>>>>what would you hide the satellite behind? (Hint: What would make you
>>>>invisible most of the time but glint brightly at only one orientation
>>>>with respect to you and to the Sun?) (Another hint: This object was
>>>>the brightest infrared source in the sky -- after the Sun, of course --
>>>>at 10 microns. How could it be so bright in the IR but nearly
>>>>invisible in the visible?)
>>>
>>>Use highly reflective flat surfaces. A cube shape would do it. You must
>>>keep the faces from pointing straight down to Earth. The satellite is
>>>bright at 10 microns because there is a 10 micron background glow in
>>>every direction.
>>
>>No, no, the last part of my answer is wrong. If it reflected background
>>radiation it would look just like the background. It must be blackbody
>>radiation.
>
>Doh. No, that can't be it either. Blackbody radiation at 10u would not be
>intense. How does the satellite downlink? 10u RF (highly encrypted of
>course)?
>
>--
>Matt BenDaniel
>matt@starmatt.com
>http://starmatt.com
>
>
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________________________________________
Paul M. Rybski, Ph.D.
Associate Professor and former Chair, Dept. of Physics, and
Director, Whitewater Observatory
University of WI-Whitewater
Whitewater, WI 53190-1790
Office FAX: (414) 472-5633
Email address: rybskip@uww.edu
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