Re: Analysis of Fading of TIPS Tether

From: Willie Koorts (
Date: Fri Aug 02 2002 - 04:05:33 EDT

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    On Thu, 1 Aug 2002, Ted Molczan wrote:
    > The main finding is that the fading began soon after deployment and
    > continued for about 500 days. It was rapid at first and then became more
    > gradual. There has been little additional fading over the 2.5 years
    > ending March 2002.
    > The apparently immediate onset of fading, initially rapid, then more
    > gradual, suggests to me that the cause was darkening of the tether due
    > to exposure to sunlight.
    Thanks Ted for raising this very interesting issue, particularly for the
    analysis, putting our suspicions into real numbers, proving they were
    Although fading presents one logical explanation, I've been intrigued by
    tether visibility since the first ones were launched.  Without consulting
    the SeeSat-L archives but from memory (shaky ground, I know! ;-) at the
    time of SEDS and TSS, I remember the lengthy discussions we had about just
    how it is possible to see such a thin cable at such a distance.  I don't
    think we ever got a logical conclusion?  We have since taken it for
    granted that they are visible and stopped asking why.
    If I can come back to this question, one probable explanation at the time
    was ionization.  It was suggested that there is interaction between the
    tether and the few remaining atoms/molecules in space.  This theory was
    more valid for the first low flying tethers but when TiPS was put much
    higher, this theory was not supported much any more.
    Other discussions about possible "discharges" around the tether still
    interested me since, part of my work has to do with high vacuum systems
    where enemy number one is "outgassing" of materials.  We go to great
    lenghts to avoid using materials with high outgassing inside high vacuum
    systems - even brass, because of its zinc content, is to be avoided let
    alone plastics, PVC's, etc. which are absolutely horrible.
    One reference I picked up doing a search of the archives was  where Dave English referred
    to the last paragraphs on
    where it says:
    "Another part of the PEST experiment will be checking out an oddity noted
    during the second Tethered Satellite System flight. "We noticed something
    strange in the characteristics of the RM400 conducting thermal coating
    used on the tethered satellite," Stone explained. "The data suggested
    tremendous emissions of secondary electrons due to particle bombardment or
    solar ultraviolet or both. We had no reason to suppose that the RM400
    coating would behave in this way before the TSS mission."
    So, whether its electrons or molecules, its still a possible theory of
    tether visibility to me.  The fading effect supports it even more since,
    as with outgassing in a high vacuum system, if you could afford to wait a
    long enough, your outgassing problems will gradually go away.
    Ever wondered why that "new car smell" goes away after some time?  That's
    when most of the plastisizers in the plastics have evaporated.  Now you
    know what causes that oily layer on the inside of the windows when your
    new car had been parked in the sun.  Sorry, I'm getting off topic.
    Thanks Kevin for the warning about ProSEDS - please keep us updated.
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