RE: Lacrosse 5 "disappearance trick" captured

From: Ted Molczan (
Date: Thu Jul 27 2006 - 05:05:39 EDT

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    Marco Langbroek responded to Allen Thomson:
    > > Lacrosse 5 is still doing its odd rapid "disappearance trick"...
    > > 
    > > As has probably been mentioned, the only explanations that seem 
    > > to make sense are that it has a large specular or very black 
    > > surface that hides the main body at certain angles. The specular
    > > surface would hide the main body when it's oriented to show the
    > > observer a view of black space. What that surface might be is a
    > > planar radar antenna or maybe (I don't think so, but maybe) a 
    > > solar panel.
    > It has to be something like that, yes. Back in March I have 
    > reported a number of timings for the "disappearance trick" 
    > too so perhaps it is possible to correlate these to a certain 
    > spacecraft attitude.
    There seems to be some consensus among analysts that Lacrosse's radar antenna
    was dish-shaped. Here is Charles Vick's conceptual drawing:
    To replace the dish with a planar antenna, would be a fairly significant design
    change. Have the observers who take high-resolution images of spacecraft reached
    any firm conclusions on this?
    > Lacrosse 5 clearly is an odd bird compared to the earlier Lacrosses:
    > * it is brighter (visually and photographically);
    > * instead of red-orange it is yellow in colour;
    > * the other Lacrosse-birds don't do the "disappearance-trick"
    >    (instead, they show short flares)
    It is also the first not to employ a frozen orbit.
    Considering that the program must be about 25 years old, it is not surprising to
    see some changes. 
    Ted Molczan
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