RE: FENGYUN 1C satellite and debris in 3D

From: Bob Christy (rdc@zarya.info)
Date: Thu Jan 25 2007 - 18:45:42 EST

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    FY-1C was an imaging meteorological satellite in a near-circular orbit so
    the outcome of an impact at perigee would be very similar to that of an
    impact at apogee.
    
    The general orbit of fragments from a collision is dictated by the vector
    sum of the velocities of the two objects. There will be a scatter of values
    because fragments fly off in all directions.
    
    Using "forward" and "front" to refer the direction of travel for one of the
    objects (let's say a satellite in circular orbit), logic says to me:
    
    1 - an impact from in front will result in a majority of fragments having
    elliptical orbits with apogees near to the height of the original orbit and
    at the impact location,
    
    2 - an impact from behind will result in a majority of fragments having
    elliptical orbits with perigees near to the height of the original orbit and
    at the impact location,
    
    3 - an impact from above will result in a majority of fragments having
    elliptical orbits with perigees lower than the original satellite and
    further forward forward round the orbit relative to the point of impact -
    apogees will be higher than the original satellite,
    
    4 - an impact from below will result in a majority of fragments having
    elliptical orbits with perigees lower than the original satellite but
    backwards round the orbit relative to the point of impact - apogees will be
    higher than the original satellite,
    
    5 - an impact from the side will result in a majority of fragments having
    orbits similar to the original satellite but with a changed inclination -
    the actual change will depend on the side that was hit and whether the
    satellite was on a northbound or southbound orbital leg.
    
    The picture could also be clouded if the impactor itself produced a
    significant number of fragments with orbital velocity, but its trajectory it
    is highly likely to have been sub-orbital so fragments are unlikely.
    
    There would need to be published orbits of a lot more fragments than we have
    seen so far before we can draw meaningful conclusions - and then anyone
    wanting to publish those conclusions would need authorisation through
    SpaceTrack (!). 
    
    The small quantity of new objects listed so far is well short of the
    "thousands" of fragments reported when the news story first broke. I have
    only managed to draw one conclusion from them.
    
    Bob Christy
    
    
    > -----Original Message-----
    > From: Tom Wagner [mailto:sciteach@mchsi.com] 
    > Sent: 25 January 2007 02:13
    > To: SeeSat-L@satobs.org
    > Subject: FENGYUN 1C satellite and debris in 3D
    > 
    > I found a way to place a maximum of 17 satellites into a free 
    > planetarium 
    > program called Celestia . I uploaded 17 recent TLEs for the 
    > FENGYOU 1C 
    > satellite and debris. Screen captures can be seen at the 
    > following URLs.
    > 
    > 
    > 
    > The first two are set up for cross-eyed stereo viewing. All 
    > show the debris 
    > and the original satellite as 200 km diameter spheres. Can't 
    > miss them that 
    > way! The original satellite, I believe that's what the TLE 
    > that didn't say 
    > debris was for, is labeled. It's interesting to see how the 
    > inclination of 
    > one of the 16 pieces has changed from the original orbit. 
    > There may be 
    > others like it too.
    > 
    > 
    > 
    > http://i138.photobucket.com/albums/q262/IowaTom/FENGYUN1CDebris.jpg
    > 
    > http://i138.photobucket.com/albums/q262/IowaTom/Fengyun1Corbits.jpg
    > 
    > 
    > 
    > If anyone wants help in learning how to see two images at 
    > once, one with 
    > each eye, feel free to ask. I've trained many people how to do it.
    > 
    > 
    > 
    > These last two shots show two different perspectives.
    > 
    > 
    > 
    > http://i138.photobucket.com/albums/q262/IowaTom/sideview.jpg
    > 
    > http://i138.photobucket.com/albums/q262/IowaTom/inclinations.jpg
    > 
    > I wonder if it got hit when it was at its perigee?
    > 
    > 
    > 
    > Tom  Iowa  USA 
    > 
    > 
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