Re: Admin: policy for reporting high resolutionground-basedimageryofEarth satellites

From: Ralf Vandebergh (ralf.vandebergh@home.nl)
Date: Sun Aug 15 2010 - 18:04:25 UTC

  • Next message: Paul Grace: "RE: Admin: policy for reporting high resolution ground-based imageryof Earth satellites"

    Hi Greg and others,
    
    ''the case of ISS it is possible to confirm real features but for other, smaller, satellites where one does not have many photographs etc to check against there is always the nagging possibility that something may not be 100% correct.''
    
    I Agree with this. Especially interpreting a small satellite on an image is very difficult and a few years ago when my obtained resolution was lower,
    it sometimes even was hard to interprete Space Shuttle images, mostly because you never can compare directly a telescopic image with an image
    taken from the ISS or in case of a satellite compared to a factory-image of the satellite. This is caused due to the shadow and light play with
    often very high contrasts in combination to the limited resolution. 
    
    Therefore, I work with the use of a fixed and 'calibrated' system. I use the same imaging technique (tracking/scale/processing) for the smaller
    objects as for the recognizable objects like the ISS.  This is the best method to get reliable results and in most cases the obtained satellite
    images are very well comparable to known models or other imagery (like the recent Lacrosse images), but in some cases the results can
    be differ and that's interesting and fascinating. When not working using a fixed system, this determination would be impossible.
    
    When some one recently posted his arguments that lot's of the detail in satellite images would be artificial, which he claimed using
    an image of the star Vega, I felt a little frustrated, not in the last place because it was directly linked to my work. Here is why:
    It cost me several years to get at the level to be able to eliminate these problems and in my earlier stages I would have read the 
    arguments more carefully. But now I'm at the level that I overwon these problems but I could have claimed the same things about
    3 years ago when I had less experience if I wanted. 
    
    Some examples:
    
    When I take an image of a small or high satellite in poor seeing, you will in many cases indeed get
    a series of frames with in every frame a deformed object and on every frame the object has a different 
    shape. In such a case you can't claim a certain interpretation of the object as you don't have a 
    reliable comparison. When you image a lot of satellites, you often will be suffered by this case.
    Only solution is to show patience and wait until another opportunity with better seeing.
    
    When I take an image of another mabye bigger satellite in good seeing, I clearly get a series of frames 
    with a fixed position and a fixed shape of the object. For exampe you see a body and a solar panel 
    oriented at the same way in every frame, aside some small variations which are caused by seeing diferences. 
    Now you have good comparison and you can interprete the object at some way. In any case you can claim 
    that the captured details are real, and in that case I report the images of the objects.
    
    So an conclusion can be that patience is one of the most important things in satellite imaging.
    I had a few nice passes of  small and high sat Cosmos 44  from the mid 60's this summer. 
    I would have loved to show here images of it, but some attempts failed due to clouds, and the remaining 
    ones were poor seeing, so I only has frames with no comparison, so I can't claim any interpretion of the object, 
    and I decided to not publish them. Bad luck on this one, but next time better. This happens 5 of the 10
    imaging sessions on satellites but the remaining 5 provide enough satisfaction to continue imaging....
    
    This is a little insight in how I work and I hope this also helps other people interested in the matter
    
    Best regards,
    Ralf Vandebergh
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