Re: Delta 2 R/B listed

From: Frank@reednavigation.com
Date: Fri Sep 06 2013 - 22:13:01 UTC

  • Next message: Waldo Kitty: "Re: A unusal satellite (?)"

    Bjorn Gimle, you wrote:
     "In this case, the Epoch (10043.72050712 = day 43 of 2010) is extremely old.
    When the date is more realistic, and the orbit is nearly circular, I use 0.05 / ndot2 (0.02340000) as an estimate of remaining days in orbit (ie about 2 days)"
    
    Thank you. I'm trying to understand two things:
    1) Why is this satellite still listed in a current set of TLE data? Is this a heavens-above anomaly, or is it happening somewhere else? 
    2) Would the calculation that you suggest combined with the orbital epoch provide a good test to exclude a satellite? That is, if Epoch+0.05/ndot2 yields a date before today's date, should it be safe to tag it as "probably decayed" (for eccentricity<0.2 maybe)? And if the difference between that calculated decay date and today's date is, let's say, greater than ten days (a significantly larger time difference, in other words), is there any way that it might not yet be decayed? I understand your point about higher eccentricity orbits so might it be safer to use a test based on calculated perigee? Maybe if the perigee is below 50km I can safely drop it from a prediction list??
    3) What is the maximum age that we should consider even remotely acceptable for a TLE set for current predictions? 
    
    -FER
    
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