Re: 5 future epoch TLEs

From: Allen Thomson (
Date: Thu Apr 13 2000 - 06:36:54 PDT

  • Next message: David Brierley: "DMB Obs Apr 9-10"

    Back on March 24, John Gardner asked about some TLEs that had future epochs.
    I forwarded the message to Tom Kelso of Celestrak for comment and have now
    received the following reply, which is posted here with his permission.
    AT: This appeared on SeeSat -- could you provide any enlightenment about
    AT: SPACECOM generates "future" TLEs for these high-altitude objects? I
    AT: the topic has come up before, but I don't remember the answer.
    AT: Posting the answer to SeeSat would be desirable -- I can relay it if
    AT: rather not do it yourself.
    > I'm not sure I can answer your question. According to the way NORAD
    > 'describes' the process of generating element sets, this should not
    > What it suggests is that someone is generating these element sets outside
    > of the normal process, which would make the quality of the data somewhat
    > suspect. Whether these are being produced by their own analysts or, more
    > likely, by someone else is hard to say. My guess would be that NORAD is
    > able to track these objects adequately using the current Space
    > Network. These objects are difficult to track with either radar or optical
    > systems. As a result, they probably went to one of the special radar
    > such as Haystack, to do the tracking. Odds are that they have a different
    > process and even use different software to produce the data. While this
    > would make the data suspect, you should be cautious about results for
    > objects anyway since the SGP4/SDP4 orbital model assumes low-eccentricity
    > orbits and so is not intended for tracking objects in these orbits (you
    > violating one of the key mathematical assumptions used to develop the
    > model). I hope that answers your question to some extent, even if it isn't
    > the way you expected. Please feel free to share whatever portions of my
    > response with whomever you'd like.  - TS
    > Dr TS Kelso
    > CelesTrak WWW,
    > E-Mail:
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