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    $\begingroup$ I had thought the problem was a difference in time scales. The Observer Table time is expressed as UT (i.e. UTC), while the Vector Table time is TDB. There is a difference of 69.184 seconds between the two (UTC + 69.184 seconds = TDB). However, when I attempt to compensate, the range problem that you highlight does not disappear. $\endgroup$
    – Bob Werner
    Commented Dec 4, 2022 at 19:44
  • $\begingroup$ @BobWerner It's a mystery! BTW, Delta T at that time was only ~40.455 s. I rediscovered that since Oct 2021 Horizons allows you to specify UT or TT (not just TDB) for vector tables, elements tables must use TDB. $\endgroup$
    – PM 2Ring
    Commented Dec 5, 2022 at 9:22
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    $\begingroup$ One possible source of the difference is the observer tables are "apparent" coordinates, where the vector table are geometric coordinates (e.g. not adjusted for light time, annual aberration, etc). I also noticed the vector table lists the "Center-site name" as "Body Center" for the vector table and "GEOCENTRIC" for the observer table. Since the Earth's center vs center of mass is about 40Km, that would align with different centers being used. $\endgroup$
    – Greg Miller
    Commented Dec 6, 2022 at 13:35
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    $\begingroup$ However, there is another difference between the two table types. By default, Observer tables use UTC, but Vector tables use TDB. But it's possible to explicitly state which time scale you want to use. So the numbers you appended to the end of your question have an extra difference caused by that time scale difference of ~40.455 seconds. $\endgroup$
    – PM 2Ring
    Commented Dec 6, 2022 at 15:19
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    $\begingroup$ Maybe give it a few more days. You never know, someone might have a perfectly logical explanation. $\endgroup$
    – PM 2Ring
    Commented Dec 6, 2022 at 17:16