Re: Iridium spares

From: Sebastian Stabroth (
Date: Wed Feb 13 2002 - 15:07:40 EST

  • Next message: Alan Pickup: "Decay watch: 2002 February 13"

    Hi Rob & list,
    > (spare).  The lower orbit of Iridium 86 would ordinarily have had
    > a faster nodal precession rate; however, in 86's case the impact of
    > the higher inclination (86.52 deg vs. 86.40 deg for Iridium 83)
    > almost exactly cancels the effect of the lower orbit.  This says
    > to me that this is not an accident -- that the inclination is
    > deliberately higher for the spares in order to maintain the RAAN
    > alignment.
    thank you for pointing that out very clearly.
    What remains is the question of how do the sat operators put a spare
    in a different orbital plane if they would have to do it? Since
    maneuvers normal to the plane are expensive I now wonder whether they
    would change the RAAN with a simple maneuver at the apex of the orbit
    or change the inclination more to let a spare drift at a higher rate.
    With the latter one needs at least another maneuver to get back to the
    original inclination and also time, but on the other side it would
    cost less fuel perhaps ...
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