Re: (Bulge) Orbital Mechanics Question.

From: Bjoern Gimle (b_gimle@algonet.se)
Date: Tue May 23 2000 - 13:42:13 PDT

  • Next message: JAY RESPLER: "Re: elements from OIG, etc"

    > Is there is an effect due to the Earth's equatorial bulge? When the
    > satellite is at the extremes of its angular track does the bulge pull it
    > into more of an equatorial orbit? Obviously this will be a very small
    effect
    > because the earth is almost spherical - but is it significant for LEOs?
    
    The largest effect of the bulge constantly pulling towards the equator plane
    is the precession of nodes: A satellite will have its next equator crossing
    less than 180 degrees from the previous (disregarding Earth's rotation), ie.
    with inclination < 90 degrees the nodes will precess west, > 90 degrees they
    will precess east. The effect is largest for a LEO with a low inclination,
    but measured cross-track it is largest for i=45 deg.
    ISS             20.0  4.0  0.0  2.5 d   70       342 x 333 km
    1 25544U 98067A   00131.47902778  .00059387  00000-0  34950-3 0  6284
    2 25544  51.5844 331.8932 0006529 167.2015 212.0047 15.77600877 84019
    ISS             20.0  4.0  0.0  2.5 d   70       341 x 332 km
    1 25544U 98067A   00134.16383102  .00070901  00000-0  40876-3 0  6387
    2 25544  51.5842 318.0107 0006443 178.7508 340.7746 15.77992122 84435
    
    (331.8932-318.0107)/2.3152 days =5.9962 deg/day; or about 550 km cross-track
    per day!
    
    
    -- bjorn.gimle@tietotech.se (office)                         --
    -- b_gimle@algonet.se (home)  http://www.algonet.se/~b_gimle --
    -- COSPAR 5919, MALMA,    59.2615 N, 18.6206 E, 33 m         --
    -- COSPAR 5918, HAMMARBY, 59.2985 N, 18.1045 E, 44 m         --
    -- SeeSat-L / Visual Satellite Observer Home Page found at   --
    -- http://www2.satellite.eu.org/satintro.html      --
    
    
    
    -----------------------------------------------------------------
    Unsubscribe from SeeSat-L by sending a message with 'unsubscribe'
    in the SUBJECT to SeeSat-L-request@lists.satellite.eu.org
    http://www2.satellite.eu.org/seesat/seesatindex.html
    



    This archive was generated by hypermail 2b29 : Tue May 23 2000 - 14:33:58 PDT