Re: Lunar Geosynch orbit question !

From: Rick Baldridge (
Date: Wed Jun 27 2001 - 22:42:53 PDT

  • Next message: Paul Gabriel: "obs 28jun 01179.1"

    Jim King wrote:
    > Since the Moon always keeps the same face towards the Earth wouldn't a
    > "lunasynch" sat be at the L2 Earth-Moon Lagrange point?
    Not quite.  L2 Lagrange point is on a LINE with the Sun and the Earth,
    further out than the Earth, with the Moon's orbit well inside.  L2 does NOT
    follow the Moon, therefore, it does NOT stay in-sync with the "far side" of
    the Moon. (Although since L2 is downsteam of the Moon and the Earth, it DOES
    see mostly the "dark" side of the Moon with some small phase being possible,
    and ALWAYS the dark side of the Earth!)  The Moon is only downstream AND
    in-line with the Sun and Earth at Full Moon. (For purists, I won't get more
    technical than that!)
    > Anybody know the distance from the Moon of the Earth-Moon L2?  Would a sat
    > Earth-Moon L2 ever be visible from the Earth?
    L2 is 1.5 million kilometers from Earth, away from the Sun side, according
    to a nice graphic that can be seen in this week's AVIATION WEEK and Space
    Technology Magazine (June 25, 2001 p. 85) and at the link below. The
    article, which neatly describes the MAP Mission (Microwave Antisotropy
    Probe) that is a complement to the COBE spacecraft with higher resolution,
    is destined for the L2 point with launch scheduled for June 30th..  The Next
    Generation Space Telescope may also be bound for this point in space.  Both
    spacecraft would be in a somewhat large "halo" orbit around L2, passing well
    north and south of the unstable position.  It would therefore be lit almost
    all of the time (eclipses by Earth's shadow would be rare if non-existant).
    However, a satellite near the L2 point would be exceedingly faint -- not an
    easy target even in a very large amateur instrument.
    A nice graphic of the MAP Mission and its L2 halo orbit can be found at:
    Rick Baldridge
    Campbell, CA
    Unsubscribe from SeeSat-L by sending a message with 'unsubscribe'
    in the SUBJECT to

    This archive was generated by hypermail 2b29 : Wed Jun 27 2001 - 23:15:35 PDT