RE: DMB Obs Aug 14-15

From: Brierley David (
Date: Thu Aug 17 2000 - 02:24:24 PDT

  • Next message: Russell: "AUG16.OBS"

    > Thanks for the explanation of your post.  I have two questions whose
    > answers may
    > be involved.
    > First, what is the history of your choice of these four Noss
    > satellites?  I
    > haven't looked at your other posts in view of this but I assume they
    > are also
    > observations of the same satellites?
    The NOSS launches are interesting because they all produced three
    satellites which for a few years flew in a formation which looks like a
    triangle from the ground.  There was a leading satellite, a trailing
    satellite following 16 seconds behind, and an outlier.  In the case of
    the type 1 launches, there was another satellite always called A with a
    slightly higher mean motion.  The much brighter type 2 launches have a
    smaller triangle.
    > Second, I see six observations for the first object:
    > > IntlId SiteYYMMDDHHMMSSss  Sss  TCHHMMmm   DDMMm   Mm E
    > > 8401204267500081422175832  010  12173764  +48324   2  5
    > > 8401203267500081422181718  010  12173604  +48495   2  5
    > > 8401206267500081422190931  010  12202443  +68212   15 5
    > > 8401203267500081422203486  010  12013070  +66068   15 5
    > > 8401201267500081422295428  010  12163423  +57481   3  5
    > > 8401201267500081422300646  010  12164100  +62180   1  5
    I think you have misunderstood my posting.  There are three objects
    here, namely 8401204, 8401203, 8401206 and 8401201.  These correspond to
    the leader, 84-12D, the trailer 84-12C, the outlier 84-12F, and 84-12A
    which is currently in the process of slowly overtaking the others.
    > So the observations, presumably of the minutest positions of the
    > object, are 19,
    > 52, 85, 20, and 12 seconds apart.   Not to mention of course that your
    > next set
    > of observations starts 5 minutes later.   How do you physically get
    > this many
    > observations?  Do you have a single skychart printed out with
    > landmarks already
    > planned for marking the positions?  You have a stopwatch, the chart
    > and a pen, a
    > light, and a set of binocs, at least.
    I use the star charts from Atlas Coeli by Becvar, glued onto sheets of
    cardboard.  Since it's rarely possible to observe a satellite south of
    -25 deg Declination from the UK, there are only 11 charts.
    Before observing, I make a schedule of the satellites I plan to observe
    at the head of a sheet of paper.  From the schedule I mark the tracks of
    the next batch of satellites on the appropriate charts in pencil.  Then
    I go in the back garden (US yard), and sit in a deck-chair with the
    charts on the ground beside me.  Binoculars, split-action (Casio)
    stopwatch, red torch and pencil complete the equipment.  The stopwatch
    runs continuously, showing a time within a few seconds of UT.  I can
    make two timings (a split time and a lap time) before having to read the
    I find a position in the sky where the first satellite is going to pass,
    and wait for it to arrive, counting seconds to the predicted time to try
    and avoid being distracted by an early stray.  When the satellite passes
    a memorable star or pair of stars, I make a timing.  I may follow it for
    30 secs or so and repeat the process.  I then make little sketches on my
    schedule of the relevant stars and where the satellite was in relation
    to them, and record the times.  This takes about 20 seconds, and then
    I'm ready for the next satellite.
    In the case of 84-12D and C, I was able to use the same star group.  I
    had memorised where F would be a minute later, and in fact got a
    position on it 52 seconds later.  I've discovered that the third
    observation is NOT of 84-12C and may be a stray.  84-12A came along 9
    minutes later, not 20 seconds as you surmise.
    >     Do you have three arms?  :-)
    No, but I have lots of practice.  I started using binoculars and
    stopwatch in 1962.  Also I have two deckchairs so that I don't have to
    keep moving them around the garden.
    > How on earth do you get all this on the night in the light of a full
    > moon?
    By using 20x80 binoculars which I can usually hold steady enough with
    the chair supporting both elbows and my head.  And by being fortunate
    enough to live in a part of the world where winds between SW and NW
    bring nice clean air off the Atlantic.  The limiting magnitude for
    satellites was about +8.5.
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