Confusing one sat for another
Walter Nissen (dk058@cleveland.Freenet.Edu)
Fri, 13 Oct 1995 10:28:07 -0400
SeeSat-L subscribers,
Mike and I have had an e-mail discussion for a couple or more years, at a
very low frequency, regarding the possibility of an observer confusing the
identifications of two unrelated satellites. I.e., how likely it is that
an observer can know that a certain satellite is due at a certain point at
a certain time, look there, find a satellite and be mistaken about its
identity, i.e., think that he has found his target when actually he has
found a different satellite. Both of us agree to a great extent about
this; we both know it is possible; we both know it is unlikely. Still we
have taken somewhat distinct positions, with mine being that if I haven't
done it yet, I surely will; and his being that it is very unlikely.
It may be that our differing views reflect our different observing
equipment. As I understand it, Mike usually uses a 10" with setting
circles. I usually use 7x35s with a 10 degree field of view. I suppose
Mike's field of view is smaller.
Perhaps another difference is in our ability to focus on the task at hand.
I have in my imagination an image of Mike, clear-headed, observing from an
isolated site with few distractions. I generally observe from a much more
complicated environment, both physically and mentally.
Perhaps our willingness or ability to spend time updating elsets, or
automating the update process plays a role, because a reluctance to
believe that a satellite could be "that" early or late can help spot a
problem.
Over the years I have had some close calls, with some clue alerting me to
a troublesome situation, such as accidental comparison of the lines for
two objects in the QuickSat output (unfortunately, it is my experience
that usually two similar lines will be separated by an object or objects
on a very different trajectory), the appearance of two objects where I
expected one, a large magnitude discrepancy, a large speed discrepancy or
unexpected flashing (or its absence). Of course, I have no way to
directly count the occasions when I have been confused and have not
detected it.
All this has been a preface to the message below.
Mike,
Last night I experienced my most dramatic identification confusion yet.
About 951012 102403 I was looking for
C* 1805
1 17191U 86097A 95284.48270344 .00000306 00000-0 32584-4 0 6520
2 17191 82.5060 86.4279 0016844 128.6200 231.6527 14.85419345477558
which is one of the members of the C* 1933 family of sometimes irregular
flashers, when I visually acquired an object with a suitable appearance.
I proceeded to follow it for close to 3 minutes. It was steady. I timed
the acquisition and loss of "signal" accurate to a few of tenths of a
second. Had it not passed an obstruction I wanted to measure, that would
have been the sum and substance of the observation. I put the
observations in my log and the matter might have ended there.
However, when I calculated its altitude at 951012 102647.66 from its
elset, I computed a value about 12 or 14 degrees lower than what I
expected based on what I observed. This discrepancy motivated me to check
for candidates which might have confused me.
M* 1-2
1 08026U 75064A 95283.93384962 .00000022 00000-0 56358-5 0 5788
2 08026 81.2734 85.8023 0022454 249.6581 110.2176 14.08759057 40414
popped right out, because it followed a very similar path and was only a
half minute ahead of C* 1805. I will look for elsets from closer to the
time of the observation in a couple of days, but I fully expect that they
will confirm the fact that I was confused by M* 1-2.
I don't claim that I was careful enough, nor that I should not have been
more careful. I would happily blame morning metabolism for the problem.
I just claim that we all have to be very careful to avoid failing victim
to such confusion.
On an almost completely different subject, I concur with your tentative
conclusions about M* 1-10. Good job. I fully expect that your
identifications will be confirmed by subsequent investigation. I will
observe when possible, and encourage others to do so.
Cheers.
Walter Nissen dk058@cleveland.freenet.edu 216-243-4980
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A bad plan is better than no plan at all.