Re: Failed Orbcomm obs

Craig Cholar (3432P@VM1.CC.NPS.NAVY.MIL)
Mon, 29 Dec 97 18:51:35 PST

Ron Lee remarked about the run of bad luck he's been having in attempting
to see the new Orbcomms.  Ron, you're not alone.  I've tried to see two
morning passes, under absolutlely clear skies, and only saw the Pegasus
rocket, 25120/97084J, which was easily seen with binos on a 41 deg.
pass in the south.   For the Orbcomm cluster, I tried using my newtonian
scope, positioning it where Skymap predicted they would pass through
(roughly Az 160 El 25 for both passes).

I now think I missed them because I misinterpreted the Skymap plot of the
region of sky between Virgo and Corvus.   Skymap shows two stars in the
mag 3 range only a few degrees apart from each other, but out in the
field I could only readily see one of the pair at one power.  Here
are the stars, as described by Skymap:

SAO #181695  Mag 3.5  RA 13h 29m 35.76s  Dec -23 16' 8.8"
SAO #181543  Mag 3.3  RA 13h 18m 48.38s  Dec -23 9' 33.0"   gamma Hya

They are about 10 deg. below Spica, halfway between Spica and Corvus.  I
just found out using Redshift that the first star is variable, with a
magnitude variation of 8.5!  No wonder the current sky isn't matching
the plots! (that sound you hear is my head banging against the wall)

I think I was accidently using the wrong star as my starting point to
position my scope before manually slewing to the part of the sky where
the Orbcomms were expected.  As it turns out, they passed about a few
degrees outside my FOV both mornings, but I began scanning with binos
when it became apparent the first few weren't showing up on time;  no
luck.  I should note that my SE horizons are partially obscured by
trees, so I could only scan a portion of the predicted tracks.  With
clearer horizons, I might have picked them up.

There are other stars in Skymap plots with misleading magnitudes, such as
the variable star that shows up in Corona Borealis that I don't recall
ever being obvious.  Too bad these variable stars aren't color coded
somehow, to make them stand out from the others.

Getting back to the Orbcomms, if you're like me and enjoy seeing what
satellites actually look like, check out the photos and an artist's
rendition of the Orbcomm satellites at their website.  The Orbcomms
have an interesting configuration I've never seen before.

Small thumbnail graphics are at:
or just go directly to the 800x600 42k JPEGs:  photo of sat  artist's rendition   undergoing assembly

The elsets are now in the OIG thirty.tle file, with the designation
FM-5 through FM-12, and the K object is called HAPS.  I wonder what
the abbreviations FM and HAPS designate?

The first cluster of five are currently separated by gaps of 6, 26, 10,
and 31 seconds.  The second cluster of three arrives about 3 minutes
later, with 23 and 21 second gaps between them.  The rocket and HAPS
aren't close at all to the Orbcomms anymore.

I hope everyone had a pleasant holiday.  Here in California, until today
I've had totally cloud free days and nights for about a week.  So much
for El Nino.  I bagged quite a few new debris objects and obscure Cosmos
satellites during the clear spell, but those Orbcomms were frustrating.

 Craig Cholar    3432P@VM1.CC.NPS.NAVY.MIL
 Marina, California
 36 41 10.3N,  121 48 17.9W    (36.6862, -121.8050)      UTC -8