TiPS Obs 051197

jamesv@softcom.net
Sun, 11 May 1997 00:20:47 -0700

As part of Mike McCants' and Craig Cholar's discussion about TiPS elsets,
Mike wrote:

>I have accurate observations from Russell Eberst and David Brierley
>on 4 nights from April 7 to 17 and the 97067 elset was in error
>by only 2 seconds (after 40 days).  The drag term on the tether
>seems to be amazingly stable.
>
>Here is an elset for the next 40 days.  :-)
>
>TiPS          
>1 23937U 96029  F 97107.40770066 0.00000285  00000-0  35692-3 0    00
>2 23937  63.4304  94.1625 0024001   0.1002 359.8998 13.63930668    09

I observed TiPS tonight with a 60mm refractor at 33x.  Timed its passage by
an SAO catalog star in Draco (16h00m18s +58d56m, 8.0 mag, J2000).

TiPS position: RA 15h 59m, Dec +58.9d 
Time: 04:31:48.6 UT May 11, 1997

Using SGP4, the above elset predicted 16h 01.1m, +58.8d at 04:31:48.  

So, I confirm that the above elset is "amazingly stable" -- the elset at
23.8 days old is less than one second off.  The actual track was close too;
TiPS was about 0.1 deg to the west of the predicted track.  (I fixed that
by tweaking the RAAN down to 94.0850 instead of 94.1625).

The latest elset on the TiPS homepage at NRL has this elset:
(http://hyperspace.nrl.navy.mil/tips/tips.els)

TiPS(NRL)          
1 23937U 96029  F 97129.48611111 -.00000184  00000 0  -2297-2 0  0000
2 23937  63.4295  35.6460 0032778 357.9624  51.1837 13.63953135  4258

is good along track (16h 0.0m, +58.9d) but has TiPS a full 10 seconds late
despite being only 1.7 days past epoch.  Making the drag term positive
doesn't help; seems wrong even at epoch.


_______________________________________________________
Jim Varney        jamesv@softcom.net     Sacramento, CA
           121^ 23' 54" W,  38^ 27' 28" N