Re: Obs USA 129

Tony Beresford (
Mon, 23 Aug 1999 15:42:00 +0930

At 14:36 23/08/1999 , you wrote:

>Attempted Chandra- CXO, 25867, but could not acquire.  What's its standard 
>magnitude?  Is there a newer, (newer than 99219.38932609), elset?, 
All the existing elsets for CXO from OIG are completely out of date
Jim. Despite the earlier epoch the 99216 one more closely reflects
the orbit, and it hasnt been updated to reflect the last perigee
raising burn. Obviously US SPACECOM isnt tracking the spacecraft,
and providing TLE's to OIG. Just as obviosly nobody else is providing
OIG with TLEs

Jonathon McDowell kindly published an osculating state
vector that does on Seesat and Ted Molczan produced a
TLE from it which was posted on Seesat. Such a process is not really valid.
For lack of anything else here it is again 
Chandra         15.0  4.0  0.0  4.2 d
1 25867U 99040  B 99219.45833333  .00000000  00000-0  00000-0 0    05
2 25867  28.4518 194.1107 8016020 271.0755 180.3370  0.37800574    01

As the SDP4 orbit propogator wont handle the larger lunar pertubations
if nothing else and its mixing orbit propogators to use the TLE in
Mike McCant's highfly. 
George Lewis started the process to get  Chandra orbit on JPL's horizon system,
which has the chandra approval. I patched in a value of mag 4.2 into
highfly.mag  file . This gives around mag 15.5 at the apogee of 140,000Km.
So visual sighting at apogee seems to require a rather large aperture.
On the other hand 30cm Lx-200 telescopes routinely image mag 18 asteroids
with CCD imagers with exposures of a minute or so.
Tony Beresford