Update on Shuttle/C895r encounter

Matson, Robert (ROBERT.D.MATSON@cpmx.saic.com)
Fri, 11 Dec 1998 16:06:22 -0800

An update on the Shuttle/Cosmos 895r encounter early Saturday morning:

I'm posting this message here in case someone can get a message to
NASA and/or astronauts in time.  Since the last Shuttle reboost has
been cancelled, there will be a fairly close fly-by of the Cosmos 895
rocket body (R/B) early Saturday morning, Dec. 12th, at around 3:05:37 UT.
The booster is predicted to come within 15 km of the Shuttle/ISS complex
about 5 minutes after sunrise on board (i.e. both C895r and the Shuttle
will be sunlit).

Where should the astronauts look?  I've rerun the numbers using the
very latest Shuttle elements, and a 1-day fresher TLE for C895r.  From
Cosmos 895 R/B will come out of shadow around 3:02 UT, between Cygnus
& Aquila at RA 20h 12m, Dec 25.7 deg.  The magnitude will only be about 6.4
at this time.  By 3:03 the range is down to 1000 km, and the brightness has
increased to mag 5.7.  By 3:04 the range has dropped to 625 km, visual
magnitude 4.7, and the rocket body will be slowly moving north.

At 3:05, the range is 240 km, magnitude 2.6.  Motion is definitely
noticeable now.  30 seconds later, the range has dropped by almost a
factor of 5 to 51 km.  The satellite should be zipping across the long
axis of the Northern Cross (Cygnus).  At 3:05:32 it passes close to
Delta-Cyg, moving at more than 3 degrees per second at magnitude -1.
In a blink, it speeds thru Draco and the Little Dipper, peaking at
magnitude -3.5 at closest approach (~14 km range).  A few seconds later
it will have dimmed and slowed noticeably as it heads off to the dim
stars of Cancer.

Because of the extremely close range, and the resulting high parallax,
even small changes in the predicted satellite positions greatly alter
the apparent trajectory at close approach.  However, the start and end
points will not change significantly in the short time remaining.  --Rob