Re: NEAR Earth Swing-By

Craig Cholar (3432P@VM1.CC.NPS.NAVY.MIL)
Sun, 11 Jan 98 02:44:15 PST

Ron Lee commented on the ability of Randy John's Skysat to predict
the NEAR orbital path.  A few days ago I asked Randy if he knew where
NEAR would be in the sky for the San Francisco bay area (he lives about
a hundred miles north of me), and he showed me how to have Skysat do
the prediction.  Just feed it the following three lines of data as
the TLE file:

1 XYZ KM 98023.30759792       1045.844      -5701.724       3757.666
2                            -3.445125      -7.184133      -9.942337X

Skysat will automatically recognize this elset as a state vector.  When
Skysat displays the 'Command?' prompt, enter: S
Randy said that might help the search logic by turning off the sun check.
It will then ask for a starting UT date and time.  I used 23-Jan-1998 06:43
since that was one minute before the centertime of the NEAR glint for my
location, as determined from the movie.

The next prompt was duration, which I defaulted to 1 hour.
The mininum altitude prompt was next.  I entered 0
For 'Search Text?' I just pressed enter since the elset file consisted
only of the state vector above.

Voila!  Skysat displayed the RA/Dec and Alt/Az, and I used the up/down arrow
keys and PgUp/PgDn to adjust the time and display the track.

For my location approx 100 miles south of San Francisco, here's where I'm
going to look Jan 22nd at 10:44pm Pacific Standard Time:

Alt= 54, Az=302   RA=03h 35m  Dec=47:52

This puts it in Perseus.  Just for fun, I ran Skysat for the location that
the NEAR website says will be underneath the lowest flyover point (Ahvaz Iran),
and Skysat showed a daytime overhead pass very close to the correct time.
For those who want to duplicate that pass, enter these parameters:
Longitude (west)= 311
Latitude= 31.1900
Start date & time: 23-Jan-1998 07:00
Duration: 1 hour  (default)
Minimum Altitude: 0

Randy said to use at least version 0.6 of Skysat.  The latest version is
0.62, available at:
DOS, WIN 3.1, WIN95, Win/NT, and OS/2 only.  If you can't run it, and
want to try seeing the NEAR glint, I can try to run predictions (US only)
if you send me your lat/long, timezone, and the time you think the glint
will occur, based on the movie.  I doubt your altitude is important since
NEAR won't be very near at all <g>.  The distance to my predicted glint
is 17389km (10805 miles).

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