Re: Friday Obs. - Galileo IUS Confirmed

Sat, 26 Apr 1997 16:35:51 -0400 (EDT)

On Sat, 26 Apr 1997, Robert Sheaffer wrote:

> Well, if it's in the list, with a proper Standard Magnitude, then the
> prediction programs will generate correct positions with correct
> magnitude when it's at perigee. When it's not, the prediction programs
> will correctly figure out that it falls below the cutoff magnitude,
> and ignore it. Shouldn't the list contain all objects that are
> SOMETIMES quite bright? 
> What exactly IS this thing, anyway? And what are the parameters of
> its orbit?

About six years ago, the Galileo r/b caused quite a stir when it made a 
perigee pass over Texas at about zero magnitude.  At the time, we didn't have
access to the whole elset database, and it took a little while until someone
identified it.  (I think it was someone at JSC with access to the big list.)

I have also seen the Magellan r/b, which is in a similar orbit.  My obs 
wasn't at perigee, but it was quite a satisfying object at 5000 km.

There are a LOT of sometimes-bright objects in GTO, most notably the Centaurs
and the IUS's.  They are (generally) left out of the selected elset lists
because there are so many, and each one is only occasionally bright, 
since it has to be very near perigee (only tiny fraction of each orbit),
perigee has to fall near the terminator (it often doesn't), and the perigee
latitude has to be near observers (for US observers, it is often too far
south).  Molczan does include (I believe) the Centaurs with unusually low
apogees (near 10,000 km), since they are more frequently near perigee, and
are easy to track throughout their orbit.  Also, a few Centaurs with 
prominent flash patterns are included.

Oh, one other GTO family that I particularly like -- the Leasat r/b's.  They
are kind of interesting tumblers.  

-- Sean Sullivan