RE: Observations Monday Evening (Feb. 18 UT)

Ted Molczan (molczan@fox.nstn.ca)
Tue, 18 Feb 1997 10:42:43 -0500

Robert Sheaffer wrote:

>02:53:37 Appulse of unexpected satellite with Delta Hydrae (mag 4.2),
>         satellite magnitude approx same as star. Matches well with
>         predicted path of #5282, Cosmos 426 rocket. However, the
>         predicted magnitude of that satellite using the magnitude in
>         Moclzan.tle is only 5.8. Hence, it was at least 1.5 mags
>        brighter than expected.

This object is one of hundreds of Tsyklon upper stages
in orbit. Rainer Kracht analyzed over 600 of Russell
Eberst's accurate magnitude/position observations of these
objects, and found a mean std mag of 5.45, which is the 
value I have assigned to all such objects in my n2l file.

In my experience, elongated objects, such as most rocket 
bodies, exhibit a maximum variation of about 1-1.5 mag
from the mean, so your obs seems to have been at the
upper extreme of brightness for this class of object,
at the observed range and phase angle.

Since this object was not included in Rainer's report,
your obs has prompted me to re-evaluate its std mag.
Fortunately, Russell Eberst observed 71052B many times.
Based on his last 25 obs, back to Feb'93, I found its
std mag to be about 0.8 mag brighter than the Tsyklon
average. Accordingly, I have revised the std mag to 4.7. 
This should ensure that the vast majority of predictions 
will now fall well within +/- 1 magnitude of observations.

Clear skies!
Ted Molczan