RE: Zenits and payloads

Ted Molczan (molczan@neocom.ca)
Thu, 9 Nov 1995 13:09:25 -0500

Walter Nissen asked:
 
>Ted, (or Mike, from the observational side), 
>do you have strong evidence to divide these payloads into rectangular and 
>spherical groups, as the sizes indicate? 

I use several references to determine the general shape and dimensions
of satellites. The principal one was the RAE Table of Satellites, which
was published until January 1992. It includes a brief entry for each object,
providing mass, shape and dimensions, when the information is available.
In many cases the information is labeled as an estimate. Another good
one is THE COMPLETE ENCYCLOPEDIA OF SPACE SATELLITES, 
Giovanni Caprara, 1986, (P) Portland House, ISBN 0-517-61776-5. It 
provides brief descriptions of most of the satellites launched up to the 
mid-80's, often including mass, shape and dimensions, and many very 
good line drawings. It includes similar information on many satellites that 
had not yet been launched, so it is not as out of date as the date of 
publication suggests. In any case, the data on old objects is very valuable 
to visual observers.

Most objects can be easily classified into one of the three basic shapes I
use in my data base: sphere, cylinder or rectangular prism. Generally,
I ignore appendages, such as solar panels, radar panels, antennas and
booms. If I have reason to believe (this is a judgment call) an appendage 
is likely to contribute greatly to the appearance (usually magnitude) of an
object, then I try to account for it by exaggerating the dimensions, or choosing
a different shape. If I do not know the dimensions of an object, then I issue 
a guesstimate, based on a sphere, typically 1m, 3m ,5m or larger. You see 
many such designations in my most recent entries, largely due to the lack 
of a ready reference, such as the RAE Table. I do not have the time to 
contact the owners of these objects to obtain the information, but perhaps 
someone would like to take on that job, and share his/her findings.

Some day, I would like to replace or augment the dimensions with true
standard magnitudes, determined through observation. Russell Eberst's
observations are a treasure trove of magnitude data. The main task
will be to reconstruct the circumstances of the observations, i.e. range
and solar phase angle. Once that is done, it should be relatively easy
to determine means and standard deviations of magnitude.

For the time being, my present system provides a rough idea of magnitude,
which is conservative (too faint) by about 1 magnitude.

bye for now