how useful are these old elsets?

Ryan Rudnicki (RR03@swt.edu)
Tue, 14 Jan 1997 08:20:33 -0600 (CST)

Folks:

I am currently using SatSpy Version 2.0 at to predict satellite passages. 
(Demo version available at http://www.usa.net/acappella/satspy/satspy.htm)
Each time you enter the program, you have to specify which .tle file you 
want to open, and upon opening it, the program shows you how many elsets 
were loaded and how many were rejected because of "old age".  A little 
concerned about this apparent discrimination against senior elsets, I 
used one of the program's nifty features, clicking on a button to sort 
the elsets by age.  I was then easily able to identify the rejected elsets.  
A subset of the list of rejected elsets is reproduced below.  In some 
"notes to the user" SatSpy's author, Dave Cappellucci, writes that elsets 
over 30 days old should probably be discarded, especially for LEO objects.

My question:  Why are the elements below in the .tle file?  Are the objects 
whose elset age is over 1000 days still in orbit?  Are these orbits stable 
enough that they don't need refreshing too often?  Is it a case of too many 
satellites and too few refreshers?  The .tle file I'm using is a Ted Molczan 
file dated 09.I.97 and downloaded from Mike McCants' web site.

Thanks, 
Ryan Rudnicki 
rr03@swt.edu


Elset summary: sorted by age, ascending


Sat#  Common Name   Intl Desgn  Period Eccen  Incl    AGE    Std Mag

23728 USA 116         95066  A   97.4  0.0525  97.9  101.9    5.1
22251 USA 86          92083  A   99.0  0.0422  97.8  101.9    5.1
13172 KH 9-17 ELINT   82041  C   98.0  0.0003  96.0  107.9    8.9
14143 NOSS 5 (C)      83056  C  107.4  0.0353  63.4  121.0    8.0
 9415 DMSP B5D1-1     76091  A  101.1  0.0016  98.7  128.0    6.5
23712 Milstar DFS 2   95060  A 1436.1  0.0002   3.5  180.1   -0.2
23030 Step 1          94017  A   95.9  0.0009 105.0  741.3    8.3
15423 KH 11-6         84122  A   97.3  0.0124  97.9  823.3   (N/A)
10033 DMSP B5D1-2     77044  A  101.0  0.0041  99.0  858.1    6.5
20344 USA 40 r        89061  D  184.6  0.3596  57.0 2225.4    6.8
14690 NOSS 6 (A)      84012  A  107.4  0.0141  63.4 2427.9    6.8
10594 NOSS 2 (F)      77112  F  107.4  0.0318  63.4 2436.9    8.0
14144 NOSS 5 (D)      83056  D  107.5  0.0136  63.4 2444.1    8.0