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