re: USA 125 r2 aka 96038C - identification

Philip Chien (
Sat, 18 Dec 1999 14:08:45 -0500

"Ted Molczan" <> said:

>This is a follow-up to David Brierley's earlier post of his observations of
>this object, and Pierre Neirinck's first elements:
>USA 125 r2       2.0  0.0  0.0  6.2 v
>1 23947U 96038  C 99350.31952770  .00003200  00000-0  14718-2 0    13
>2 23947  55.3273 330.1598 5035331  55.8656 342.1975  5.47041462    00
>This object appears to be the perigee kick motor of USA 125 (96038A / 23945),
>which was launched in early July 1996, and tracked by several SeeSat-L
>96038A had visual characteristics similar to 89061B and 92086B, both of which
>went to Molniya orbits, so that became the expectation for 96038A. The first
>manoeuvre should have resulted in a 2 m diameter rocket motor in an
>intermediate highly elliptical orbit.

These payloads are the Satellite Data Systems (SDS) second generation relay
satellites which Sean Sullivan and I "discovered" back in 1992.  The first
two were launched on the shuttle, the last on a Titan IV.  In all three
cases the same upper stage was used, a Minuteman III (Orbus 7) motor which
was contained within the satellite at launch.  My catalog has a length of
2.27 meters and diameter of 1.3 meters for the Orbus 7.

The upper stage is part of the satellite when it fires but ejected after it
has finished its burn.  The same system was used for the unclassified
Syncom IV-5 (Leasat) shuttle launched wide-body satellites.  I know Sean
has seen the Orbus 7s from the Syncom launches and would assume that there
have been enough observations for an empirical standard magnitude to be

Presumably the PKMs from the classified and unclassified satellites would
have the same magnitude. ;-)

>96038A was last reported seen at day 96190.9465 by Pierre Neirinck, and first
>reported missing at day 96191.2597 by an observer who prefers anonymity, which
>indicated that the expected major maneouvre had taken place.
>This is Pierre's final 96038A elset:
>1 23945U 96038  A 96191.18012210  .00044450  00000-0  15298-3 0    97
>2 23945  54.9692 157.6756 0006456 325.6910  34.4399 15.88888486    00
>Precessing the suspected 96038C back to the mid-point of the period during
>which the maneouvre likely took place, day 96191.1, 96038C and 96038A would
>have been within 8.7 deg of each other in RAAN; and 96038C would have had an
>argument of perigee of about 287 deg - about as expected for a Molniya orbit.

What's intriguing is with the discovery of a decent orbit for the perigee
motor, it should be possible to derive an estimated orbit for the primary
(classified) USA 125 payload, even though it's in a high altitude
elliptical orbit.  With any luck its orbit, plus the known launch times of
the other two SDS-2 satellites can be used to derive elements for the
entire constellation.

Philip Chien, KC4YER
Earth News
world (in)famous writer, science fiction fan, ham radio operator,
all-around nice guy, etc.

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