more curiosity and DSP-19

Philip Chien (kc4yer@amsat.org)
Thu, 15 Apr 1999 15:37:03 -0400

This post is copyright 1999 Philip Chien and may not be reproduced or
distributed outside of the Internet Seesat email list without permission.


On Friday April 9th three object were tracked in orbit from the Titan
IV-DSP-19 launch.  They were USA 142 (DSP-19) 1999 17A, the Titan 4 rocket
body 1999 17B, and IUS (1) 1999 17C.

Based on the available information about the anomaly the implication was
that the IUS's two components never separated, hence the lack of an IUS (2)
component.  However the serial number 25672 was reserved for it anyway.

On Wednesday two additional pieces from the launch were reported by OIG -
1999 17D 25672 IUS (2) and 1999 17E 25675 USA 142 Debris.

Of the five objects currently tracked only the Titan rocket body has
unclassified elements, as would be expected.

On some previous DSP launches debris object were tracked, Jonathan McDowell
lists them as sensor covers.  This kind of makes sense.  For the launch of
a DSP from the shuttle 'shower cap' covers were placed over some of the
sensors and reeled off with fishing line-like mechanisms since the
shuttle's cargo bay is fairly dirty by spacecraft standards.  So it's
possible the 1999 17E debris object is a normal DSP cover (whether it came
off accidentally or intentionally).

The Air Force put out a press release stating that the spacecraft is "in a
safe configuration but spinning abnormally".


Based on the information available Friday I had assumed the following
sequence of events -


Nominal Titan IVB launch in to 100 x 400 nm parking orbit.
IUS/DSP separates from Titan IV 2nd stage
Normal IUS first stage burn.  Roughly 400 x 19,000 nm orbit achieved.
IUS 2nd stage does not separate from first stage (abnormal condition)
IUS computer shuts stage down to prevent 2nd stage from firing.
spacecraft separates at planned time, but in an incorrect orbit.

This scenario accounts for the single IUS component in orbit, the nominal
separation time reported by the Air Force, and much of the confusion.

But it doesn't explain the additional IUS (2) component which was announced
on Wednesday April 14th.

I highly doubt that USSPACECOM was putting out purposely false information
on Friday, if anything they'd want to include the IUS(2) since the lack of
it in the catalog was my first indication that something was wrong.
Clearly by that point they were tracking DSP-19 since it was cataloged.  So
the logical assumption is that USSPACECOM only tracked three pieces in
orbit on Friday.

One scenario is the IUS decided to separate between Friday and Wednesday.
But that seems unlikely.  Another possibility is USSPACECOM didn't find the
IUS(2) stage until Wednesday, this would explain saving the serial number
for it.  But it seems strange that they could find the satellite in the
incorrect orbit on Friday but didn't notice the IUS stage which would have
still been extremely close by.

Another possibility is the IUS first and second stage did separate, but
there was a problem with the second stage firing and it remained attached
to the satellite.  So the three objects tracked Friday would have been the
Titan rocket body, IUS first stage, and combined IUS second stage and DSP.
This would assume that the Air Force gave out incorrect information that
spacecraft separation had occurred on time.  But how could the IUS second
stage separate from the payload several days later?  By this time the IUS
second stage's batteries would _have_ to be dead.  And I doubt that there
would be any way for the spacecraft to order separation from the IUS second
stage.


It's interesting to speculate that the debris object was not intended to
come off when it did.  One possibility would be one of the satellite's
deployable solar panels which might make an interesting visual flasher if
it's ever found.  The debris object is cataloged as USA 142 debris which
implies satellite-related, but there's always the possibility that it's
part of the IUS.

Obviously if hundreds of objects associated with the launch suddenly start
showing up in the catalog that would imply something a bit more dramatic
....


BTW - the Titan IV R/B will be making excellent visual passes in my area
next week.  Ought to be interesting to look for (OBJ Seesat coment).


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