25 Jul 99 Delta/Globalstar Burn Obs

Ron Lee (ronlee@pcisys.net)
Mon, 26 Jul 1999 03:49:35 GMT

Scheduled times for the burns were 9:34:23-9:34:28 UT for the evasive
burn and 9:41:53-9:41:59.6 UT for the depletion burn.    UT times
reported were taken from my tape recording of the observation this
morning (25 Jul 99) and are subject to some error so do not take them
for absolute times.

According to my prelaunch elset, the objects should have exited Earth
shadow about 10 seconds prior to the evasive burn.  My first annotated
event was at 9:34:25 UT and was probably the initial portion of the
burn.  By 09:34:32 I noted the northwesterly direction of the plume.

At 09:34:47 UTI could still see some of the plume although it was
minimal.  9:35:08 UT I noted two dots that were Globalstar satellites
and the Delta second stage moving away to the southeast.   The two
dots were the same orientation as the 10 Jul 99 launch.

9:36:20 UT the separation of the rocket body was well to the southeast
of the Globalstars.

At 9:40:36 UT I reacquired the objects after starting my camera.  The
rocket was about one degree to the right of the satellites
(south-southeast relative to the orbit).  At this time I am looking to
the east at an elevation of about 45-48 degrees.  (Evasive burn was
azimuth 195; elevation 33 degrees.)

9:42:00 I noted a plume from the rocket that was directed to the
northeast relative to the orbital motion.  The plume was semicircular
with the concave portion towards the rocket.  A short gap then another
faint (light gray) plume then at 9:42:06 UT a really bright, white
plume.

The bright white plume was noted to be turning at 9:42:21 UT (to the
left from my perspective) and the plume rapidly expanded to the
Christmas tree shape Randy John described.  At 9:42:36 UT I looked at
it with the naked eye (easy) and it was about 2 degrees in size.

At 9:42:48 UT no more turning was noted or further discharge of
propellant. The actual stop time of discharge was not noted but was
after 9:42:21 UT.

At 9:43:28 UT it was still nice.  9:44:15 UT still visible to naked
eye at about 3 degree size approaching/in  Auriga.    9:44:45 UT it
was getting fainter.  9:45:49 UT still visible in binoculars faintly
and ended session at 9:45:55 UT with it essentially gone.

ANALYSIS:   This was my second event in about two weeks.  I did better
this time but am not perfect at recording details since I missed the
ending of the bright plume.  However, I believe I understand what is
happening and why the depletion burn appears great while the evasive
burn has been disappointing both times.

Basically, the burn of a liquid propellant engine produces few
particulates to reflect sunlight.  Hence the little amount of plume
seen at the evasive burn and beginning/end of the depletion burn is
perhaps less completely burn propellants.  The gap I saw in the faint
plume of the depletion burn was better burned portion of the event.

The bright plume, visible to the naked eye, is dumped excess
propellants.  Since they are liquid, they would easily reflect
sunlight.

I just received a report from an observer in Australia who failed to
see the circularization burn unaided.  This makes sense when you
consider the minimal visibility of the evasive and depletion burns.  I
suspect that it would have been visible with binoculars and would
suggest that for future attempts.

I will venture a guess that solid rocket burns may be more visible
since there would be significant particulates expelled during the
burn.

Most of the observation was made with 7x50 binoculars and was required
except for the excess propellant dump.  

Ron Lee
Falcon, CO USA