RE: Titan 4 to launch from VAFB 16 July

Ted Molczan (molczan@fox.nstn.ca)
Tue, 10 Jun 1997 09:38:35 -0400 

John Pike wrote:

>The RUMINT is that the launch window is
>
>2230 15 July thru 
>0230 16 July 
>
>[PDT?? almost certainly]
>
>Almost certainly Lacrosse, just from time alone

That is equal to 16 Jul 97, 05:30 to 09:30 UTC.

Assuming that it is desired to build a constellation
with Lacrosse 2, here are some possibilities. First,
note that Lacrosse 2's orbital plane will be over the
launch site, south-bound, at about 03:57 UTC. This
means that the launch window would place Lacrosse 3
east of Lacrosse 2 (91017A):

Launch    Deg East
 UTC     of 91017A

09:56       90 
09:30       83.5
07:56       60
07:14       49.4
06:56       45
05:56       30
05:35       24.7

Assuming your Rumint is accurate, then 09:56 is 
automatically ruled out; however, a 90 deg spacing
is common for two satellite constellations. A launch
at 09:30, the very end of the window, would yield
83.5 deg, which might be close enough to 90 deg.
A 90 deg spacing affords broadly spaced coverage
over a 24 hour period.

My favourite is 07:14, which yields a 49.4 deg
spacing. This may seem like an odd-ball value; however,
it duplicates the philosophy of the Keyholes, by spacing
the planes by the amount of Earth's rotation through
two Lacrosse orbital revolutions, including precession
due to Earth's oblateness. This spacing affords a large
number of repeated ground-tracks within a 2 satellite
constellation, over short periods of time. I believe
that Keyhole would benefit more from this, since it
suffers from cloud-cover problems. However, both systems
might benefit from repeat coverage for the purpose of
near-real-time detection of changes, such as motion of 
vehicles.

All of the other spacings imply constellations of more
than two spacecraft. My guess is that in these times 
of reduced threat and deficit-fighting, they will live
with two satellites.

For each day of launch delay, the above times would
be 15 minutes earlier. Also, there is several minutes
"slop" in those times, since I have not taken the time 
to account for the time taken to achieve orbit. That
can wait until we get closer to launch.

Finally, I have not yet looked at the possibility that
this will be a NOSS launch. I do not have time for that
right now, but I hope to do so when we get closer to
launch.

Ted Molczan