VAFB Titan IV launch likely to be Lacrosse 4

Ted Molczan (
Thu, 20 May 1999 16:25:29 -0400

The launch period is on 22 May 99, from 07:00 to 11:00 UTC. Thank you Allen
Thomson, for the heads up.

Based on the NOTAMS co-ordinates, the orbital inclination will be about 68
deg, which suggests a replacement for the aged Lacrosse 2.

During the launch period, Lacrosse 2's orbital plane makes a south-bound
pass over VAFB. My guess is that this launch is Lacrosse 4, and that it will
lift-off about 8:54 UTC, consistent with the payload entering the same plane
as Lacrosse 2.

Based on the Lacrosse 2 launch, I expect the Titan IV 2nd stage to enter the
following approximate orbit, which should yield reasonably accurate

Lacrosse 4 r     9.8  3.0  0.0  4.8 v
1 99143U 99142  B 99142.37445602  .00000000  00000-0  00000-0 0    00
2 99143  68.0000  88.4000 0185900 179.0000 325.7000 15.05989000    06

I have not made a comprehensive analysis of visibility windows; however, it
appears that observers north of about 45 N will have the best seats in the
house, assuming that my guess of the lift-off time is correct.


In Oct'97, Bjoern Gimle noted that Lacrosse 2's orbital plane was 20 deg
east of VAFB at the time of Lacrosse 3's launch. I note that if my guess of
the upcoming launch time is correct, then Lacrosse 3's orbital plane will be
20 deg east of the launch site at lift-off. This may be a coincidence, and
not an operational requirement. Due to their different rates of precession,
the planes of Lacrosse 2 and 3 drift relative one another, so the scenario
of launching Lacrosse 4 into the plane of Lacrosse 2, when Lacrosse 3's
plane is 20 deg east, would not occur very often. Perhaps going co-planar
with Lacrosse 2 is desirable, but not an absolute requirement.

Of course, it is more than likely that my guess of the launch time will
prove totally wrong, so when it occurs, I will revise the above elements to
reflect the actual time of launch.

Ted Molczan