[Launch Alert] Launch Today?

[Brian Webb]

                             LAUNCH ALERT
 				  
                              Brian Webb
                     Ventura County, California
                         kd6nrp at earthlink.net
                     http://www.spacearchive.info
		       
		              2008 December 23 (Tuesday) 18:29 PST
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                            LAUNCH TODAY?

This evening I received an e-mail from Chris Wojcieszyn asking if
there was a Vandenberg launch today. He was driving north on the 405
freeway this morning near Westwood and spotted "a launch trail of
smoke going up" at about 9:45.

There was no launch from Vandenberg this morning, but Chris' e-mail is
one of a handful of such reports I receive every year and is worth
discussing.

First, ALL launches from Vandenberg AFB are announced in advance by
Air Force and in this newsletter. That said, Vandenberg isn't the only
place where rockets and missiles are launched along the California
coast. In the past, missiles have been launched from Navy ships and
submarines offshore, from Air Force carge planes, and San from Nicolas
Island. So it's within the realm of probability that you may spot a
launch even though there is nothing scheduled from Vandenberg.

It's more likely that Chris saw one of the numerous jet contrails that
cross the sky during this time of year. If my memory serves me
correctly, in this part of the world contrails occur in a portion of
the atmosphere some 5,000 feet thick called the "contrail zone".

This zone has a mean altitude of 33,000-38,000 feet. The height of
this zone varies with the time of year. During the summer, it's higher
than where most passenger jets fly. However, during the winter, the
contrail zone is much lower and coincides with the height at which
many jets fly.

Depending on your point of view, a jet contrail may appear to be
steeply inclined when in fact it's level.

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