[Launch Alert] Saturday Vandenberg Launch

[Launch Alert]

                             LAUNCH ALERT
 				  
			      Brian Webb
		  launch-alert-editor at earthlink.net
	                www.spacearchive.info
		       
			   2018 September 12 (Wednesday) 19:17 PDT
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                     SATURDAY VANDENBERG LAUNCH
                           by Brian Webb

A Delta II rocket carrying a NASA satellite is scheduled for launch
from Vandenberg AFB, California this Saturday morning (September 15)
during a 05:46-06:26 PDT launch window.

Following liftoff from Space Launch Complex 2-West, the rocket will
climb vertically for several seconds before beginning a gradual turn
towards the south. If the launch goes as planned, the Delta will place
NASA's IceSat-2 elevation measuring satellite into orbit.

Weather permitting, the early portion of the launch could be visible
to the unaided eye as far away as Santa Rosa, Marysville, Fresno,
Bakersfield, San Bernardino, and Mexicali, California and Ensenada,
Mexico. Observers located further east may have difficulty seeing the
launch because of the brightness of the sky from the approaching
sunrise.

The vehicle's flame will initially be a bright orange color due to the
four solid rocket motors (SRMs) strapped to the rocket's first stage.
Following SRM burnout and jettison, the spent motors will continue to
burn as they tumble and fall away and may appear to flash. Meanwhile,
the rocket's first stage engine will continue running and the Delta
will resemble a slowly moving white star until Main Engine Cutoff
(MECO) near stage 1/stage 2 separation.

If the launch happens early in the window, a Twilight Effect will not
occur because it's too early for the Delta to catch the sun's rays
during the first stage burn. However, observers in dark locations may
still be able to see the dim, tenuous exhaust plume behind the rocket.
A photograph of a Delta II launch under similar lighting conditions (a
dawn launch, but too long before sunrise for a Twilight Effect) is
posted at http://www.spacearchive.info/delta-ii-iridium-ms-11.htm.

However, there is still an opportunity for a Twilight Effect to happen.
If liftoff takes place at 06:00, the vehicle will enter sunlight at T+
3 minutes 55 seconds (near the end of the first stage burn). A 06:26
PDT liftoff has the Delta entering sunlight much earlier at T+ 1 minute
45 seconds. Even if a Twilight Effect occurs, it will probably be
underwhelming since the sunlight will be reflecting off of the plume
(a dusk Twilight Effect tends to be more impressive because the
sunlight shines through the exhaust plume as seen from the western U.S.
and Mexico).

If you plan to view the launch near the coast, be aware there's a real
possibility the event could be obscured by low clouds or fog. For the
best view, find an observing site above the haze or marine layer with
an unobstructed horizon towards the launch site and downrange ocean
area.

Regardless of where you plan to go to view the launch, allow yourself
enough time to get there well before liftoff. After you arrive, be
aware of your surroundings and possible hazards such as traffic.

For launch status and countdown information, go to:

     https://spaceflightnow.com 

     https://www.nasa.gov/live/

     https://www.ulalaunch.com

For information on viewing Vandenberg rocket and missile launches, go
to:

     www.spacearchive.info/vafbview.htm

If you plan to use an Internet countdown feed for launch event cueing,
be aware the feed may be delayed by more than a minute. Instead, use a
GPS receiver or another source such as the National Institute of
Standards and Technology (www.time.gov) to obtain the exact time.

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                             QUESTIONS?

Because of time limitations and other priorities, I am unable to
answer reader questions.

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Copyright 2018, Brian Webb. All rights reserved. No portion of this
newsletter may be used without identifying Launch Alert as the
source and providing a functioning hyperlink or text that point to
http://www.spacearchive.info/newsletter.htm.