Minotaur launch could create light show
By Janene Scully/Associate Editor

A hybrid rocket set to carry a military research satellite to space near sunset Thursday could provide a colorful light show in the autumn skies.

The Minotaur rocket and its classified payload are scheduled to blast off between 7:24 and 7:40 p.m. from Space Launch Complex-8, the most southern launch pad at Vandenberg Air Force Base.

The ground-launched hybrid - its lower portion is a retired Minuteman missile and its upper segments are Pegasus rocket parts - is assembled by Orbital Sciences Corp.

"Everything looks good. The team's in place. It looks like we're set to go," Barry Beneski, spokesman for Orbital Sciences, said Tuesday.

Launches can be delayed by technical problems or unfavorable weather. Thursday's predicted weather appears perfect for a blastoff, but not so great for viewing.

The forecast includes a shallow marine layer returning to shore, with an area of thick cirrus clouds traveling over Vandenberg leading to dense fog that would obscure visibility to about one mile.

If the launch has to be delayed 24 hours, visibility improves to three miles while conditions remain suitable for blastoff.

Because of its sunset liftoff, this space booster could create a light show called a "twilight phenomenon," although cloudy skies would reduce the view for local residents. And the potential for a spectacular display will diminish with every minute the liftoff is delayed within the mission's 16-minute launch window.

The unusual twilight phenomenon is created when a rocket or missile blasts off just before sunrise or after sunset.

Often mistaken for a launch flop, the light show has nothing to do with a mission's success or failure. Rather, the phenomenon is created when unused propellant particles and water are left in the wake of a launch. When those particles freeze in the upper atmosphere, the fragments reflect sunlight, producing a kaleidoscope of colors including green, blue, white and rose.

Each occurrence looks somewhat different - sometimes it looks like the interior of an abalone shell and other times it's a colorful contrail - as high-level winds paint a pattern using the sky as a canvas.

Depending on cloud cover, reports of sighting a twilight phenomenon typically flood the Vandenberg Public Affairs Office from throughout California and as far away as Nevada, Arizona and beyond.

Minotaur will ferry the Defense Advanced Research Projects Agency's Streak spacecraft, which military officials are remaining tight-lipped about. Even the costs of the mission, they say, are classified.

Streak is expected to demonstrate technology for future low-earth-orbit satellites and gather information about conditions that could affect future low-earth-orbit spacecraft.

Janene Scully can be reached at 739-2214 or janscully@santa mariatimes.com.

September 21, 2005

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