An early morning missile test over a remote part of New Mexico is expected to produce a contrail that will be visible across the Southwest on Thursday, and authorities says they're preparing for a flood of phone calls and emails from curious onlookers.

The unarmed Juno target missile will be launched between 6:30 and 7:30 a.m. MST from an old military depot in western New Mexico. The destination is White Sands Missile Range, some 215 miles away.

On its way to White Sands, the missile will drop a booster into a safety zone on private and national forest land north of Datil, New Mexico. Roadblocks have been set up in the area.

A similar launch in 2012 created a buzz when reports flooded in about a colorful contrail that was visible from southern Colorado west to Salt Lake City, Phoenix and Las Vegas.

This time, officials are sharing information about the launch with communities as far away as Palm Springs, California.

It's the contrail that causes the commotion.

"It's hard to describe, but it's very unusual so that's why we get the calls," White Sands spokeswoman Cammy Montoya said Wednesday. "People want to know: What happened, is it a UFO, what's going on?"

How spectacular the show will be depends on the conditions at the time of the launch. For example, the rising sun has to illuminate the twisting cloud-like formation in just the right way. Then the amount of crystallization of water vapor in the atmosphere is another factor that can affect color.

The contrail could last up to 45 minutes, but officials say that also depends on atmospheric conditions.

White Sands officials said the airspace over Fort Wingate, the site of the launch, and the drop zone for the booster will be restricted for several hours Thursday. The airspace over White Sands is already a restricted zone.

Since 1997, there have been 14 target missions from Fort Wingate to White Sands. The last one was in September 2012.

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Follow Susan Montoya Bryan on Twitter: http://www.twitter.com/susanmbryanNM