Sunday night is the last chance for the launch of the Black Brant XII rocket from NASA's Wallops Flight Facility in Virginia whose vapor trail could be visible from the Seacoast just after sundown at 8:04 p.m.

NASA has been trying to launch the rocket since a week ago Friday but has been thwarted by clouds, wind, and rain in Virginia and on its launch path. Saturday night cloudy skies over Bermuda were to blame for the launch being scrubbed.

"A 'normal' rocket would almost certainly have been able to successfully launch on one of these attempts. However, since this spacecraft is specifically performing an experiment releasing "vapor tracers" into the upper atmosphere, the conditions have to be just right," Townsquare Media meteorologist Dan Zarrow said. "That means wind speeds high up in the atmosphere must be light enough, and cloud cover downrange must be minimal."

"We want to thank you all for sticking it out with us so far! We're just as hype as everyone is to get this rocket launched. Fingers crossed for better weather," NASA Wallops said in a message on their Twitter account.

"It'll be partly cloudy and hopefully it'll work out to see it," National Weather Service meteorologist Margaret Curtis told Seacoast Current. "I'm putting it back on my phone and we'll hope for a launch."

If you see the vapor from the rocket launch send your pictures to reporter Dan Alexander at  Dan.Alexander@townsquaremedia.com, via Twitter @DanAlexanderNH, or via the Seacoast Current app.

What rocket is being launched?

A four-stage Black Brant XII rocket is scheduled to be launched at 8:04 p.m., just after sunset, with a launch window of 40 minutes. The launch was originally scheduled for Friday, May 7 but was scrubbed due to weather most every night since. The launch was canceled Thursday and postponed until Saturday because the rocket came in contact with launcher support during launch preparations.

Where can I see the rocket?

It could be visible over much of the eastern United States.

What you'll see will be the release of barium vapor 9 or 10 minutes into the launch forming two green-violet clouds that may be visible for about 30-60 seconds in northeastern Massachusetts and southern New Hampshire including the immediate Seacoast and 60 to 90 seconds in southern Maine.

Rocket emissions cause weird colors

Immediately after the vapor is released, spherical clouds will form which are a mixture of green and violet and last about 30 seconds. After exposure to sunlight, the vapor clouds quickly ionize and take on a violet color.

The barium vapor is not harmful to the environment or public health.

Livestream video of rocket launch

Live coverage of the mission will be available on the Wallops IBM video site (beginning at 7:40 p.m.

If you see the vapor from the rocket launch send your pictures to reporter Dan Alexander at  Dan.Alexander@townsquaremedia.com, via Twitter @DanAlexanderNH or via the Seacoast Current app.

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