Cloudy Sunday

NOCTILUCENT CLOUDS FROM SPACE: This week, sky watchers near the Arctic Circle have reported nightly displays of bright noctilucent clouds.  The silvery ripples of NLCs look amazing from the ground, but they look even better from space.  NASA’s AIM spacecraft took this picture of the entire Arctic surrounded by an electric-blue glow on July 24th:

Regular readers of Spaceweather.com have been waiting for this image since June. Normally, AIM  transmits pictures of NLCs every day, but the regular flow of data was interrupted months ago. The reason has to do with the spacecraft’s orbit. Since AIM was launched in 2007, its orbit has been precessing–that is, slowly rotating with respect to the planet below. Eventually, accumulated changes in AIM’s orbital elements required a new way of pointing the spacecraft’s instruments. Mission controllers have been working on that problem all summer long–and it has finally been solved.

“We are thrilled to be back in business,” says Prof. Cora Randall, a member of the AIM science team at the University of Colorado’s Department of Atmospheric and Oceanic Sciences. “Our orbit will continue to evolve, but at this point we believe that we know how to control the pointing under the anticipated orbit parameters.”

NLCs are, essentially, clouds of frosted meteor smoke. They form when wisps of summertime water vapor rise toward the top of Earth’s atmosphere. Water molecules stick to the microscopic debris of disintegrated meteoroids, assembling themselves into tiny crystals of ice that glow beautifully in sunlight at the edge of space.

Thanks to the efforts of the AIM team, you can see these strange clouds not only from Earth, but also from Earth orbit. AIM images are published every day right here on Spaceweather.com.