The recent launch of STS-119 provided a great demonstration of noctilucent clouds. Launch was at 7:43 PM shortly after sunset. I viewed the launch from southern Florida just North of Naples. As the Shuttle rose into the sky, it’s exhaust trail was highlighted with the red glow of the setting sun. As the shuttle reached an altitude of 60+ miles, it rose above the setting sun and it’s exhaust was directly highlighted with the full spectrum of sunlight. The image above was captured at 8:00 PM. Several minutes later the lower portion of the exhaust trail was no longer highlighted leaving only the bright luminesence of the man made cloud in the upper atmosphere. Over the next hour, the exhaust plume slowly dissipated and finally disappeared as the upper atmosphered darkened with the setting sun.
Here is a video of the launch taken near Titusville. Near the end of the video you can see the developing man made noctilucent cloud.
Very thin clouds in the upper atmosphere are often not visible unless they are highlighted in an otherwise dark sky. These clouds typically appear during summer when water vapor content in the upper atmosphere is at it’s highest. The exhaust from the space shuttle is predominately water vapor and can be a direct source of noctilucent ice crystals.
