The PoSSUM Noctilucent Cloud Tomography Experiment seeks to answer two critical questions relating to our understanding of our upper atmosphere:
1. Employ noctilucent cloud and OH-layer imaging and tomography to characterize the roles of gravity wave and instability dynamics in the mixing and transport processes of the upper atmosphere.
2. Characterize the geometry of noctilucent cloud particles to better understand their growth and sublimation processes.
The PoSSUMCam system will be used to obtain high-resolution imagery of noctilucent clouds microfeatures as the spacecraft passes through the cloud layer, much like an MRI creates 3D representations of the human body. These images will be used to build extremely high-resolution models of the small-scale structures of noctilucent cloud layers through modeling algorithms developed for the program. These structures have been difficult to resolve from previous means of observation from space-based or ground-based imagers but are believed to contain most of the information pertaining to energy and momentum deposition in the upper atmosphere.
Each PoSSUM Tomography Experiment sortie will employ a manned reusable suborbital vehicle from a high-latitude spaceport. Project PoSSUM noctilucent cloud campaigns require launches from latitudes where noctilucent clouds could be observed, since noctilucent clouds form generally at latitudes higher than 60 degrees. The clouds also form with greater intensity at higher latitudes. PoSSUM noctilucent cloud campaigns are planned from Spaceport Sweden, which is located in northern Sweden at a latitude of 68 degrees, and Eielson AFB, near Fairbanks Alaska.
When strong cloud formations are observed from the ground or from LiDAR, the spacecraft will be launched to an altitude that transitions the noctilucent cloud layer. The clouds will be under direct illumination from the sun and the attitude of the spacecraft would be oriented north to the presumed region of highest cloud density. Launch opportunities could not be guaranteed on any specific night as there is no way to predict on what days the noctilucent clouds will be present. However, historical trends indicate one good opportunity every five days. A ‘Commit to Launch’ decision will be made when strong cloud formations are observed from local ground-based LiDAR.