Responsible: Jonas Hedin, Misha Khaplanov, Jörg Gumbel, Jacek Stegman, Georg Witt
The ALOMAR observatory at the Andøya Rocket Range in Norway is a system of high quality ground-based experimental facilities for studies of the middle atmosphere. A new EU contract concerning the enhanced Alomar Research Infrastructure (eARI) has sponsored two sounding rocket launches from Andøya. The rockets are divided into one launch in noctilucent cloud conditions in June 2006, the other for ionospheric experiments at higher altitudes in January 2007. MISU is involved in both rocket projects. Costs of launch, integration and transports are covered by the EU contract.
For the summer flight, the MISU middle atmosphere group is preparing the experiment SLAM (Scattered Lyman-Alpha in the Mesosphere). SLAM will study the 121.6 nm hydrogen Lyman-α radiation field in the sunlit mesopause environment. The Lyman-α line is the only far-UV feature capable of penetration into the mesosphere. Because of its energy, Lyman-α is capable of ionising nitric oxide. It thus constitutes the source of the ionospheric D-layer and the starting point in the complicated ion chemistry of the cold mesopause region. Photolysis by Lyman-α is also the major sink water vapour in the mesosphere. Since one has to do with resonance radiation, the Lyman-a line is diffusively scattered by the hydrogen atoms of the geocorona, a light source comparable at low altitudes to direct sunlight.
The presence of a mesospheric ice particles (noctilucent clouds) is expected to modify the radiative transfer of the Lyman-α line. With SLAM we will for the first time investigated mesospheric ice particles by optical measurements at this short wavelength. As a complement to common remote sensing and in situ techniques at longer wavelengths, this will provide important new insights about the NLC particle population.
Return to the MISU Research Page.
Last updated: January 21, 2006
Jörg Gumbel (gumbel@misu.su.se)