C.-F. Enell, et al.
The Hotel Payload 2 campaign: Overview of NO, O and electron density measurements in the upper mesosphere and lower thermosphere
Journal of Atmospheric and Solar-Terrestrial Physics (Layered Phenomena in the Mesopause Region), 73(14), 2228-2236, 2011; doi:,


The ALOMAR eARI Hotel Payload 2 (HotPay 2) rocket campaign took place at Andøya Rocket Range, Norway, in January 2008. The rocket was launched on January 31, 2008 at 19:14 UT, when auroral activity appeared after a long geomagnetically quiet period. In this paper we present an overview of the HotPay 2 measurements of upper mesospheric and lower thermospheric (UMLT) electron, atomic oxygen (O) and nitric oxide (NO) densities. [O] and [NO] were retrieved from a set of three photometers, Night-Time Emissions from the Mesosphere and Ionosphere (NEMI). Faraday rotation receivers on the rocket and the EISCAT UHF incoherent scatter radar provided simultaneous electron density profiles, whereas the ALOMAR Na lidar and meteor radar measured the temperature profile and wind. The aurora was also observed with ground-based imagers. The retrieved oxygen number density profile has a maximum at 89 km, some 10 km lower than expected from earlier measurements and modelled profiles based on climatological averages (such as the MSIS model), and the retrieved NO densities are also lower than the expected. Satellite measurements indicate that subsidence over the winter pole controlled the densities. Quantitative chemistry model results based on climatological average atmospheric density and temperature profiles were, therefore, not in good agreement with the measured profiles. The Hotel Payload 2 measurements thus confirm the importance of downward transport from the thermosphere into the winter polar vortex.


  author = "C.-F. Enell and J. Hedin and J. Stegman and G. Witt and M. Friedrich and W. Singer and G. Baumgarten and B. Kaifler and U.-P. Hoppe and B. Gustavsson and U. Brändström and M. Khaplanov and A. Kero and T. Ulich and E. Turunen",
  title = "The Hotel Payload 2 campaign: Overview of NO, O and electron density measurements in the upper mesosphere and lower thermosphere",
  year = 2011,
  journal = "Journal of Atmospheric and Solar-Terrestrial Physics",
  volume = 73,
  number = 14,
  pages = "2228-2236",
  month = "Sep",
  keywords = "UMLT, NO",
  doi = "",
  url = "",
  note = "Layered Phenomena in the Mesopause Region"
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