UARS MLS Arctic Observations: February 2000

The UARS MLS instrument was taken out of "standby" mode on 31 January 2000, and operated for the first time since 27 July 1999. The objective of these observations was to obtain information on Arctic vortex ozone chemistry through measurements of ClO, HNO3 and O3. Observations started on 1 February and continued through 13 February.

MLS was operated in a mode where limb scans were attempted between ~50N and ~80N latitudes on the "day" (southgoing) side of the orbit. The reason for the abbreviated latitude range is because of antenna scan mechanism "slips" that had plagued MLS before going into standby mode last July. Scans were concentrated in the Arctic to increase the probability of obtaining useful measurements there, and on the "day" side of the orbit for measurements of enhanced lower stratospheric ClO. As was the mode of operation before going into standby, only the MLS 205 GHz radiometer was turned on. This radiometer provides the primary measurements of O3, ClO and HNO3.

Fortuitously, no scan slips occurred during these observations and the 205 GHz electronics worked flawlessly - as they were doing before going into standby mode. Unfortunately, a large fraction of the limb scans were lost due to telemetry gaps in the satellite data stream.

Data from these observations were processed by the MLS team at JPL, and will be catalogued on the UARS CDHF and transferred to the GSFC DAAC for public distribution. Questions on the data, and their availability, should be addressed to the individual on the MLS team responsible for the particular data product: Joe Waters ( for ClO, Lucien Froidevaux ( for O3, and Michelle Santee ( for HNO3.

This page maintained by Joe Waters ( Last updated 24 February 2000.