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A-SMLS (The Airborne Scanning Microwave Limb Sounder)

A-SMLS is an instrument designed to fly onboard the NASA ER-2 aircraft, making wide-swath vertical profile observations of the composition of the upper troposphere and lower stratosphere (~10 – 20 km altitude) at 340 GHz. Observing a ~300km-wide swath ahead of the aircraft in a 2D raster scan (azimuth and elevation), A-SMLS is designed to measure water vapor, ozone, and carbon monoxide with a 10 x 10km horizontal resolution (across and along-track).

A-SMLS is ideally suited to provide high spatial resolution measurements of upper troposphere and lower stratosphere (UTLS) composition needed to improve our understanding of key atmospheric processes including:

  • Convective uplift of air and associated trace gases from the surface to the upper troposphere.
  • Long-range transport of pollution plumes (including those uplifted by convective).
  • Air exchange between the troposphere and the stratosphere.

As such, A-SMLS observations from the ER-2 will prove to be a valuable asset in future multi-instrumental field campaigns, e.g. utilizing the wide swath to provide context for more detailed in-situ measurements by aircraft in the stratosphere or at lower altitudes.

Additionally, A-SMLS presents a unique opportunity as a pathfinder for future MLS class instruments, using the latest generation receivers and spectrometers to demonstrate these technologies in advance of them being proposed for future spaceflight opportunities.

A-SMLS was originally developed under NASA’s Instrument Incubator Program and flew on the WB-57 aircraft in July and September 2012. This version of the instrument used 4 K-cooled superconducting microwave receivers, requiring a liquid Helium-filled dewar. The instrument was subsequently adapted for the NASA ER-2 aircraft, on which it flew in March 2015.

A-SMLS was recently updated to use new 340 GHz microwave receivers that can operate both at room temperature and at cryogenic temperatures. A new mechanical cooler was installed to hold the receiver at ~70 K, removing the need for liquid helium cooling. Upgrades to the mirror pointing system and pilot instrument control and aircraft telemetry interface are underway. Test flights of this new configuration are planned for Summer/Fall 2023.


Photo of Timothy Crawford
Timothy Crawford
Laboratory Studies And Atmospheric Observations
Photo of Nathaniel Livesey
Nathaniel Livesey
Earth Science - Assistant Section Manager, Principal Investigator, Aura Microwave Limb Sounder
Photo of Luis Millán
Luis Millán
Stratosphere And Upper Troposphere
Photo of Carl Percival
Carl Percival
Laboratory Studies And Atmospheric Observations - Group Supervisor
Photo of Frank Winiberg
Frank Winiberg
Laboratory Studies And Atmospheric Observations - Scientist