Enhancing the Capabilities of the Global Aerosol Monitoring Systems (GAMS)

The Global Aerosol Measurement System (GAMS) project is developing a new, low cost satellite capability for measuring the properties and distributions of particles in the upper troposphere and lower stratosphere (collectively, the UTLS).  This altitude region is important because there have been observed increases in the amount of particles in the UTLS.  These particles typically reflect sunlight back into space and cool the Earth.  GAMS will measure the altitudes and amounts of these particles by looking to the side of the spacecraft, through the thickness of Earth’s atmosphere, and provide detailed information about how particles are changing in the UTLS.

The goal of the Global Aerosol Measurement System (GAMS) project is to develop needed technologies and observation strategies to optimally measure the distributions and properties of particles in the upper troposphere and lower stratosphere (UTLS).  The GAMS concept is based on the limb-scattering measurement techniques used on past sensors, most directly from the heritage of the Ozone Mapping and Profiling Suite (OMPS) Limb Profiler (LP) currently flying on board the Suomi National Polar-orbiting Partnership (NPP) spacecraft.  OMPS-LP was launched on Suomi NPP in 2011, with the next planned launch of this instrument in 2022 on the next generation Joint Polar Satellite System-2 (JPSS-2).  Because of the length of time between the NPP and JPSS-2 launches there is the potential for a significant data gap for these important measurements.  The GAMS concept is intended to be a simple and low cost measurement system that could be ready to fill such a gap.

The current OMPS-LP system measures light reflected by particles in the UTLS by looking behind the Suomi NPP path, looking through the thickness of Earth’s atmosphere (i.e., the limb).  Although OMPS-LP has proven capable of detecting the presence of background particles in the UTLS, as well as particles from volcanic eruptions and meteorites entering Earth’s atmosphere from space, it has very limited spatial coverage and suffers from sensitivity issues since it preferentially sees particles in one direct with respect to the sun.  GAMS seeks to overcome both limitations by making measurements of reflected light In two or more directions relative to the spacecraft flight.  Because GAMS focuses only on the limb profiling capabilities (versus the more comprehensive but more complicated OMPS system) it can be contained in a relatively smaller spacecraft, which will reduce deployment costs.  Additional increased spatial coverage can be realized by flying multiple copies of the GAMS instrument in different orbits.

In this stage of the GAMS project we are working to develop capabilities for adding additional spectral channels to our detector system.  We initially targeting 350 nm for altitude registration and 675 nm for aerosol detection.  We are now developing an extension to include an additional channel at 1020 nm for aerosol detection.  This channel will provide additional sensitivity to aerosol in the lower stratosphere, provides heritage overlap with other sensors (e.g., SAGE), and paired with the 675 nm channel provides additional information to recover other aspects of the aerosol distribution (e.g., particle size).  We are additionally developing an observation simulator based on model output from the NASA Goddard Earth Observing System (GEOS-5) atmospheric model.  This will allow us to prototype assimilation methodologies to ingest the eventual GAMS observations into aerosol prediction models.