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The advent of small satellites and miniaturized instrument technology enables a new paradigm for observation from Low Earth Orbit (LEO). Passive microwave radiometer systems, such as SSM/I, AMSR-E, AMSU, ATMS, WindSat and GMI, have been providing important Earth observations for over 30 years, including but not limited to surface wind vector, atmospheric and surface temperature, water vapor, clouds, precipitation, snow and sea ice. Over the past several years, there has been a push to develop small satellite solutions for these critical measurements. The lower deployment cost of small satellites allows us to consider new ways to use these systems for Earth observation. Specifically, we may consider homogenous or heterogeneous constellations with the sensor elements either distributed in several orbit planes to improve revisit time, or as closely spaced trains to resolved short time scale processes, such as developing convection.
In this presentation, we will discuss three recently developed, complementary small satellite technology demonstration sensors that span the capability currently offered by the existing fleet of microwave environmental sensors. These systems are COWVR, a low-frequency fully-polarimetric conical imager, TEMPEST-D, a mm-wave cross-track imager/sounder and TWICE, a conical sub-mm wave imager/sounder. COWVR is a technology demonstration sensor for the US Air Force designed to be a small-satellite equivalent to sensors such as SSM/I, AMSR, WindSat and GMI. TEMPEST-D is a NASA Earth Ventures technology demonstration project and has equivalence with cross-track sounders such as AMSU, ATMS and MHS. TWICE, built under a NASA technology project, covers frequencies band not yet flown in space. Combined, these systems offer the potential to image the Earth from 6-800 GHz. When deployed in a constellation, they enable new observations of dynamic physical processes and coupling between land, ocean, atmosphere and cryosphere.
In this presentation, we will highlight the sensor design and status of each of the three radiometer technology demonstration projects. TEMPEST-D has been continuously operating on-orbit since September 2018 and COWVR is due to launch no earlier than January 2021. We will describe unique observations enabled by these systems when used in constellations, including time resolved measurements of dynamic atmospheric processes (e.g. developing convection) simultaneously with surface and atmospheric fluxes. We will show measured performance comparisons between these new small-sat sensors to the equivalent operational sensor, giving examples of on-orbit comparisons for TEMPEST-D and pre-launch measured data from COWVR and TWICE. Finally, we will discuss new mission concepts enabled by constellation sensor trains and distributed constellations, particularly as it relates to the observation goals identified in the US NRC Decadal Survey. We will highlight the potential for multi-sensor small-satellite constellations, showing recently acquired passive microwave and precipitation radar data from TEMPEST-D and RainCube.
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