The Stabilized Radiometer Platforms (STRAPs): description and planned upgrades

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Description

Measurements of solar and infrared irradiance by instruments rigidly mounted to an aircraft have historically been plagued by the introduction of offsets and fluctuations into the data that are due solely to the pitch and roll movements of the aircraft. To address this problem, two STabilized RAdiometer Platforms (STRAPs) were developed through collaboration between the Naval Postgraduate School (NPS) Center for Interdisciplinary Remotely Piloted Aircraft Studies (CIRPAS), the Naval Research Laboratory (NRL), and Sandia National Laboratories (SNL). The platforms were designed and built through an Office of Naval Research (ONR) Small Business Innovation Research (SBIR) grant by L-3 Communications Sonoma EO (formerly Sonoma Design Group). Each STRAP is capable of being mounted on the top (or bottom) of an aircraft, and each utilizes a self-contained, coupled Inertial Navigation System-GPS pair to actively keep a set of uplooking (or downlooking) radiometers horizontally level to within ±0.020 degrees for aircraft pitch and roll angles of up to approximately ±10 degrees. The system update rate of 100 Hz is fast enough to allow the STRAPs to compensate for most pitch and roll changes experienced in normal flight and in turbulence. The STRAPs have been flown in a handful of field campaigns and test flights that have illustrated their ability to work extremely well, greatly increasing the accuracy and quantity of solar and IR irradiance measurements from aircraft. However, the STRAPs also experienced various failures during these flights that highlighted the need to increase their reliability. The DOE ARM Aerial Facility (AAF) is funding the maturation and hardening of the two currently existing STRAP instruments. Specifically, upgrades will be made to the navigational computer hardware components, the platform control software, and the operating system of each of the STRAPs. These upgrades will make the STRAPs more robust and better suited for use in field studies or routine flights and will provide the atmospheric science community with two valuable tools for accurately characterizing the radiative balance of the Earth's atmosphere for climate- and weather-related studies.