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Aircraft and Payload
The solar-electric Pathfinder-Plus UAV operates at altitudes up to 80,000 feet (25 km), with 150 pound (68 kg) payload capacity and cruise airspeed near 20 knots (wind dependent). The solar cells and battery backup currently provide 18 hour endurance; "extreme" endurance capability (weeks to months) is envisioned by complementary use of solar cells during daytime and fuel cells at night. The aircraft is constructed of ultra lightweight composite materials and has net weight of just 650 pounds (295 kg). The UAV was developed under NASA's Environmental Research Aircraft and Sensor Technology (ERAST) Program.
The imaging payload used for the coffee mission consisted of two high spatial resolution digital camera systems:
1) A DuncanTech MS3100 is designed for true multispectral narrow-band visible and near-infrared imaging. It utilizes a single lens and dichroic prism to direct incoming light onto 3 separate 1280 by 1024 CCD arrays. The 3 arrays are co-registered to better than one-half pixel throughout. Narrow-band trim filters are inserted in front of each CCD array to customize the spectral response according to user needs; current filters provide channel centers at 760 nm, 660 nm and 580 nm. A Nikon 35 mm lens provides an 8.5 by 10.6 degree field of view, with spatial resolution of appx. 1 m from flight altitude of 20,000 ft.
2) A Hasselblad 555ELD camera body and lens, equipped with a Kodak Professional DCS Pro Back with 4000 x 4000 CCD array, is used for high spatial resolution color imaging. Using a color filter array, each pixel element was exposed to only one color of light (red, green, or blue); software interpolation is subsequently performed to generate a full 3-band color image. A 100 mm lens provides a 20.3-degree field of view in both the cross- and along-track dimensions, with spatial resolution of appx. 0.5 m from flight altitude of 20,000 ft.
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