In the late 1990s NASA Ames needed fast, full-range solar spectra from aircraft for the Department of Energy's ARM-UAV programme: a General Atomics Altus II (a civilian Predator derivative) flying above cloud in formation with a manned Twin Otter below, measuring how clouds transmit and absorb sunlight. Compact diode-array spectrometers of the day stopped at silicon's 1000 nm limit, so Macam supplied a unique dual-grating Monolight system: two gratings on one rotating shaft, a silicon photodiode to 1050 nm and a cooled InGaAs detector to 2200 nm, with new PC/104 electronics.
My job was the software: customising the Monolight application for the instrument, and writing DOS-based telemetry code that decided which spectral data earned its place in a 9600 baud slice of the shared S-band downlink, so scientists on the ground saw meaningful spectra in real time. All of it was written and supported from Edinburgh by email; UK evenings overlapped California mornings, so replies came back in near real time. The instrument made its first science flights in the Kauai '99 campaign, April to May 1999, flying above sub-tropical cirrus while a lidar fired down through the cloud to the aircraft below.
Programme record: Stephens et al., Bull. Amer. Meteor. Soc., 81, 2915–2938 (2000).
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