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The NITELite (Night Imaging of Terrestrial Environments Lite) system is a method of collecting regional-scale light emissions data from a latex high-altitude balloon (LHAB) platform. An LHAB can reach altitudes of 25-30km from where the nighttime imaging is performed. LHAB missions are relatively low cost (<$2000US/flight) and easy to repeat. A NITELite mission collects data with high resolution (<10m/px), color information (RGB) over a region of thousands of square kilometers. This system provides a new source of data for remote sensing of artificial light at night (ALAN) research, filling the data gap between aerial and satellite observations.
The imaging sequence consists of rapidly capturing 5 RAW images with a 50ms exposure from each camera followed by a 100ms compressed TIFF that acts as a thumbnail. The three cameras are set to image at near synchronous timing every ~7s. A one-hour imaging routine produces 465 complete swaths.
The ACS is a cylindrical programmable venting system that is inserted into the neck of the balloon after it is filled for flight. At a preprogrammed altitude – determined by wind models and desired imaging target – the ACS opens allowing the helium to flow out. As the helium is released the ascent velocity slows. An on-board pressure sensor measures the change in altitude. Once the ACS detects the ascent has stopped, it closes the valve to maintain neutral buoyancy.
The On-Board Computer (OBC) provides a feed of information to the imaging computer to tag images as they are recorded. That information includes latitude, longitude, altitude and a timestamp from a GPS unit.