Photon/Optical Detectors
VAE
The Visible Airglow Experiment (VAE) on Atmosphere Explorers C, -D and -E (AE-C, -D, -E) is an airglow photometer designed to measure various thermospherlc emission features during the day and night both at low latitudes and in auroras. The photometer has two distinct optical channels, a high sensitlvity channel (channel 2) with a large field of view (3 degrees half angle cone) and a low sensitivity channel (channel 1) with a narrow field of view (3/4 degree half angle cone) to resolve small airglow features. The system is protected by a combination 100 to 1 attenuating system and a cathode back biasing scheme which allows measurements of maximum sensitivity within a fraction of a second of viewing the bright limb of the earth. The experimental design allows six atmospheric emissions from the near ultraviolet to the near infrared to be monitored regularly on each satellite. The six filters are mounted on a wheel along with a dark position and calibrate position. The calibration source is made of phosphor and is activated by radioactive promethium. Each optical system employs a combination of a simple objective lens and field stop to define the angular field of view. The integration periods for channels 1 and 2 are 32 and 120 msec, respectively. [Source: NASA]