AGL is originally designed for measuring airglow emissions, but is used to measure an auroral emission in the present experiment. It measures column emission rate of an emission on board a sounding rocket penetrating the emission layer. From the measured column emission rate, the total precipitating energy input into the atmosphere may be estimated. From the measured volume emission rate profile, the characteristic energy of the precipitating particles may be estimated. These parameters are important in interpretation of the experiment.
AGL is a small photometer consisting of a band-pass filter, a lens, a PMT and electronics to process the data to the telemetry system. The band-pass filter has central wavelength of 557.7 nm with FWHM of 6.1 nm, and select the auroral green line. The lens and a field-stop on the focal plain determine a circle field of view with a diameter of 6°. The PMT has a multi-alkali photo-cathode sensitive at 300-650 nm. The PMT is set in a small air-tight room to prevent it from discharging. The line of sight is set in the direction 60° away from the spin-axis. A smaller offset angle was preferred (usually 30°), however the configuration of the lower rocket stage does not allow it. A LED set in the optics emit 30 ms every 1 minute to check the normal operation of the system.
Figure 1. AGL optics.
S. Komada (U Tokyo), N. Iwagami (U Tokyo), AD Co., Ltd.