This Document describes the BARREL Balloon 1L Optical Photometer Instrument.

Objective: To detect the Flux of visible Light at Wavelengths near 486.1 nm during a Relativistic Electron Precipitation Event. This will determine whether there are Protons accompanying the precipitating Electrons. Emissions near 486.1 nm are a Signature of precipitating Protons. Correlated Proton and Relativistic Electron Precipitation would support scattering by EMIC (Electromagnetic Ion Cyclotron) Waves at the Precipitation Mechanism. How it works: The Photons are collected through a Collimator Tube that restricts the Field of View to a Cone approximately 5° full-width angle, tilted at 35° from the Zenith. A 2.5 nm wide Hβ Filter is mounted near the Base of the Collimator. Each Photon incident on the 5 cm Diameter Photomultiplier Tube results in the Generation of a Charge Pulse. These Pulses then go into a charge-sensitive Pre-Amplifier, Discriminator, and Shaping Electronics, producing a TTL Pulse for each incident Photon. By counting the Number of Pulses, the Flux of the precipitating Protons can be determined. This Description is adapted from Reference #1 in the Information URL List.