A low light level slow scan TV camera for satellite application

A short description of the Owl satellite TV camera system and of several unique design features used with the secondary electron conduction (SEC) camera tube is presented. The dependence of the SNR on the scanning speed is analyzed, and the SNR is maximized for an amplifier employing a low noise field-effect transistor. The optimum scanning speed corresponds to an amplifier using a bandwidth of 8 kHz and a gate biasing resistor of a value in excess of 250 MΩ. To satisfy the requirements of optimum scan rate and low data telemetry bandwidth, an intermittent scanning procedure is employed in which the scanning beam touches the unscanned area of the target in a fraction of the scanning time only. This procedure combines the advantages of low noise level and high efficiency charge removal in a single scan. The single exposure scan feature reduces the efficiency of the TV system unless a small bias illumination is applied on the photosensitive surface to avoid the ineffiencies caused by the velocity distribution of the scanning beam.