Terrestrial black hole for measuring high-rejection off-axis response

An off-axis scatter facility was developed to support the Space Dynamics Laboratory in a number of earth limb measurement programs where the off-axis performance of the sensors was critical to the validity of the data. The facility was developed from three fundamental assumptions. (1) Careful control of any light scattered from the optical system being measured to make certain that it did not return to re-enter the system and corrupt the measurement. (2) Use of black specular surfaces in a unique shape to direct and attenuate scattered light. (3) Utilization of clean room technology to filter air to reduce scattering from particulates in the air and to prevent dust from degrading the specularity of the special surfaces. Therewithal analyses of atmospheric and surface scattering showed that surface scattering effects could be suppressed below atmospheric scattering limits by use of properly shaped specular walls. Analysis of measurements made in the facility demonstrated that the measurements were limited by Rayleigh scattering from the air molecules in the facility and not from dust or water droplets in the air nor from scattering from any chamber surfaces. Measurements of the Cassini narrow field camera showed a noise floor at 2.8E-12 of on-axis response.