Stray light modeling and performance of the 15 cm deep space optical communications transceiver (DSOCT)

The Deep Space Optical Communications Transceiver (DSOCT) was developed as a small demonstrator testbed for evaluating optical components and systems for a deep space optical communications system. The need for a low-scatter optical system derives from the requirement for the transceiver to operate to within 2 degree solar elongation angles. An experiment in which the terminal was set up on Earth and pointed near the Sun demonstrated the terminal's ability to achieve Earth-background limited operation somewhere between 2 and 5 degrees of the edge of the solar disk, depending on the Earth-radiance background assumed as the lower bound for background light and the sky radiance conditions during the experiment. Stray light analysis matches the measured scatter to within a factor of 3, and identifies the system's secondary mirror as the main source of concern.