Pointing, acquisition, and tracking architecture tools for deep-space optical communications

Deep-Space Optical Communications is a key emerging technology that is being pursued for high data-rate communications, which may enable rates up to ten times more than current Ka-band technology. Increasing the frequency of communication, from Ka-band to optical, allows for a higher data rate transfers. However, as the frequency of communication increases, the beam divergence decreases. Less beam divergence requires more accurate and precise pointing to make contact with the receiver. This would require a three-order-of-magnitude improvement from Ka-Band (similar to 1 mrad) to optical (similar to 1 urad) in the required pointing. Finding an architecture that can provide the necessary pointing capability is driven by many factors, such as allocated signal loss due to pointing, range to Earth, spacecraft disturbance profile, spacecraft base pointing capability, isolation scheme, and detector characteristics. We have developed a suite of tools to 1) flow down a set of pointing requirements (Error Budget Tool), 2) determine a set of architectures capable of meeting the requirements (Pointing Architecture Tool), and 3) assess the performance of possible architecture over the mission trajectory (Systems Engineering Tool). This paper describes the three tools and details their use through the case study of the Asteroid Retrieval Mission. Finally, this paper details which aspects of the pointing, acquisition, and tracking subsystem still require technology infusion, and the future steps needed to implement these pointing architectures.