High Data Rates from the Outer Solar System

Outer planet missions play an important role in JPL and NASA's space exploration objectives in the coming decades. This paper assesses the technical options available for ensuring that the Deep Space Network (DSN) can enable future missions to the outer Solar System and recommend investment options for flight and ground communication systems and technologies that would meet the future data return requirements. The major takeaways are summarized as follow: a) Given the current and near-term state of technology development there are major challenges in operating optical links at outer planet distances (e.g., Sun-Earth angle effects, spacecraft power available for the laser, optical ground network development plans, etc.). b) Due to the spacecraft limitations at outer planet distances, e.g., antenna pointing and solar/Radioisotope Thermoelectric Generator (RTG) power, the ‘biggest bang for the buck’ on enhancing data return is by improving the capabilities of the DSN at Ka-band. c) Concurrently with enhancing DSN capabilities at Ka-band, NASA should encourage the use of Ka-band in missions by actively incentivizing the use of Ka-band on high-rate science downlinks using technologies already available today, while retaining X-band capability for low-rate telemetry, commanding, and emergency support. To improve DSN capabilities at Ka-band, we consider two alternative approaches: 1) operation use of 34-m Beam Waveguide (BWG) arrays, and 2) upgrading the 70-m antennas. For each option, we quantify the expected performance and compare it against known upcoming users. We describe past DSN development and flight demonstrations, summarize the technological advances conducted to-date, and identify additional engineering work required to operationalize the system. We recommend the following: a) For arraying of 34-m BWG at Ka-band, additional demonstration activities are needed to better characterize the system performance under different conditions, including operations in adverse weather conditions or close to a hot body source. b) For upgrading the 70-m antennas, new holography measurements (and panel setting) should be conducted, and operational versions of previously prototyped gravity compensation systems like array feeds and deformable flat plates should be developed and installed. Using these approaches, we expect the DSN downlink performance at Ka-band to improve by 4–6 dB compared to X-band, providing an increase in downlink data rate of 2.5x to 4x.