Interstellar Probe: Telecommunications Design Trades

The Interstellar Probe mission presents the ambitious challenge of launching a spacecraft for interstellar exploration by 2030. Achieving interstellar distances via either a Solar Oberth Maneuver (SOM) or Jupiter gravity-assist (JGA), state-of-the-art technologies are pushed to provide a system capable of surviving 50 years through the extreme hot temperatures of the solar environment and extreme cold of deep space, while meeting communications requirements at distances up to 1000 AU. Previous published work summarized the telecommunications tradespace and baseline design for an Interstellar Probe mission based on a Jupiter gravity assist (JGA). This paper furthers this work by discussing design changes necessary to support a Solar Oberth Maneuver, presenting options on extending mission life beyond the 50-year nominal mission in an effort to reach the goal of 1000 AU, and presents implications on the choice of exit target due to the reliance on primarily Northern Hemisphere ground assets. Compared to the Jupiter gravity assist mission design, the SOM option significantly reduces the amount of aperture available for communications. The heat shield used to provide thermal protection during the SOM dictates the aperture available for communications. Operating at higher frequency is immediately advantageous in an aperture-limited case. However, the longevity of the mission does not allow for use of typical mechanical pointing technologies like reaction wheels. Given these size and pointing restrictions on spacecraft communications, investigation into alternative pointing technologies and comparison between X-band, Ka-band, and optical communication systems are presented. Ultimately, the concept study chose the JGA option as baseline. To support communications to and through interstellar space, ground systems require increasing aperture. This work, as well as previous work, explores the notional case of using the Next-Generation Very Large Array (ngVLA) as a ground asset for the science downlink. Such expansion of operational communications ground capability is a key enabling concept for supporting communications and retrieval of science data from 1000 AU.