Some Challenges in Low-Mass Interstellar Probe Communication Downlinks

Author: David G Messerschmitt, Roger Strauch Professor Emeritus, Electrical Engineering and Computer Sciences, University of California at Berkeley

Abstract Background: We have done a preliminary paper design of a downlink from a swarm or armada of low-mass interstellar probes for returning scientific data from the vicinity of Proxima Centari. The primary goal is to identify major challenges or showstoppers if such a downlink were to be constructed using currently available off-the-shelf technology, and thereby provide direction and motivation to future research on the constituent design challenges and technologies. In this talk we summarize our findings, which conclude that there are no fundamental physical constraints, but currently available technologies fall significantly short in several areas and there are other major design challenges with uncertain solutions. The greatest identified challenges are in mass constraints, multiplexing communication from multiple probes, attitude control and pointing accuracy, and Doppler shifts due to uncertainty in probe velocity. The greatest technology challenges are electrical power, high power and wavelength-agile optical sources, very selective and wavelength-agile banks of optical bandpass filters, and single-photon detectors with extremely low dark-count rates. In each of these cases we describe the nature of the difficulties we encounter and their origins in the overall design.

Abstract Background: In a recent paper* we have done a preliminary paper design of a downlink from a swarm or armada of low-mass interstellar probes for returning scientific data from the vicinity of Proxima Centari.

*P. Lubin, D Messerschmitt, and I. Morrison, Interstellar Mission Communications Low Background Regime, soon to be replaced by Challenges in Scientific Data Communication from Low-Mass Interstellar Probes.

Abstract Objectives:
The primary goal of this talk is to identify major challenges or showstoppers if such a downlink were to be constructed using currently available off-the-shelf technology, and thereby provide direction and motivation to future research on the constituent design challenges and technologies.

Abstract Methods:
We utilize the methodologies of communication engineering. The physical layer (sources, apertures, detectors) are modeled statistically, and results from the information theory are utilized to determine the theoretical limits on reliable communication of scientific data. To understand the implications of physical device technologies, model parameters are varied.

Abstract Results: While we conclude that there are no fundamental physical constraints, currently available technologies fall significantly short in several areas and there are other major design challenges with uncertain solutions. In each of these cases we describe the nature of the difficulties we encounter and their origins in the overall design.

Abstract Conclusions: The greatest identified challenges are in mass constraints, multiplexing communication from multiple probes, attitude control and pointing accuracy, and Doppler shifts due to uncertainty in probe velocity. The greatest technology challenges are electrical power, high power and wavelength-agile optical sources, very selective and wavelength-agile banks of optical bandpass filters, and single-photon detectors with extremely low dark-count rates.