A Starshot Communication Downlink
Kevin L. G. Parkin

TL;DR
This paper estimates the data transmission rate of a laser communication link from a Starshot sailcraft to Earth, considering various physical and environmental factors, and discusses how to optimize the downlink speed post-transit.
Contribution
It provides a detailed analysis of the raw data rate achievable for Starshot's interstellar communication, incorporating realistic noise and optical effects, and explores methods to improve downlink performance.
Findings
Estimated raw data rate of 260 bit/s to 1.5 kbit/s during transit.
Downlink speed can recover to full rate within four months after transit.
Use of a coronagraph could enable full-rate downlink sooner.
Abstract
Breakthrough Starshot is an initiative to propel a sailcraft to Alpha Centauri within the next generation. As the sailcraft transits Alpha Centauri at 0.2 c, it looks for signs of life by imaging planets and gathering other scientific data. After the transit, the 4.1-meter diameter sailcraft downlinks its data to an Earth-based receiver. The present work estimates the raw data rate of a 1.02 {\mu}m, 100 Watt laser that is received at 1.25 {\mu}m by a 30-meter telescope. The telescope receives 288 signal photons per second (-133 dBm) from the sailcraft after accounting for optical gains (+296 dBi), conventional losses (-476 dB), relativistic effects (-3.5 dB), and link margin (-3.0 dB). For this photon-starved Poisson channel with 0.1 nm equivalent noise bandwidth, 90% detector quantum efficiency, 1024-ary PPM modulation, and 10^-3 raw bit error rate, the raw data rate is 260 bit/s…
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Taxonomy
TopicsAstronomy and Astrophysical Research · Stellar, planetary, and galactic studies · Astronomical Observations and Instrumentation
