Challenges in Scientific Data Communication from Low-mass Interstellar Probes

Abstract

Interstellar distances are vast. Electromagnetic propagation delay grows in proportion to distance, and the propagation power loss grows as the square of distance. These are severe challenges for communication with interstellar spacecraft and probes.Those who launch such missions may be motivated to achieve scientific returns within a human lifespan or the career of a space scientist or engineer. This leads to the conclusion that such craft or probes must travel at a significant fraction of the speed of light, c. This in turn requires great energy resources to impart high kinetic energy, which puts a premium on a spacecraft or probe with a small mass budget.However, a small total mass implies even less mass allocated to the communication subsystem. This makes it difficult to capture a significant scientific return, which is enabled in part by the volume and reliability of scientific data.In this tutorial white paper, we discuss the various issues surrounding the design of a communication downlink from a spacecraft or probe at interstellar distances with a constrained mass budget.

Chasing nomadic worlds: A new class of deep space missions

“…Laser sails were formulated and modeled less than a decade after the construction of the first working lasers [176,177], and many publications have subsequently explored their feasibility [e.g., 178,179,180,181,182]. It is worth noting that the ballistic assumption outlined in Section 4.1 is generally valid for laser sails [183].…”

Superconducting photon detectors

“…SNSPDs have also been employed in receivers for space-to-ground classical communications such as the NASA 2014 LADEE Lunar Laser Communications (LLCD) demonstration [179]. SNSPDs are expected to be deployed for the upcoming NASA Deep Space Optical Communications (DSOC) mission [180] and are under consideration for futuristic proposals such as Breakthrough Starshot [181]. Waveguide integrated SNSPDs [153 -155] offer a scalable platform for photonic computing with single photon signals.…”

The First Interstellar Astronauts Will Not Be Human

“…Other challenges include high propagation loss from diffraction, interfering background radiation, and ground-based reception issues related to atmospheric turbulence, scattering, and weather. To avoid data volume limitations, careful attention must be paid to: (1) rendering the communication link as energy efficient as possible, (2) aggressive compression of the data, and (3) use of reception optics at larger aperture sizes [1,7]. Larger distances and power losses may be compensated by transmitting at a lower data rate and longer times, with a possible mission design to include a nuclear battery.…”

“…A highly selective optical bandpass filter will mitigate the radiation from the Earth's atmosphere (if ground-based), our solar system dust emission and scattering, and nearby stars to improve communication. Communications issues are further discussed in various papers from within the directed energy community [1,7].…”