Physical Layer Communications Technologies

Although terrestrial wireless communications often must function under harsh environmental conditions, there are peculiar demands on communications systems for planetary exploration. For example, the mil-spec electronics temperature range is generally regarded as -55-+125 °C. A probe on the surface of Venus will experience a nearly constant operational temperature of +460 °C. Conversely, the temperature of Europa at the equator never exceeds ≈-140 °C, and the temperature at the poles never exceeds ≈-220 °C. The (physical layer) communications channel for each represents unique challenges, which are described. For example, RF opacity of the toxic Venus atmosphere is inversely proportional to wavelength ${(}mathit{lambda}{)}$ squared, imposing an upper limit to a viable lander-to-orbiter link frequency. Similarly, communicating from Europa's presumed deeply buried liquid ocean through a thick, briny (electrically conductive) ice layer renders a conventional RF link useless. Plus, Europa receives approximately 5.4 Sv of radiation per day, roughly 1,000 times the average annual dose experienced by humans on Earth (only a fraction of that comes from outer space). © 2000-2012 IEEE.