When it comes to wireless communications, the choice of X-ray
wavelengths aren't a part of the electromagnetic spectrum that first
comes to mind.
However, NASA is about to demonstrate X-ray communications in space
using experimental technology on the International Space Station.
So why X-rays?
Space communications has long exploited L-band, at 1 GHz for systems
such as GPS, S-band, at 2 GHz, which was used on the Apollo missions,
Ku-band at up to 18 GHz for broadcast services and even Ka-band, up to
31 GHz, which state-of the-art communications satellites such as the NBN
Sky Muster satellite deploy.
In the electromagnetic spectrum, light is at even higher frequencies
from 3 THz in the far infrared (1 Tera Hertz = 1000 Giga Hertz) to 30 PHz
in the extreme ultraviolet (1 Peta Hertz = 1000 Tera Hertz).
X-rays are at even higher frequencies still, with soft X-rays starting at
300 PHz.
So X-rays have the potential to provide faster rates of information
transfer, tighter beams for more secure links and the ability to
communicate in previously unavailable regions, such as
through RF blocking plasma sheaths whilst a vehicle is
undergoing re-entry.
All this is made possible by advances such as microelectronic devices
fabricated using extreme ultraviolet lithography and the emerging
field of diffraction-limited X-ray optics.
NASA today have issued a press release of the experiments that
will be conducted on board the ISS using what they term 'XCOM'.
Press release here :-
https://www.nasa.gov/feature/goddard...tions-in-space
Background paper "The Role of X-rays in Future Space Navigation
and Communication" by Winternitz et. al. 2013 :-
https://ntrs.nasa.gov/archive/nasa/c...0160000804.pdf