Ground-based gamma-ray telescopes as ground stations in deep-space lasercom

As the amount of information to be transmitted from deep-space rapidly increases, the radiofrequency technology bas become a bottleneck in space communications. RF is already limiting the scientific outcome of deep-space missions and could be a significant obstacle in the developing of manned missions. Lasercom holds the promise to solve this problem, as it will considerably increase the data rate while decreasing the energy, mass and volume of onboard communication systems. A key strategy to optimize the lasercom technology is to shift the complexity from the space systems towards the ground systems. In RF deep-space communications, where the received power is the main limitation, the traditional approach to boost the data throughput has been increasing the receiver's aperture, e.g. the 70-m antennas in the NASA's Deep Space Network. Optical communications also can benefit from this strategy, thus 10-m class telescopes have typically been suggested to support future deep-space links. However, the cost of big telescopes increase exponentially with their aperture, and new ideas are needed to optimize this ratio. Here, the use of ground-based gamma-ray telescopes, known as Cherenkov telescopes, is suggested. These are optical telescopes designed to maximize the receiver's aperture at a minimum cost with some relaxed requirements. As they are used in an array configuration and multiple identical units need to be built, each element of the telescope is designed to minimize its cost. Furthermore, the native array configuration would facilitate the joint operation of Cherenkov and lasercom telescopes. These telescopes offer very big apertures, ranging from several meters to almost 30 meters, which could greatly improve the performance of optical ground stations. The key elements of these telescopes have been studied applied to lasercom, reaching the conclusion that it could be an interesting strategy to include them in the future development of an optical deep-space network.