HERMES & GrailQuest: Hunting for Gravitational Wave Electromagnetic Counterparts Probing Space-Time Quantum Foam

I discuss how several of the proposed models for space-time quantization predict an energy-dependent speed for photons. Although the predicted discrepancies with the general speed of light are minuscule, I discuss how it is possible to detect this intriguing signature of space-time granularity with a new concept of a modular observatory for photons in the energy band 10 keV− 30 MeV. This observatory may consist of a swarm of micro/nano-satellites in low orbits. Sub-microsecond time resolution and a wide energy band allow probing tiny energy-dependent delays, expected to be the signature of the granular structure of space-time in several of the proposed theories of Quantum Gravity.
Moreover, this kind of experiment allows performing temporal triangulation of high signal-to-noise impulsive events with positional accuracies of a few arc-seconds, making an observatory like that a promising hunter for the elusive electromagnetic counterparts of Gravitational Waves.