Abstract:

We present a scheme for verifiable location reporting of small satellites, or small sats. The decreasing size of small sats makes them harder to track optically. We propose to verify satellite locations by having the satellites verify the correctness of each other’s positions by occasionally completing cryptographically-secure, telemetry-based challenges that are secured on a permissioned blockchain.
In the scheme, we update an a posteriori position estimate using self-reporting. The self-reported data is verified by requiring that satellites periodically complete challenges through which it becomes possible to determine the correctness of position using bilateration. To avoid equivocation, the challenges are cryptographically secured by wrapping a challenge in layers that can be removed only by the satellite that is targeted by the challenger. The blockchain is used to secure a list of locations so that verification can be done asynchronously. This is necessary because satellite communication can be significantly delayed. The blockchain is permissioned and operated by constellations, not individual satellites, and does not require that any satellite host a node.