The Self-Navigating Autonomous Reconnaissance and Communication platform, commonly referred to as SNARC, was a small stealthy fusion-powered robotic spy only slightly larger than a human being.
They had decent AI capability, were capable of speeds of up to Mach 2 in atmosphere and even faster outside it, and could stay airborne for months. A SNARC could deploy recoverable, almost microscopic-sized remotes of its own.
Nimue Alban's PICA had a large store of SNARCs in her cave under the Mountains of Light. She had sixteen of them deployed above major towns and cities of Safehold at the beginning of her mission, concentrating on recording the local languages and dialects. (OAR)
After assuming the identity of Merlin Athrawes, the PICA continued to use the SNARCs and their remotes to spy on the enemies of Charis, as well as to keep track of the Charisian fleets active around the world. (BSRA, BHD)