SWARM‘s network of nano-satellites (they’re only 11 x 11 x 2.8 cm) use a low frequency lora radio (around 150MHz) to link up Swarm modems on the ground, via base stations. The tiny satellites are in orbits around 450 km. A small module can be used to send and receive data.

Small packets can be sent (up to 192 bytes) using a simple protocol and they appear on Swarm’s cloud for automatic transfer/access. The data plan is only $5 per month per device.

We carried out some experiments with their dev-kit.

Design issues:

During transmissions (about 4s) the modem uses roughly 1.2A so a good power supply is needed. The passes are roughly every hour so an on-board planner may be needed to save time waiting for one. The simplest antenna is a 150MHz 1/4 wave stick – which is OK for us as we plan to only use them on base stations.