Swarm Preparing for 150 CubeSat Constellation
Swarm Technologies is making progress on launching its 150 CubeSat strong IoT constellation. As IEEE reported on January 3, 2019, Swarm submitted a request to the FCC for permission to launch its full constellation into low Earth orbit (LEO). Swarm has indicated that it will be ready to launch at least four more satellites as soon as March 1. Global competition in the IoT satellite field is fierce, with Swarm pushing hard to gain market share for itself.
Swarm Technologies (often called Swarm) is a Los Altos, California based satellite company founded in 2016. They have venture capital funding from Social Capital (who has also funded rocket startup Relativity). Swarm designs, builds, and operates low-cost satellites that enable global internet of things (IoT) connectivity. Some examples of IoT devices Swarm's constellation would work with include monitoring shipping containers, remote energy installations, ships, vehicles, and remote sensors. These IoT devices use very low bandwidth, but can be isolated from existing internet infrastructure. An omnipresent satellite overhead enables internet connectivity.
Swarm's plan is to launch a constellation of CubeSats that will relay data from IoT sensors back to ground stations for dissemination to customers. Each satellite will only be able to communicate with ground based stations and not with each other. This architecture will likely have a multi-minute time delay that is suitable for non-time sensitive uses.
Each Swarm CubeSat is called a SpaceBEE, and is 0.25U in size (10 by 10 by 2.8 cm). They are likely on the upper range of a picosatellite (0.1 and 1 kg), if not slightly above that. The satellites contain chassis mounted solar panels, VHF radios and antennas, and magnetorquers. The FCC request mentions operating the radios in the 137-138 MHz and 148-149.95 MHz bands. The magnetorquers provide the only maneuverability for the spacecraft since they lack thrusters. Magnetorquers have no moving parts and create force by using an electromagnetically generated field to interact with Earth's magnetic field. The atmospheric drag in the planned orbit is still a more powerful force and will deorbit each spacecraft after a few years.
The SpaceBEEs operate in LEO orbits at altitudes between 450 and 550 km. For context, the International Space Station (ISS) maintains an orbit between 330 and 435 km. Because of this there is concern related to the SpaceBEEs transiting the ISS's orbit. Each SpaceBEE will have to pass through this altitude because they lack thrusters to push them to a higher orbit. The atmospheric drag in LEO continually slows spacecraft down, decreasing their altitude. Swarm stated in their FCC filing that they will use the magnetorquers to orient the satellites to provide maximum drag, accelerating the orbital decay and minimizing the time spent in the ISS's orbit. Each SpaceBEE is expected to remain in orbit between four and nine years.
The FCC previously blocked an application from Swarm based on the size of each satellite and the difficulty of tracking each satellite by the U.S. military's Space Surveillance Network (SSN). Swarm controversially launched four CubeSats anyway without FCC permission. Since then, however, Swarm has addressed the tracking concern by placing passive Van Atta retro-reflectors on each satellite. These increase the radar cross-section of each satellite, allowing ground radar to more easily track them. Sara Spangelo, CEO of Swarm, stated in a December 2018 blog post that the retro-reflectors give each SpaceBEE a larger radar cross-section than other CubeSats in similar orbits.
The SpaceBEEs are not the smallest satellites ever launched. That title goes to the "chip satellites" (femtosatellites) that are a few grams. The KickSat 1 mission was approved and launched in 2014 to deploy 128 Sprites, 3.5 by 3.5 cm satellite on a chip that weighed 5 grams each. However, a technical failure prevented the KickSat CubeSat from deploying the Sprites before the spacecraft deorbited. KickSat 2 is a reflight containing improved hardware and 100 Sprites. It was approved and launched in December 2018 with NanoRacks on board Cygnus CRS-10 to the ISS, and will be deployed in February 2019.
The next step for Swarm is to convince the FCC that it should be allowed to launch and operate its CubeSats. Swarm already has seven satellites in orbit, including four that launched in January 2018 and three that launched in December 2018. If the FCC's objection is completely related to spacecraft tracking, then examining Swarm's current spacecraft will provide the data needed to evaluate the request. Unfortunately, the FCC is not processing any requests while the US government is shut down. We will likely have to wait a few more weeks before learning if Swarm’s request will be approved.
Swarm is drastically aiding the new space economy, both technically and legally. It was only a matter of time before a US company launched an unauthorized vehicle, and the ensuing discussions about how satellites should be approved are very important. Additionally, every future constellation should consider their impact on space debris and how they plan to mitigate it. Swarm has their work cut out for them, but they appear to be moving in the right direction to make their constellation a reality.
Manchester, Zachary, Mason Peck, and Andrew Filo. "Kicksat: A crowd-funded mission to demonstrate the world’s smallest spacecraft." (2013).