No Job Is Too Small for Compact Geostationary Satellites
Astranis and GapSat will launch GEO smallsats in 2020 and 2021 to fill gaps in satellite coverage
A typical geostationary satellite isas big as a van, as heavy as a hippopotamus, and as long-lived as a horse. These parameters shorten the list of companies and countries that can afford to build and operate the things.
Even so, such communications satellites have been critically important because their signals reach places that would otherwise be tricky or impossible to connect. For example, they can cover rural areas that are too expensive to hook up with optical fiber, and they provide Wi-Fi services to airliners and wireless communications to ocean-going ships.
The problem with these giant satellites is the cost of designing, building, and launching them. To become competitive, some companies are therefore scaling down: They're building geostationary “smallsats."
Two companies, Astranis and GapSat, plan to launch GEO smallsats in 2020 and 2021, respectively. Both companies acknowledge that there will always be a place for those hulking, minibus-size satellites. But they say there are plenty of business opportunities for a smaller, lighter, more flexible version—opportunities that the newly popular low Earth orbit (LEO) satellite constellations aren't well suited for.
Market forces have made GEO smallsats desirable; technological advances have made them feasible. The most important innovations are in software-defined radio and in rocket launching and propulsion.
One reason geostationary satellites have to be so large is the sheer bulk of their analog radio components. “The biggest things are the filters," says John Gedmark, the CEO and cofounder of Astranis, referring to the electronic component that keeps out unwanted radio frequencies. “This is hardware that's bolted onto waveguides, and it's very large and made of metal."
Waveguides are essentially hollow metal tubes that carry a signal between transmitters and receivers to the actual antennas. For C-band frequencies, for instance, waveguides can be 3.5 centimeters wide. While that may not seem so big, analog satellites need a waveguide for every frequency they send and receive over, and the number of waveguides can add up quickly. Combined, the waveguides, filters, and other signal equipment are a massive, expensive volume of hardware that, until recently, had no work-around.
Software-defined radio provides a much more compact digital alternative. Although SDR as a concept has been around for decades, in recent years improved processors have made it increasingly practical to replace analog parts with much smaller digital equivalents.
Another technological improvement with an even longer pedigree is electric propulsion, which generates thrust by accelerating ionized propellant through an electric field. This method generates less thrust than chemical systems, which means it takes longer to move a satellite into a new orbit. However, electric propulsion gets far more mileage out of a given quantity of propellant, and that saves a lot of space and weight.
It's worth mentioning that a smallsat may not be as minuscule as its name suggests. Just how small it can be depends on whom you're talking to. For example, GapSat's satellite, GapSat-2, weighs 20 kilograms and takes up about as much space as a mailbox, according to David Gilmore, the company's chief operating officer. At one end, the smallest smallsats—sometimes called microsats or nanosats—are similar in size to CubeSats. Those briefcase-size things are being developed by SpaceX, OneWeb, and other companies for use in massive LEO constellations.
The miniaturization of geostationary satellites owes as much to market forces as to technology. Back in the 1970s, demand for broad spectrum access (for example, to broadcast television) favored large satellites bearing tons of transponders that could broadcast across many frequencies. But most of the fruits of the wireless spectrum have been harvested. Business opportunities now center on the scraps of spectrum remaining.
“There's a lot of snippets of spectrum left over that the big guys have left behind," says Rob Schwarz, the chief technology officer of space infrastructure at Maxar Technologies in Palo Alto, Calif. “That doesn't fit into that big-satellite business model."
Instead, companies like Astranis and GapSat are building business models around narrower spectrum access, transmitting over a smaller range of frequencies or covering a more localized geographic area.
Meanwhile, private rocket firms are cutting the cost of putting things up in orbit. SpaceX and Blue Origin have both developed reusable rockets that reduce costs per launch. And it's easy enough to design rockets specifically to carry a lot of small packages rather than one huge one, which means the cost of a single launch can be spread over many more satellites.
That's not to say that van-size GEO satellites are going extinct. “So there's a trend to building bigger, more complicated, more sophisticated, much more expensive, and much higher-bandwidth satellites that make all the satellites ever built in the history of the world pale in comparison," says Gregg Daffner, the chief executive officer of GapSat. These are the satellites that will replace today's GEO communications satellites, the ones that can give wide-spectrum coverage to an entire continent.
But a second trend, the one GapSat is betting on, is that the new GEO smallsats won't directly compete against those hemisphere-covering behemoths.
“For a customer that has the spectrum and the market demand, bigger is still better," says Maxar's Schwarz. “The challenge is whether or not their business case can consume a terabit per second. It's sort of like going to Costco—you get the cheapest possible package of ground beef, but if you're alone, you've got to wonder, am I going to eat 25 pounds of ground beef?" Companies like Astranis and GapSat are looking for the consumers that need just a bit of spectrum for only a very narrow application.
Astranis, for example, is targeting service providers that have no need for a terabit per second. “The smaller size means we can find customers who are interested in most, if not all, of the satellite's capacity right off the bat," says CEO Gedmark. Bigger satellites, for comparison, can take years to sell all their available spectrum: Astranis instead intends to launch each satellite already knowing what the specific single customer is. Astranis plans to launch its first satellite on a SpaceX Falcon 9 rocket in the last quarter of 2020. The satellite, which is for Alaska-based service provider Pacific Dataport, will have 7.5 gigabits per second of capacity in the Ka-band (26.5 to 40 gigahertz).
According to Gedmark, preventing overheating was one of the biggest technical challenges Astranis faced, because of the great power the company is packing into a small volume. There's no air up there to carry away excess heat, so the satellite is entirely reliant on thermal radiation.
Although the Astranis satellite in many ways functions like a larger communications satellite, just for customers that need less capacity, GapSat—as its name implies—is looking to plug holes in the coverage of those larger satellites. Often, satellite service providers find that for a few months they need to supply a bit more bandwidth than a satellite in orbit can currently handle. That typically means they'll need to borrow bandwidth from another satellite, which can involve tricky negotiations. Instead, GapSat believes, GEO smallsats can meet these temporary demands.
Historically, GapSat has been a bandwidth broker, connecting customers that needed temporary coverage with satellite operators that were in a position to offer it. Now the company plans to launch GapSat-2 to provide its own temporary service. The satellite would sit in place for just a few months before moving to another orbital slot for the next customer.
However, GapSat's plan created a bit of a design conundrum. On the one hand, GapSat-2 needed to be small, to keep costs manageable and to be able to quickly shift into a new orbital slot. On the other, the satellite also had to work in whatever frequencies each customer required. Daffner calls the specifics of the company's solution its “secret sauce," but the upshot is that GapSat has developed wideband transponders to offer coverage in the Ku-band (12 to 18 GHz), Ka-band (26.5 to 40 GHz), and V/Q-band (33 to 75 GHz), depending on what each customer needs.
Don't expect there to be much of a clash between the smallsat companies and the companies deploying LEO constellations. Gedmark says there's little to no overlap between the two emerging forms of space-based communications.
He notes that because LEO constellations are closer to Earth, they have an advantage for customers that require low latency. LEO constellations may be a better choice for real-time voice communications, for example. If you've ever been on a phone call with a delay, you know how jarring it can be to have to wait for the other person to respond to what you said. However, by their nature, LEO constellations are all-or-nothing affairs because you need most if not all of the constellation in space to reliably provide coverage, whereas a small GEO satellite can start operating all by itself.
Astranis and GapSat will test that proposition soon after they launch in late 2020 and early 2021, respectively. They'll be joined by Ovzon and Saturn Satellite Networks, which are also building GEO smallsats for 2021 launches as well.
There's one final area in which the Astranis and GapSat satellites will differ from the larger communications satellites: their life span. GapSat-2 will have to be raised into a graveyard orbit after roughly 6 years, compared with 20 to 25 years for today's huge GEO satellites. Astranis is also intentionally shooting for shorter life spans than those common for GEO satellites.
“And that is a good thing!" Gedmark says. “You just get that much faster of an injection of new technology up there, rather than having these incredibly long, 25-year technology cycles. That's just not the world we live in anymore."
This article appears in the January 2020 print issue as “Geostationary Satellites for Small Jobs."
The article has been updated from its print version to reflect the most recent information on GapSat's plans.