Depending on the application, government and military satellite communications (SATCOM) customers rely on the connectivity and coverage provided by satellites predominantly in the Geostationary Orbit (GEO), Medium Earth Orbit (MEO), or Low Earth Orbit (LEO). Each orbit has its pros and cons, with some being better suited or less suited for various applications and use cases.

But as military and government SATCOM requirements become more complex, satellite providers are beginning to fine-tune the capabilities they provide to their customers by leveraging the best facets of all orbits to deliver blended and resilient, multi-orbit SATCOM services optimized to meet their customers’ needs.

To learn more about each orbit’s connectivity strengths and weaknesses, how SATCOM providers leverage an all-orbit strategy to fill orbital coverage and latency gaps, and how government and military applications can benefit from an “all-orbit strategy”, the Government Satellite Report sat down with SES Space and Defense’s Vice President of Product Management, Michael Geist.

Here is what he had to say:

Government Satellite Report (GSR): For our readers who may not be familiar, can you break down the differences between LEO, MEO, and GEO?

Michael Geist: The most basic difference between these three different orbits pertains to the altitude plane in which each satellite constellation resides. LEO is situated between about 300 kilometers to about 2,000 kilometers above Earth, with MEO sitting at around 8,000 kilometers and GEO about 36,000 kilometers.

GSR: And why do those altitudes matter?

Michael Geist: They matter for a variety of reasons pertaining to application and user experience, and two critical aspects of that involve latency – the time that it takes for information to travel from Earth up to space and back down again – and coverage in terms of how many satellites are required to enable a worldwide presence.

For example, when we consider global or worldwide coverage with a LEO constellation, it takes hundreds or thousands of satellites to provide constellation objective presence. Whereas MEO only takes six satellites to provide a worldwide presence, and GEO only takes three satellites for the same.

Another difference between LEO, MEO, and GEO is the typical satellite lifespan in each of the orbits. LEO satellites typically have about a three to five-year lifespan. MEO satellite constellations have about a 10 to 12-year lifespan. And GEO has a 15 plus year lifespan.

“As SATCOM service providers, we have to take into consideration how many customers there may be for a given application – and the market acceptable Average Price per Unit and Average Revenue per User  – are required to close a business case.” – Michael Geist

Those average lifespans are important to consider from a business case perspective because we can then think about how much the asset costs. And how often do I have to replace it? How much money does it cost and how long does it take to put that constellation into space? How often do my customers have to refresh their user equipment, and other things of that nature?

When developing a business case for providing SATCOM services, you have to consider the cost of putting a constellation into space and the associated terrestrial networks on the ground to serve customers, as well as the amount of capacity those constellations may provide to support the ability to service a number of customers. As SATCOM service providers, we have to take into consideration how many customers there may be for a given application – and the market acceptable Average Price per Unit and Average Revenue per User  – are required to close a business case.

Then we should consider what we can do with that capacity, and what we can’t, while also keeping in mind how much capacity there is per on-orbit asset. And does the orbit match the different applications that we may be trying to serve?

For non-geostationary orbits, service providers also have to think about the availability of a constellation in regard to the dwell time of the individual satellites over specific geographic latitudes. And by that, I mean that for inclined plane constellations, satellite dwell time at high latitudes far exceeds dwell time around the equator. If we look at a typical large LEO constellation, there may be thousands of satellites spending a majority of them dwelling at the highest latitudes, spending their least amount of time around the equator. That has an implication on the amount of availability that customers would have in areas that have the largest populations. In order to have more capacity near the equatorial region, you’d need more satellites in your constellation.

And then when you combine that with factors like equivalent power flux density limits around the equator for non-interference operation with GEO satellites, that has another impact on how much throughput at a given frequency that providers can push through a satellite and constellation. And how many satellites they’ll need to deliver the service they’re promising.

All of these different nuanced considerations come into play and have an effect on both the service provider and the user.

GSR: How do they differ regarding the SATCOM coverage, availability, and latency they provide? And which orbits are best suited for internet traffic, enterprise traffic, and broadcast connectivity?

Michael Geist: LEO typically has an end-to-end latency of under 100 milliseconds, which includes physical layer and network latency with perhaps some congestion depending upon where and how you measure it. There’s another metric that one of our aviation partners refers to called “stick-to-glass” latency. To understand stick-to-glass latency, think in terms of flying an unmanned aerial vehicle. There’s what you see on the screen, there’s you maneuvering a stick in your hand, and then the time it takes for the UAV to react to the stick maneuver. That’s typically referred to as stick-to-glass latency. There are other metrics as well like “User Experience Latency” which is quite similar to stick-to-glass latency but can be different for different user applications, for example machine-to-machine applications or human-to-machine applications.

“SES’s O3b mPOWER constellation is specifically designed for enterprise class services, whether they’re fixed, on-the-move, on land, at sea, in the air or even in space.” – Michael Geist

If we get back to stick-to-glass latency though, you’ll find that it’s typically around 250 milliseconds for LEO. MEO has a network layer latency of about 150 milliseconds but with a stick-to-glass latency of 250 to 350 milliseconds. GEO has a network layer latency of 650 to 850 milliseconds, but a stick-to-glass latency of a little over a second. Latency ranges quite a bit between the different constellations. But that doesn’t mean that latency is the only factor of importance when determining the quality of an orbit for a given application.

When you think about coverage, LEO has a very small coverage area. MEO has a medium coverage area, and GEO has a very large coverage area. From an application standpoint, GEO makes a lot of sense for broadcast applications, because you can transmit something once and reach a lot of users simultaneously. Quite the opposite is true for LEO. In LEO, to broadcast something, you have to broadcast many hundreds or many thousands of times to hit every user within a geographic coverage area, because of the small coverage area per satellite.

MEO is in the middle of that. MEO isn’t typically thought of for wide-area broadcasts however, because it’s highly efficient and very fast for enterprise-related applications. SES’s O3b mPOWER constellation is specifically designed for enterprise class services, whether they’re fixed, on-the-move, on land, at sea, in the air or even in space. GEO is clearly the best solution for broadcast traffic. I would argue that before the emergence of LEO, GEO was also a fantastic choice for Direct-To-Home Internet traffic in areas lacking other means of broadband connectivity. Companies like ViaSat and Hughes have been the predominant GEO space-based Direct-To-Home satellite internet companies. Then with the emergence of LEO – just from a fundamental technical and not necessarily a business case financial standpoint – LEO is probably the best technical solution for home internet connectivity.

For enterprise traffic, that’s where MEO finds its strength. It’s extremely fast, ranging from many tens or hundreds of Megabits per second to Gigabits per second in speed. It’s extremely efficient in terms of the waveforms that it uses. And it has a system latency that matches well with cloud-native applications. So, I would put enterprise traffic squarely in the area of MEO and what we do with O3b mPOWER.

GSR: Since some orbits are better suited than others in terms of coverage, connectivity, and low-latency requirements, is it possible for SATCOM providers to leverage all three to fill in each other’s gaps?

Michael Geist: Yes, I would say I think that we’re soon going to find a time when simultaneous multi-orbit connectivity is more commonplace or completely commonplace. I say that because frequency is a finite resource, and as demand per user terminal exceeds the availability of the finite resource from a single orbit or a single satellite to a single use or user terminal, then this will become more than normal.

“O3b mPOWER is certainly a relevant, high-value component of a multi-orbit strategy.” – Michael Geist

We’re already seeing this in the cruise market. SES provides half of a service offering with one of our cruise partners where we – as a prime contractor – have been contracted to deliver a blended MEO/LEO service capability because neither LEO nor MEO can solely deliver the types of throughputs that are required on their own. By combining them, the cruise industry gets the best of MEO for guaranteed enterprise traffic for business operations, crew traffic, and things of that nature – combined with the best of LEO for large amounts of best-effort internet traffic. Together, they meet the total aggregate throughput capacity requirements of our cruise industry partners.

I project that perhaps in the next 10 years, we will see that pattern find its way into the aviation market as passenger capacity demand continues to increase, and perhaps in other markets as well.

GSR: How does the O3b mPOWER constellation fit into the all-orbit concept? Is it capable of leveraging all three orbits in conjunction with one another to provide maximum scalability and availability performance to government and military customers?

Michael Geist: O3b mPOWER is certainly a relevant, high-value component of a multi-orbit strategy. In particular, O3b mPOWER is best utilized as an enterprise solution – with its low latency, extremely high throughput, fantastic frequency and network efficiency, and maximum flexibility in terms of waveforms and antennas – providing an interoperable solution with other orbital solutions that exist in the marketplace today.

In other words, the best multi-orbit capabilities will be the ones that do not require the user to have to install a different antenna for every service solution that they want to use. The best multi-orbit solutions will involve the ability for a user to integrate a single-user terminal solution that allows them to operate over multiple different orbits, either independently or – at some point in the future – simultaneously.

“Any application where SATCOM is the primary tether to a remote user’s network is going to benefit from multi-orbit solutions.” – Michael Geist

GSR: What are some government and military applications and use cases that successfully leverage all three orbits? What role does multi-band resiliency play when facing threats from near-peer adversaries?

Michael Geist: Any application where SATCOM is the primary tether to a remote user’s network is going to benefit from multi-orbit solutions. Our near-peer adversaries are going to attempt to eliminate our communications options, so as long as we have resilience relative to networks and orbits, then we’ll be in a better position, especially when our warfighters are on the front line. In some cases, SATCOM is the only option they have as far as reach back goes, so resilience is critical.

Government or military applications currently leveraging multi-orbit capabilities include things like aero command and control, aero ISR, naval applications where our Navy partners desire independent command and control, MWR functionalities, and land common move applications – and the number of examples is growing.

The number of examples 10 years ago was zero, and if it wasn’t zero it might have been one. I just named five or six different applications. If you talk to me in 10 years, I think we’re going to find other sets of applications where it’s becoming more and more required. It’s definitely an exciting time to be an integrated multi-orbit service provider.

Click the video below to watch Michael Geist’s full presentation on the value of all orbits.