Inmarsat Vs Iridium:  Which Network Is Best?

Being able to communicate at sea is vital. If you find yourself in a sticky situation without the ability to call for help, then your chances of survival plummet.

So, you have your VHF radio and cellular phone, but you need a satellite phone for your passage through remote areas. This brings us to the most established and trusted network operators: Inmarsat and Iridium. 

To help you make the right decision, we’ll discuss the following:

1️⃣ They use different satellite configurations that each have their unique beneifts and drawbacks

2️⃣ Both can transfer data efficiently but these costs can vary significantly, especially if you factor in the additional hardware required.

3️⃣ Iridium has a better connection in ultra-remote areas and while on the move. 

So keep reading to learn about the practicality of using a satellite phone on the ocean, specifically focusing on these popular network choices.

⚖️ Notable Differences Between Inmarsat And Iridium

Although prices have declined, satellite phones and communication systems are still costly. The worst thing you can do is buy the first one without figuring out if it is the best for your sailing needs

It may surprise you to learn how much the two systems can differ and how those differences can affect you.

And to better understand these differences, we first need to know how their networks are set up. 

Inmarsat Uses GEO Satellites

Inmarsat is the biggest name in satellite communication. This shouldn’t be a surprise seeing as how they have been around since 1979.

Inmarsat was developed by the International Maritime Organization as part of SOLAS (Safety of Life at Sea). 

For many years Inmarsat’s satellite constellation comprised 3 geostationary satellites. Each of these covered approximately a third of the Earth’s surface. 

Geostationary satellites orbit the Earth at 22 236 miles, which is ridiculously high.

At this altitude, the speed at which the satellite is orbiting matches the Earth’s natural rotation. In other words, the satellite appears to stand still relative to the Earth’s surface. 

This is why they are called geostationary, or GEO satellites. 

Over the years, Inmarsat has added to its fleet of GEO satellites, with each new generation adding more capabilities.

As of 2023, there are 14 satellites keeping watch over the planet. Importantly, these satellites orbit around and focus on the equator. 

In conjunction with these satellites, there are also several ground stations worldwide.

So, the communication path on the Inmarsat system is from your satellite phone to one of the satellites.

Then it goes to a ground station and through the local networks to the receiver and back. 

Iridium Uses LEO Satellites

Iridium was first dreamt up a decade after Inmarsat was launched. The idea was to establish a truly global satellite communication system.

And in 1997, the first of many Iridium Low Earth Orbit, or “LEO” satellites, were launched. 

Unlike GEO satellites that maintain a constant view of the Earth, LEO satellites swarm around a much closer orbit.

And they do this at speeds of around 18000 miles per hour. Their orbit is approximately 485 miles high and runs around the poles instead of the equator. 

One of the challenges of a low earth orbit is that satellites don’t have a full view of the surface.

But Iridium has built a near constellation of 75 satellites to compensate for this shortcoming. Of these, 66 are operational; the rest act as backups should one fail. 

Together these satellites form an interwoven mesh. This mesh helps transfer communication and data. In other words, your call will jump from satellite to satellite to create a path to the closest ground station. 

Inmarsat Has Difficulty With Motion And The Poles

Both Inmarsat and Iridium have benefits and drawbacks from their respective approaches.

Inmarsat has two notable drawbacks that you need to consider. Firstly, you need to understand that the GEO satellites are standing still relative to your position on the ground.

This means that you either have a signal or you don’t. And if you don’t have reception, you will need to move to connect to a satellite. 

This becomes more problematic the further you venture from the equator. A tall mountain can block your signal at about 60 degrees north and south of the equator. Further than that, you can be blocked by the horizon. 

For this reason, Inmarsat isn’t recommended for people who venture close to the poles. 

The second drawback is that you should stand still once you have reception.

Because the satellites are stationary, it is possible for you to move out of the line of sight and then have your call interrupted. 

Iridium Can Struggle At The Equator

Because Iridium’s orbit patch is around the poles, the satellites are spread out the furthest at the equator.

This distance, plus the movement of the satellites, means an increased chance of signal interruption close to the equator. 

While the motion of the satellites is usually an advantage, it also leads to occasions of dropped reception of varying quality. 

Inmarsat Has High Transfer Rate Offerings

Inmarsat’s stationary satellites might be a disadvantage if you are in the poles or moving.

But, if you are standing still with a clear line of sight to a satellite, you are unlikely to have any reception drops. 

Inmarsat’s recently added their 6th generation satellites. These allow you to get much higher data transfer rates than Iridium.

But not if you only buy a phone. You will need to buy into their BGAN system to get the high data transfer rate.

You can reach transfer rates of up to 1100 kilobytes per second using Inmarsat’s BGAN systems.

This is impressive for satellite connectivity but comes at an equally remarkable cost.

Check out the video below, where Barry and Tyler walk you through what I’ve just touched on.

Iridium Rules The Poles

Unlike Inmarsat, if you use Iridium and don’t have reception, there is a chance that another satellite might find you soon.

Iridium’s connection time is typically faster than Inmarsat’s because of the moving satellites. 

Also, their swarm of satellites is concentrated around the poles.

This means that if you want to venture above or below 60 degrees from the equator, you are probably better off taking an iridium device. 

🔎 The Key Similarities Between Inmarsat And Iridium

The differences between Inmarsat and Iridium are pretty significant. But there are also several similarities. 

1️⃣ The price point is one such similarity. Sure, they aren’t the same, and Iridium hardware is more expensive.

But the price difference is around $250, depending on your chosen device. And that isn’t a lot if you already pay more than $1000 for a sat phone.

Similarly, airtime and data prices across the satellite connection board tend to follow a competitive trend.

So, you will need to shop around for deals to save a buck here and there. But it’ll still be far more expensive than your cellphone data. 

2️⃣ Secondly, there aren’t many significant differences between the physical phone devices. But the Inmarsat phone does have better battery life. 

3️⃣ Finally, both Inmarsat and Iridium offer pieces of hardware that create a hotspot. In the case of Iridium, you can get the Iridium GO, which is very basic but works well enough. 

Inmarsat offers a range of devices under their BGAN systems. These also create hotspots with much higher data transfer rates. But they must point at a satellite. 

🎯 Which Option Is The Best For You?

With this information, you should now be able to determine which network will best suit your needs. 

If you plan on venturing to the poles, or even beyond 60 degrees north or south, you should get an Iridium eco-system. This will ensure that you have a stable connection in those ultra-remote areas. 

Likewise, suppose dropping connections while in motion concerns you. In that case, Iridium could also be the best choice for you.

But, if you are going to operate closer to the equator, and need a faster connection, then you need to invest in an Inmarsat BGAN system.

If you just want the cheapest yet most reliable satellite phone, Inmarsat has you covered. 

🔑 Key Takeaways

Consider if it’s worth getting a satellite phone based on your sailing needs. Are you going to be closer to the poles of the equator?

The answer will ultimately dictate your choice between Iridium and Inmarsat.

UtilityUseful in remote areasUseful in remote areas
Global CoverageYes (with a few remote exceptions)Yes (with a few remote exceptions)
Satellite TypeGEO (Geostationary Orbit) satellites orbiting around the equatorGEO (Geostationary Orbit) satellites, orbiting around the equator
Communication IssuesMay experience issues at the equatorHas trouble communicating at the poles
BandwidthLower bandwidth optionsHigher bandwidth options

💡 Editor’s Tip: Iridium has a better connection in ultra-remote areas and while on the move. 

For the sake of thoroughness, why not compare Globalstar against Iridium to further understand the differences between satellite communication systems?

I’m the founder and chief editor here at Sailing Savvy. I spent a decade working as a professional mariner and currently, I mix those experiences with digital publishing. Welcome, and I hope that we can be the hub you need for safe passage.