As a ham radio operator, AMSAT, the amateur radio satellite program, has always been a particular
interest of mine. When the first Orbiting Satellite Carrying Amateur Radio (OSCAR)
satellite launched in 1961, a healthy investment in equipment was required just
to track and receive telemetry from the satellite. And, you had to be quick, as
OSCAR was not in Geostationary Earth Orbit (GEO),
affording only a few minutes of “RF line of sight” with
Add 50 plus years to the
technological clock, and things have changed dramatically. Equipment has
improved, and pricing has dropped to where it is possible for an individual to
belong to a satellite-based communications network that provides voice and data
communications anywhere in the world.
In fact, several companies would love
to have your business. For this article, I’ll focus on Iridium Communications, which has a unique approach. And, the company has a new product I think you’ll find
Iridium satellite network
Most satellite communications systems use the GEO approach but not Iridium, which uses 66 active satellites forming a Low Earth Orbit (LEO) grid
around the entire planet.
Each satellite is traveling at 16,832
miles per hour and circles the planet every 100 minutes (YouTube video). For the system engineers, consider
Iridium’s satellite network as a self-healing meshed constellation of
interconnected, cross-linked nodes.
Here’s how a phone call using
Iridium’s satellite constellation works:
- An Iridium customer places a call.
- The satellite phone connects with the Iridium satellite overhead.
- The voice traffic relays among the satellites until it reaches the
satellite closest to the location of the person comprising the other half of
- The voice traffic is then relayed to that person’s satellite phone or
an Iridium gateway back on Earth if the call was placed to a terrestrial phone.
- The gateway, if required, would transfer the traffic to the appropriate
ground-based telecommunications network, which then routes the traffic to the
Iridium customers do not have to
worry about RF line of sight like I did with OSCAR. The Iridium satellite in
contact with the satellite phone will seamlessly pass the connection to the
next satellite coming into RF line of sight before contact is lost.
Overall, it is an impressive
undertaking. I’m still trying to grasp how they keep all those satellites from
crashing into each other.
LEO vs. GEO
You may be wondering why Iridium decided
to place its satellites in LEO, when spacing two to five satellites in GEO would
provide the same coverage and be significantly less complicated to manage. The
reason is 21,820 miles and the latency that distance causes. In order to obtain
GEO (always in RF line of sight), a satellite needs to be positioned
approximately 22, 300 miles from the Earth. Iridium explains why
the company prefers to use LEO:
“At only 476 miles from the Earth,
the proximity of Iridium’s LEO network means a shorter transmission path and
stronger signals, permitting the use of smaller omnidirectional antennas for
mobile handheld units.”
Iridium also believes using LEO
- The lowest latency of voice and data communications
- The shortest registration time
- The lowest communication delays of all mobile satellite service
Satellite equivalent of the MiFi
That’s my overview of satellite
communications. Now, I’d like to introduce you to Iridium GO!:
“Iridium GO! enables satellite
connectivity for your mobile devices where terrestrial networks cannot. Simply
flip up the integrated antenna and the battery-powered unit connects quickly
and automatically to the Iridium LEO satellite constellation to create an
anywhere Wi-Fi hotspot within approximately a 30.5 meter (100 foot) radius.”
With Iridium GO! you have a MiFi on steroids:
a portable device capable of sending voice and data traffic to anywhere in the
world from anywhere in the world. There is a catch.
Iridium GO!’s data-link speed will remind
you of bygone days and 25-45 Kb/sec modems. If you’re patient, Iridium is working on its NEXT satellite constellation, which will have data-link speeds approaching 1 Mb/sec.
Another reason to be patient is that Iridium GO! is not slated to be released until the second quarter of
Two distinct advantages of Iridium GO! are: not requiring a satellite phone, and having voice and Internet access anywhere you happen to be. What impresses me the most is how Iridium packs all of that
technology into a device that’s not much bigger than my MiFi.
Image of the LEO and GEO orbit elevations is courtesy of mapmaker.meteor.wisc.edu. Images of Iridium GO! and the satellite mesh
network are courtesy of Iridium.