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 the satellite.
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 interesting.
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 conversation.
- 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 non-satellite phone.
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 provides:
- The lowest latency of voice and data communications
- The shortest registration time
- The lowest communication delays of all mobile satellite service providers
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 2014.
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.
Information is my field...Writing is my passion...Coupling the two is my mission.