The Iridium Satellite Constellation

This Sunday I’ll be introducing a new segment called Sunday’s Satellite. Every week I will feature a new orbiter, and explore how these sophisticated spacecraft assist humanity from their heavenly vantage. For my first choice, although I was tempted to start at the beginning with Sputnik, I decided to skip ahead to some satellites with a little more flare, the Iridium Satellite Constellation.

Most of us have witnessed a satellite pass at some time in our lives. They are those stars that wander steadily across the sky, probably taking secret government pictures of your underwear. Thousands of man-made satellites now orbit the earth, providing services we take for granted everyday. Their reflective solar panels and antennas catch the sun at favorable angles and they become visible in the night sky. Some orbiters flash erratically as they roll or tumble through space, and while most appear no brighter than the average star, Iridium’s network of communications satellites can produce flashes that appear over 55x brighter than Venus, a phenomena known as an Iridium flare.

The first time I saw an iridium flare, I braced myself for the end of the world. It was a cloudier night, with only a few clear bright stars, when suddenly something lit up the clouds with an increasing intensity. In those 3 seconds of unreal brightness, I envisioned Earth being incinerated by a gamma ray burst, or some hard, fast comet aimed right at my head. Instead, the light disappeared into the clouds, and I was left with a mystery. I wondered what could have produced such an intense burst of light, and finding out the answer would spark my interest in satellites and astronomy. My search would bring me to heavens-above.com, a website that tracks visible satellites based on the user’s location. I could now pinpoint when and where in the sky a flare would happen, and that kind of information could make me a shaman in some tribes!

Every other night I would drag my roommates out flare hunting, exciting the neighbors with my incessant sky watching. We were lucky enough to see a shuttle re-entry, the International Space Station, AND an Iridium flare, all in one beautiful, clear night! Like a nerdy master of ceremonies with his cue cards, I introduced every passing act during its procession across the sky. If you have never seen a flare for yourself, I found a video that represents the experience quite well. Notice a likeness to the end of days?

The Satellites

The Iridium constellation is a network of 66 communications satellites that provides voice and date coverage to every corner of the planet. The satellites have the unique ability to send seamless transmissions between themselves, which means that communication is possible in areas like the poles and open oceans, where land based coverage isn’t currently provided. Today the network is the only mobile satellite service that offers complete world coverage, and the first provider to relay data between its satellites in orbit.

The program began in the 1980’s fueled by Motorola, and originally called for 77 space vehicles, the atomic number of Iridium, plus several spares in a lower orbit ready in the event of a failure. This global communications grid would cross-link satellites using microwave bands in the electromagnetic spectrum, a characteristic still unique to the fleet. Most notably, they are designed with 3, highly reflective, silver coated main mission antennas, fixed at a 40 degree angles from the body of the spacecraft. These door-sized antennas are responsible for flaring, as they momentarily reflect the intensity of the sun, and spark a religion in some remote tribe. Calculating when, where and how brightly these flashes will occur requires some very intense computational mathematics, performed at the click of a button thanks to sites like Heavens Above.

The vehicles were produced and launched during an ambitious launch campaign in 1997 and ’98, their fast production made possible by innovative new methods that mass-produced the orbiters on a gimble. During an especially productive period, the company was churning out a new satellite every 4.3 days at a record low-cost of only $5 million per vehicle. All 66 satellites and 6 spares were delivered into their low earth orbits of 750km, by Russian, Chinese and US rockets, achieving a perfect success rate of 15/15 launches. However the failures of Iridium would soon overshadow its successes, when its over-priced services failed to catch on with a public already at-play with their new cellular phones. The company would buckle under enormous debt, and file for bankruptcy only a few years later. The $7 billion network  was sold for a mere $25 million,  with Boeing now in-charge of satellite operations. Services were triumphantly restored in 2001, with new technologies and new satellites launched the next year. Today the constellation is an invaluable tool to government agencies, aerospace and maritime industries, and disaster relief efforts.

An Iridium satellite made headlines recently when it was involved in the in world’s first orbital collision involving active satellites. Iridium 33 and Russian satellite Kosmos 2251 collided at speeds of 27000 kph over Siberia, creating an orbiting debris field of over 500 pieces. The incident fueled concerns that the cluttering of space is becoming a serious problem for the future of the space industry. For now, the orbit of every stray screw and panel is carefully observed in an attempt to protect our assets in orbit, but sooner or later we are probably going to need a fleet of trash collecting recycle-sats. A Sunday’s satellite for 2015?