Satellites have been much in the news recently–or, if you were trying to watch CBC Newsworld last week, in the absence of news. The failure of the Anik E-2 satellite drove home as nothing else could have just how important satellites have become to our everyday lives. (People really sit up and take note when you deprive them of television. As Dire Straits put it so succinctly, “I want my MTV!”!)
An artificial satellite is a man-made object orbiting the Earth. An object orbits when its horizontal velocity is so high that the Earth curves away from it as fast as gravity pulls it down. At sea level, orbital velocity is approximately 28,500 kilometres an hour, but of course we don’t orbit anything at sea level, since it would make huge holes in beachfront property.
The higher you go, the lower the orbital velocity, but the longer it takes to circle the Earth. At 35,840 kilometres a satellite orbits the Earth once every 24 hours at only 11,050 kilometres an hour. Since it orbits at the same speed as the Earth rotates, it’s called “synchronous.” If it also orbits around the equator it’s “geostationary,” because it’s always over the same point on the Earth’s surface.
Isaac Newton grasped the possibility of orbiting an artificial satellite in 1687, but it took the development of rockets in the 20th century to make it a reality. In 1955 the USSR (remember it?) and the U.S. both announced plans to launch satellites for the International Geophysical Year. The USSR shocked everyone by doing it first, orbiting Sputnik 1 on October 4, 1957. The U.S., after a series of embarrassing failures, orbited Explorer 1 on Jan. 31, 1958.
The first satellites explored the space environment (Explorer, for example, discovered the Van Allen radiation belts that encircle the Earth), and also proved the feasibility of satellites. Since 1957 several thousand satellites have been placed in orbit, performing a variety of tasks. There are communications satellites, scientific research satellites, navigation satellites, reconnaissance satellites, weather satellites and land and sea observation satellites.
First proposed by science fiction writer Arthur C. Clarke in the 1940s, communications satellites allow radio and television signals to be transmitted around the globe, without the horizon getting in the way. The first communications satellites were just silver balls off of which signals could be bounced. Today’s satellites receive signals and then actively amplify and re-transmit them to satellite dishes worldwide.
Some satellites serve the whole globe; others, such as the ill-fated Anik E-2, serve particular countries. It was actually Anik E-1, a sister satellite to Anik E-2, that malfunctioned first, but ground technicians were able to recover it. They’d just done so when Anik E-2 went out.
Both satellites are in geostationary orbits 36,000 kilometres above the equator, with their transmitters aimed at Canada. At that distance, a shift of just two degrees in direction can cause the signal to miss its receiving stations by as much as 2,500 kilometres. Anik E-1 was out of position for about eight hours, disrupting TV, radio and telephone signals. So far Anik E-2 is still out. Many specialty and U.S. channels were off the air last week as a result. Most have been shifted to other satellites, but they’re still out in some regions, because satellite dishes have to be re-aimed and that’s not always easy.
Both satellites appear to have been hit by an intense electromagnetic storm thrown off by the sun. The theory is that the storm charged the Anik E-2 satellite with electricity, blowing a circuit. Anik E-2, as big as a delivery truck and costing $300 million, was launched just two years ago and was supposed to last for 12 years. And just to make Telesat Canada really happy, it wasn’t insured. (Most satellites aren’t. Considering what I have to pay for insurance just because I drive a sports car, I’m not surprised.)
Scientific research satellites study space itself. Probably the most famous is the Hubble Space Telescope, designed to provide images of the universe undistorted by Earth’s atmosphere. Instead, it provided images of the universe distorted by its own misplaced mirror. However, the recent repair mission by space shuttle astronauts has been incredibly successful. New images being received now indicate that Hubble’s myopic days are over.
Navigational satellites emit continuous radio signals that allow people on the ground to pinpoint their location anywhere on the Earth. Forget sextants: most ships now fix their positions via the Global Positioning System satellites that encircle our planet.
Reconnaissance satellites are military satellites designed to monitor troop movements, detect missile launches, track warships, etc. They were used extensively in the search for Scud missile launchers during the Gulf War, for example.
The first weather satellite was launched in 1960, and since 1966 the entire Earth has been photographed at least once a day on a continuous basis. Satellite data is combined with ground-based observations to greatly enhance weather forecasting. One example: before satellites, hurricanes struck coastal areas with little or no warning. Today, thanks primarily to weather satellites, even horrendous storms like last year’s Hurricane Andrew cause relatively little loss of life.
Land and sea observation satellites are scientific satellites that study the Earth instead of space. Using not just optical sensors, but also microwave, X-ray and infrared sensors, satellites can provide valuable information on global wheat production, deforestation, mineral and oil deposits, pollution, etc.
The only down side to the plethora of satellites orbiting the Earth is that, believe it or not, it’s getting crowded out there. And it’s not just the satellites: there’s a lot of pure junk floating around, from nuts and bolts to flecks of paint. And if you think a fleck of paint isn’t a problem, think again: on at least one occasion the space shuttle has returned from a mission with a nasty little crater in one of its windows. The culprit? A fleck of paint.
Anything moving at several tens of thousands of kilometres an hour packs quite a wallop. There is concern that if efforts aren’t made to control space junk, we may eventually seal ourselves inside a ring of garbage so extensive we won’t be able to launch anything into space without it running the risk of being damaged or destroyed.
If that happened, we’d end up with a world without artificial satellites once again–and as we in Canada have just discovered, it would be a very different world from the one we’ve grown accustomed to.
