Putting Satellites in Their Place
It takes quite a bit of rocket science to get a man-made satellite into orbit above the earth. Aside from the fact that the rocket must be built and then successfully launched, there’s plenty of science involved in placing the satellite in the most favorable orbit. Orbit and altitude depend upon the type of satellite being placed into orbit.
Most satellites are custom-built according to the purpose of the satellite, though some are mass produced. Examples of mass production satellites include global positioning systems, or GPS, and iridium satellites that provide voice and data communications to satellite phones, pagers, and integrated transceivers over the entire earth.
Satellites get launched into orbit by riding on a rocket, or as payload in the space shuttle cargo hold. Several countries have the technology to launch rockets. At first, rockets are launched straight up and then, via an inertial guidance system, the rocket is tilted to the correct course in a pre-calculated flight plan.
An inertial guidance system (IGS) inside the rocket makes it possible for a satellite to be placed into a precise orbit. IGS employs the use of gyroscopes and accelerometers mounted in gimbals. The gyroscopes’ axes are always pointing in the same direction. Accelerometers can detect changes in acceleration on three different axes. The IGS can calculate the satellites correct orbit and altitude by knowing the rocket’s exact launch position and changes in rocket speed during flight.
Communication satellites relay data and voice communication to earth. Transmitter-responders (transponders, for short) on board the satellite are an electronic device used to wirelessly receive and transmit electrical signals. There many be a payload of up to 20 or 30 responders on board one communications satellite. In addition, the transponder also amplifies and filters signals which maintain the link from satellite to earth.
There are as many factors involved in getting satellites into orbit above the earth as there are satellites. It is a technology that we usually take for granted, but affects our lives so many ways on a daily basis.