We talked with Jasmin Jajina, a systems engineer with OnStar. We asked her what students should know when studying satellites. Here's what she had to say:
Terrestrial satellites revolve around the earth in four categories of orbits:
Satellites in Low Earth Orbit must travel at high speeds in order to stay in orbit, as per the physics of centripetal forces. They are typically used for remote sensing and weather prediction.
A satellite in Polar Orbit is in a north-south Low Earth Orbit.
Satellites in Geo-synchronous Equatorial Orbit (GEO) have a larger orbit radius and maintain a fixed position relative to the earth. Most communications satellites are GEO satellites.
A satellite in elliptical orbit follows an elliptical path in a north-south direction. Communication satellites in elliptical orbits cover the high northern and southern hemispheres not otherwise covered by geo-synchronous satellites.
Satellites are launched into space via a multi-stage rocket launch vehicle that ensures that the satellite is placed in orbit at the appropriate velocity to counter the earth’s gravity.
The cellular network is a terrestrial network of cell towers and Mobile Switching Centers that connect into the regular wire-line. As a mobile cell-phone user travels from point A to point B, his/her active call is handed off from one cell tower to another. Cell-phones use radio waves to communicate with cell towers.
OnStar-equipped vehicles use the U.S. military’s GPS satellites to measure their current location. OnStar uses terrestrial cellular technology to communicate (data and voice) between the vehicle and the OnStar Call Center or to allow customers to make personal calls.
Read the rest of the interview with Ms. Jijina >>
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