Georbit Essay, Research Paper

Physics

Geosynchronous Orbits

Geosynchronous Orbits + Geostationary Orbits

Webster’s dictionary defines a Geostationary orbit as of, relating to, or being a

satellite that travels above Earth’s equator from west to east at an altitude of

approximately 35,900 kilometers (22,300 miles) and at a speed matching that of Earth’s

rotation, thus remaining stationary in relation to Earth. 2. Of, relating to, or being the

orbit of such a satellite. In plain English, a satellite matches the earth’s rotation making it

seemingly hover over one spot of the globe enabling coverage of half the earth’s surface.

Three such satellites, appropriately spaced longitudinally, have worldwide coverage

except for relatively small areas over the poles. Three main classes are typically placed

into a GSO: Communications, missile early warning, and navigational satellites. The uses

are unlimited ranging from commercial use to weather forecasts!

The GSO originated in the mid-1970’s. The U.S. Air Force designed a two-stage

interim upper stage (later renamed inertial upper stage, or IUS) to carry satellites

weighing as much as 5,000 pounds (2,300 kg) from the shuttle to Geostationary orbit,

and a three-stage version for boosting NASA’ s space probes from the shuttle into

interplanetary trajectories. IUS development problems, however, prompted NASA in the

early 1980′ s to design a widebody version of the Centaur upper stage to replace

the three-stage IUS.

In its first use (1983) aboard the shuttle, the IUS’s second-stage nozzle burned

through and left the first Tracking and Data Relay Satellite (TDRS-1) in a useless orbit.

Ground controllers were able to use the satellite’s onboard thrusters to put it in the

proper Geostationary orbit over a period of weeks, but the IUS was grounded until the

nozzle problem was resolved.

Because the IUS was too large and expensive for most satellites going

to Geostationary orbit, McDonnell Douglas developed the payload assist module, a

special cradle with a turntable to spin and then release satellites. A small rocket motor

and the satellite’s own rockets then boost it into Geostationary orbit.