Introduction to Microgravity
Tutorial on Microgravity Research

Tutorial on Microgravity Research


Geosynchronous Earth Orbit (GEO): The geosynchronous orbit is at the altitude of 22,300 miles above the earth. Satellites that provide continuous communications services or weather data are placed in geosynchronous orbit at a distance from the Earth of 22,282 miles. These satellites circle the Earth in 24 hours--the same time it takes the Earth to rotate one time. If these satellites are positioned over the equator and travel in the same direction as the Earth rotates, they appear "fixed" with respect to a given spot on Earth. Satellites in GEO are always able to "see" the receiving stations below, and a satellite in this high orbit can cover a large part of the planet; three satellites can cover the globe, except for the parts near the north and south poles.

Geostationary Transfer Orbit (GTO): This orbit is at 100 miles above Earths surface, from where a satellite may be boosted on to geosynchronous orbit.

License: Grant permission for a company to utilize a patent or technology. Typically, the company which owns the patent receives an intitial payment plus a royalty fee for granting permission to utilize the patent or technology. Royalty fees between 1-5% of gross revenues are typical.

Lower Earth Orbit (LEO) satellite: Low earth orbit satellites orbit the earth at a distance between 150 to 1000 miles above the surface of the earth. Because these satellites are close to the Earth, they must travel very fast to avoid being pulled out of orbit by gravity and crashing into the Earth. Satellites in low Earth orbit travel about 17,500 miles per hour. These satellites can circle the Earth in about an hour and a half.

Medium Earth Orbit (MEO) satellite: Medium earth orbit satellites orbit the earth at a distance between 4000 to 7000 miles above the surface of the earth. Communications satellites that cover the north pole and the south pole are placed in a medium altitude, oval orbit. Receivers on the ground must track these satellites. Because their orbits are larger than LEOs, they stay in sight of the ground receiving stations for a longer time.

Microgravity: Also called weightlessness or zero gravity, it is the absence of gravity. It is bested illustrated by astronauts floating in their spacecraft. They are floating because they are in a microgravity environment. Besides astronauts, many people experience microgravity every day by riding roller coasters or jumping off diving boards. It is the "free fall" period of these activities when the microgravity occurs and of course only lasts for a short period of time.

Orbit: When a satellite is launched, it is placed in orbit around the Earth. The Earth's gravity holds the satellite in a certain path as it goes around the Earth, and that path is called an "orbit."

Payload: The satellite, instrument package, or equipment carried by the rocket for the flight. It is the cargo. Typically it is the reason why the "customer" is paying for the flight.

Patent: Grants the owner a legitimate monopoly on the right to exclude others the making or selling of an invention. In the United States and most major countries that monopoly is for 20 years.

Sounding Rocket: The rocket goes up and comes down in the same general vecinity, never getting into orbit. Todays sounding rockets can provide between 3 to 9 minutes of microgravity at a cost of approximately $1,000,000 per launch and payloads weighing around 1000 pounds (which equates to $1000 per pound).

Suborbital: The flight of a rocket which goes up and comes down but never orbits the Earth. It can be the flight of a child's rocket which goes 1000 feet high or a sounding rocket that goes 1000 miles high.

Zero Gravity: See "microgravity."