What is a Satellite? | How it works.
Credit: NASA
A satellite is an object in space that orbits or circles around a bigger object. There are two kinds of satellites: natural (such as the moon orbiting the Earth) or artificial (such as the International Space Station orbiting the Earth).
There are dozens upon dozens of natural satellites in the solar system, with almost every planet having at least one moon. Saturn, for example, has at least 53 natural satellites, and between 2004 and 2017, it also had an artificial one — the Cassini spacecraft, which explored the ringed planet and its moons.
How Satellites Work?
Not so long ago, satellites were exotic, top-secret devices. They were used primarily in a military capacity, for activities such as navigation and espionage. Now they are an essential part of our daily lives. We see and recognize their use in weather reports, television transmission by DIRECTV and the DISH Network, and everyday telephone calls. In many other instances, satellites play a background role that escapes our notice:
- Some newspapers and magazines are more timely because they transmit their text and images to multiple printing sites via satellite to speed local distribution.
- Before sending signals down the wire into our houses, cable television depends on satellites to distribute its transmissions.
- The most reliable taxi and limousine drivers are sometimes using the satellite-based Global Positioning System (GPS) to take us to the proper destination.
Fig. NAVSTAR GPS
- The Goods We buy often reach distributors and retailers more efficient and safety because trucking firms the progress of their vehicles with the same GPS. Somethimes firmes will eventell their drivers that they are driving too fast.
- Emergency radio beacons from downed aircraft and distressed ships may reach search and rescue teams when satellite reley the signal.
Whose Satellite Was the First to Orbit Earth?
The Soviet Sputnik satellite was the first to orbit Earth, launched on October 4, 1957.
Fig. Sputnik 1, the first satellite, shown with four whip antennas
Photo courtesy NASA
Because of Soviet government secrecy at the time, no photographs were taken of this famous launch. Sputnik was a 23-inch (58-cm),184-pound (83-kg) metal ball. Although it was a remarkable achievement, Sputnik's contents seem meager by today's standards:
- Thermometer
- Battery
- Radio transmitter - changed the tone of its beeps to match temperature changes
- Nitrogen gas - pressurized the interior of the satellite
On the outside of Sputnik, four whip antennas transmitted on shortwave frequencies above and below what is today's Citizens Band (27MHz). According to the Space Satellite Handbook, by Anthony R.Curtis:
After 92 days, gravity took over and Sputnik burned in Earth'satmosphere. Thirty days after the Sputnik launch, the dog Laika orbited in a half-ton Sputnik satellite with an air supply for the dog. It burned in the atmosphere in April 1958.
How is a Satellite Launched into an Orbit?
All satellites today get into orbit by riding on a rocket or by riding in the cargo bay of the Space Shuttle. Several countries and businesses have rocket launch capabilities, and satellites as large as
several tons make it safely into orbit on a regular basis.
ARIANE 44L (four liquid strapon
boosters) at liftoff from
French Guiana, October 1998
Photo courtesy Arianespace
For most satellite launches, the scheduled launch rocket is aimed straight up at first. This gets the rocket through the thickest part of the atmosphere most quickly and best minimizes fuel consumption.
After a rocket launches straight up, the rocket control mechanism uses the inertial guidance system to calculate necessary adjustments to the rocket's nozzles to tilt the rocket to the course described in the flight plan. In most cases, the flight plan calls for the rocket to head east because Earth rotates to the east, giving the launch vehicle a free boost. The strength of this boost depends on the rotational velocity of Earth at the launch location. The boost is greatest at the equator, where the distance around Earth is greatest and so rotation is fastest.