Satellites and sensors

Satellites and Sensors

A satellite is an object that moves around
a larger object. Earth is a satellite because
it moves around the sun. The moon is a
satellite because it moves around Earth.

But here we are referring to “human-made”

satellites. These objects are launched into space and orbit Earth, or another body in space, and carry instruments for collecting information and communicating it back to the earth

 

How Many Are There?

There are approximately 3,000 satellites operating

in Earth orbit, according to the US Government.There are another 8,000 dead satellites and rocketparts in orbit. Smaller orbital debris or “space junk”is of growing concern as it can damage active satellites.There are currently over 20,000 pieces of trackable debris 3.6 inches (10cm) or larger resulting mostly from explosions and collisions. Because of the extreme velocities, pieces of debris as small as 1mm can cause significant damage in the eventof a collision.

Kinds of Satellites

There are many different kinds of satellites designed for many different purposes. They can be grouped in the following general categories. This exhibit focuses on the first two categories.

• Weather and Atmosphere Monitoring

• Earth Observation and Mapping

• Astronomical and Planetary Exploration

• Communication

• Navigation (GPS)

• Military

  

Artists’ conception of satellites on the left depicting (clockwise from top left): GOES-R (future geostationary, weather), Landsat-7 (Earth Observing), QuickSCAT (Earth Observing,winds), NOAA-18 (current polar orbit, weather), GPS Block IIIA (future GPS),Sentinel Ib (future European C-BandRadar). 

Sensors

Satellites are equipped with one or more sensors or

instruments depending on their purpose. Some

sensors are passive and record reflected solar radiation

(such as visible light) and emissive radiation

(such as thermal energy). Other instruments are

active and send pulses of energy (by radar or laser)

through the atmosphere to the surface of the Earth

and record the returning signal. The science of satellite

observation is called “remote sensing.” Sensors