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A spy satellite launched by NASA in December of 1988. Lacrosse's main instrument, like most spy satellites, was its image sensor. It also carried Synthetic Aperture Radar (SAR).

NASA's Long Duration Exposure Facility (LDEF) was launched in 1984 to study the effect of spending a long time exposed to the harsh conditions of space on different materials. In orbit for over five years, LDEF carried 57 experiments belonging to more than 200 investigators from universities, private companies, and NASA centres.

light year:
The distance that light travels in one year. Since light travels at 3.0 x 108 metres per second, then light travelling for one year would travel a total distance of 946.08 x 1013 metres in total. Since that's a really big number, it's easier to call that number one light year.

low Earth orbit:
An orbit within the Earth's atmosphere, but at its highest layer. Any satellite in a low Earth orbit can make observations of the Earth from fairly low down.

A NASA space exploration satellite that was launched from the Atlantis space shuttle in May 1989. Magellan produced photograph-like images of Venus' surface using a radar system that could see through Venus' many clouds.

The space around the Earth in which ions (charged particles) are controlled by the Earth's own magnetic field.

Mariner 2:
A NASA space exploration satellite that measured the temperatures of the clouds and surface of Venus. It was launched on August 27, 1962.

Mars Observer:
A NASA space probe launched September 1992 to study Mars.

Measurements of Pollution in the Troposphere (MOPITT):
An instrument, designed and built by Canada, to measure the global distribution of carbon monoxide and methane in the troposphere. In 1998, Canada's MOPITT will be on board the first of NASA's Earth Observing System.

meridian lines:
The imaginary lines that were drawn on the globe for navigational purposes. Meridian lines mark longitude and run through both the north and the south poles. They separate the Earth into time zones and they are used to indicate a coordinate on the Earth. The Greenwich meridian is the central meridian line from which all time zones are set.

Someone who studies the weather. Often, the person on the evening news who talks about the weather forecast is a meteorologist.

A geostationary weather satellite launched by the European Space Agency (ESA) and now operated by the company Eumetsat. The most recent version of Meteosat was launched in June 1988. It provides weather imaging of the Earth at both visible light and infrared wavelengths.

The basic unit for measuring length in the International System of Units (SI). This system is Canada's official system of measurement.

A form of electromagnetic radiation that is beyond the range of the visible light spectrum. Microwaves have very high frequencies and wavelengths of 1 mm to 50 cm.

Stands for Manned Maneuvering Unit. Astronauts on board a NASA space shuttle can strap on this large rocket backpack and maneuver during a spacewalk (officially known as an Extra Vehicular Activity) instead of remaining tethered to the shuttle or to the Canadarm.

A powerful communications satellite launched by the Canadian firm TMI Communications on April 20, 1996. MSat was Canada's first satellite designed to serve mobile users, especially those in remote areas out of the reach of conventional communication systems.

The trade name of DuPont for their product used as thermal blanketing. It is a very thin material that has a shiny appearance. It is often used as an insulator in satellites, as well as for things on Earth like juice box packaging and emergency first-aid blankets.

An acronym for the United States National Aeronautics and Space Administration. NASA was created by Congress in 1958 to do three things: conduct aeronautical and space activities, create a science program using aeronautical and space vehicles, and inform the public as widely as possible about agency activities and their benefits.

navigation satellite:
A type of satellite that gives ships and aircraft their coordinate positions on the Earth. Navigation satellites were developed in the 1950's, and they rely on the doppler effect to calculate the position of vessels emitting a radio signal. Navigation satellites are also widely used by the military.

A series of American navigation satellites. The first satellite in the Navstar system was launched in 1978. Currently, there are 24 orbiting Navstar satellites. The three-dimensional satellite navigational system of Navstar enables a traveller to find out his or her position anywhere on or above the planet.

Near Infrared Camera and Multi-Object Spectrometer (NICMOS):
An example of an infrared camera that is currently in use aboard the Hubble Space Telescope.

Cloud of glowing gas in space, lit up by hot young stars within it.

At its launch on July 12,1989, the largest civilian telecommunications satellite in the world. Olympus was an experimental satellite built for the European Space Agency (ESA) by British Aerospace.

The path of a satellite, planet, or heavenly body around another, larger, body in space. For example, the Earth is in orbit around the Sun. The Moon is in orbit around the Earth. Orbits differ in their eccentricities.

A very small piece of matter that moves and has energy. Particles are the fundamental things that make up the universe.

The equipment carried into space by a space vehicle. The payload of a satellite includes all of the instruments and science experiments - anything that is not essential to basic functioning of the satellite, but used for science, data collection, or tools.

Payload Bay:
The storage compartment of NASA's space shuttle. The Payload Bay, found on the top of the space shuttle, has large doors that open into space. When satellites are sent into space aboard the space shuttle, they are held in the Payload Bay.

Gas that has very high numbers of ions (charged particles). In a plasma, the number of free electrons is almost the same as the number of positive ions.

Satellite launched on February 24, 1996 by NASA in the Global Geospace Science project. Polar is an atmospheric studies satellite in polar orbit. One purpose of Polar is to gather information that will help scientists protect future satellites from radiation and other atmospheric dangers.

polar orbit:
Usually has an angle of inclination of 90 degrees to the equator. On every pass around the Earth, it passes over both the north and south poles. Therefore, as the Earth rotates to the east underneath the satellite which is travelling north and south, it can cover the entire Earth's surface. A polar orbiting satellite covers the entire globe every 14 days.

The result of light being passed through a filter that makes the light travel in all different directions, therefore making different rays of the light behave differently from one another. The filter is called a polarizing filter.

Puts out tremendous amounts of energy from a very small source. Known as the most intense concentrations of energy in the entire universe, quasars shine with the light of a hundred galaxies, but they are no larger than our solar system.

By emitting high frequency radio waves and measuring where and how fast they were reflected, a radar instrument can measure things like distance, direction, speed, etc. A radar instrument can "see" objects in the dark as well as penetrate cloud cover.

A revolutionary new satellite launched by the Canadian Space Agency on November 4, 1995. This remote sensing satellite uses radar to take images useful for agriculture, oceanography, forestry, hydrology, geology, cartography, and meteorology.

The harmful combination of waves and particles, known as high energy rays, emitted from a source.

radio telescope:
An instrument to pick up radio waves for analysis. Radio telescopes "see" things that are too far away to see in normal light by usimg radio waves. Satellites often use parabolic dishes with radio telescopes.

An instrument to measure the changing levels of radiation as well as visible and infrared light. They can produce cloud images even at night.

reconnaisance satellite:
Also called a spy satellite because it is used to spy on other countries. It can provide intelligence information on military activities, detect missile launches or nuclear explosions, and pick up and record radio and radar transmissions while passing over a country. It can also be used as an orbital weapon by placing warheads on a low orbit satellite to be launched at a ground target, but this is not a recommended or frequent use of satellites.

remote sensing:
The process of collecting data about something from a point far away. A satellite making observations of the Earth, therefore, is using its equipment for remote sensing.

remote sensing satellite:
A type of satellite that performs remote sensing from space. Remote sensing satellites generally monitor important resources for humans. For example, they might be used to track animal migration, locate mineral deposits, watch agricultural crops for weather damage, or see how fast the forests are being cut down. Because they are in space, remote sensing satellites are ideal for monitoring areas with harsh climates or difficult terrains.

An instrument that receives and retransmits signals anytime the satellite is close enough to be in contact with a ground station.

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