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- David Florida Laboratory:
- A Canadian laboratory in Ottawa where satellite equipment is tested before launch to make sure that it can withstand the shock of launch and the harsh conditions of space.
- dawn-to-dusk orbit:
- A type of sun-synchronous
orbit where the satellite is always in the sun. This allows the
satellite to be powered almost entirely by its solar panels.
- Deep Space Network:
- A worldwide effort, coordinated by NASA, that communicates with spacecraft in an Earth orbit at any time in that spacecraft's orbital period. There are three ground stations in the Deep Space Network, each at a different place on the globe so that they can each reach a spacecraft when it is over a different position on the Earth. The ground stations have very large dishes that act as antennas to receive and transmit signals to the spacecraft. There is also a control centre on Earth, run by NASA, that coordinates all the transmissions.
- design criteria:
- Guidelines or specifications that an engineer must decide on before designing something. Design criteria are generally written as: "the ____, the better". For example, some satellite design criteria are "the lighter, the better" and "the more durable, the better".
- doppler effect:
- An apparent shift in the frequency of a wave. For example, when
someone is listening to the sound of an ambulance siren, and that person is
staying still but the ambulance is driving by, the person will hear a change
in pitch of the ambulance siren. That change in pitch is caused by the
doppler effect. The frequency of a sound wave determines the pitch, and the
distance of the source of the sound from the sound's observer determines the
amount that the frequency seems to have shifted, known as the doppler shift.
- downlinked:
- The process by which a satellite sends information from space back to Earth. The satellite translates its computer information into radio waves and sends those waves back to Earth via its antenna. On Earth, another antenna, usually in the form of a dish, picks up the radio waves and translates them back into a form that computers can understand.
- eccentricity:
- Eccentricity is a measure of how circular a satellite’s orbit is. For a perfectly circular orbit the eccentricity is zero; elliptical orbits have eccentricities between zero and one. The higher the eccentricity, the more "squashed" the orbit is.
- electromagnetic spectrum:
- Different kinds of
electromagnetic waves can be classified by their wavelenghts. They are
classified into sections called bands. The electromagnetic spectrum is the
collection of these bands. The following types of waves make up the
electromagnetic spectrum: gamma rays, x-rays, ultraviolet rays, visible
light, infrared waves, and radio waves. The length of these waves ranges
from 10-12 metres to 102 metres long; this is known as
the wavelength. Click here for
a picture of the electromagnetic spectrum.
- electron:
- A small charged particle with a negative charge. Every atom has electrons. The number of electrons is different in every element. A transfer of electrons produces electricity.
- elliptical
orbit:
- An orbit where the satellite moves in a big ellipse (a
shape like a flattened circle). A satellite in an elliptical orbit is
sometimes close to the object it is orbiting and sometimes far away from it.
A satellite in an elliptical orbit, especially a highly eccentric one, will move faster when it
is close to the planet and slower when it is far away. An elliptical orbit
can be useful to a communications
satellite.
- encryption device:
- An instrument often used in spy satellites. It encodes digital images or data before it is sent back to Earth.
- equator:
- The imaginary circle drawn around the middle of the Earth. It runs east-west, marking latitude (side to side). It is found halfway between the north pole and the south pole.
- equatorial orbit:
- The satellite flies along the line of the Earth's equator. Equatorial orbits can be useful for satellites observing tropical weather patterns, as they can monitor cloud conditions around the globe.
- Faint Object Camera (FOC):
- An instrument built by the European Space Agency, which is currently in
use on the Hubble Space Telescope.
- focal length:
- The distance needed between a lens and an object to make the object visible and in focus. The human eye has different focal lengths depending on how much the muscles in the eye around the lens are contracted. That is how the human eye focuses.
- footprint:
- The area with which a satellite in
geostationary
orbit can communicate. A footprint can be as large as an
entire country; for example, many Canadian satellites have footprints almost
the entire size of Canada, from coast to coast. Click here for a picture of a satellite's footprint.
- frequency:
- The number of times a wave
completes its cycle per unit of time. The frequency of a soundwave
determines the pitch. Usually, frequency is measured in Hz
which is the number of cycles (undulations) of the wave per second. Click
here for a picture of a wave
cycle.
- frequency bands:
- The grouping together of electromagnetic waves of a similar frequency. In spectroscopic studies, one type of wave from the electromagnetic spectrum will show up as a band of colour that can be interpreted as a frequency band. This allows scientists to figure out what kind of energy is coming from a particular source For example, X-rays would make up a frequency band. Some bands are wider than others.
- Galileo:
- A NASA space exploration satellite that was launched on October 18, 1989. Galileo was sent to Jupiter to study the planet's atmosphere , moons, and surrounding magnetosphere, for 2 years starting in December 1995. It was named for the Italian Renaissance scientist who discovered Jupiter's major moons in 1610 with the first astronomical telescope.
- geomagnetic:
- Having to do with the magnetic properties of the Earth. Geomagnetic activity includes anything that changes the numbers of charged particles found in one area of the Earth.
- geostationary
(geosynchronous) orbit:
- An orbit in which a satellite appears
to remain in the same spot in the sky all the time. When a satellite is in
geostationary orbit, it travels at exactly the same speed as the Earth is
rotating below it. A satellite in geostationary orbit is very high up, at
35 850 km above the Earth. Geostationary satellites are always located
directly above the equator. The area with which a satellite in
geostationary orbit can communicate is called its footprint.
- Global Positioning System (GPS):
- A satellite technology that uses mathematics to calculate the position in three dimensions (latitude, longitude, and altitude) of something on the Earth by measuring the time it takes for the satellite's radio transmissions, travelling at the speed of light, to reach the a receiver on the ground. It requires a fleet of satellites in space. Applications of this technology include determining a position on the Earth, measuring the Earth's movement after an earthquake, or locating drop points for airlifted relief supplies.
- grapple fixture:
- A long metal pin affixed to satellites so that they can be grasped by the Canadarm for launch, retrieval, or repair.
- Greenwich meridian:
- The central meridian line from which all time zones are set.
- gyroscope:
- A spherical object that spins stably in all three planes. It takes a lot of energy to move a gyroscope because its spin is so stable. Satellites can either spin themselves, acting as large gyroscopes, or they can have small internal gyroscopes which act as sensors to tell the satellite when its direction is changing, so the satellite can correct the problem using its thrusters. Gyroscopes have long been used as a tool to keep ships and airplanes stable. They are also common as toys.
- Hermes:
- The first satellite to experiment with small satellite dishes for television. This use of small dishes made live news reports from remote locations possible. The Canadian Hermes satellite was launched on January 17, 1976.
- Hertz:
- an SI unit for measuring frequency. It is measured in cycles per second where a cycle is one full undulation of a wave. The symbol for a Hertz is Hz; one million Hz is known as MHz; one billion Hz is known as GHz.
- Hubble Space Telescope:
- A satellite launched by NASA in April, 1990. It
is the largest telescope ever built to go into space. It is known as an
astronomical observatory - in both senses of the word! Hubble is extremely
powerful, able to look deep into space to study distant galaxies and
stars.
- infrared:
- Light waves that are slightly longer than visible light waves. They are found to the right of visible light in the electromagnetic spectrum. Infrared rays create most of the heat from sunlight and incandescent light bulbs.
- infrared camera:
- An instrument that measures heat. Infrared cameras are often used to detect weather patterns or volcanic erruptions.
- internal computer:
- The satellite's method of storing and analyzing data collected by the
satellite, and a way of controlling its various systems. The technical term
for this satellite subsystem is TT&C (Telemetry, Tracking, and
Control).
- ion:
- An atom or a molecule that has lost or
gained an electron. An ion is also known as a charged particle. Ions are
usually more reactive than neutral, uncharged particles. They cause all
sorts of things from static electricity and chemical reactions like smog, to
body processes like cellular respiration and digestion.
- ionization:
- The process of becoming an ion.
- ionosonde:
- an instrument used to measure the ionization of gases in the atmosphere of a planet or a moon.
- ionosphere:
- a region of gases, very high up in the atmosphere, that contains ionized gases.
- ISDN lines:
- ISDN stands for Integrated Services Digital Network. Normally, people are connected from their home to the phone company through a phone line. When using a modem to connect to the Internet, the signals would go through this phone line. People can, however, also use a digital connection for their phones and modems. When connecting to the Internet, where all the data is digital because it is stored on computers, the connection through the ISDN line is much faster with fewer errors.
- ISIS:
- An acronym for the International Satellites for Ionospheric Studies program. After the successful launch of Canada's first satellite, Alouette, Canada and NASA embarked on this international project for atmospheric studies. The ISIS program launched Alouette 2, ISIS 1, and ISIS 2.
- Klein, George:
- A National Research Council engineer who solved an important engineering problem in the design of Alouette, Canada's first satellite. Klein invented STEM antennas, allowing Alouette to have the necessary long antennas while still being small in size.
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