APPENDIX A: LEARNING THE LANGUAGE KEY SPACE TERMS AND ACRONYMS

• Antenna—A device for transmitting and receiving radio waves. Depending on its use and operating frequency, antennas can be a single piece of wire, a grid of wires, a sophisticated parabolic-shaped dish or an array of electronic elements.

• Apogee—The point at which a spacecraft is at its farthest point from the Earth’s surface.

• Astrobiology—Study of life on planets.

• Astronautics—The science of space travel, including the building and operating of space vehicles.

• Attitude—The position of a spacecraft as determined by the inclination of its axis to some point of reference.

• Attitude control—The orientation of the satellite in relationship to the Earth and Sun.

• Bandwidth—A measure of spectrum frequency use or capacity.

• Bioastronautics—Study of the effects of space travel on plant or animal life.

• Bus—The electronic brain of a satellite.

• C-band—Frequency range from 4-8 GHz. Primarily used for satellite communications, for full-time satellite TV networks or raw satellite feeds

• Celestial mechanics—Study of orbital paths of celestial bodies under the influence of gravitational fields.

• COTS—Commercial off-the-shelf.

• Cryogenic—Generally refers to liquids or the use of liquids at super-cold temperatures.

• DBS—Direct broadcast satellite, such as direct-to-home television or radio.

• Delta V—Velocity changes that enable a space vehicle to change its trajectory.

• DoD—US Department of Defense.

• Downlink data—The frequency range utilized by the satellite to retransmit signals to Earth for reception.

• DTH—Acronym for direct-to-home. Refers to direct broadcast satellite television and radio services.

• Earth station—Term used to describe the combination of an antenna, low-noise amplifier, down-converter, and receiver electronics used to receive a signal transmitted by a satellite.

• Eccentric orbit—An elliptical orbit, one with a very high apogee and a low perigee.

• Eclipse—When a satellite passes through the line between Earth and the Sun or Earth and the Moon.

• Equatorial orbit—An orbit with a plane parallel to the Earth’s equator.

• Escape velocity—The velocity a vehicle must attain in order to overcome the gravitational field.

• ESA—European Space Agency.

• Expendable launch vehicle (ELV)—A rocket that can only be launched once and whose components cannot be refurbished for future use.

• Fairing—The area of the launch vehicle where a payload is attached until its release into orbit.

• FCC—Federal Communications Commission.

• FEMA—Federal Emergency Management Agency.

• Footprint—A map of the signal strength showing the power contours of equal signal strengths as they cover the Earth’s surface.

• Frequency—Number of times that an alternating current goes through its complete cycle in one second of time.

• Frequency coordination—A process to eliminate frequency interference among different satellite systems or among terrestrial microwave systems and satellites.

• FSS—Fixed–satellite service—refers to services using satellites in geostationary orbit.

• Fuel cell—Miniature electric power plants.

• GEO—Geostationary Earth orbit or geosynchronous Earth orbit.

• Geostationary Earth orbit—The point in space at which an object will revolve at the same speed as a point on Earth. From Earth, the object appears to be stationary.

• Geosynchronous Earth orbit—See above.

• GIS—Geographical information system.

• GPS—Global Positioning System for satellites.

• Guidance, navigation, and control (GN&C)—System that measures the velocity and directory of the spacecraft, compares it with its memory, and issues commands for corrections.

• Hypersonic—Speeds faster than Mach 5 (five times the speed of sound).

• Inclination—The angle of an orbit. Equatorial orbit has an inclination of zero, a polar Earth orbit has an inclination of 90 degrees.

• Insurance—Multiple types of coverage exist to reduce financial risks related to the satellite, launch, and on-orbit operation.

• Integration—Technical activity regarding the combining of different systems and/or components, such as placing a satellite inside the launch vehicle.

• Ka-band—Frequency range from 26–40 GHz. Used for satellite communications

• Ku-band—Frequency range from 12–18 GHz. Used for satellite communications

• L-band—Frequency range from 1–2 GHz. Used for GPS carriers and also satellite mobile phones, such as Iridium; Inmarsat, etc.

• Launch vehicle—A vehicle that is used to deliver payloads from Earth to space. Also see entries for expendable launch vehicle and reusable launch vehicle.

• LEO—Low Earth orbit.

• Man-rated/Human-rated—Equipment considered reliable enough to be used by people.

• Mobile satellite services (MSS)—Satellite-based mobile telecommunications systems that provide coverage over extended areas including remote locations. These usually operate in a low- or near-Earth orbit to reduce signal delay.

• Mux/Demux—A multiplexer combines several different signals (e.g., video, audio, data) onto a single communications channel for transmission. Demultiplexing separates each signal at the receiving end.

• NOAA—National Oceanic and Atmospheric Administration.

• Orbit—The path of a body under the influence of gravitational or other force around another body.

• Orbital period—The time it takes to complete one orbit.

• Orbital velocity—The speed required to establish and maintain a spacecraft in orbit.

• Payload—The cargo that is being carried for a mission.

• Perigee—The point in an orbit at which the spacecraft is closest to Earth.

• Period—The amount of time that it takes a satellite to complete one revolution of its orbit.

• Polar orbit—An orbit with its plane aligned parallel with the polar axis of Earth.

• R&D—Research and development.

• RDT&E—Research, development, test, and evaluation.

• Receiver—An electronic device that enables a particular satellite signal to be separated from all others being received by an Earth station, and converts the signal into a format for video, voice, or data.

• Remote sensing—The collection of data from a distant location. Remotely sensed data is typically collected from sensors located on an aircraft, balloon, or spacecraft.

• Reusable launch vehicle (RLV)—A rocket that, after placing its payload in space, is returned to Earth and refurbished for future flights.

• RF—Radiofrequency.

• Rocket—See launch vehicle.

• Satellite—Sophisticated electronic device operating outside Earth that enables a variety of activities.

• Sensor—An electronic device that monitors or collects data.

• Slot—The longitudinal position in geostationary orbit at which a communications satellite is located.

• Sounding rocket—A research rocket that sends equipment to the upper atmosphere, takes measurements, and returns to Earth.

• Specific impulse—A means of expressing rocket performance.

• Spectrum—Range of electromagnetic radio frequencies used in the transmission of voice, data, and video.

• Spin-off—Commercial or other benefits derived from space research.

• Support services—Includes technical and business support activities, such as legal and licensing, finance, consulting, and publishing.

• Telemetry—Technique whereby information on the health, activity, and location of a spacecraft is measured and transmitted to Earth.

• Teleport—A facility that provides uplink and downlink services.

• Three-axis stabilization—Type of spacecraft stabilization in which the body maintains a fixed attitude relative to the orbital track and Earth’s surface.

• Transfer orbit—A highly elliptical orbit that is used as an intermediate stage for placing satellites in geostationary orbit.

• Transponder—A combination receiver, frequency converter, and transmitter package that is a physical part of a communications satellite.

• Turnkey—A system that is supplied, installed, and sometimes managed by one vendor or manufacturer.

• Uplink data—Earth to space communications pathway.

• USAF—United States Air Force.

• Value-added provider—An organization that modifies an existing product or data source before delivering it to the end customer. In remote sensing, value-added providers manipulate the raw data into more usable forms, such as a graphical map.

• VSAT—Acronym for very small aperture terminal. Refers to small Earth stations. Many are used to connect remote locations with a central computer, such as those for ATM bank machines, credit card processing, etc. Can also refer to systems enabling consumer / remote access to broadband.

• Window—Limited time period during which a space vehicle can be launched, if it is to accomplish its mission.