Glossary - I

Impulse
the change in momentum of an object as a result of a force applied to it
(physics)

Inbound
in a VSAT system, a carrier transmitted from remote terminals to the hub
(satellite communications)

Inclination
1: the angle between an object’s equator and an external reference plane, for example the angle between a planet’s equator and the plane of the ecliptic
(orbital geometry)

Inclination
2: the angle between a satellite's orbital plane and the plane of the equator
(orbital geometry)

Inclined orbit
1: a geostationary orbit in which north-south station keeping has been stopped to conserve fuel and extend lifetime and hence the satellite wanders about the nominal location
(satellite communications)

Inclined orbit
2: an orbit inclined with respect to the plane of the earth's equator
(orbital geometry)

Inclinometer
a device used to measure a vertical angle; used in dish installation
(earth station technology)

Inferior planet
a planet which orbits the Sun within the orbit of the Earth (ie Mercury and Venus)
(planetary science)

Inferior conjunction
an alignment of the Earth, Sun and either Mercury or Venus on the same side of the Sun
(astronomy)

Infrared
a form of electromagnetic radiation between visible light and microwaves in the electromagnetic spectrum; infrared radiation has a wavelength between about 1 mm (300 GHz) and 700 nm (430 THz)
(physics)

Integrated Receiver Decoder
a receiver for compressed digital television signals which includes a decoder and an authorisation device
(earth station technology)

Interference
unwanted signals, opposed to noise, received with the desired signal which degrade the quality of the wanted signal
(communications)

International Space Station (ISS)
a large modular space station in low Earth orbit built and operated by five space agencies - NASA (USA), Roscosmos (Russia), ESA (Europe), JAXA (Japan) and CSA (Canada)
(human spaceflight)

Internet of Things (IoT)
an interconnected network of devices with sensors and processing which exchange data with other IoT devices and the cloud across the internet
(communications)

Intersatellite link
a direct communications link between two orbiting satellites which does not use an intermediary earth station
(spacecraft technology)

Ion
an atom or molecule which has either a positive of negative electrical charge as a result of either losing or gaining one or more electrons, or as the result of a covalent bond between atoms being broken
(physics)

Ionising radiation
high energy radiation which ionises the atoms or molecules of material it passes through; ionising radiation includes gamma rays, X-rays, high energy ultraviolet radiation, and most subatomic particles
(physics)

Isotropic
having the same properties in all directions
(technology)

Isotropic antenna
theoretical antenna which has the same gain, and therefore radiates the same power, in all directions
(technology)