Accelerometer: An instrument that measures changes in acceleration of the vehicle in which it is installed


Apogee: The farthest point reached by a satellite orbiting the Earth


ASI - Italian Space Agency: National public body under the Ministry of Universities and Research, which coordinates the efforts and Italy's investments in the Space sector - site


C-Band: Frequency band with transmission (uplink) between 5.925 and 6.425 GHz and reception (downlink) between 3.7 and 4.2 GHz. C-band is primarily used for voice and data communications and for backhauling


CNES - Centre National d'Études Spatiales: French national space agency - site


Core Ground Segment: It includes all the elements for monitoring and controlling the satellite and for downloading, processing and disseminating the data to the users. The main elements are: the Satellite Control Centre, responsible for all aspects of flight operations, including monitoring and control, the execution of all platform activities and command of payload schedules, the Ground Station, where the TT&C and payload data are downlinked, the Mission Planning system, responsible for mission planning activities, the Flight Dynamic system, to deliver the orbital information.


DLR - Deutsches Zentrum für Luft-und Raumfahrt: German space agency - site


Downlink: Transmission of a signal from the satellite to the earth. In a network it is typically referred to the link between a network hub over the satellite to a remote site


ENVISAT - ENVIronment SATellite: ESA environmental satellite that observes the atmosphere, ocean, land, and ice, with the goal of aiding environmental studies and climate change. The mission was declared over in 2012 - site


EO - Earth Observation


ESA - European Space Agency: Participated by 17 states that collaborate on Space projects - site


Escape velocity: The velocity that a body must reach to escape the gravitational pull of the planet. This depends on the mass of the planet itself


ESOC – European Space Operation Centre: The European Space Operation Centre of ESA, located in Darmstadt, Germany. The control of the satellites, from their launch and throughout the duration of their mission in orbit, is managed by ESOC and 9 control stations, scattered throughout the world, which transmit the commands for positioning and activation of the on-board equipment - site


EVA - Extra-Vehicular Activity: Extra-vehicular activity means the operation carried out by the astronauts when leaving the ISS to perform their duties


Geostationary orbit: The orbit at a height of 35,785 km above the Equator on which telecommunications satellites are located. On this orbit, satellites rotate in synchrony with the rotation of the Earth and therefore appear stationary to earth antennae. In this way it is possible to ensure their continuous use


GMES - Global Monitoring for Environment and Security: A European Union-led initiative to perform and provide Earth monitoring in six areas: marine, land, atmosphere, emergency, security, and climate change - site


GIS - Geographical Information System: System that gathers, transforms and displays space data for a vast range of purposes


GPS - Global Positioning System: Constellation of radio-transmitter satellites for navigation built by the US Department of Defence. It is used to determine at any place on Earth the three-dimensional positioning of an object located on the surface of the Earth or in the vicinity thereof


Gyroscope: Rotating physical device which, due to the law of conservation of angular momentum, tends to hold its spin axis oriented in a fixed direction. It is a vital instrument on board satellites to manage their position


Ground Segment: All the earth stations that are operating within a particular satellite system or network. These can be connected to the end-user's equipment directly or via a terrestrial network


Heliosynchronous orbit: Orbit synchronised with the rotation of the Earth around the Sun so that its passage over the same area always occurs at the same local time


High Gain Antenna: Parabolic antenna that sends data with a beam concentrated and focused on the terrestrial antennas


IOT - In Orbit Test: Test activity to verify the correct behaviour of on-board equipment on newly launched satellites


IOV - In Orbit Validation: Test activity to validate on-board equipment on newly launched satellites


ISS - International Space Station: The large inhabited base in orbit around the Earth at a height of 400 km. As big as a football pitch, it was built by the United States, Russia, Europe, Japan and Canada. Six astronauts live permanently on board carrying out scientific and technological research, Earth observations and astronomical research


Ka-band: Frequency band with transmission (uplink) between 26.5 and 40 GHz and reception (downlink) between 18 and 20 GHz. Ka-band is primarily used in the consumer and residential market for broadband satellite communications, but lately it has also found use in the corporate and military sectors (Ka-MIL)


Ku-band: Frequency band with transmission (uplink) at 14 GHz and reception (downlink) between 10.9 and 12.75 GHz. Ku-band allows the use of smaller antennas than for C-band. It is also used for direct-to-home television services


L-band: Band of frequencies between 1 and 2 GHz, mainly used for Mobile Satellite Services


Launch services: All those activities relevant  to the launch phase, including ensurance services, rocket ordering, assembly and stacking, payload integration, and ultimately conducting the launch itself



LEOP - Launch and Early Orbit Phase: The critical first few orbits where appendage deployments are performed and the satellite is brought into a stable configuration


NASA - National Aeronautics and Space Administration: Space agency of the United States of America - site


MEO - Medium Earth Orbit: A satellite with an orbit around the earth between 1,000 and 22,300 miles above the earth's surface. MEOs are mainly used in geographical positioning systems and are not stationary in relation to the rotation of the earth


Molniya orbit: A very elliptical orbit so called because of the name of the satellites that use it. It was chosen by the Russian to locate their telecommunication satellites. For much of the time during the most distant phase from Earth, the satellite appears almost stationary in the sky


Microgravity: Condition existing on board a spacecraft in orbit around the Earth at not too high a distance where there is no total absence of gravity. Its value is much lower than the acceleration of gravity measured on Earth


Mission Control Centre - MCC: An entity that manages flying spacecraft, usually from the point of lift-off until the end of the mission. A staff of flight controllers and other support personnel monitor all aspects of the mission using telemetry, and send commands to the spacecraft using ground stations


Multi-spectral sensors: Are able to gather data in various bands of the electromagnetic spectrum that are useful for developing applications in the areas of meteorology and climate and applications for environmental monitoring or for land monitoring in general. It is this latter category, in particular, which makes use of sensors that gather detailed information about the nature of the ground. By applying a specific algorithm for processing multi-spectral images, it is possible to determine the nature of the type of ground and to differentiate, within the scene observed by the satellite, pixels of vegetation, open land, water, ice, etc.


Payload: The load carried on board a rocket: for example, a satellite


Perigee: The nearest point reached by a satellite along the orbit around the Earth


Polar orbit: Orbit that passes above or in the immediate vicinity of the poles, hence a satellite that follows this orbit can observe the entire surface of the Earth. It is the typical orbit for Earth observation satellites


Reaction wheels: Wheels existing on board satellites which, by rotating at different speeds, change the orientation of the spacecraft


Remote sensing: The sounding carried out by Earth observation satellites through which the characteristics of the surface passed over are studied. Remote sensing uses optical or radar techniques


SAR - Synthetic Aperture Radar: An instrument, mounted on board aircraft and satellites, which emits electromagnetic radiation and records the power of the signal reflected by the surface and also calculates the time between the emission and the return of the same signal. So, a SAR image is defined by the amplitude and phase of the signal returned by the surface investigated. In particular, the phase difference between two SAR acquisitions of the same scene depends on the area’s topography, so SAR Interferometry is used in the generation of digital elevation models


Satellite stabilised on three axes: To meet more sophisticated requirements in relation to pointing of telecommunications satellites, Earth observation and science in general, a technique has been developed which involves the three axes of the satellite. This has also allowed the use of solar panels capable of providing greater quantities of energy and which cannot be used in spun satellites


Solar wind: Flow of electrically charged particles, made up especially of electrons and protons. Depending on the Sun’s activity, the speed is several hundred kilometres per second. The solar wind affects the behaviour and service life of satellites around the Earth


Spaceport: A centre providing interconnections between different forms of telecommunications, especially one that links satellites to ground-based communications


Spectral band: Interval in the electromagnetic spectrum defined by two wavelengths or two frequencies


Spun satellite: A satellite that rotates on its vertical axis and in this way is stabilised on its orbit.


Telemetry: Coded radio communication from the satellite to the ground for the transmission of data relating to the functioning and configuration of the satellite


Remote Sensing: The fathoming carried out by the Earth observation satellites to study the characteristics of areas being covered. Remote sensing uses optical or radar techniques


TT&C - Tracking, Telemetry and Command:

Tracking: Process of continuously adjusting the orientation of an antenna so that its boresight follows the movements of the satellite about its nominal position.

Telemetry: Coded radio communication from the satellite to the ground for the transmission of data relating to the functioning and configuration of the satellite.

Command: The transmission of coded signals towards a satellite to initiate, modify or terminate equipment functions on-board the satellite.


Uplink: Transmission of a signal from the remote router to a satellite to a hub


Value Added Reseller: The seller of a product/service, generally originated from a supplier in a more "simple" format, ie. covering a limited number of elements of the value chain, which, in reselling the service to third parties, adds other components in the chain, according to their specific expertise


White room: environment in which spacecraft are assembled. Inside the room, air is filtered to eliminate particles that could damage the craft’s systems once in space


X-Band: frequency band with transmission (uplink) between 7.9 and 8.4 GHz and reception (downlink) between 7.25 and 7.75 GHz. X-band is primarily used for military communications