Glossary - M

Magnetar
a neutron star with an extremely high magnetic field
(astrophysics)

Magnetosphere
the volume of space around a planet in which the planet’s magnetic field is dominant
(planetary science)

Mass spectrometer
a scientific instrument which measures the mass to charge ratio of ions and which is used to identify unknown compounds (by their molecular weight), to quantify the composition of materials (by plotting the proportions of a sample by molecular weight) and determining the structure and chemical properties of known compounds
(technology)

Mean solar time
a time standard based on an average of the variations caused by the Earth’s non-circular orbit
(orbits)

Mean Time To Failure (MTTF)
the average time for a system to operate without developing a fault
(technology)

Mean Time To Repair (MTTR)
the average time taken to correct a fault in a system
(technology)

Meridian
a great circle which passes through the north and south poles; also called lines of longitude
(orbits)

Mesh
network topology in which every node can communicate directly with any other node
(communications)

Meshed VSAT
type of VSAT network in which connections are made directly between remote terminals; the hub in such a network is only responsible for signalling and network management
(satellite communications)

Mesosphere
a layer in the Earth’s atmosphere between the stratosphere and the thermosphere with an altitude from 50 to 85 km
(atmospheric physics)

Meteor
a meteoroid which is passing through a planetary atmosphere and which is generally visible (either optically or as a radar return) because of heating due to atmospheric friction
(astronomy, planetary science)

Meteorite
a rocky and/or metallic body (usually from less than a millimetre to several metres across) which originated from space and which has come to rest on or under the surface of a planet, moon, dwarf planet or asteroid
(astronomy, planetary science)

Meteroid
small rocky or metallic object which orbits the Sun and which range in size from a grain of dust to a metre across
(astronomy, planetary science)

Micrometeroid
small rocky or metallic object which orbits the Sun which is smaller in size than a grain of dust
(astronomy, planetary science)

Microwaves (MW)
a form of electromagnetic radiation with a frequency in the range 1 to 100 GHz
(physics)

Milky Way
the galaxy we inhabit
(astronomy)

Mission specialist
an astronaut responsible for operating specific spacecraft or space station systems, carrying out payload and experimental activities and performing spacewalks
(human spaceflight)

Modem
the modulator/demodulator block in an earth station
(satellite communications)

Modulation
the process of superimposing a baseband signal on a carrier for transmission
(communications)

Modulator
a device which modulates a carrier
(communications)

Molniya orbit
inclined elliptical orbit used by some Russian communications satellites; the orbit was designed so that the satellite is visible at high latitudes and yet only moves slowly across the sky for several hours each orbit making tracking simple
(orbits)

Multifeed system
a consumer antenna system with two or more feeds and LNBs used to receive signals from two or more satellites
(satellite communications, broadcasting)

Multiple access
technique whereby several users can, simultaneously or at different times, use a particular piece of repeater bandwidth
(communications)

Multiplexing
technique of combining several signals into a single signal for transmission
(communications)