An Etymological Dictionary of Astronomy and Astrophysics
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A man-made equipment that orbits around Earth or a solar system body.

→ artificial; → satellite.

Any of satellites which either share the same orbit or which occupy immediately adjacent orbits that change periodically as the satellites approach one another (Ellis et al., 2007, Planetary Ring Systems, Springer).

→ co-orbital; → satellite.

The four largest and brightest satellites of → Jupiter, that is: → Io (Jupiter I), → Europa, → Ganymede, and → Callisto.

Galileo, who had discovered them, called them Sidera Medicæa "Medicean Stars" in honor of the Medici family. → Galilean Moons; → satellite.

A type of Earth observing satellite used to measure the location of points on Earth's surface with great accuracy. Their observations help determine the exact size and shape of Earth, act as references for mapping, and track movements of Earth's crust.

→ geodesy; → satellite

A European Space Agency (ESA) mission to perform imaging photometry and spectroscopy in the → far infrared and → submillimeter regions of the electromagnetic spectrum, covering approximately the 55-672 µm range. In fact Herschel is the first space facility dedicated to these wavelength ranges. It carries a 3.5 m diameter passively cooled mirror. The science payload complement - two cameras/medium resolution spectrometers (PACS and SPIRE) and a very high resolution → superheterodyne spectrometer (HIFI) - are housed in a superfluid helium cryostat. Herschel was launched on 14 May 2009, together with the → Planck Satellite. Its observing position lies at the L2 → Lagrangian point, some 1.5 million km from Earth. Herschel is designed, among other things, to study the formation of galaxies in the early Universe, and to investigate the formation of stars and their interaction with the → interstellar medium.

→ Herschel; → satellite.

An orbiting infrared telescope (60 cm mirror) which successfully operated from launch in January 1983 until the supply of coolant ran out in November 1983. It was a collaborative mission between NASA, the Netherlands, and the UK, and mapped 95% of the whole sky in the wavelength bands 12, 25, 60, and 100 microns.

→ infrared; → astronomical; → satellite.

A satellite whose orbit around its planet is eccentric, inclined with respect to the equatorial plane, and relatively far from the planet. Strong solar perturbations cause the orbit to precess. → regular satellite.

→ irregular; → satellite.

The observed underabundance, by one or two orders of magnitude, of → dwarf galaxies orbiting → spiral galaxies compared to their number predicted by the standard model. The → cold dark matter (CDM) model predicts that dwarf galaxies are the building blocks of large galaxies like the Milky Way and should largely outnumber them. Dwarf galaxies form first, they merge into bigger and bigger galaxies, and galaxies into groups of galaxies. The dark matter halos, however, are very dense, and dwarf halos are not destroyed in the merging, resulting in their large predicted number, in numerical simulations.

Probably first dealt with in an article entitled "Where Are the Missing Galactic Satellites?" (Lypin et al. 1999, ApJ 522, 82); → missing mass; → satellite; → problem.

A solar system → object that → revolves around a → primary body and is not man made.

→ natural; → satellite.

A European Space Agency (ESA) mission to map the full sky in the 30 GHz to 1 THz range and to measure the → anisotropies of the → cosmic microwave background (CMB) with a sensitivity set by fundamental limits, i.e. photon noise and contamination by foregrounds. It was launched on 14 May 2009, together with the → Herschel Satellite. Its observing position is a halo orbit around the L2 → Lagrangian point, some 1.5 million km from Earth. Its → Gregorian-like off-axis telescope has an effective aperture of 1.5 m and images the sky on two sets of feed-horns. The Low Frequency Instrument (LFI, at frequencies 30, 44, 70 GHz) amplifies with High Electron Mobility Transistors cooled at 20 K the radiation collected by 13 horns. The High Frequency Instrument (HFI, at 100, 143, 217, 353, 545, 857 GHz) detects the shorter waves with 52 bolometers cooled at only 0.1 degree above the → absolute zero. Both instruments can detect both the total intensity and polarization of photons. The Planck mission is intended to provide maps with a sensitivity of a few micro-Kelvin and an angular resolution down to 5 arcmin, which is considered as a major improvement with respect to the Wilkinson Microwave Anisotropy Probe (→ WMAP) launched by the NASA in 2002. Planck will provide a major source of information relevant to several cosmological and astrophysical issues, such as testing theories of the early Universe and the origin of cosmic structure. It will also provide to astronomers 9 complete maps of the full sky at wavelengths from 0.3 mm to 1 cm, that complement the 4 maps taken by the → IRAS satellite in the 2.5 to 100 micrometer range.

→ Planck; → satellite.

A satellite that revolves around the Earth in an almost north-south orbit, passing close to both poles. The orbits are sun synchronous, allowing the satellite to cross the equator at the same local time each day. These satellites orbit at a height of 830-880 km and take about 100 minutes to complete a turn around the Earth.

→ polar; → orbit; → satellite.

An asteroid moving around the Sun having the same mean motion and mean → longitude as a planet, but a different → eccentricity. The asteroid remains near the planet much like a satellite even when its distance is large enough so that it is well outside the planet's → Hill sphere. The quasi-satellite motion is one class of possible → co-orbital motions of small bodies in 1:1 mean-motion → resonance with a planet. If the quasi-satellite orbit is coplanar with the planet, then the motion is stable in the → secular approximation. When the orbits are inclined enough, an asteroid can be trapped into such a motion for a finite period of time. Earth has several quasi-satellites (mainly 3753 Cruithne, 2002 AA₂₉, 2003 YN₁₀₇), also does Venus (the only one so far discovered, 2002 VE₆₈). The possibility of such orbits was first suggested by J. Jackson (1913, MNRAS 74, 62).

The term quasi-satellite was first used by S. Mikkola & K. Innanen 1997, The Dynamical Behaviour of our Planetary System; Proceedings, p. 345); → quasi-; → satellite.

A satellite that revolves around its planet in an equatorial orbit of low or moderate eccentricity close to the planet. One example of a regular satellite system is the Galilean satellites of Jupiter.

→ regular; → satellite.

1) A body that revolves around a planet; a moon. → Galilean satellite; → regular satellite; → irregular satellite.
2) Something that depends on, accompanies, or serves something else. → satellite galaxy; → satellite line.

From M.Fr. satellite, from L. satellitem "attendant."

1) Mâhvâré, from mâh, → moon, + -vâré, -vâr similarity suffix.
2) Bandevâr, from bandé "bound, fastened; (devoted) servant, domestic;" Mid.Pers. bandag, from bastan, band-, vastan "to bind, shut" (O.Pers./Av. band- "to bind, fetter," banda- "band, tie" (cf. Skt. bandh- "to bind, tie, fasten;" PIE *bhendh- "to bind;" Ger. binden; E. bind).

A galaxy that orbits a larger one due to gravitational attraction. The Milky Way has at least ten satellite galaxies: the Large Magellanic Cloud, the Small Magellanic Cloud, Ursa Minor Dwarf, Draco Dwarf, Sculptor Dwarf, Sextans Dwarf, Carina Dwarf, Fornax Dwarf, Ursa Major I, and → Sagittarius Dwarf Elliptical Galaxy.

→ satellite; → galaxy.

Radio astro.: Of an OH source, which emits at 1665 and 1667 MHz as the main frequencies, one of the lines arising from transitions at 1612 and 1730 MHz.

→ satellite; → line.

A space vehicle designed to orbit about the Sun.

→ solar; → satellite.

An artificial satellite in a synchronous orbit. → geostationary orbit

→ stationary; → satellite.

A → NASA space telescope devoted to the hunt for planets orbiting the brightest stars in the sky, launched on April 18, 2018. The mission is planned to monitor at least 200,000 stars for signs of → exoplanets using the → planetary transit method. TESS is equipped with four identical refractive → cameras with a combined → field of view (FOV) of 24 × 96 degrees. Each camera consists of a → CCD detector assembly, a → lens assembly, and a lens hood. The → entrance pupil diameter is 10.5 cm and the wavelength range 600 to 1,000 nm. The satellite is a follow-up of NASA's → Kepler spacecraft, but focuses on stars that are 30 to 100 times brighter than those Kepler examined.

→ transit; → exoplanet; → survey.