Nançay Radio Telescope
Encyclopedia
The Nançay Decimetric Radio Telescope (official abbreviation NRT) is located in the small commune
of Nançay
, two hours' drive south of Paris
, France
. The radio telescope
saw first light
in 1965, after an inauguration by the then French president, Charles de Gaulle
. It is one of the largest radio telescopes in the world. It is located at a latitude and longitude of 47°23′N 2°12′E.
The NRT is a transit instrument of the unusual Kraus-type
design, with two mirror
s. The flat, tilting primary mirror
consists of ten panels, each 20 m long and 40 m (131 ft) high; it reflects radio
waves towards the fixed secondary mirror
460 m away. The secondary mirror is shaped as a section of a sphere
with a radius
of 560 m: (1837 ft) it focuses
the radio waves towards a mobile focal carriage that contains antennas
and other receiving equipment. Both mirrors are covered with a metal mesh with square holes 12.5 mm on a side and a surface that is accurate to about 5 mm. The primary mirror tilts North-South to select any objects along the meridian
, while the focal carriage moves East-West along a railroad track to follow objects across the sky. The NRT is capable of observing objects with a declination
greater that −39°. Objects near the equator
can only be tracked for about an hour, but objects nearer the zenith
can be tracked for longer. Observations are typically undertaken at frequencies
of 1,400 MHz (equivalent to a wavelength
of 21 cm), 1,660 MHz (18 cm) and 3,330 MHz (9 cm).
The central fifth of the NRT was constructed in 1961 as a proof of concept. The remainder was completed in 1964, and officially opened in 1965. Scientific observations started in 1967.
The Kraus-type design, named after Dr. John D. Kraus (1910–2004), has been used first at the Ohio State University
Big Ear Telescope
.
Communes of France
The commune is the lowest level of administrative division in the French Republic. French communes are roughly equivalent to incorporated municipalities or villages in the United States or Gemeinden in Germany...
of Nançay
Nançay
Nançay is a commune in the Cher department in central France.-Geography:The village is located south of the Sologne and north-east of Vierzon. The Rère flows southwestward through the middle of the commune.-History:...
, two hours' drive south of Paris
Paris
Paris is the capital and largest city in France, situated on the river Seine, in northern France, at the heart of the Île-de-France region...
, France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
. The radio telescope
Radio telescope
A radio telescope is a form of directional radio antenna used in radio astronomy. The same types of antennas are also used in tracking and collecting data from satellites and space probes...
saw first light
First light
In astronomy, first light is the first use of a telescope to take an astronomical image after it has been constructed. This is often not the first viewing using the telescope; optical tests have likely already been performed during daylight to adjust the components...
in 1965, after an inauguration by the then French president, Charles de Gaulle
Charles de Gaulle
Charles André Joseph Marie de Gaulle was a French general and statesman who led the Free French Forces during World War II. He later founded the French Fifth Republic in 1958 and served as its first President from 1959 to 1969....
. It is one of the largest radio telescopes in the world. It is located at a latitude and longitude of 47°23′N 2°12′E.
The NRT is a transit instrument of the unusual Kraus-type
Kraus-type
The Kraus-type radio telescope design was created by Dr. John D. Kraus .Kraus-type telescopes are transit instruments, where the flat primary reflects radio light towards the spherical secondary, which focuses it towards a mobile focal carriage...
design, with two mirror
Mirror
A mirror is an object that reflects light or sound in a way that preserves much of its original quality prior to its contact with the mirror. Some mirrors also filter out some wavelengths, while preserving other wavelengths in the reflection...
s. The flat, tilting primary mirror
Primary mirror
A primary mirror is the principal light-gathering surface of a reflecting telescope.-Description:The primary mirror of a reflecting telescope is a spherical or parabolic shaped disks of polished reflective metal , or in later telescopes, glass or other material coated with a reflective layer...
consists of ten panels, each 20 m long and 40 m (131 ft) high; it reflects radio
Radio
Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...
waves towards the fixed secondary mirror
Secondary mirror
A secondary mirror is the second deflecting or focusing mirror element in a reflecting telescope. Light gathered by the primary mirror is directed towards a focal point typically past the location of the secondary. Secondary mirrors in the form of an optically flat diagonal mirror are used to...
460 m away. The secondary mirror is shaped as a section of a sphere
Sphere
A sphere is a perfectly round geometrical object in three-dimensional space, such as the shape of a round ball. Like a circle in two dimensions, a perfect sphere is completely symmetrical around its center, with all points on the surface lying the same distance r from the center point...
with a radius
Radius
In classical geometry, a radius of a circle or sphere is any line segment from its center to its perimeter. By extension, the radius of a circle or sphere is the length of any such segment, which is half the diameter. If the object does not have an obvious center, the term may refer to its...
of 560 m: (1837 ft) it focuses
Focus (optics)
In geometrical optics, a focus, also called an image point, is the point where light rays originating from a point on the object converge. Although the focus is conceptually a point, physically the focus has a spatial extent, called the blur circle. This non-ideal focusing may be caused by...
the radio waves towards a mobile focal carriage that contains antennas
Antenna (radio)
An antenna is an electrical device which converts electric currents into radio waves, and vice versa. It is usually used with a radio transmitter or radio receiver...
and other receiving equipment. Both mirrors are covered with a metal mesh with square holes 12.5 mm on a side and a surface that is accurate to about 5 mm. The primary mirror tilts North-South to select any objects along the meridian
Meridian (astronomy)
This article is about the astronomical concept. For other uses of the word, see Meridian.In the sky, a meridian is an imaginary great circle on the celestial sphere. It passes through the north point on the horizon, through the celestial pole, up to the zenith, through the south point on the...
, while the focal carriage moves East-West along a railroad track to follow objects across the sky. The NRT is capable of observing objects with a declination
Declination
In astronomy, declination is one of the two coordinates of the equatorial coordinate system, the other being either right ascension or hour angle. Declination in astronomy is comparable to geographic latitude, but projected onto the celestial sphere. Declination is measured in degrees north and...
greater that −39°. Objects near the equator
Equator
An equator is the intersection of a sphere's surface with the plane perpendicular to the sphere's axis of rotation and containing the sphere's center of mass....
can only be tracked for about an hour, but objects nearer the zenith
Zenith
The zenith is an imaginary point directly "above" a particular location, on the imaginary celestial sphere. "Above" means in the vertical direction opposite to the apparent gravitational force at that location. The opposite direction, i.e...
can be tracked for longer. Observations are typically undertaken at frequencies
Frequency
Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...
of 1,400 MHz (equivalent to a wavelength
Wavelength
In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...
of 21 cm), 1,660 MHz (18 cm) and 3,330 MHz (9 cm).
The central fifth of the NRT was constructed in 1961 as a proof of concept. The remainder was completed in 1964, and officially opened in 1965. Scientific observations started in 1967.
The Kraus-type design, named after Dr. John D. Kraus (1910–2004), has been used first at the Ohio State University
Ohio State University
The Ohio State University, commonly referred to as Ohio State, is a public research university located in Columbus, Ohio. It was originally founded in 1870 as a land-grant university and is currently the third largest university campus in the United States...
Big Ear Telescope
The Big Ear
The Ohio State University Radio Observatory was a Kraus-type radio telescope located on the grounds of the Perkins Observatory at Ohio Wesleyan University from 1963 to 1998. Known as "Big Ear", the observatory was part of The Ohio State University's Search for Extraterrestrial Intelligence project...
.
External links
- Nançay Observatory (Official site, in English)
- The Decimetric Radiotelescope
- Technical information
- Pôle des Étoiles touristic facilities: guided tours, planetarium shows, exhibits
- Google Maps