SOPHIE échelle spectrograph
Encyclopedia
The SOPHIE échelle spectrograph is a high-resolution echelle
spectrograph
installed on the 1.93m reflector telescope at the Haute-Provence Observatory
located in south-eastern France
. The purpose of this instrument is asteroseismology
and extrasolar planet
detection by the radial velocity method. It builds upon and replaces the older ELODIE spectrograph
. This instrument was made available for use by the general astronomical community October 2006.
wavelength
range is from 387.2 to 694.3 nanometers. The spectrograph is fed from the Cassegrain
focus
through either one of two separate optical fiber
sets, yielding two different spectral resolutions (HE and HR modes). The instrument is entirely computer-controlled. A standard data reduction pipeline automatically processes the data upon every CCD
readout cycle.
HR mode is the high resolution mode. This mode incorporates a 40 micrometre exit slit to achieve high spectral resolution
of R = 75000.
HE mode is the high efficiency mode. This mode is used when a higher throughput is desired particularly in the case of faint objects spectral resolution
is set to R = 40000.
The R2 échelle
diffraction grating
has 52.65 grooves per millimeter and was manufactured by Richardson Gratings. It is blazed
at 65° its size is 20.4 cm x 40.8 cm. It is mounted in a fixed configuration. The spectrum
is projected onto the E2V Technologies type 44-82 CCD
detector of 4096 x 2048 pixels kept at a constant temperature of –100°C. This grating yields 41 spectral orders, of which 39 are currently extracted, to obtain wavelengths between 387.2 nm and 694.3 nm.
=14.5 object in HE mode. The stability of radial velocity measurements in HR mode is 3–4 m/s over several months. The short term stability has been measured to be 1.3 m/s.
Echelle grating
An echelle grating is a type of diffraction grating which is characterised by a relatively low groove density but is optimized for high diffraction orders. Echelle gratings are, like other types of diffraction grating, used in spectrometers and similar instruments, such as HARPS, and numerous...
spectrograph
Spectrograph
A spectrograph is an instrument that separates an incoming wave into a frequency spectrum. There are several kinds of machines referred to as spectrographs, depending on the precise nature of the waves...
installed on the 1.93m reflector telescope at the Haute-Provence Observatory
Haute-Provence Observatory
The Observatoire de Haute-Provence was established in 1937 as a national facility for French astronomers. Astronomical observations began in 1943 using the 1.20 m telescope, and the first research papers based on observations made at the observatory were published in 1944...
located in south-eastern 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 purpose of this instrument is asteroseismology
Asteroseismology
Asteroseismology also known as stellar seismology is the science that studies the internal structure of pulsating stars by the interpretation of their frequency spectra. Different oscillation modes penetrate to different depths inside the star...
and extrasolar planet
Extrasolar planet
An extrasolar planet, or exoplanet, is a planet outside the Solar System. A total of such planets have been identified as of . It is now known that a substantial fraction of stars have planets, including perhaps half of all Sun-like stars...
detection by the radial velocity method. It builds upon and replaces the older ELODIE spectrograph
ELODIE spectrograph
ELODIE was an echelle type spectrograph installed at the Observatoire de Haute-Provence 1.93m reflector in south-eastern France for the . Its optical instrumentation was developed by André Baranne from the Marseille Observatory. The purpose of this instrument was extrasolar planet detection by the...
. This instrument was made available for use by the general astronomical community October 2006.
Characteristics
The electromagnetic spectrumElectromagnetic spectrum
The electromagnetic spectrum is the range of all possible frequencies of electromagnetic radiation. The "electromagnetic spectrum" of an object is the characteristic distribution of electromagnetic radiation emitted or absorbed by that particular object....
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...
range is from 387.2 to 694.3 nanometers. The spectrograph is fed from the Cassegrain
Cassegrain reflector
The Cassegrain reflector is a combination of a primary concave mirror and a secondary convex mirror, often used in optical telescopes and radio antennas....
focus
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...
through either one of two separate optical fiber
Optical fiber
An optical fiber is a flexible, transparent fiber made of a pure glass not much wider than a human hair. It functions as a waveguide, or "light pipe", to transmit light between the two ends of the fiber. The field of applied science and engineering concerned with the design and application of...
sets, yielding two different spectral resolutions (HE and HR modes). The instrument is entirely computer-controlled. A standard data reduction pipeline automatically processes the data upon every CCD
Charge-coupled device
A charge-coupled device is a device for the movement of electrical charge, usually from within the device to an area where the charge can be manipulated, for example conversion into a digital value. This is achieved by "shifting" the signals between stages within the device one at a time...
readout cycle.
HR mode is the high resolution mode. This mode incorporates a 40 micrometre exit slit to achieve high spectral resolution
Spectral resolution
The spectral resolution of a spectrograph, or, more generally, of a frequency spectrum, is a measure of its ability to resolve features in the electromagnetic spectrum...
of R = 75000.
HE mode is the high efficiency mode. This mode is used when a higher throughput is desired particularly in the case of faint objects spectral resolution
Spectral resolution
The spectral resolution of a spectrograph, or, more generally, of a frequency spectrum, is a measure of its ability to resolve features in the electromagnetic spectrum...
is set to R = 40000.
The R2 échelle
Echelle grating
An echelle grating is a type of diffraction grating which is characterised by a relatively low groove density but is optimized for high diffraction orders. Echelle gratings are, like other types of diffraction grating, used in spectrometers and similar instruments, such as HARPS, and numerous...
diffraction grating
Diffraction grating
In optics, a diffraction grating is an optical component with a periodic structure, which splits and diffracts light into several beams travelling in different directions. The directions of these beams depend on the spacing of the grating and the wavelength of the light so that the grating acts as...
has 52.65 grooves per millimeter and was manufactured by Richardson Gratings. It is blazed
Blazed grating
A blazed grating is a special type of diffraction grating.Blazed gratings produce maximum efficiency at a specified wavelength; that is, a diffraction grating that is "blazed at 250nm" will operate most efficiently when light with a wavelength of 250 nm passes through the grating.Like standard...
at 65° its size is 20.4 cm x 40.8 cm. It is mounted in a fixed configuration. The spectrum
Spectrum
A spectrum is a condition that is not limited to a specific set of values but can vary infinitely within a continuum. The word saw its first scientific use within the field of optics to describe the rainbow of colors in visible light when separated using a prism; it has since been applied by...
is projected onto the E2V Technologies type 44-82 CCD
Charge-coupled device
A charge-coupled device is a device for the movement of electrical charge, usually from within the device to an area where the charge can be manipulated, for example conversion into a digital value. This is achieved by "shifting" the signals between stages within the device one at a time...
detector of 4096 x 2048 pixels kept at a constant temperature of –100°C. This grating yields 41 spectral orders, of which 39 are currently extracted, to obtain wavelengths between 387.2 nm and 694.3 nm.
Performance
A S/N (per pixel) of 27 (in V) was reached in 90 min for a VApparent magnitude
The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...
=14.5 object in HE mode. The stability of radial velocity measurements in HR mode is 3–4 m/s over several months. The short term stability has been measured to be 1.3 m/s.