SOXS in a nutshell
SOXS is a multi-wavelength (350-2040 nm), medium resolution spectrograph mounted at the Nasmyth focus of the NTT. It consists of two spectroscopic arms, each with optimised optics, dispersive elements, and detectors. The Acquisition camera can be used to obtain complementary images:
UV-VIS, wavelength range 350-850 nm
NIR, wavelength range 795-2040 nm
Each of the two spectroscopic arms is an independent echelle spectrograph with its slit mask. The incoming light is split into the two arms via a dichroics (including a relatively wide overlap reigion, 795-850 nm, for the separation of the UV-VIS and NIR). For each arm the spectral format is fixed. The 4 orders in the UV-VIS are straight lines, whereas in 15 orders in the NIR arm are curved.
Two piezo controlled mirrors, located in front of each arm, guarantee that the optical path is maintained aligned against instrument flexure and corrected for differential atmospheric refraction between the telescope guiding wavelength and the arm central wavelengths.
One pairs of ADC (Atmospheric Dispersion Corrector) prisms in the optical path of the UV-VIS arm compensate for the atmospheric dispersion. No ADC is mounted in front of the NIR arm.
The Acquisition and Guiding system consists of a 3.5’x3.5’ (square) Field of View scientific CCD for target acquisition. A filter wheel equipped with the ugrizy SDSS filters is available (together with Cousin V). There is no secondary guiding.
An internal calibration unit, equipped with Pen-ray (Ar, He, Ne, and Xe), Th-Ar, Halogen, and D2 lamps is used for the calibration frames (flats, arcs, order definition, format check, 2dmaps).
For both arms there are 0.5”, 1”, 1.5” and 5” slits. The UV-VIS and NIR slits are 12 arcsec long.
Schematic overview of the instrument:
