The near-infrared / red focal instrument of the VLTI, called AMBER will operate between 1 and 2.5 Ám in a first phase (2001-2003) with two UTs. This instrument has been designed for three beams to be able to perform images through phase closure techniques. The wavelength coverage will be extended in a second phase down to 0.6 Ám at the time the ATs become operational. The magnitude limit of AMBER is expected to reach K=20 when a bright reference star is available and K=14 otherwhise. The main scientific objectives are the investigation at very high angular resolution of disks and jets around young stellar objects and AGN dust tori with a spectral resolution up to 10000.
AMBER - SPG
The Arcetri Infrared Instrumental Group is involved in design, building and testing the Spectrograph (SPG) of the instrument. The cold spectroraph of AMBER (indicated by the acronym SPG in AMBER documentation), besides operating the spectral dispersion of incoming beams, includes the following functions:
* Formation of an image of the fiber outputs at cryogenic temperature and filtering of thermal radiation from this image by means of suitable spatial filters * Formation of a parallel beam * Accurate spatial filtering of the pupils * Separation of specroscopic beams from photometric beams * Spectral analysis at three resolving power values * Formation of images on the detector plane All this functions are accomplished in the spectral range which covers the astronomical near-infrared bands J, H, K, that is 1.0 to 2.4 Ám. The optics and the support structure are contained in a vacuum tight cryostat which allows the cooling of all functions to the working temperature of about 77 K by means of liquid nitrogen at atmospheric pressure.
AMBER, the near-infrared/red focal instrument of the VLTI, operates in the bands J, H, and, K (ie 1.0 to 2.4 um). The instrument has been designed to be used with two or three beams, thus enabling also the use of closure phase techniques. The magnitude limit of AMBER is K=7 with Low Resolution (LR) on UTs, K=4 with Medium Resolution (MRK) on the UTs.
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