Expected Performances

The overall spectral layouts, instrumental efficiencies and limiting magnitudes of GIANO are summarized in the following sections.

Spectral Layout

The spectral range covered is complete up to about 1.8 μm and $\simeq$ 70% complete at 2.45 μm. This follows from the requirement of maximizing the resolving power without excessively decreasing the spectral coverage at the longer wavelengths.
Indeed, since larger arrays or coarser gratings are not commercially available, resolutions larger than about 35,000 necessarily imply a limitation on the spectral coverage in the K band.
Nevertheless, the missing part of the K band can be always made observable by rotating the grating.

Distribution of light on the array in the HR mode. The green circles show the positions where the spot diagrams have been extracted. The echellogram for the SHR mode has the same format with the wavelengths shifted by about half an order.

Limiting magnitudes

The instrument overall efficiency is expected to be 13% in K and H and 10% in J.
The array noise is 12 e&oline.
Ttypical values of the sky bacground in between the OH lines are 17, 15.5 and 13 mag per square arcsec in J, H and K, respectively.
The resulting limiting magnitudes for representative observing setups are listed in the following Table.

HR mode, R=46,000 slit=0.5" seeing=1.0"
Band	S/N=100 in 1hr	S/N=10 in 1hr
J	11.7	15.1
H	11.6	14.9
K	11.0	14.1
HR mode, R=23,000 slit=1.0" seeing=1.0"
Band	S/N=100 in 1hr	S/N=10 in 1hr
J	13.1	16.2
H	12.9	16.0
K	12.2	15.0

Expected limiting magnitudes for different spectral resolution and S/N per resolution element.