The Exposure Time Calculator will be updated with few expected changes in the instrument. It is based on current knowledge on instrumental efficiency, detector characteristics. The presently used characteristics are the following:

RON	5 electrons
DC	0.007 electron/s
Velocity bin	2.28 km/s
Individual exposure time	5.57 s
Extracted pixels	35
Efficiency	Y:3% J:5.5% H:10% K:9%
Stellar Templates	Phoenix library
Atmospheric Templates	Maunakea from ATRAN

The ETC can be used both ways: 1) to calculate the SNR per 2.28-km/s bin for a set of magnitude, star temperature, seeing, and total integration time (top example below) or 2) to estimate the exposure time needed to reach a given SNR per 2.28-km/s bin (bottom example below).

The SNR of the center of each order is given in the "detailed output". Regions of low SNR correspond to low-transmission bands of the Earth atmosphere. The variations of the SNR with airmass and H2O column density are low, according to the used models. The SNR is more sensitive to extinction and seeing. The plot below shows an example of the SNR spectrum for a mH=10 with an effective exposure time of 1 hour.