*Proposers to the observing call for NEID should use this calculator to estimate
the exposure times for their observations given a target SNR or RV precision,
and the inverse of those functions. This exposure time calculator was written
by the NEID Science Team and is based on initial best-estimates for the total
system throughput as a function of wavelength, precision from the default data
pipeline, and based on template stellar spectra at vsini = 2 km/s and solar
metallicity. All throughput estimates are deliberately conservative, and there
is an additional 30% margin built-in on top of this conservatism.
This calculator will be updated as better estimates of system performance
become available, and as on-sky performance is measured.*

**Calculate Radial Velocity Precision**

** Notes and Caveats **

- Note that this exposure time calculator reports only the photon noise contribution to the RV precision. This contribution must be added in quadrature to the 27 cm/s instrumental floor to determine the total measurement precision.

- Saturation happens at **SNR = 625.** Do not go over this limit.

- Maximum exposure time is calculated as the exposure time to reach non-linearity for * any * order. This occurs at approx. SNR = 480.

- SNR is reported per 1D extracted pixel. The NEID resolution element is approx. 5 pixels wide.