Tmt comp background

MODHIS Sensitivity


Presented are sensitivity calculations for point source, on-axis targets with a range of object temperatures and magnitudes.  We present computed signal-to-noise per wavelength bin, cross-correlation signal-to-noise, and the RV precision.  vsini is assumed to be zero in all cases, i.e. calculations are all done for face on systems.

All calculations are done for 10 minute exposure time. Scaling the SNR to other exposure times is simply done as the square root of the ratio of exposure times.

All calculations are done using PSIsim by Jean-Baptiste Ruffio. The full PSIsim package is available here.

For direct imaging cases and other questions, please direct enquiries to

For MODHIS, the oversampling in the spectral direction is 3x the resolution of the instrument. Here, a bin (or pixel) corresponds to 1/3 of a spectral resolution element. The SNR per bin presented is the maximum value over the spectral bandpass and is relevant for cases where fits are made to individual spectral lines.

The Cross Correlaion Function (CCF) SNR represents the information content in the spectrum and is used when inferring stellar/planet properties. The CCF SNR “combines” the signal from all the spectral features across the entire wavelength range.

Values of the performance in any band is given as a function of the K band magnitude.

Disclaimer: Values presented are expected to change slightly as the instrument design matures. The values presented are believed to give a good indication of instrument performance and accurate enough for the development of science cases.


When determining the CCF SNR values, the assumed line strengths are from the Phoenix stellar models.