[en] Cosmic Ray Tau Neutrino Telescopes (CRTNT) for sub-EeV cosmic ray measurement is discussed. Performances of a stereoscope configuration with a tower of telescopes plus two side-triggers are studied. This is done by using a detailed detector simulation driven by Corsika. Detector aperture as a function of shower energy above 10¹⁷ eV is calculated. Event rate of about 20k per year for the second knee measurement is estimated. Event rate for cross calibration with detectors working on higher energy range is also estimated. Different configurations of the detectors are tried for optimization. (authors)