Two-coordinate pointing and tracking system for an infrared Fouriertransform spectrometer

摘要

We describe a 1-inch aperture pointing system realized with a rope transmission driven by geared stepper motors foroperation at the surface of Mars. The system is intended to serve in the Fourier-transform spectrometer to observe boththe sun through the atmosphere and the thermal emission of the atmosphere. The scanner covers a full 2π field of view(the upper hemisphere). The accuracy of 0.1 mrad (～21 arcsec) for the sun tracking is achieved using an automaticcontrol system with an IR array sensor (32×32) in the loop. The optics of the pointing system consists of three flatmirrors and a germanium inlet window. The mass of the subsystem does not exceed 0.8 kg. The design accounts for thenecessity of dust protection in the Martian environment. The effect of a finite accuracy of the pointing and tracking onthe instrument signal to noise ratio is modeled.