Determination of Martian Surface Reflectivity from 0.4 to 1.1 Micron
Using a Vidicon Spectrometer

Douglas John Mink

Submitted to the Department of Earth and Planetary Science in partial fulfillment of the requirements for the degree of Master of Science on May 23, 1974


A new astronomical instrument, the vidicon spectrometer, is being developed at the M.l.T. Planetary Astronomy Laboratory. Based on the silicon diode vidicon system currently in use there, a low dispersion prism is added between the vidicon image tube and the telescope, allowing digital vidicon photographs to be taken of spectra. These spectra are stored on magnetic tape and computer processed to create intensity vs. wavelength curves for stars and planets. The high spatial resolution of the vidicon image tube, combined with a higher spectral resolution than photometer filters currently in use at M.I.T. give this instrument potential in the study of planetary surface composition from spectral reflectivity. Procedures for reducing the vidicon images to spectra have been tested on a set of spectra of two stars and the planet Mars. It is concluded that the vidicon response is not linear enough with variations in exposure time at low levels of incoming light for consistent star spectra, although it uorks well with Mars due to the planet's larger intensity where the vidicon tube has its poorest response. The spectrometer slit is so narrow (one second of arc for this data) that wavelength-dependent variations in refraction of light from a point source by the atmosphere cause star spectra of variable quality. Because of the low quality of the star spectra, direct spectral reflectivity measurements (which are obtained using Mars to star ratios) proved to be impossible. Although further tests of the spectral and intensity response of the silicon diode vidicon should be carried out in the laboratory before good results can be guaranteed, the present Mars spectra may probably be used in conjunction with photometer-derived reflectivity data to expand coverage of the surface of Mars.

Thesis Advisor: Thomas B. McCord
Title: Associate Professor of Planetary .Physics

[Thesis as PDF file]