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