Papers
This page provides some original measurements of the 1994-95 apparition of Mars, as observed from T1m at Pic du Midi. This work was published in:
- S. Erard (1997) Mars’ 1995 opposition from Pic du Midi (abstract). In Lunar and Planetary Science XXVIII, pp. 339-340. Lunar and Planetary Institute, Houston.
- S. Erard (2000) The 1994-95 apparition of Mars observed from Pic-du-Midi. Planet Space Sci. 48, 1271-1287.
(PDF reprint ; ~800 Kb).
Abstract from the PSS paper:
Abstract from the PSS paper:
The 1995 apparition of Mars was monitored with the Pic-du-Midi 1-m telescope from October 1994 to March 1995. Several thousand images were acquired with a CCD camera through various filters ranging from 0.4 to 1.05 µm. These images complete HST observations of the same apparition with a spatial resolution reduced by a factor of ~4, but with a better time resolution. Low resolution spectra were also acquired through a set of interferential filters at opposition, providing indications of mineralogical composition of surface materials. The only significant surface variations during the period are observed in the Cerberus area, which brightened at the end of winter. The whole apparition was very cloudy. The north Polar Hood dissipated in early December (Ls ~ 25°). Migration of polar clouds to the equator is observed between January 31 and February 6 (Ls ~ 50°-55°). Then an Encircling Cloud Belt obscured most of the surface from February 22 to 24 at least (Ls ~ 62°). The north polar cap regression is similar to that observed by Mariner 9, although several internal rifts developed during early spring, in particular the dark Lowell band and Rima Tenuis. A standstill is observed in the polar cap regression curve from Ls = 55° to 70° at latitude ~70°, at least in the 135-300° longitude range. The very strong spectral feature at 0.95 µm reported from HST observations of Olympia Planitia in July 1995 is not observed in the Pic-du-Midi images. The intermediate-dark region of Propontis I exhibits ferric absorption features consistent with high concentrations of crystalline hematite or other dark ferric materials.
Data
Limit of the north polar cap as a function of time (Ls) and longitude
This file contains the data for Fig. 10 in the PSS paper.
Each different image is described with the date, solar longitude and central longitude in the image ('Long centrale'). A list of mesurements relative to the image follows, which gives the latitude of the cap limit ('position limite') at several longitudes, with error bar. In some instances, there are two images for the same day, in which case only the central longitude is indicated before the second group of measurements.
Visible - NIR spectra from interferential filters
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Selected spectra reconstructed from images acquired through the interferential filters on February 6th, and corrected from limb darkening with a Minnaert function. Spectra are averaged over 20 to 40 pixels, in areas shown in Fig. 5a. The signal to noise ratio is about 500. The error bars represent the maximum uncertainty related to the Minnaert exponent, and are therefore correlated at different wavelengths. Spectra are scaled to radiance factor [Fig. 6 in the PSS paper]. |
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Spectral ratio of the interferential filters images showed in polar-Lambert projection (down to the Equator), with Minnaert correction applied. (a) Ratio of 0.73 µm to 0.58 µm intensities; the footprints of the spectra in Fig. 6 are shown in white [Fig. 5a in the PSS paper]. |
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The following files contain data for Fig. 6 in the PSS paper:
Each spectrum is an average from about 30 pixels. The files contain five columns, which give respectively the wavelength, the nomalized reflectance, its variation in the area (standard deviation between averaged pixels), the minimum and maxium observed within the area. The reflectance is afterward scaled so that the Elysium spectrum matches the reference spectrum from Ophir Planum. The band width of the filters is given in the paper.
