Engineering topics
Publications and source records attributed to Simmons, K. E..
The photopolarimeter instrument on Voyager 2 was used to obtain a map of Jupiter at an effective wavelength of 2400 angstroms. Analysis of a typical north-south swath used to make this map shows strong absorption at high latitudes by a molecular or particulate constituent in the Jovian atmosphere. At 65 deg north latitude, the absorbing constituent extends to altitudes above the 50-millibar pressure level
Results are reported for optical-wavelength photopolarimetry of Ganymede from Voyager 1. A phase coefficient of 0.011 + or - 0.001 mag/deg and an opposition effect of 0.17 + or - 0.03 mag are derived. It is shown that Ganymede's surface is probably more porous than Callisto's and that micrometeoroids may continuously roughen the surface of Ganymede.
Analysis of the bright-limb profiles obtained by the Mariner 9 ultraviolet spectrometer during the December 1971 dust storm on Mars shows that the dust extended to an altitude of plus or minus 10 km, with a sharp cutoff in altitude distribution. Above the dust layer, the reflected signal is characterized by Rayleigh scattering in the wavelength interval 2100 to 3500 A. Detached haze layers were detected at an altitude of 70 plus or minus 10 km at the top of the dust layer. The haze layers have a nominal optical thickness of about 0.0001 and a geometrical thickness of 3 to 10 km and are probably a condensate of small CO2 or H2O ice particles (mean radius less than 0.1 micron). Similar features were revealed in Mariner 9 TV pictures of the limb.
Ultraviolet spectrometer measurements of the reflectance at 3050 A are modeled to give pressure-altitudes for Mars assuming a quiescent atmosphere. Ultraviolet light that is Rayleigh-scattered by the Mars molecular atmosphere, with allowance for uniform turbidity, is proportional to surface pressure independent of atmospheric temperature structure. All model constants except the over-all scaling factors are found by requiring ultraviolet spectrometer pressures of 47 locations on the planet to be the same when measured at different geometries. The overall scaling factor is found by intercomparison with Mariner 9 occultation pressures. Comparison with other Mars pressure-altitude measurements show deviations from the assumption of uniform turbidity to occur over the Hesperia plateau for ultraviolet measurements obtained during the 13-26 February 1972 time period.