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Alfredo Escalante

Publications and source records attributed to Alfredo Escalante.

2 recordsLinked to original sources

The Visual Monitoring Camera (VMC) on Mars Express: a new science instrument made from an old webcam orbiting Mars

The Visual Monitoring Camera (VMC) is a small imaging instrument onboard Mars Express with a field of view of ~40x30 degrees. The camera was initially intended to provide visual confirmation of the separation of the Beagle 2 lander and has similar technical specifications to a typical webcam of the 2000s. In 2007, a few years after the end of its original mission, VMC was turned on again to obtain full-disk images of Mars to be used for outreach purposes. As VMC obtained more images, the scientific potential of the camera became evident, and in 2018 the camera was given an upgraded status of a new scientific instrument, with science goals in the field of Martian atmosphere meteorology. The wide Field of View of the camera combined with the orbit of Mars Express enable the acquisition of full-disk images of the planet showing different local times, which for a long time has been rare among orbital missions around Mars. The small data volume of images also allows videos that show the atmospheric dynamics of dust and cloud systems to be obtained. This paper is intended to be the new reference paper for VMC as a scientific instrument, and thus provides an overview of the updated procedures to plan, command and execute science observations of the Martian atmosphere. These observations produce valuable science data that is calibrated and distributed to the community for scientific use.

astro-ph.IM↗

Re-evaluation of Lunar X-ray observations by Apollo 15 & 16

The Apollo 15 & 16 missions were the first to explore the Lunar surface chemistry by investigating about 10% of the Lunar surface using a remote sensing X-ray fluorescence spectrometer experiment. The data obtained have been extensively used to study Lunar formation history and geological evolution. In this work, a re-evaluation of the Apollo 15 & 16 X-ray fluorescence experiment is conducted with the aim of obtaining up-to-date empirical values for aluminum (Al) and magnesium (Mg) concentrations relative to silicon (Si) of the upper Lunar surface. An updated instrument response, a newly reconstructed Lunar trajectory orbit, and improved intensity ratio calculations were used to obtain new intensity ratio maps. The resulting Lunar Al/Si and Mg/Al X-ray maps show a clear distinction in Lunar mare and highland regions. The mean Al/Si and Mg/Al intensity ratios for the mare regions obtained from the newly obtained maps are 0.54$\pm$0.07 and 0.54$\pm$0.17, respectively; for the highland regions, the values are 0.76$\pm$0.07 and 1.07$\pm$0.13, respectively. For the Mg/Si intensity ratio, no clear distinction between Lunar features is obtained and we derived a mean value of 0.47$\pm$0.13. Our determined intensity ratios are lower than previously published. These values can be used to infer concentration ratios when accounting for Solar activity, inter-orbit variability, and measurements from different instruments. We employed a correction to infer concentration ratios by comparing our intensity ratios directly to Lunar rock concentrations obtained from various Lunar missions.

astro-ph.EP↗