arXiv subjects

Clément Royer

Publications and source records attributed to Clément Royer.

3 recordsLinked to original sources

arXiv2022

Properties of the Nili Fossae Olivine-clay-carbonate lithology: orbital and in situ at Séítah

We examine the observed properties of the Nili Fossae olivine-clay-carbonate lithology from orbital data and in situ by the Mars 2020 rover at the Séítah unit in Jezero crater, including: 1) composition (Liu, 2022) 2) grain size (Tice, 2022) 3) inferred viscosity (calculated based on geochemistry collected by SuperCam (Wiens, 2022)). Based on the low viscosity and distribution of the unit we postulate a flood lava origin for the olivine-clay-carbonate at Séítah. We include a new CRISM map of the clay 2.38 μm band and use in situ data to show that the clay in the olivine cumulate in the Séítah formation is consistent with talc or serpentine from Mars 2020 SuperCam LIBS and VISIR and MastCam-Z observations. We discuss two intertwining aspects of the history of the lithology: 1) the emplacement and properties of the cumulate layer within a lava lake, based on terrestrial analogs in the Pilbara, Western Australia, and using previously published models of flood lavas and lava lakes, and 2) the limited extent of post emplacement alteration, including clay and carbonate alteration (Clave, 2022; Mandon, 2022).

astro-ph.EP↗

arXiv2021

The SuperCam Infrared Spectrometer for the Perseverance Rover of the Mars2020 mission

We present the Infrared spectrometer of SuperCam Instrument Suite that enables the Mars 2020 Perseverance Rover to study remotely the Martian mineralogy within the Jezero crater. The SuperCam IR spectrometer is designed to acquire spectra in the 1.3-2.6 $μ$m domain at a spectral resolution ranging from 5 to 20~nm. The field-of-view of 1.15 mrad, is coaligned with the boresights of the other remote-sensing techniques provided by SuperCam: laser-induced breakdown spectroscopy, remote time-resolved Raman and luminescence spectroscopies, and visible reflectance spectroscopy, and micro-imaging. The IR spectra can be acquired from the robotic-arm workspace to long-distances, in order to explore the mineralogical diversity of the Jezero crater, guide the Perseverance Rover in its sampling task, and to document the samples' environment. We present the design, the performance, the radiometric calibration, and the anticipated operations at the surface of Mars.

astro-ph.EP↗

arXiv2020

Trust-Region Newton-CG with Strong Second-Order Complexity Guarantees for Nonconvex Optimization

Worst-case complexity guarantees for nonconvex optimization algorithms have been a topic of growing interest. Multiple frameworks that achieve the best known complexity bounds among a broad class of first- and second-order strategies have been proposed. These methods have often been designed primarily with complexity guarantees in mind and, as a result, represent a departure from the algorithms that have proved to be the most effective in practice. In this paper, we consider trust-region Newton methods, one of the most popular classes of algorithms for solving nonconvex optimization problems. By introducing slight modifications to the original scheme, we obtain two methods -- one based on exact subproblem solves and one exploiting inexact subproblem solves as in the popular "trust-region Newton-Conjugate-Gradient" (trust-region Newton-CG) method -- with iteration and operation complexity bounds that match the best known bounds for the aforementioned class of first- and second-order methods. The resulting trust-region Newton-CG method also retains the attractive practical behavior of classical trust-region Newton-CG, which we demonstrate with numerical comparisons on a standard benchmark test set.

math.OC↗