Real-time on-board orbit determination with DORIS

A spaceborne orbit determination system is being developed by the French Space Agency (CNES) for the SPOT 4 satellite. It processes DORIS measurements to produce an orbit with an accuracy of about 50O meters rms. In order to evaluate the reliability of the software, it was combined with the MERCATOR man/machine interface and used to process the TOPEX/Poseidon DORIS data in near real time during the validation phase of the instrument, at JPL and at CNES. This paper gives an overview of the orbit determination system and presents the results of the TOPEX/Poseidon experiment

Torsion and Nonmetricity in Scalar-Tensor Theories of Gravity

We show that the gravitational field equations derived from an action composed of i) an arbitrary function of the scalar curvature and other scalar fields plus ii) connection-independent kinetic and source terms, are identical whether one chooses nonmetricity to vanish and have non-zero torsion or vice versa.Comment: 10 page

Black Holes with Weyl Charge and Non-Riemannian Waves

A simple modification to Einstein's theory of gravity in terms of a non-Riemannian connection is examined. A new tensor-variational approach yields field equations that possess a covariance similar to the gauge covariance of electromagnetism. These equations are shown to possess solutions analogous to those found in the Einstein-Maxwell system. In particular one finds gravi-electric and gravi-magnetic charges contributing to a spherically symmetric static Reissner-Nordstr\"om metric. Such Weyl ``charges'' provide a source for the non-Riemannian torsion and metric gradient fields instead of the electromagnetic field. The theory suggests that matter may be endowed with gravitational charges that couple to gravity in a manner analogous to electromagnetic couplings in an electromagnetic field. The nature of gravitational coupling to spinor matter in this theory is also investigated and a solution exhibiting a plane-symmetric gravitational metric wave coupled via non-Riemannian waves to a propagating spinor field is presented.Comment: 18 pages Plain Tex (No Figures), Classical and Quantum Gravit

The SuperCam Instrument Suite on the Mars 2020 Rover: Science Objectives and Mast-Unit Description

On the NASA 2020 rover mission to Jezero crater, the remote determination of the texture, mineralogy and chemistry of rocks is essential to quickly and thoroughly characterize an area and to optimize the selection of samples for return to Earth. As part of the Perseverance payload, SuperCam is a suite of five techniques that provide critical and complementary observations via Laser-Induced Breakdown Spectroscopy (LIBS), Time-Resolved Raman and Luminescence (TRR/L), visible and near-infrared spectroscopy (VISIR), high-resolution color imaging (RMI), and acoustic recording (MIC). SuperCam operates at remote distances, primarily 2-7 m, while providing data at sub-mm to mm scales. We report on SuperCam's science objectives in the context of the Mars 2020 mission goals and ways the different techniques can address these questions. The instrument is made up of three separate subsystems: the Mast Unit is designed and built in France; the Body Unit is provided by the United States; the calibration target holder is contributed by Spain, and the targets themselves by the entire science team. This publication focuses on the design, development, and tests of the Mast Unit; companion papers describe the other units. The goal of this work is to provide an understanding of the technical choices made, the constraints that were imposed, and ultimately the validated performance of the flight model as it leaves Earth, and it will serve as the foundation for Mars operations and future processing of the data.In France was provided by the Centre National d'Etudes Spatiales (CNES). Human resources were provided in part by the Centre National de la Recherche Scientifique (CNRS) and universities. Funding was provided in the US by NASA's Mars Exploration Program. Some funding of data analyses at Los Alamos National Laboratory (LANL) was provided by laboratory-directed research and development funds

Disentangling Lipid Isomers by High-Resolution Differential Ion Mobility Spectrometry/Ozone-Induced Dissociation of Metalated Species

The preponderance and functional importance of isomeric biomolecules have become topical in biochemistry. Therefore, one must distinguish and identify all such forms across compound classes, over a wide dynamic range as minor species often have critical activities. With all the power of modern mass spectrometry for compositional assignments by accurate mass, the identical precursor and often fragment ion masses render this task a steep challenge. This is recognized in proteomics and epigenetics, where proteoforms are disentangled and characterized employing novel separations and non-ergodic dissociation mechanisms. This issue is equally pertinent to lipidomics, where the lack of isomeric depth has thwarted the deciphering of functional networks. Here we introduce a new platform, where the isomeric lipids separated by high-resolution differential ion mobility spectrometry (FAIMS) are identified using ozone-induced dissociation (OzID). Cationization by metals (here K+, Ag+, and especially Cu+) broadly improves the FAIMS resolution of isomers with alternative C═C double bond (DB) positions or stereochemistry, presumably via metal attaching to the DB and reshaping the ion around it. However, the OzID yield diminishes for Ag+ and vanishes for Cu+ adducts. Argentination still strikes the best compromise between efficient separation and diagnostic fragmentation for optimal FAIMS/OzID performance.</p

Finding Desirable Orbit Options for the "Extension of Life" Phase of Jason-1

International audienceThe ageing of Jason-1, the risk of losing control of the satellite, and the collision risk with TOPEX/Poseidon (still in orbit and no longer maneuverable) initiated a reflection on a so-called "extension of life phase" (EoL) phase that would involve moving Jason-1 to a new orbit to mitigate collision risks while optimizing its science return. This paper describes three practical consequences of any such EoL phase: 1) the ability to build an unprecedented low inclination and high precision geodetic dataset, 2) the loss of coordination with Jason-2 and the associated mesoscale (and sea state) sampling degradation, and 3) the increased topography height error budget stemming from the use of a gridded mean sea surface in place of the classical repeat track analysis that operational systems have been using and improving for almost two decades. More than 17,000 potential orbits were analyzed to identify desirable altitude ranges that could host a Jason-1 EoL phase. The objective was to minimize the sampling degradation of ocean observations (primary objective of Jason-1) while securing a good geodetic EoL dataset (secondary objective of Jason-1). After a first automated screening and scoring process, the final orbit candidates are analyzed through an end-to-end Observing System Simulation Experiment (OSSE) protocol, assessing the multimission observational capability of the EoL phase in a DUACS/AVISO-like system. All EoL orbits are shown to be largely inferior to the interleaved orbit as far as oceanography is concerned. Yet some EoL options are shown to be more desirable than others because their sampling patterns blend well with Jason-2. Good geodetic orbit options could provide a unique bathymetry-oriented dataset and help improve gridded mean sea surfaces (MSS), while repetitive options with a short cycle could cancel some additional EoL errors if a conservative repeat track strategy is preferred