Spectrometric characteristics of the surface of Phobos from data obtained by HRSC on Mars Express

We investigate the spectral reflectance of the surface of Phobos using remote sensing data obtained by the HRSC on the European Mars Express mission. Color ratios reveal that the Phobos surface is heterogeneous, in agreement with previous studies based on Phobos-2 and Mars Reconnaissance Orbiter data

A Framework for Art-directed Augmentation of Human Motion in Videos on Mobile Devices

This paper presents a framework and mobile video editing app for interactive artistic augmentation of human motion in videos. While creating motion effects with industry-standard software is time-intensive and requires expertise, and popular video ef fect apps have limited customization options, our approach enables a multitude of art-directable, highly customizable motion effects. We propose a graph-based video processing framework that uses mobile-optimized machine learning models for hu man segmentation and pose estimation to augment RGB video data, enabling the rendering and animation of content-adaptive graphical elements that highlight and emphasize motion. Our modular framework architecture enables effect designers to create diverse motion effects that include body pose-based effects such as glow stick or light trail effects, silhouette-based effects such as halos and outlines, and layer-based effects that provide depth perception and enable interaction with virtual object

Mars moon ephemerides after 14 years of Mars Express data

The Mars Express (MEX) mission has been successfully operated around Mars since 2004. Among many results, MEX has provided some of the most accurate astrometric data of the two Mars moons, Phobos and Deimos. We present new ephemerides of the Mars moons benefitting from all previously published astrometric data to the most recent MEX SRC data. Observations from 1877 until 2018 and including spacecraft measurements from Mariner 9 to MEX were included. Assuming a homogeneous interior, we fitted the forced libration amplitude of Phobos simultaneously with the Martian tidal k2∕Q ratio and the initial state of the moons. Our solution of the physical libration 1.09 ± 0.01 degrees deviates notably from the homogeneous solution. Considering the very low error bar, however, this may essentially suggest the necessity to consider higher order harmonics with an improved rotation model in the future. While most data could be successfully fitted, we found a disagreement between the Mars Reconnaissance Orbiter and the Mars Express astrometric data at the kilometer level, probably associated with a biased phase correction. The current solution precision is expected at the level of a few hundred meters for Phobos and several hundred meters for Deimos for the coming years. The real accuracy of our new ephemerides will have to be confirmed by comparison with independent observational means

New Astrometric Observations of Deimos with the SRC on Mars Express

Between July 2005 and July 2011 Mars Express performed 50 Deimos approaches. 136 super resolution channel (SRC) images were acquired and used for astrometric (positional) measurements of the small Martian satellite. For this study, we have developed a new technique, in which the center-of-figure of the odd-shaped Deimos is determined by fitting the predicted to the observed satellite limb. The prediction of the limb was made based on the moon’s known shape model. The camera pointing was verified and corrected for by means of background star observations. We obtained a set of spacecraft-centered Deimos coordinates with accuracies between 0.6 and 3.6 km (1σ). Comparisons with current orbit models indicate that Deimos is ahead of or falling behind its predicted position along its track by as much as +3.4 km or  −4.7 km, respectively, depending on the chosen model. Our data may be used to improve the orbit models of the satellite

A new astrometric measurement and reduction of USNO photographic observations of Phobos and Deimos: 1967–1997

Context. Accurate positional measurements of planets and satellites are used to improve our knowledge of both their orbits and their dynamics and to infer the accuracy of the planet and satellite ephemerides. Aims. In the framework of the European FP7 ESPaCE program, we provide the positions of Mars, Phobos, and Deimos taken with the US Naval Observatory 61-inch astrometric reflector and 26-inch refractor from 1967 to 1997. Methods. Four hundred twenty five astrophotographic plates were measured with the digitizer of the Royal Observatory of Belgium and reduced through an optimal process that includes image, instrumental, and spherical corrections using the UCAC4 catalog to provide the most accurate equatorial (RA, Dec) positions. Results. We compared the observed positions of the planet Mars and its satellites with the theoretical positions from INPOP13c and DE430 planetary ephemerides and from NOE MarsSatV1_0 and MAR097 satellite ephemerides. The rms residuals in RA and Dec of one position are less than 62 mas or about 20 km at the opposition of Mars. The rms intersatellite residuals in RA and Dec of one position are less than 40 mas or about 13 km at Mars. This accuracy is comparable to the most recent CCD observations. We also fitted the NOE model to the new computed positions and compared the orbital evolution of Phobos and Deimos with those derived from the same model, but only fitted to spacecraft data. Our results show that astrophotographic plate data can now compete with those of old spacecraft

Astrometric observations of Phobos with the SRC on Mars Express

Aims. From April 2008 to August 2011 Mars Express carried out 74 Phobos flybys at distances between 669 and 5579 km. Images taken with the Super Resolution Channel (SRC) were used to determine the spacecraft-centered right ascension and declination of this Martian moon. Methods. Image positions of Phobos were measured using the limb-fit and control-point measurement techniques. Camera pointing and pointing drift were controlled by means of background star observations that were compared to corresponding positions from reference catalogs. Blurred and noisy images were restored by applying an image-based point spread function in a Richardson-Lucy deconvolution. Results. Here, we report on a set of 158 Phobos astrometric observations with estimated accuracies between 0.224 and 3.405 km circular w.r.t. the line of sight to the satellite. Control point measurements yield slightly more accurate results than the limb fit ones. Our observations are in good agreement with the current Phobos ephemerides by the Jet Propulsion Laboratory (JPL) and the Royal Observatory of Belgium (ROB) with mean offsets of up to 335 m. Our data can be used for the maintenance and update of these models

VizieR Online Data Catalog: Mars moon ephemerides for 14yrs Mars Express data (Lainey+, 2021)

Table 2: Mean (ν) and standard deviation (σ) on separation s and position angle p (multiplied by the separation) in seconds of degrees for each satellite. N is the number of observations by satellite (one number per coordinate). The year appearing next to each observatory name corresponds to the observed Mars opposition. Table 3: Mean (ν) and standard deviation (σ) on right ascension and declination in seconds of degrees for each satellite. }N} is the number of observations by satellite. Table 4: Mean (ν) and standard deviation (σ) on right ascension and declination for each satellite. Both angles are multiplied by the distance spacecraft-moon to obtain kilometers. }N} is the number of observations by satellite. In the Pasewaldt et al. (2015) publication positions of Phobos have been determined using control point (CP) and/or limb point (LF) measurements. The former are based on the satellite's control network, a set of identifiable surface features well-distributed over the body's surface and defining its reference system. Recent MEX SRC measurements have been distinguished into observations made during linear and non-linear pointing variations. If the observations' pre-fit residuals deviated by more than three sigma from the mean value, they have been additionally categorised as an outlier. In case of only a few outliers it could not be clarified whether they have been related to non-linear variations in pointing or not. Some measurements are based on fits of the shape model-derived limb to only very short limb point arcs in the image (see also subsection 3.2.1). Table 5: Mean (ν) and standard deviation (σ) on sample and line in pixel and kilometer for each satellite. }N} is the number of observations by satellite. MRO (single) gathers data where only one moon was observable at a time. Table 6: Initial conditions and related uncertainties of Phobos and Deimos in the ICRF after fit at initial epoch J2000 (Julian day 2451545.0). Units are }km} and }km/sec}. All digits have been kept for reproducibility of our results. (5 data files)