Earth Polychromatic Imaging Camera Geolocation; Strategies to Reduce Uncertainty

Earth Polychromatic Imaging Camera occupies a unique point of view for an Earth imager by being located approximately 1.5 million km from the planet at Earth-Sun Lagrange point, L1. This creates a number of unique challenges in geolocation, some of which are distance and mission specific. To solve these problems, algorithmic adaptations need to be made for calculations used for standard geolocation solutions, as well as artificial intelligence-based corrections for star tracker attitude and optical issues. This paper discusses methods for resolving these issues and bringing the geolocation solution to within requirements.

Earth Imaging From the Surface of the Moon With a DSCOVR/EPIC-Type Camera

The Earth Polychromatic Imaging Camera (EPIC) on the Deep Space Climate Observatory (DSCOVR) satellite observes the entire Sun-illuminated Earth from sunrise to sunset from the L1 Sun-Earth Lagrange point. The L1 location, however, confines the observed phase angles to ∼2°–12°, a nearly backscattering direction, precluding any information on the bidirectional surface reflectance factor (BRF) or cloud/aerosol phase function. Deploying an analog of EPIC on the Moon’s surface would offer a unique opportunity to image the full range of Earth phases, including observing ocean/cloud glint reflection for different phase angles; monitoring of transient volcanic clouds; detection of circum-polar mesospheric and stratospheric clouds; estimating the surface BRF and full phase-angle integrated albedo; and monitoring of vegetation characteristics for different phase angles.

Modeling the nonaxisymmetric structure in the HD 163296 disk with planet-disk interaction

Context. High-resolution ALMA observations such as the DSHARP campaign have revealed a variety of rich substructures in numerous protoplanetary disks. These structures consist of rings, gaps, and asymmetric features. It has been debated whether planets can be accounted for among these substructures in the dust continuum. Characterizing the origin of asymmetries, as seen in HD 163296, might lead to a better understanding of planet formation and the underlying physical parameters of the system. Aims. We test the possibility that the formation of the crescent-shaped asymmetry in the HD 163296 disk can be attributed to planet-disk interaction. The goal is to obtain constraints on planet masses, eccentricities, and disk viscosities. Furthermore, we test the reproducibility of the two prominent rings in the HD 163296 disk at 67 and 100 au. Methods. We performed two-dimensional, multi-fluid, hydrodynamical simulations with the FARGO3D code, including three embedded planets in the setup. Dust is described via the pressureless fluid approach and distributed over eight size bins. The resulting grids were post-processed with the radiative transfer code RADMC-3D and CASA software to model the synthetic observations. Results. We find that the crescent-shaped asymmetry can be qualitatively modeled with a Jupiter mass planet at a radial distance of 48 au. Dust is trapped in the trailing Lagrange point L5, preferably, with a mass of between 10 and 15 earth masses. The observation of such a feature constrains the level of viscosity and planetary mass. Increased values of eccentricity of the innermost Jupiter mass planet negatively impacts the stability of the crescent-shaped feature and does not reproduce the observed radial proximity to the first prominent ring in the system. Generally, a low level of viscosity (α ≤ 2 × 10−3) is necessary to allow for the existence of such a feature. Including dust feedback in the leading point, L4, can dominantly capture dust for dust grains with an initial Stokes number ≤ 3.6 × 10−2. In the synthetic ALMA observation of the model with dust feedback, two crescent-shaped features are visible. The observational results suggest a negligible effect on the part of dust feedback since only one such feature has been detected so far. The dust-to-gas ratio may thus be overestimated in the models. Additionally, the planet mass growth time scale does not strongly affect the formation of such asymmetries in the co-orbital region.

Prediction of the Dst Geomagnetic Index Using Adaptive Methods

The potential is investigated of predicting the time series of the Dst geomagnetic index using various adaptive methods: artificial neural networks (classical multilayer perceptrons), decision trees (random forest), gradient boosting. The prediction is based on the parameters of the solar wind and interplanetary magnetic field measured at the Lagrange point L1 in the ACE spacecraft experiment. It is shown that the best prediction skill of the three adaptive methods is demonstrated by gradient boosting.

Space Weather Monitoring Based on Surface Magnetic Observations (РС Index)

Polar cap magnetic activity (РС index) is an indicator of solar wind energy that enters the magnetosphere (Resolutions of XXII IAGA Assembly, 2013). Usually, the PC index follows changes in the interplanetary electric field EKL, that is estimated from measurement data on solar wind parameters at the Lagrange point L1 (available at the OMNI website). However, during the period of magnetic field perturbations, the correspondence between EKL and PC is often disturbed. To reveal the regularity of disturbances, the correlation was analyzed between the PC index and the computed field EKL during magnetic substorms, which are considered as an independent indicator of the impact of perturbed solar wind on the magnetosphere. The independent analysis for the PCN and PCS indices demonstrated that the magnetic activity in the winter polar cap (PCwinter) provides statistically more correct results than the magnetic activity in the summer cap (PCsummer). The correlation between the PCwinter and the computed field EKL (R > 0.5) was observed for ~80% of the analyzed substorms. In the other cases (20%), the correlation was low or even negative, even though substorms were evidently associated with the PC index growth. So, in these cases, the computed field EKL did not contact with the magnetosphere. Hence, the PC index allows verifying the real field EKL affecting the magnetosphere and checking in such way whether the solar wind registered at the Lagrange point contacted with the magnetosphere (data from the OMNI website).

A pair of Jovian Trojans at the L4 Lagrange point

ABSTRACT Asteroid pairs, two objects that are not gravitationally bound to one another, but share a common origin, have been discovered in the Main belt and Hungaria populations. Such pairs are of major interest, as the study of their evolution under a variety of dynamical influences can indicate the time since the pair was created. To date, no asteroid pairs have been found in the Jovian Trojans, despite the presence of several binaries and collisional families in the population. The search for pairs in the Jovian Trojan population is of particular interest, given the importance of the Trojans as tracers of planetary migration during the Solar system’s youth. Here we report a discovery of the first pair, (258656) 2002 ES76 and 2013 CC41, in the Jovian Trojans. The two objects are approximately the same size and are located very close to the L4 Lagrange point. Using numerical integrations, we find that the pair is at least 360 Myr old, though its age could be as high as several Gyrs. The existence of the (258656) 2002 ES76–2013 CC41 pair implies there could be many such pairs scattered through the Trojan population. Our preferred formation mechanism for the newly discovered pair is through the dissociation of an ancient binary system, triggered by a sub-catastrophic impact, but we can not rule out rotation fission of a single object driven by YORP torques. A by-product of our work is an up-to-date catalogue of Jovian Trojan proper elements, which we have made available for further studies.