Subjects -> ASTRONOMY (Total: 94 journals)
 Showing 1 - 46 of 46 Journals sorted alphabetically Advances in Astronomy       (Followers: 51) Annual Review of Astronomy and Astrophysics       (Followers: 39) Annual Review of Earth and Planetary Sciences       (Followers: 63) Artificial Satellites       (Followers: 23) Astrobiology       (Followers: 14) Astronomical & Astrophysical Transactions: The Journal of the Eurasian Astronomical Society       (Followers: 6) Astronomical Journal       (Followers: 8) Astronomical Review       (Followers: 4) Astronomische Nachrichten       (Followers: 4) Astronomy & Geophysics       (Followers: 48) Astronomy and Astrophysics       (Followers: 60) Astronomy and Astrophysics       (Followers: 32) Astronomy and Computing       (Followers: 2) Astronomy Letters       (Followers: 22) Astronomy Reports       (Followers: 15) Astronomy Studies Development       (Followers: 12) Astroparticle Physics       (Followers: 8) Astrophysical Bulletin       (Followers: 3) Astrophysical Journal       (Followers: 19) Astrophysical Journal Letters       (Followers: 14) Astrophysical Journal Supplement Series       (Followers: 14) Astrophysics       (Followers: 29) Astrophysics and Space Science       (Followers: 46) Astrophysics and Space Sciences Transactions (ASTRA)       (Followers: 56) Astropolitics: The International Journal of Space Politics & Policy       (Followers: 12) Celestial Mechanics and Dynamical Astronomy       (Followers: 11) Chinese Astronomy and Astrophysics       (Followers: 24) Colloid Journal       (Followers: 3) Comptes Rendus Physique       (Followers: 2) Computational Astrophysics and Cosmology       (Followers: 3) COSPAR Colloquia Series       (Followers: 11) Earth, Moon, and Planets       (Followers: 55) Earth, Planets and Space       (Followers: 74) EAS Publications Series       (Followers: 8) EPL Europhysics Letters       (Followers: 8) Experimental Astronomy       (Followers: 39) Expert Opinion on Astronomy and Astrophysics       (Followers: 7) Extreme Life, Biospeology & Astrobiology - International Journal of the Bioflux Society       (Followers: 6) Few-Body Systems       (Followers: 1) Foundations of Physics       (Followers: 41) Frontiers in Astronomy and Space Sciences       (Followers: 12) Galaxies       (Followers: 6) Globe, The       (Followers: 4) Gravitation and Cosmology       (Followers: 4) Icarus       (Followers: 75) International Journal of Advanced Astronomy       (Followers: 28) International Journal of Astrobiology       (Followers: 4) International Journal of Astronomy       (Followers: 19) International Journal of Astronomy and Astrophysics       (Followers: 29) International Journal of Satellite Communications Policy and Management       (Followers: 13) International Letters of Chemistry, Physics and Astronomy       (Followers: 12) ISRN Astronomy and Astrophysics       (Followers: 7) Journal for the History of Astronomy       (Followers: 19) Journal of Astrobiology & Outreach       (Followers: 3) Journal of Astronomical Instrumentation       (Followers: 3) Journal of Astronomical Telescopes, Instruments, and Systems       (Followers: 5) Journal of Astrophysics       (Followers: 26) Journal of Astrophysics and Astronomy       (Followers: 52) Journal of Atmospheric and Solar-Terrestrial Physics       (Followers: 199) Journal of Cosmology and Astroparticle Physics       (Followers: 38) Journal of Geophysical Research : Planets       (Followers: 178) Journal of Geophysical Research : Space Physics       (Followers: 178) Journal of High Energy Astrophysics       (Followers: 22) Kinematics and Physics of Celestial Bodies       (Followers: 10) KronoScope       (Followers: 1) Macalester Journal of Physics and Astronomy       (Followers: 4) MNASSA : Monthly Notes of the Astronomical Society of South Africa       (Followers: 1) Molecular Astrophysics       (Followers: 1) Monthly Notices of the Royal Astronomical Society       (Followers: 14) Monthly Notices of the Royal Astronomical Society : Letters Nature Astronomy       (Followers: 8) New Astronomy       (Followers: 27) New Astronomy Reviews       (Followers: 17) Nonlinear Dynamics       (Followers: 19) NRIAG Journal of Astronomy and Geophysics       (Followers: 5) Open Astronomy       (Followers: 2) Physics of the Dark Universe       (Followers: 4) Planetary and Space Science       (Followers: 101) Planetary Science       (Followers: 52) Proceedings of the International Astronomical Union       (Followers: 2) Publications of the Astronomical Society of Australia       (Followers: 2) Publications of the Astronomical Society of Japan       (Followers: 3) Publications of the Astronomical Society of the Pacific       (Followers: 4) Research & Reviews : Journal of Space Science & Technology       (Followers: 17) Research in Astronomy and Astrophysics       (Followers: 29) Revista Mexicana de Astronomía y Astrofísica       (Followers: 2) Science China Physics, Mechanics & Astronomy       (Followers: 4) Solar Physics       (Followers: 34) Solar System Research       (Followers: 14) Space Science International       (Followers: 192) Space Science Reviews       (Followers: 97) Space Weather       (Followers: 24) Transport and Aerospace Engineering       (Followers: 13) Universe       (Followers: 5)
Similar Journals
 Space Science ReviewsJournal Prestige (SJR): 3.262 Citation Impact (citeScore): 7Number of Followers: 97      Hybrid journal (It can contain Open Access articles) ISSN (Print) 1572-9672 - ISSN (Online) 0038-6308 Published by Springer-Verlag  [2626 journals]
• SERENA: Particle Instrument Suite for Determining the Sun-Mercury
Interaction from BepiColombo
• Abstract: Abstract The ESA-JAXA BepiColombo mission to Mercury will provide simultaneous measurements from two spacecraft, offering an unprecedented opportunity to investigate magnetospheric and exospheric particle dynamics at Mercury as well as their interactions with solar wind, solar radiation, and interplanetary dust. The particle instrument suite SERENA (Search for Exospheric Refilling and Emitted Natural Abundances) is flying in space on-board the BepiColombo Mercury Planetary Orbiter (MPO) and is the only instrument for ion and neutral particle detection aboard the MPO. It comprises four independent sensors: ELENA for neutral particle flow detection, Strofio for neutral gas detection, PICAM for planetary ions observations, and MIPA, mostly for solar wind ion measurements. SERENA is managed by a System Control Unit located inside the ELENA box. In the present paper the scientific goals of this suite are described, and then the four units are detailed, as well as their major features and calibration results. Finally, the SERENA operational activities are shown during the orbital path around Mercury, with also some reference to the activities planned during the long cruise phase.
PubDate: 2021-01-12

• The Physics of Accretion Discs, Winds and Jets in Tidal Disruption Events
• Abstract: Abstract Accretion onto black holes is an efficient mechanism in converting the gas mass-energy into energetic outputs as radiation, wind and jet. Tidal disruption events, in which stars are tidally torn apart and then accreted onto supermassive black holes, offer unique opportunities of studying the accretion physics as well as the wind and jet launching physics across different accretion regimes. In this review, we systematically describe and discuss the models that have been developed to study the accretion flows and jets in tidal disruption events. A good knowledge of these physics is not only needed for understanding the emissions of the observed events, but also crucial for probing the general relativistic space-time around black holes and the demographics of supermassive black holes via tidal disruption events.
PubDate: 2021-01-12

• Mars Oxygen ISRU Experiment (MOXIE)
• Abstract: Abstract MOXIE is a technology demonstration that addresses the Mars 2020 (Perseverance) objective of preparing for future human exploration by demonstrating In Situ Resource Utilization (ISRU) in the form of dissociating atmospheric CO2 into O2. The primary goals of the MOXIE project are to verify and validate the technology of Mars ISRU as a springboard for the future, and to establish achievable performance requirements and design approaches that will lead to a full-scale ISRU system based on MOXIE technology. MOXIE has three top-level requirements: to be capable of producing at least 6 g/hr of oxygen in the context of the Mars 2020 mission (assuming atmospheric intake at 5 Torr, typical of Jezero Crater, and $$0~^{\circ}\text{C}$$ , typical of the rover interior); to produce oxygen with $$>98\%$$ purity; and to meet these first two requirements for at least 10 operational cycles after delivery. Since MOXIE is expected to operate in all seasons and at all times of day and night on Mars, these requirements are intended to be satisfied under worst-case environmental conditions, including during a dust storm, if possible.
PubDate: 2021-01-06

• Proton Aurora and Optical Emissions in the Subauroral Region
• Abstract: Abstract Optical structures located equatorward of the main auroral oval often exhibit different morphologies and dynamics than structures at higher latitudes. In some cases, questions arise regarding the formation mechanisms of these photon-emitting phenomena. New developments in space and ground-based instruments have enabled us to acquire a clearer view of the processes playing a role in the formation of subauroral structures. In addition, the discovery of new optical structures helps us improve our understanding of the latitudinal and altitudinal coupling that takes place in the subauroral region. However, several questions remain unanswered, requiring the development of new instruments and analysis techniques. We discuss optical phenomena in the subauroral region, summarize observational results, present conclusions about their origin, and pose a number of open questions that warrant further investigation of proton aurora, detached subauroral arcs and spots, stable auroral red (SAR) arcs, and STEVE (Strong Thermal Emission Velocity Enhancement).
PubDate: 2021-01-06

• The Mars Orbiter Subsurface Investigation Radar (MOSIR) on China’s
Tianwen-1 Mission
• Abstract: Abstract China launched Tianwen-1 spacecraft successfully on July 23rd, 2020. The Mars Orbiter Subsurface Investigation Radar (MOSIR) is a subsurface radar sounder as a scientific instrument onboard Tianwen-1 orbiter. It is designed to study the compositions of Martian surface material, subsurface structure, and the ionosphere’s total electron content. It can also perform passive observations in a transfer orbit to Mars. The subsurface stratigraphic structure is critical to the study on Mars geological and climatic evolution history. Considering the optimal tradeoff between penetrating depth and range resolution, MOSIR operates at low-frequency and high-frequency channels, with the frequency bands of 10–15 MHz or 15–20 MHz and 30–50 MHz, respectively. MOSIR provides a penetration depth of more than 100 m with a vertical resolution of 7.5 m (20 MHz bandwidth) and 30 m (5 MHz bandwidth) in free space. The range and azimuth focusing techniques are applied in ground data processing to achieve the resolution of several hundred meters (along-track) and several thousand meters (cross-track). MOSIR is intended to search for water ice and liquid water that may be associated with signs of life in the polar layered deposits, Tianwen-1 landing site, and other selected areas.
PubDate: 2021-01-06

• Formation of Venus, Earth and Mars: Constrained by Isotopes
• Abstract: Abstract Here we discuss the current state of knowledge of terrestrial planet formation from the aspects of different planet formation models and isotopic data from 182Hf-182W, U-Pb, lithophile-siderophile elements, 48Ca/44Ca isotope samples from planetary building blocks, recent reproduction attempts from 36Ar/38Ar, 20Ne/22Ne, 36Ar/22Ne isotope ratios in Venus’ and Earth’s atmospheres, the expected solar 3He abundance in Earth’s deep mantle and Earth’s D/H sea water ratios that shed light on the accretion time of the early protoplanets. Accretion scenarios that can explain the different isotope ratios, including a Moon-forming event ca. 50 Myr after the formation of the Solar System, support the theory that the bulk of Earth’s mass (≥80%) most likely accreted within 10–30 Myr. From a combined analysis of the before mentioned isotopes, one finds that proto-Earth accreted most likely a mass of 0.5–0.6 $$M$$ Earth within the first ≈3–4.5 Myr, the approximate lifetime of the protoplanetary disk. For Venus, the available atmospheric noble gas data are too uncertain for constraining the planet’s accretion scenario accurately. However, from the available imprecise Ar and Ne isotope measurements, one finds that proto-Venus could have grown to a mass of up to 0.85–1.0  $$M$$ Venus before the disk dissipated. Classical terrestrial planet formation models have struggled to grow large planetary embryos, or even cores of giant planets, quickly from the tiniest materials within the typical lifetime of protoplanetary disks. Pebble accretion could solve this long-standing time scale controversy. Pebble accretion and streaming instabilities produce large planetesimals that grow into Mars-sized and larger planetary embryos during this early accretion phase. The later stage of accretion can be explained well with the Grand-Tack model as well as the annulus and depleted disk models. The relative roles of pebble accretion and planetesimal accretion/giant impacts are poorly understood and should be investigated with N-body simulations that include pebbles and multiple protoplanets. To summarise, different isotopic dating methods and the latest terrestrial planet formation models indicate that the accretion process from dust settling, planetesimal formation, and growth to large planetary embryos and protoplanets is a fast process that occurred to a great extent in the Solar System within the lifetime of the protoplanetary disk.
PubDate: 2020-12-22

• Landing Site Selection and Overview of China’s Lunar Landing
Missions
• Abstract: Abstract Landing site selection is of fundamental importance for lunar landing mission and it is closely related to the scientific goals of the mission. According to the widely concerned lunar science goals and the landing site selection of the ongoing lunar missions; China has carried out the selection of landing site for a series of Chang’ E (CE) missions. Under this background, this paper firstly introduced the principles, process, method and result of landing site selection of China’s Lunar Exploration Program (CLEP), and then analyzed the support of the selected landing sites to the corresponding lunar research. This study also pointed out the outcomes that could possibly contribute to the key lunar questions on the basis of the selected landing sites of CE-4 and CE-5 such as deep material in South Pole-Aitken (SPA) basin, lunar chronology, volcanic thermodynamics and geological structure evolution history of the Moon. Finally, this approach analyzed the development trend of China’s follow-up lunar landing missions, and suggested that the South Pole Region of the Moon could be the landing site of high priority for the future CE missions.
PubDate: 2020-12-22

• Science Goals and Mission Objectives for the Future Exploration of Ice
Giants Systems: A Horizon 2061 Perspective
• Abstract: Abstract The comparative study of planetary systems is a unique source of new scientific insight: following the six “key science questions” of the “Planetary Exploration, Horizon 2061” long-term foresight exercise, it can reveal to us the diversity of their objects (Question 1) and of their architectures (Question 2), help us better understand their origins (Question 3) and how they work (Question 4), find and characterize habitable worlds (Question 5), and ultimately, search for alien life (Question 6). But a huge “knowledge gap” exists which limits the applicability of this approach in the solar system itself: two of its secondary planetary systems, the ice giant systems of Uranus and Neptune, remain poorly explored. Starting from an analysis of our current limited knowledge of solar system ice giants and their systems in the light of these six key science questions, we show that a long-term plan for the space exploration of ice giants and their systems will greatly contribute to answer these questions. To do so, we identify the key measurements needed to address each of these questions, the destinations to choose (Uranus, Neptune, Triton or a subset of them), the combinations of space platform(s) and the types of flight sequences needed. We then examine the different launch windows available until 2061, using a Jupiter fly-by, to send a mission to Uranus or Neptune, and find that: (1) an optimized choice of platforms and flight sequences makes it possible to address a broad range of the key science questions with one mission at one of the planets. Combining an atmospheric entry probe with an orbiter tour starting on a high-inclination, low periapse orbit, followed by a sequence of lower inclination orbits (or the other way around) appears to be an optimal choice. (2) a combination of two missions to each of the ice giant systems, to be flown in parallel or in sequence, will address five out of the six key questions and establish the prerequisites to address the sixth one: searching for life at one of the most promising Ice Giant moons. (3) The 2032 Jupiter fly-by window, which offers a unique opportunity to implement this plan, should be considered in priority; if this window cannot be met, using the 2036 Jupiter fly-by window to send a mission to Uranus first, and then the 2045 window for a mission to Neptune, will allow one to achieve the same objectives; as a back-up option, one should consider an orbiter + probe mission to one of the planets and a close fly-by of the other planet to deliver a probe into its atmosphere, using the opportunity of a future mission on its way to Kuiper Belt Objects or the interstellar medium; (4) based on the examination of the habitability of the different moons by the first two missions, a third one can be properly designed to search for life at the most promising moon, likely Triton, or one of the active moons of Uranus. Thus, by 2061 the first two missions of this plan can be implemented and a third mission focusing on the search for life can be designed. Given that such a plan may be out of reach of a single national agency, international collaboration is the most promising way to implement it.
PubDate: 2020-12-21

• The Sampling and Caching Subsystem (SCS) for the Scientific Exploration of
Jezero Crater by the Mars 2020 Perseverance Rover
• Abstract: Abstract The Mars 2020 mission seeks to conduct a new scientific exploration on the surface of Mars. The Perseverance Rover will be sent to the surface of the Jezero Crater region to study its habitability, search for biosignatures of past life, acquire and cache samples for potential return, and prepare for possible human missions. To enable these objectives, an innovative Sampling and Caching Subsystem (SCS) has been developed and tested to allow the Perseverance Rover to acquire and cache rock core and regolith samples, prepare abraded rock surfaces, and support proximity science instruments. The SCS consists of the Robotic Arm (RA), the Turret and Corer, and the Adaptive Caching Assembly (ACA). These elements reside and interact both inside and outside of the Perseverance Rover to enable surface interactions, sample transfer, and caching. The main body of the Turret consists of the Coring Drill (Corer) with a Launch Abrading Bit initially installed prior to launch. Mounted to the Turret main structure are two proximity science instruments, SHERLOC and PIXL, as well as the Gas Dust Removal Tool (gDRT) and the Facility Contact Sensor (FCS). These work together with the RA to provide the sample acquisition, abraded surface preparation, and proximity science functions. The ACA is a network of assemblies largely inside the front belly of the Rover, which combine to perform the sample handling and caching functions of the mission. The ACA primarily consists of the Bit Carousel, the Sample Handling Assembly (SHA), End Effector (EE), Sample Tubes and their Sample Tube Storage Assembly (STSA), Seals and their Dispenser, Volume, and Tube Assembly (DVT), the Sealing Station, the Vision Station, the Cover Parking Lot, and additional supporting hardware. These components attach to the Caching Component Mounting Deck (CCMD) that is integrated with the Rover interior. This work describes these major elements of the SCS, with an emphasis on the functionality required to perform the set of tasks and interactions required by the subsystem. Key considerations of contamination control and biological cleanliness throughout the development of these hardware elements are also discussed. Additionally, aspects of testing and validating the functionality of the SCS are described. Early prototypes and tests matured the designs over several years and eventually led to the flight hardware and integrated testing in both Earth ambient and Mars-like environments. Multiple unique testbed venues were developed and used to enable testing from low-level mechanism operation through end-to-end sampling and caching interactions with the full subsystem and flight software. Various accomplishments from these testing efforts are highlighted. These past and ongoing tests support the successful preparations of the SCS on its pathway to operations on Mars.
PubDate: 2020-12-21

• Did Mars Possess a Dense Atmosphere During the First ∼ 400 $\sim400$
Million Years'
• Abstract: Abstract It is not yet entirely clear whether Mars began as a warm and wet planet that evolved towards the present-day cold and dry body or if it always was cold and dry with just some sporadic episodes of liquid water on its surface. An important clue into this question can be gained by studying the earliest evolution of the Martian atmosphere and whether it was dense and stable to maintain a warm and wet climate or tenuous and susceptible to strong atmospheric escape. In this review we therefore discuss relevant aspects for the evolution and stability of a potential early Martian atmosphere. This contains the EUV flux evolution of the young Sun, the formation timescale and volatile inventory of the planet including volcanic degassing, impact delivery and removal, the loss of the catastrophically outgassed steam atmosphere, atmosphere-surface interactions, as well as thermal and non-thermal escape processes affecting a potential secondary atmosphere at early Mars. While early non-thermal atmospheric escape at Mars before 4 billion years ago is poorly understood, in particular in view of its ancient intrinsic magnetic field, research on thermal escape processes and the stability of a CO2-dominated atmosphere around Mars against high EUV fluxes indicate that volatile delivery and volcanic degassing cannot counterbalance the strong atmospheric escape. Therefore, a catastrophically outgassed steam atmosphere of several bars of CO2 and H2O, or CO and H2 for reduced conditions, through solidification of the Martian magma ocean could have been lost within just a few million years. Thereafter, Mars likely could not build up a dense secondary atmosphere during its first $$\sim400$$ million years but might only have possessed an atmosphere sporadically during events of strong volcanic degassing, potentially also including SO2. This indicates that before $$\sim4.1$$ billion years ago Mars indeed might have been cold and dry with at maximum short and sporadic warmer periods. A denser CO2- or CO-dominated atmosphere, however, might have built up afterwards but must have been lost later-on due to non-thermal escape processes and sequestration into the ground.
PubDate: 2020-12-21

• The SuperCam Instrument Suite on the NASA Mars 2020 Rover: Body Unit and
Combined System Tests
• Abstract: Abstract The SuperCam instrument suite provides the Mars 2020 rover, Perseverance, with a number of versatile remote-sensing techniques that can be used at long distance as well as within the robotic-arm workspace. These include laser-induced breakdown spectroscopy (LIBS), remote time-resolved Raman and luminescence spectroscopies, and visible and infrared (VISIR; separately referred to as VIS and IR) reflectance spectroscopy. A remote micro-imager (RMI) provides high-resolution color context imaging, and a microphone can be used as a stand-alone tool for environmental studies or to determine physical properties of rocks and soils from shock waves of laser-produced plasmas. SuperCam is built in three parts: The mast unit (MU), consisting of the laser, telescope, RMI, IR spectrometer, and associated electronics, is described in a companion paper. The on-board calibration targets are described in another companion paper. Here we describe SuperCam’s body unit (BU) and testing of the integrated instrument. The BU, mounted inside the rover body, receives light from the MU via a 5.8 m optical fiber. The light is split into three wavelength bands by a demultiplexer, and is routed via fiber bundles to three optical spectrometers, two of which (UV and violet; 245–340 and 385–465 nm) are crossed Czerny-Turner reflection spectrometers, nearly identical to their counterparts on ChemCam. The third is a high-efficiency transmission spectrometer containing an optical intensifier capable of gating exposures to 100 ns or longer, with variable delay times relative to the laser pulse. This spectrometer covers 535–853 nm ( $$105\text{--}7070~\text{cm}^{-1}$$ Raman shift relative to the 532 nm green laser beam) with $$12~\text{cm}^{-1}$$ full-width at half-maximum peak resolution in the Raman fingerprint region. The BU electronics boards interface with the rover and control the instrument, returning data to the rover. Thermal systems maintain a warm temperature during cruise to Mars to avoid contamination on the optics, and cool the detectors during operations on Mars. Results obtained with the integrated instrument demonstrate its capabilities for LIBS, for which a library of 332 standards was developed. Examples of Raman and VISIR spectroscopy are shown, demonstrating clear mineral identification with both techniques. Luminescence spectra demonstrate the utility of having both spectral and temporal dimensions. Finally, RMI and microphone tests on the rover demonstrate the capabilities of these subsystems as well.
PubDate: 2020-12-21

• Editorial to the Topical Collection: In Situ Exploration of the Ice
Giants: Science and Technology
• PubDate: 2020-12-16

• Correction to: Studying the Composition and Mineralogy of the Hermean
Surface with the Mercury Radiometer and Thermal Infrared Spectrometer
(MERTIS) for the BepiColombo Mission: An Update
• Abstract: A Correction to this paper has been published: https://doi.org/10.1007/s11214-020-00780-w
PubDate: 2020-12-14

• Meteorological Predictions for Mars 2020 Perseverance Rover Landing Site
at Jezero Crater
• Abstract: Abstract The Mars Regional Atmospheric Modeling System (MRAMS) and a nested simulation of the Mars Weather Research and Forecasting model (MarsWRF) are used to predict the local meteorological conditions at the Mars 2020 Perseverance rover landing site inside Jezero crater (Mars). These predictions are complemented with the COmplutense and MIchigan MArs Radiative Transfer model (COMIMART) and with the local Single Column Model (SCM) to further refine predictions of radiative forcing and the water cycle respectively. The primary objective is to facilitate interpretation of the meteorological measurements to be obtained by the Mars Environmental Dynamics Analyzer (MEDA) aboard the rover, but also to provide predictions of the meteorological phenomena and seasonal changes that might impact operations, from both a risk perspective and from the perspective of being better prepared to make certain measurements. A full diurnal cycle at four different seasons ( $$\text{L}_{\mathrm{s}}$$   $$0^{\circ}$$ , $$90^{\circ}$$ , $$180^{\circ}$$ , and $$270^{\circ}$$ ) is investigated. Air and ground temperatures, pressure, wind speed and direction, surface radiative fluxes and moisture data are modeled. The good agreement between observations and modeling in prior works [Pla-Garcia et al. in Icarus 280:103–113, 2016; Newman et al. in Icarus 291:203–231, 2017; Vicente-Retortillo et al. in Sci. Rep. 8(1):1–8, 2018; Savijärvi et al. in Icarus, 2020] provides confidence in utilizing these models results to predict the meteorological environment at Mars 2020 Perseverance rover landing site inside Jezero crater. The data returned by MEDA will determine the extent to which this confidence was justified.
PubDate: 2020-12-14

• A Primer on Focused Solar Energetic Particle Transport
• Abstract: Abstract The basics of focused transport as applied to solar energetic particles are reviewed, paying special attention to areas of common misconception. The micro-physics of charged particles interacting with slab turbulence are investigated to illustrate the concept of pitch-angle scattering, where after the distribution function and focused transport equation are introduced as theoretical tools to describe the transport processes and it is discussed how observable quantities can be calculated from the distribution function. In particular, two approximations, the diffusion-advection and the telegraph equation, are compared in simplified situations to the full solution of the focused transport equation describing particle motion along a magnetic field line. It is shown that these approximations are insufficient to capture the complexity of the physical processes involved. To overcome such limitations, a finite-difference model, which is open for use by the public, is introduced to solve the focused transport equation. The use of the model is briefly discussed and it is shown how the model can be applied to reproduce an observed solar energetic electron event, providing insights into the acceleration and transport processes involved. Past work and literature on the application of these concepts are also reviewed, starting with the most basic models and building up to more complex models.
PubDate: 2020-12-10

• ISA, a High Sensitivity Accelerometer in the Interplanetary Space
• Abstract: Abstract ISA (Italian Spring Accelerometer) is a high sensitivity accelerometer flying, as scientific payload, on-board one of the two spacecraft (the Mercury Planetary Orbiter) of BepiColombo, the first ESA mission to Mercury. The first commissioning phase (performed in the period November 2018 - August 2019) allowed to verify the functionality of the instrument itself as well as of the related data handling and archiving system. Moreover, the acceleration measurements gathered in this time frame allow to envisage the potentiality of such an instrument as a high-accuracy monitor of the spacecraft mechanical environment.
PubDate: 2020-12-08

• Mercury Dust Monitor (MDM) Onboard the Mio Orbiter of the BepiColombo
Mission
• Abstract: Abstract An in-situ cosmic-dust instrument called the Mercury Dust Monitor (MDM) had been developed as a part of the science payload for the Mio (Mercury Magnetospheric Orbiter, MMO) stage of the joint European Space Agency (ESA)–JAXA Mercury-exploration mission. The BepiColombo spacecraft was successfully launched by an Ariane 5 rocket on October 20, 2018, and commissioning tests of the science payload were successfully completed in near-earth orbit before injection into a long journey to Mercury. MDM has a sensor consisting of four plates of piezoelectric lead zirconate titanate (PZT), which converts the mechanical stress (or strain) induced by dust-particle impacts into electrical signals. After the commencement of scientific operations, MDM will measure the impact momentum at which dust particles in orbit around the Sun collide with the sensor and record the arrival direction. This paper provides basic information concerning the MDM instrument and its predicted scientific operation as a future reference for scientific articles concerning the MDM’s observational data.
PubDate: 2020-12-08

• The Sun Through Time
• Abstract: Abstract Magnetic activity of stars like the Sun evolves in time because of spin-down owing to angular momentum removal by a magnetized stellar wind. These magnetic fields are generated by an internal dynamo driven by convection and differential rotation. Spin-down therefore converges at an age of about 700 Myr for solar-mass stars to values uniquely determined by the stellar mass and age. Before that time, however, rotation periods and their evolution depend on the initial rotation period of a star after it has lost its protostellar/protoplanetary disk. This non-unique rotational evolution implies similar non-unique evolutions for stellar winds and for the stellar high-energy output. I present a summary of evolutionary trends for stellar rotation, stellar wind mass loss and stellar high-energy output based on observations and models.
PubDate: 2020-12-08

• Mars 2020 Mission Overview
• Abstract: Abstract The Mars 2020 mission will seek the signs of ancient life on Mars and will identify, prepare, document, and cache a set of samples for possible return to Earth by a follow-on mission. Mars 2020 and its Perseverance rover thus link and further two long-held goals in planetary science: a deep search for evidence of life in a habitable extraterrestrial environment, and the return of martian samples to Earth for analysis in terrestrial laboratories. The Mars 2020 spacecraft is based on the design of the highly successful Mars Science Laboratory and its Curiosity rover, but outfitted with a sophisticated suite of new science instruments. Ground-penetrating radar will illuminate geologic structures in the shallow subsurface, while a multi-faceted weather station will document martian environmental conditions. Several instruments can be used individually or in tandem to map the color, texture, chemistry, and mineralogy of rocks and regolith at the meter scale and at the submillimeter scale. The science instruments will be used to interpret the geology of the landing site, to identify habitable paleoenvironments, to seek ancient textural, elemental, mineralogical and organic biosignatures, and to locate and characterize the most promising samples for Earth return. Once selected, ∼35 samples of rock and regolith weighing about 15 grams each will be drilled directly into ultraclean and sterile sample tubes. Perseverance will also collect blank sample tubes to monitor the evolving rover contamination environment. In addition to its scientific instruments, Perseverance hosts technology demonstrations designed to facilitate future Mars exploration. These include a device to generate oxygen gas by electrolytic decomposition of atmospheric carbon dioxide, and a small helicopter to assess performance of a rotorcraft in the thin martian atmosphere. Mars 2020 entry, descent, and landing (EDL) will use the same approach that successfully delivered Curiosity to the martian surface, but with several new features that enable the spacecraft to land at previously inaccessible landing sites. A suite of cameras and a microphone will for the first time capture the sights and sounds of EDL. Mars 2020’s landing site was chosen to maximize scientific return of the mission for astrobiology and sample return. Several billion years ago Jezero crater held a 40 km diameter, few hundred-meter-deep lake, with both an inflow and an outflow channel. A prominent delta, fine-grained lacustrine sediments, and carbonate-bearing rocks offer attractive targets for habitability and for biosignature preservation potential. In addition, a possible volcanic unit in the crater and impact megabreccia in the crater rim, along with fluvially-deposited clasts derived from the large and lithologically diverse headwaters terrain, contribute substantially to the science value of the sample cache for investigations of the history of Mars and the Solar System. Even greater diversity, including very ancient aqueously altered rocks, is accessible in a notional rover traverse that ascends out of Jezero crater and explores the surrounding Nili Planum. Mars 2020 is conceived as the first element of a multi-mission Mars Sample Return campaign. After Mars 2020 has cached the samples, a follow-on mission consisting of a fetch rover and a rocket could retrieve and package them, and then launch the package into orbit. A third mission could capture the orbiting package and return it to Earth. To facilitate the sample handoff, Perseverance could deposit its collection of filled sample tubes in one or more locations, called depots, on the planet’s surface. Alternatively, if Perseverance remains functional, it could carry some or all the samples directly to the retrieval spacecraft. The Mars 2020 mission and its Perseverance rover launched from the Eastern Range at Cape Canaveral Air Force Station, Florida, on July 30, 2020. Landing at Jezero Crater will occur on Feb 18, 2021 at about 12:30 PM Pacific Time.
PubDate: 2020-12-03

• Radiometric Calibration Targets for the Mastcam-Z Camera on the Mars 2020
Rover Mission
• Abstract: Abstract The Mastcam-Z Camera is a stereoscopic, multispectral camera with zoom capability on NASA’s Mars-2020 Perseverance rover. The Mastcam-Z relies on a set of two deck-mounted radiometric calibration targets to validate camera performance and to provide an instantaneous estimate of local irradiance and allow conversion of image data to units of reflectance (R∗ or I/F) on a tactical timescale. Here, we describe the heritage, design, and optical characterization of these targets and discuss their use during rover operations. The Mastcam-Z primary calibration target inherits features of camera calibration targets on the Mars Exploration Rovers, Phoenix and Mars Science Laboratory missions. This target will be regularly imaged during flight to accompany multispectral observations of the martian surface. The primary target consists of a gold-plated aluminum base, eight strong hollow-cylinder Sm2Co17 alloy permanent magnets mounted in the base, eight ceramic color and grayscale patches mounted over the magnets, four concentric, ceramic grayscale rings and a central aluminum shadow post (gnomon) painted with an IR-black paint. The magnets are expected to keep the central area of each patch relatively free of Martian aeolian dust. The Mastcam-Z secondary calibration target is a simple angled aluminum shelf carrying seven vertically mounted ceramic color and grayscale chips and seven identical, but horizontally mounted ceramic chips. The secondary target is intended to augment and validate the calibration-related information derived from the primary target. The Mastcam-Z radiometric calibration targets are critically important to achieving Mastcam-Z science objectives for spectroscopy and photometric properties.
PubDate: 2020-12-03

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