Electron density retrieval from occulting GNSS signals using a gradient-aided inversion technique

In the coming years, opportunities for remote sensing of electron density in the Earth’s ionosphere will expand with the advent of Galileo, which will become part of the global navigation satellite system (GNSS). Methods for accurate electron density retrieval from radio occultation data continue to improve. We describe a new method of electron density retrieval using total electron content measurements obtained in low Earth orbit. This method can be applied to data from dual-frequency receivers tracking the GPS or Galileo transmitters. This simulation study demonstrates that the method significantly improves retrieval accuracy compared to the standard Abel inversion approach that assumes a spherically symmetric ionosphere. Our method incorporates horizontal gradient information available from global maps of Total Electron Content (TEC), which are available from the International GNSS Service (IGS) on a routine basis. The combination of ground and space measurements allows us to improve the accuracy of electron density profiles near the occultation tangent point in the E and F regions of the ionosphere.     

Comparison of the magnetic field before the subsolar magnetopause with the magnetic field in the solar wind before the bow shock

Crossings of the magnetopause near the subsolar point are analyzed using data of THEMIS mission. Variations of the magnetic field near magnetopause measured by one of THEMIS satellites are studied and compared with simultaneous measurements in the solar wind by another THEMIS satellite. The time delay of the solar wind arrival at the subsolar point of the magnetopause is taken into account. 30 and 90 s averaging of the magnetic field in the magnetosheath is produced. The results of averaging are compared with the results of measurements in the solar wind before the bow shock and foreshock. It is shown, that _Bx$B_x$ component of the magnetic field near magnetopause is near to zero, which supports the possibility to consider the magnetopause as the tangential discontinuity. Comparatively good correlation of _By$B_y$ component in the solar wind and near the magnetopause is observed. The correlation of _Bz$B_z$ component near the magnetopause and IMF is practically absent, the sign of the _Bz$B_z$ near the subsolar point does not coincide with the sign of IMF _Bz$B_z$ in ∼$\sim$30% cases.     

Lunar Reconnaissance Orbiter Overview: The Instrument Suite and Mission

NASA’s Lunar Precursor Robotic Program (LPRP), formulated in response to the President’s Vision for Space Exploration, will execute a series of robotic missions that will pave the way for eventual permanent human presence on the Moon. The Lunar Reconnaissance Orbiter (LRO) is first in this series of LPRP missions, and plans to launch in October of 2008 for at least one year of operation. LRO will employ six individual instruments to produce accurate maps and high-resolution images of future landing sites, to assess potential lunar resources, and to characterize the radiation environment. LRO will also test the feasibility of one advanced technology demonstration package. The LRO payload includes: Lunar Orbiter Laser Altimeter (LOLA) which will determine the global topography of the lunar surface at high resolution, measure landing site slopes, surface roughness, and search for possible polar surface ice in shadowed regions, Lunar Reconnaissance Orbiter Camera (LROC) which will acquire targeted narrow angle images of the lunar surface capable of resolving meter-scale features to support landing site selection, as well as wide-angle images to characterize polar illumination conditions and to identify potential resources, Lunar Exploration Neutron Detector (LEND) which will map the flux of neutrons from the lunar surface to search for evidence of water ice, and will provide space radiation environment measurements that may be useful for future human exploration, Diviner Lunar Radiometer Experiment (DLRE) which will chart the temperature of the entire lunar surface at approximately 300 meter horizontal resolution to identify cold-traps and potential ice deposits, Lyman-Alpha Mapping Project (LAMP) which will map the entire lunar surface in the far ultraviolet. LAMP will search for surface ice and frost in the polar regions and provide images of permanently shadowed regions illuminated only by starlight. Cosmic Ray Telescope for the Effects of Radiation (CRaTER), which will investigate the effect of galactic cosmic rays on tissue-equivalent plastics as a constraint on models of biological response to background space radiation. The technology demonstration is an advanced radar (mini-RF) that will demonstrate X- and S-band radar imaging and interferometry using light weight synthetic aperture radar. This paper will give an introduction to each of these instruments and an overview of their objectives.     

Earth-Based Visible and Near-IR Imaging of Mercury

New planned orbiter missions to Mercury have prompted renewed efforts to investigate the surface of Mercury via ground-based remote sensing. While the highest resolution instrumentation optical telescopes (e.g., HST) cannot be used at angular distances close to the Sun, advanced ground-based astronomical techniques and modern analytical and software can be used to obtain the resolved images of the poorly known or unknown part of Mercury. Our observations of the planet presented here were carried out in many observatories at morning and evening elongation of the planet. Stacking the acquired images of the hemisphere of Mercury, which was not observed by the Mariner 10 mission (1974–1975), is presented. Huge features found there change radically the existing hypothesis that the “continental” character of a surface may be attributed to the whole planet. We present the observational method, the data analysis approach, the resulting images and obtained properties of the Mercury’s surface.     

Partially Ionized Plasmas in Astrophysics

Partially ionized plasmas are found across the Universe in many different astrophysical environments. They constitute an essential ingredient of the solar atmosphere, molecular clouds, planetary ionospheres and protoplanetary disks, among other environments, and display a richness of physical effects which are not present in fully ionized plasmas. This review provides an overview of the physics of partially ionized plasmas, including recent advances in different astrophysical areas in which partial ionization plays a fundamental role. We outline outstanding observational and theoretical questions and discuss possible directions for future progress.     

The navigational experiments on microgravitational space platform “FOTON-M2”

This paper presents the review of results of the navigating experiments which have been carried out during flight of microgravitational space platform (MSP) Foton-M2 in May–June 2005. The brief characteristic of the created MIRAGE–M equipment consisting from magnitometric system and satellite radionavigation receiver is given. The measurements have allowed to restore unguided MSP movement and to estimate a level of microaccelerations (microgravitations) onboard during flight, and have provided precision time-position binding of the research experiments. The data from the equipments transmitted on the telemetering channel have allowed testing the information technologies of virtual support of experiments in space. Flight testing of the equipment has allowed make a conclusion on usefulness of accommodation onboard the small-sized auxiliary navigating system focused for work with users of research experiments. The experiments on MSP Foton-M2 are the development of experiments with MIRAGE equipment carried out in 1999 during flight time of MSP Foton-12 [N.D. Semkin, V.V. Ivanov, V.I. Abrushkin, V.L. Balakin, I.V. Belokonov, K.E. Voronov, The experiments with magnetic fields formed by technical equipment inside Foton-12 spacecraft: the results of the MIRAGE experiments, in: Proceedings of International Conference “Scientific and Technological Experiments on Russian Foton/Bion Recoverable Satellites: Results, Problems and Outlooks”, 25–30 June 2000, pp. 116–122; V.L. Balakin, I.V. Belokonov, V.V. Ivanov, “Determination of motion of spacecraft Foton-12 as a result of magnetic fields measurement in MIRAGE experiment”, pp. 231–238 (published in the same place)].Paper is executed within the framework of the grant of the Russian Fund of Fundamental Researches 06-08-00244.     

Correction to: Backscattered Solar Lyman- $\alpha$ Emission as a Tool for the Heliospheric Boundary Exploration

Space Science Reviews - The Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) is a robotic arm-mounted instrument onboard NASA’s Perseverance...     

Mars Science Laboratory Mission and Science Investigation

Scheduled to land in August of 2012, the Mars Science Laboratory (MSL) Mission was initiated to explore the habitability of Mars. This includes both modern environments as well as ancient environments recorded by the stratigraphic rock record preserved at the Gale crater landing site. The Curiosity rover has a designed lifetime of at least one Mars year (～23?months), and drive capability of at least 20?km. Curiosity’s science payload was specifically assembled to assess habitability and includes a gas chromatograph-mass spectrometer and gas analyzer that will search for organic carbon in rocks, regolith fines, and the atmosphere (SAM instrument); an x-ray diffractometer that will determine mineralogical diversity (CheMin instrument); focusable cameras that can image landscapes and rock/regolith textures in natural color (MAHLI, MARDI, and Mastcam instruments); an alpha-particle x-ray spectrometer for in situ determination of rock and soil chemistry (APXS instrument); a?laser-induced breakdown spectrometer to remotely sense the chemical composition of rocks and minerals (ChemCam instrument); an active neutron spectrometer designed to search for water in rocks/regolith (DAN instrument); a weather station to measure modern-day environmental variables (REMS instrument); and a sensor designed for continuous monitoring of background solar and cosmic radiation (RAD instrument). The various payload elements will work together to detect and study potential sampling targets with remote and in situ measurements; to acquire samples of rock, soil, and atmosphere and analyze them in onboard analytical instruments; and to observe the environment around the rover. The 155-km diameter Gale crater was chosen as Curiosity’s field site based on several attributes: an interior mountain of ancient flat-lying strata extending almost 5?km above the elevation of the landing site; the lower few hundred meters of the mountain show a progression with relative age from clay-bearing to sulfate-bearing strata, separated by an unconformity from overlying likely anhydrous strata; the landing ellipse is characterized by a mixture of alluvial fan and high thermal inertia/high albedo stratified deposits; and a number of stratigraphically/geomorphically distinct fluvial features. Samples of the crater wall and rim rock, and more recent to currently active surface materials also may be studied. Gale has a well-defined regional context and strong evidence for a progression through multiple potentially habitable environments. These environments are represented by a stratigraphic record of extraordinary extent, and insure preservation of a rich record of the environmental history of early Mars. The interior mountain of Gale Crater has been informally designated at Mount Sharp, in honor of the pioneering planetary scientist Robert Sharp. The major subsystems of the MSL Project consist of a single rover (with science payload), a Multi-Mission Radioisotope Thermoelectric Generator, an Earth-Mars cruise stage, an entry, descent, and landing system, a launch vehicle, and the mission operations and ground data systems. The primary communication path for downlink is relay through the Mars Reconnaissance Orbiter. The primary path for uplink to the rover is Direct-from-Earth. The secondary paths for downlink are Direct-to-Earth and relay through the Mars Odyssey orbiter. Curiosity is a scaled version of the 6-wheel drive, 4-wheel steering, rocker bogie system from the Mars Exploration Rovers (MER) Spirit and Opportunity and the Mars Pathfinder Sojourner. Like Spirit and Opportunity, Curiosity offers three primary modes of navigation: blind-drive, visual odometry, and visual odometry with hazard avoidance. Creation of terrain maps based on HiRISE (High Resolution Imaging Science Experiment) and other remote sensing data were used to conduct simulated driving with Curiosity in these various modes, and allowed selection of the Gale crater landing site which requires climbing the base of a mountain to achieve its primary science goals. The Sample Acquisition, Processing, and Handling (SA/SPaH) subsystem is responsible for the acquisition of rock and soil samples from the Martian surface and the processing of these samples into fine particles that are then distributed to the analytical science instruments. The SA/SPaH subsystem is also responsible for the placement of the two contact instruments (APXS, MAHLI) on rock and soil targets. SA/SPaH consists of a robotic arm and turret-mounted devices on the end of the arm, which include a drill, brush, soil scoop, sample processing device, and the mechanical and electrical interfaces to the two contact science instruments. SA/SPaH also includes drill bit boxes, the organic check material, and an observation tray, which are all mounted on the front of the rover, and inlet cover mechanisms that are placed over the SAM and CheMin solid sample inlet tubes on the rover top deck.     

Problems of providing completeness of the methane-containing block-jet combustion in a rocket-ramjet engine's combustion chamber

Some problems of methane-containing hydrocarbon fuel combustion are discussed. It seems that reduction of methane burnout zone length is one from main problems of designing new type engine. It is very important at the creation of combustion chambers of a rocket-ramjet engine for prospective space shuttle launch vehicles.     

Large-scale solar wind stream structure at high heliolatitudes

The tilted rotator model is considered using the collisionless supersonic and superalfvenic approximation. The results show that the maximal and minimal solar wind corotating stream velocities appear at the intermediate heliospheric latitudes depending on the tilt angle. The high-speed streams with the strongest velocity difference between maximal and minimal values are expected to be observed at the middle heliolatitudes near 45 degrees. Other consequences of the model are indicated and may be checked during the rapid pole-to-pole Ulysses passage in 1994–1995.