BDS GNSS for Earth Observation

For millennia, human communities have wondered about the possibility of observing phenomena in their surroundings, and in particular those affecting the Earth on which they live. More generally, it can be conceptually defined as Earth observation (EO) and is the collection of information about the biological, chemical and physical systems of planet Earth. It can be undertaken through sensors in direct contact with the ground or airborne platforms (such as weather balloons and stations) or remote-sensing technologies. However, the definition of EO has only become significant in the last 50 years, since it has been possible to send artificial satellites out of Earth’s orbit. Referring strictly to civil applications, satellites of this type were initially designed to provide satellite images; later, their purpose expanded to include the study of information on land characteristics, growing vegetation, crops, and environmental pollution. The data collected are used for several purposes, including the identification of natural resources and the production of accurate cartography. Satellite observations can cover the land, the atmosphere, and the oceans. Remote-sensing satellites may be equipped with passive instrumentation such as infrared or cameras for imaging the visible or active instrumentation such as radar. Generally, such satellites are non-geostationary satellites, i.e., they move at a certain speed along orbits inclined with respect to the Earth’s equatorial plane, often in polar orbit, at low or medium altitude, Low Earth Orbit (LEO) and Medium Earth Orbit (MEO), thus covering the entire Earth’s surface in a certain scan time (properly called ’temporal resolution’), i.e., in a certain number of orbits around the Earth. The first remote-sensing satellites were the American NASA/USGS Landsat Program; subsequently, the European: ENVISAT (ENVironmental SATellite), ERS (European Remote-Sensing satellite), RapidEye, the French SPOT (Satellite Pour l’Observation de laTerre), and the Canadian RADARSAT satellites were launched. The IKONOS, QuickBird, and GeoEye-1 satellites were dedicated to cartography. The WorldView-1 and WorldView-2 satellites and the COSMO-SkyMed system are more recent. The latest generation are the low payloads called Small Satellites, e.g., the Chinese BuFeng-1 and Fengyun-3 series. Also, Global Navigation Satellite Systems (GNSSs) have captured the attention of researchers worldwide for a multitude of Earth monitoring and exploration applications. On the other hand, over the past 40 years, GNSSs have become an essential part of many human activities. As is widely noted, there are currently four fully operational GNSSs; two of these were developed for military purposes (American NAVstar GPS and Russian GLONASS), whilst two others were developed for civil purposes such as the Chinese BeiDou satellite navigation system (BDS) and the European Galileo. In addition, many other regional GNSSs, such as the South Korean Regional Positioning System (KPS), the Japanese quasi-zenital satellite system (QZSS), and the Indian Regional Navigation Satellite System (IRNSS/NavIC), will become available in the next few years, which will have enormous potential for scientific applications and geomatics professionals. In addition to their traditional role of providing global positioning, navigation, and timing (PNT) information, GNSS navigation signals are now being used in new and innovative ways. Across the globe, new fields of scientific study are opening up to examine how signals can provide information about the characteristics of the atmosphere and even the surfaces from which they are reflected before being collected by a receiver. EO researchers monitor global environmental systems using in situ and remote monitoring tools. Their findings provide tools to support decision makers in various areas of interest, from security to the natural environment. GNSS signals are considered an important new source of information because they are a free, real-time, and globally available resource for the EO community

Beacon Satellite Symposium: Session 5B - June 30th 2016: Radio Occultation Techniques and Measurements

During the Beacon Satellite Symposium, held in Trieste, Italy, between June 26 and July 1 2016, the JRC chaired the session 5B: Radio Occultation Techniques and Measurements. The corresponding abstract of the session is provided as follows: Since the mid-1960s, the GNSS based radio occultation technique has been used to study the structure and properties of the atmospheres of not only Earth but also other planets, such as Venus, Mars, some other outer planets, and many of their moons. By measuring the phase delay of radio waves from GNSS satellites as they are occulted by the Earth’s atmosphere, the vertical density profiles of the bending angles of radio wave trajectories can be estimated using measurements onboard LEO satellites. The success of the GPS/MET mission in 1995 inspired a number of follow‐on missions that include radio occultation experiment, including the CHAMP, GRACE, SAC-C, COSMIC, Metop-A/B, C/NOFS, and upcoming COSMIC-2 satellites. The combined profiles from these different LEO satellites provide excellent opportunities to explore the dynamics and structure of the ionosphere, especially in the regions that have been devoid of ground-based instruments, allowing for investigation of the longitudinal variability of the ionospheric density structure. This session seeks contributions that advance the application of RO technique for space weather studies. In addition, we welcome presentations exploring innovative methodologies that address the current problem on RO inversion technique at the equatorial region where ionospheric irregularity, such as sporadic E and spread F, present and degrade the linear combination technique that affect the quality of density profile extracted in the region. The session was organized among Endawoke Yizengaw (Institute for Scientific Research, Boston College), Jann-Yenq Liu (National Space Organization –NSPO- Chief Scientist), and Angela Aragon-Angel (Joint Research Centre). The session consisted of both oral and poster presentation parts. This document presents the process of the session preparation within the Beacon Satellite Symposium organization. Moreover, the abstracts of the different contributions accepted to the session are also included for completeness.JRC.E.2-Technology Innovation in Securit

gLAB upgrade with BeiDou navigation system signals

The gLAB tool suit is an educational and professional multipurpose GNSS data processing software. It has been developed by gAGE/UPC under a contract of the European Space Agency (ESA). The current version of gLAB allows full GPS data processing with High Accuracy Positioning capability (at the centimetre level), but only a very limited data handling of Galileo and GLONASS. The Chinese Global Satellite Navigation System Beidou was not included in the initial requirements of ESA. The target of this project is to upgrade gLAB with the necessary functions to allow this software to compute user solutions with the Beidou signals

Pilot Evaluation of Integrating GLONASS, Galileo and BeiDou with GPS in Araim

© 2016 Artificial Satellites. In this pilot study, availability of the Advanced Receiver Autonomous Integrity Monitoring (ARAIM) when integrating various combinations of satellite constellations including; Galileo, GLONASS and BeiDou with GPS is investigated. The Multiple Hypothesis Solution Separation method was applied using one month of real data. The data was collected at stations of known positions, located in regions that have different coverage levels by the tested constellations. While most previous studies used simulated data, the importance of using real data is twofold. It allows for the use of actual User Range Accuracy (URA) received within the satellite navigation message, which is a fundamental component for computation of the integrity protection level; and the computation of vertical position errors to validate the integrity approach. Results show that the vertical position error was always bounded by the protection level during the test period and the ARAIM availability can reach 100% of the time when using all constellations even though some constellations are yet incomplete

Analysis and Characterization of an Unclassified RFI Affecting Ionospheric Amplitude Scintillation Index over the Mediterranean Area

Radio Frequency (RF) signals transmitted by Global Navigation Satellite Systems (GNSS) are exploited as signals of opportunity in many scientific activities, ranging from sensing waterways and humidity of the terrain to the monitoring of the ionosphere. The latter can be pursued by processing the GNSS signals through dedicated ground-based monitoring equipment, such as the GNSS Ionospheric Scintillation and Total Electron Content Monitoring (GISTM) receivers. Nonetheless, GNSS signals are susceptible to intentional or unintentional RF interferences (RFIs), which may alter the calculation of the scintillation indices, thus compromising the quality of the scientific data and the reliability of the derived space weather monitoring products. Upon the observation of anomalous scintillation indices computed by a GISTM receiver in the Mediterranean area, the study presents the results of the analysis and characterization of a deliberate, unclassified interferer acting on the L1/E1 GNSS signal bands, observed and captured through an experimental, software defined radio setup. The paper also highlights the adverse impacts of the interferer on the amplitude scintillation indices employed in scientific investigations, and presents a methodology to discriminate among regular and corrupted scintillation data. To support further investigations, a dataset of baseband signals samples affected by the RFI is available at IEEE DataPort

Global monitoring of ionospheric weather by GIRO and GNSS data fusion

Prompt and accurate imaging of the ionosphere is essential to space weather services, given a broad spectrum of applications that rely on ionospherically propagating radio signals. As the 3D spatial extent of the ionosphere is vast and covered only fragmentarily, data fusion is a strong candidate for solving imaging tasks. Data fusion has been used to blend models and observations for the integrated and consistent views of geosystems. In space weather scenarios, low latency of the sensor data availability is one of the strongest requirements that limits the selection of potential datasets for fusion. Since remote plasma sensing instrumentation for ionospheric weather is complex, scarce, and prone to unavoidable data noise, conventional 3D-var assimilative schemas are not optimal. We describe a novel substantially 4D data fusion service based on near-real-time data feeds from Global Ionosphere Radio Observatory (GIRO) and Global Navigation Satellite System (GNSS) called GAMBIT (Global Assimilative Model of the Bottomside Ionosphere with Topside estimate). GAMBIT operates with a few-minute latency, and it releases, among other data products, the anomaly maps of the effective slab thickness (EST) obtained by fusing GIRO and GNSS data. The anomaly EST mapping aids understanding of the vertical plasma restructuring during disturbed conditionsPeer ReviewedPostprint (published version

gLAB upgrade with BeiDou navigation system signals

The gLAB tool suit is an educational and professional multipurpose GNSS data processing software. It has been developed by gAGE/UPC under a contract of the European Space Agency (ESA). The current version of gLAB allows full GPS data processing with High Accuracy Positioning capability (at the centimetre level), but only a very limited data handling of Galileo and GLONASS. The Chinese Global Satellite Navigation System Beidou was not included in the initial requirements of ESA. The target of this project is to upgrade gLAB with the necessary functions to allow this software to compute user solutions with the Beidou signals

First simultaneous microlensing observations by two space telescopes: Spitzer & Swift reveal a brown dwarf in event OGLE-2015-BLG-1319

Simultaneous observations of microlensing events from multiple locations allow for the breaking of degeneracies between the physical properties of the lensing system, specifically by exploring different regions of the lens plane and by directly measuring the "microlens parallax". We report the discovery of a 30-55M_J brown dwarf orbiting a K dwarf in microlensing event OGLE-2015-BLG-1319. The system is located at a distance of ∼5 kpc toward the Galactic bulge. The event was observed by several ground-based groups as well as by Spitzer and Swift, allowing the measurement of the physical properties. However, the event is still subject to an 8-fold degeneracy, in particular the well-known close-wide degeneracy, and thus the projected separation between the two lens components is either ∼0.25 AU or ∼45 AU. This is the first microlensing event observed by Swift, with the UVOT camera. We study the region of microlensing parameter space to which Swift is sensitive, finding that while for this event Swift could not measure the microlens parallax with respect to ground-based observations, it can be important for other events. Specifically, for detecting nearby brown dwarfs and free-floating planets in high magnification events