New-generation Satellite Research Articles

Modernization milestone: BeiDou M2-S initial signal analysis

The successful launch of two new-generation satellites of the BeiDou Navigation Satellite System (BDS), named BeiDou M1-S and BeiDou M2-S, marks another step in expanding BeiDou into a navigation system with global coverage. An initial characterization and analysis of the navigation signals transmitted by BeiDou M2-S is presented. For data collection, a 7.3-m high-gain antenna of the National University of Defense Technology (NUDT) ground station in Changsha (China) has been used to record the signal spectrum and the modulated chip sequences. Based on a prototype receiver, code and phase observations of BeiDou M2-S have also been collected for further analysis. The signal quality and performance of this new-generation BDS satellite are described and analyzed; a backward compatibility with older-generation satellite signals is shown.

Multivariate approach for chlorophyll-a and suspended matter retrievals in Case II type waters using hyperspectral data

Remote sensing has become promising in providing temporal and spatial information on biogeodynamics in large and open freshwater bodies. In optically complex environments, such as in the Western Basin of Lake Erie (WBLE), the water contains multiple biogeochemical constituents or colour producing agents (CPAs), such as phytoplankton, suspended matter and dissolved organic carbon; identifying and analysing such in-water constituents is crucial for understanding and assessing many biogeochemical processes. For example, concentrations of chlorophyll-a and total suspended matter can be used as proxies to assess phytoplankton dynamics and particulate loading. However, quantitative estimation of their concentrations from satellite observations is complicated when working with mixed spectral signatures. Hyperspectral remote sensing is fast emerging as a key technology for advanced and improved understanding of optically complex waters. This study estimates concentrations of chlorophyll-a and total suspended matter (TSM) in the WBLE by applying the partial least squares (PLS) method to a full range (400–900 nm) of continuous narrow spectral bands. The PLS method models the covariance between hyperspectral bands and CPAs, and identifies the optimal bands that characterize most of the variance in the CPAs. This method avoids the curse of dimensionality and the effects of multi-collinearity, a challenge that is associated with new-generation hyperspectral satellite sensors. Validation parameters for the PLS-based models produced R2 of 0.84 for chlorophyll-a (RMSE = 1.18 μg/L), and R2 of 0.90 for TSM (RMSE = 1.26 mg/L), illustrating the potential of the PLS method for isolating and extracting absorption features characterizing the various CPAs in optically complex Case II type waters.Editor Z.W. Kundzewicz Associate editor Not assigned

Complete composite binary offset carrier modulated signals and their correlation function

The formation and structure of complete composite binary offset carrier (CBOC) modulated signals are analyzed as applied to the new-generation satellite radio navigation systems (SRNSs) (in particular, the European Galileo and, presumably, Chinese BeiDou/Compass systems). The block diagram of the CBOC-signal satellite transmitter based on the coherent adaptive subcarrier modulation (CASM) algorithm is discussed. Analytical expressions for the correlation functions (CFs) characterizing the single elements of the modulating function (MF) of CBOC signals are derived at arbitrary fractional coefficients. The CFs of the single elements of the MFs of CBOC signals are represented graphically and their properties are discussed. The Fourier transforms of CFs are used to calculate the energy spectra (power spectral densities) of the single elements of the MFs of CBOC signals. CF features and the energy spectra of CBOC signals are analyzed using signals with CBOC(6, 1, a 2/11) modulation, which are typical of the European Galileo and Chinese BeiDou/Compass systems at the carrier frequency f car = 1575.42 MHz and the fractional coefficient a 2 = 1.

Use of the GOES-R Split-Window Difference to Diagnose Deepening Low-Level Water Vapor

AbstractThe depth of boundary layer water vapor plays a critical role in convective cloud formation in the warm season, but numerical models often struggle with accurate predictions of above-surface moisture. Satellite retrievals of water vapor have been developed, but they are limited by the use of a model’s first guess, instrument spectral resolution, horizontal footprint size, and vertical resolution. In 2016, Geostationary Operational Environmental Satellite-R (GOES-R), the first in a series of new-generation geostationary satellites, will be launched. Its Advanced Baseline Imager will provide unprecedented spectral, spatial, and temporal resolution. Among the bands are two centered at 10.35 and 12.3 μm. The brightness temperature difference between these bands is referred to as the split-window difference, and has been shown to provide information about atmospheric column water vapor. In this paper, the split-window difference is reexamined from the perspective of GOES-R and radiative transfer model simulations are used to better understand the factors controlling its value. It is shown that the simple split-window difference can provide useful information for forecasters about deepening low-level water vapor in a cloud-free environment.

The correlation functions of single elements of the modulating functions of double complex meander noise-like navigation signals (alternative binary offset carrier modulated signals)

The correlation characteristics of elements of complex meander pseudo-random sequences (PRSs) are analyzed. These sequences are the basis for forming double complex meander (DCM) noise-like signals (alternative binary offset carrier modulated signals—AltBOC signals) applied in new-generation satellite radio navigation systems (in particular, the European Galileo and Chinese Bei-Dou/Compass systems). Analytical expressions are obtained for the correlation functions (CFs) of single complex meander symbols (MSs) and for the cross CFs (CCFs) of the sine and cosine components of complex MSs. Formulas for the CFs of single elements of the modulating functions (MFs) of an elementary (two-component) AltBOC signal and a four-component AltBOC signal are derived for typical values of multiplicity coefficient Nm (Nm = 2 and 3). Plots of CFs and CCFs are depicted, and the properties of these functions are discussed. The Fourier transform is applied to obtain the energy spectra of single MSs of an elementary AltBOC signal and a complete four-component AltBOC signal. In the examples, the attention is focused on AltBOC signals with the AltBOC (15, 10) modulation and the repetition rate of PRS elements fs = 10 fref = 10.23 MHz, where the reference frequency is fref = 1.023 MHz.

The spectral characteristics of navigation alternative binary offset carrier modulated signals (AltBOC signals)

Analytical expressions are obtained for spectral densities and energy spectra of single elements and single periods of modulating functions of alternative binary offset carrier modulated signals (AltBOC signals) for new-generation satellite radio navigation systems (SRNSs) (in particular, the Galileo system). The spectral characteristics are presented and analyzed for an elementary (two-component) AltBOC signal, a complete AltBOC with a time-variable envelope (a four-component complete AltBOC signal), and a complete AltBOC with a constant envelope (an eight-component complete AltBOC signal) in the case when the multiplicity coefficient of meander pulses has an arbitrary value. Plots are depicted, and the properties of energy spectra of single elements of modulating functions of all groups of AltBOC signals are discussed in the cases of the following modulation types: AltBOC(10, 10), AltBOC(15, 10), AltBOC(20, 10), and AltBOC(25, 10).

Complete alternative binary offset carrier modulated signals (AltBOC signals) with variable and constant envelopes for new-generation satellite radio navigation systems

The formation and structure of four- and eight-component complete alternative binary offset carrier modulated signals (AltBOC signals) for new-generation satellite radio navigation systems (SRNSs) (in particular, the Galileo and BeiDou-2 SRNSs) are considered. A four-component complete AltBOC signal has a time-variable envelope, while the envelope of an eight-component complete AltBOC signal is constant. The envelopes and phases of such AltBOC signals are analyzed for various values of the multiplicity coefficients of meander pulses. The combination components of an eight-component complete AltBOC signal are plotted, and the features of these components that ensure the time constancy of the envelope are revealed. A classification of AltBOC signals is proposed. Practical characteristics are analyzed on the basis of the AltBOC (15, 10) modulation, which is typical of the Galileo and Compass SRNSs.

Remote sensing helps to assess natural hazards and environmental changes in Asia‐Pacific region

Conference on Remote Sensing, Natural Hazards, and Environmental Change; Singapore, 28–29 July 2011 Natural hazards and anthropogenic environmental changes, both significant in the Asia‐Pacific region, were the two themes of a conference organized by the National University of Singapore's Centre for Remote Imaging, Sensing and Processing (CRISP) and the Université Blaise Pascal's Laboratoire Magmas et Volcans. The application of satellite imagery at a wide range of resolutions, from 500 meters to 50 centimeters, was a unifying approach in many of the studies presented. The recent arrival of a new generation of satellites with extremely high resolution (50 centimeters) has improved scientists' ability to carry out detailed studies of natural hazards and environmental change.

Far-IR to Submm SEDs for local galaxies: Herschel, Planck and the HRS

AbstractThe Herschel Space Observatory and the Planck satellite are providing radical improvements to our knowledge of the spectral energy distributions of galaxies in the far-IR and submm. We here present the results of the first combination of Herschel and Planck fluxes of local galaxies from the Herschel Reference Sample (HRS) survey, covering galaxies at distances between 15 and 25 Mpc. This combination provides information on SEDs in eight bands from 60μm, using IRAS, to 1.4mm using Planck. We apply a similar fitting procedure to this data as applied to the Planck ERCSC-detected nearby galaxies and confirm the result that dust significantly colder than 20K is common in local galaxies. It is early days for this kind of study, but it is clear that the new generation of satellites are already adding considerably to our knowledge of the far-IR/submm properties of galaxies.

Complex meander pseudorandom code sequences and alternative binary offset carrier modulation (AltBOC modulation) in new-generation satellite navigation systems

Complex meander pseudorandom sequences (MPRSs) that are the basis for formation of alternative binary offset carrier modulated signals (AltBOC signals) for new-generation satellite radio navigation systems (in particular, the Galileo and Compass systems) are considered. The properties and characteristics of MPRSs are analyzed. Analytical expressions for the spectral densities and power spectrum densities of complex and complex conjugate meander symbols (MSs) of the MPRS of a ranging code are found for various values of the multiplicity coefficient of meander pulses. The modulating function of an elementary AltBOC signal is considered. The power spectrum densities of complex and complex conjugate MSs are plotted and analyzed for typical values of the multiplicity coefficient.

The statistical characteristics of navigation cosine binary offset carrier modulated signals (CosBOC signals)

The features and statistical characteristics of cosine binary offset carrier modulated signals (BOC signals) of new-generation satellite radio navigation systems, in particular the Galileo system, are considered. Analytical expressions for the correlation functions (CFs) of the cosine meander symbols (MSs) of the pseudorandom sequence of a ranging code are found for various values of the multiplicity coefficient of meander pulses. The energy spectra of cosine MSs are obtained with the help of the Fourier transform of the CFs. Plots are depicted, and the CFs and energy spectra of cosine MSs are analyzed for the following types of meander modulation: CosBOC (1,1), CosBOC (15,10), CosBOC (10,5), and CosBOC (5,2).

Space-borne SARs: impact of wavelengths and scan modes on ground motion studies

Space-borne synthetic aperture radar interferometry (INSAR) is a well-known widely used remote sensing technique to get precise (to the millimeter) surface deformation measurements on large areas (thousands of square kilometers) and high spatial density of measurement points (hundreds per square kilometer). A short review of the INSAR basics is dedicated to the readers who are not INSAR specialists. Then, an analysis of the improvement of ground motion measurement offered by multiple repeated space-borne SAR observations gathered by the new generation of satellites is given and compared with ground-based radar results. Examples from Cosmo-SkyMed and TERRASAR-X are shown and compared with C-band or L-band systems. Finally, the impact of the forthcoming C-band satellites like Sentinel 1 A, B is discussed.

Correlation functions of single symbols of meander signals in new-generation satellite radio navigation systems

Mathematical models of meander noise-like signals (binary offset carrier modulated signals (BOC signals)) of new-generation satellite radio navigation systems (SRNSs), in particular, the modernized GPS, the Galileo system, and the QZSS are presented. An analytic expression for the correlation function (CF) of single symbols of meander pulses is obtained for the arbitrary value of the multiplicity coefficient. The properties of CFs of various meander symbols are analyzed. The features of CFs are revealed for the even and odd values of the multiplicity coefficient. Examples of CFs are considered, and CFs of single symbols of BOC signals applied in new-generation SRNSs are plotted.

Mixing Diagnosis Techniques for Autonomous Satellite FDIR

Thales Alenia Space is developing a new generation of satellites dedicated to flexible and autonomous Space missions. It relies on a hierarchical component based architecture. Hierarchical layers are devoted to manage on one hand, different kind of knowledge from abstract (goal of the mission) to real (units, equipments), and on the other hand, different reaction times, from orbit's order of magnitude (planning activities) to real time (thrusting, sensing). Components are most of the time related to functional chains covering pure discrete behavior (battery management) to pure continuous one (Guidance, Navigation and Control), or mix of both leading to hybrid modeling. Due to the vast range of models (discrete, continuous, hybrid – real time, no time constraint – teleological, functional, structural, behavioral), defining a FDIR (Fault Detection, Isolation and Recovery) strategy is a challenge. Solutions have been defined by making collaborate different diagnosis techniques (analytical redundancy, consistency based approach, model checking and Hinf estimator) from several origins, locally in each component. Abstraction of the local diagnosis results is translated at satellite level under the form of events and managed by a discrete automaton based formalism. Focus of the paper is put on the knowledge's modeling from the different layers of the architecture, the diagnosis technique in relation with the different kinds of components and the description of the hierarchical diagnosis solution.

Surface Emissivity of Arctic Sea Ice at AMSU Window Frequencies

A method to retrieve the surface emissivity of sea ice at the window channels of the Advanced Microwave Sounding Unit (AMSU) radiometers in the polar region is presented. The instruments are on the new-generation satellites of the U.S. National Oceanic and Atmospheric Administration (NOAA-15, NOAA-16, and NOAA-17). The method assumes hypothetical surfaces with emissivities zero and one and simulates brightness temperatures at the top of the atmosphere using profiles of atmospheric parameters, e.g., from the European Centre for Medium-Range Weather Forecasts (ECMWF) model runs, as input for a radiative transfer model. The retrieval of surface emissivity is done by combining simulated brightness temperatures with the satellite-measured brightness temperature. The AMSU window channels differ in surface penetration depths and, thus, in the surface microphysical parameters that they depend on. Lowest layer air temperatures from ECMWF are used to infer temperatures of emitting layers at different frequencies of sea ice. A complete yearly cycle of monthly average emissivities in two selected regions (first- and multiyear ice) is giving insight into the variation of emissivities in various development stages of sea ice.

Using texture analysis to improve per-pixel classification of very high resolution images for mapping plastic greenhouses

The area occupied by plastic-covered greenhouses has undergone rapid growth in recent years, currently exceeding 500,000 ha worldwide. Due to the vast amount of input (water, fertilisers, fuel, etc.) required, and output of different agricultural wastes (vegetable, plastic, chemical, etc.), the environmental impact of this type of production system can be serious if not accompanied by sound and sustainable territorial planning. For this, the new generation of satellites which provide very high resolution imagery, such as QuickBird and IKONOS can be useful. In this study, one QuickBird and one IKONOS satellite image have been used to cover the same area under similar circumstances. The aim of this work was an exhaustive comparison of QuickBird vs. IKONOS images in land-cover detection. In terms of plastic greenhouse mapping, comparative tests were designed and implemented, each with separate objectives. Firstly, the Maximum Likelihood Classification (MLC) was applied using five different approaches combining R, G, B, NIR, and panchromatic bands. The combinations of the bands used, significantly influenced some of the indexes used to classify quality in this work. Furthermore, the quality classification of the QuickBird image was higher in all cases than that of the IKONOS image. Secondly, texture features derived from the panchromatic images at different window sizes and with different grey levels were added as a fifth band to the R, G, B, NIR images to carry out the MLC. The inclusion of texture information in the classification did not improve the classification quality. For classifications with texture information, the best accuracies were found in both images for mean and angular second moment texture parameters. The optimum window size in these texture parameters was 3×3 for IK images, while for QB images it depended on the quality index studied, but the optimum window size was around 15×15. With regard to the grey level, the optimum was 128. Thus, the optimum texture parameter depended on the main objective of the image classification. If the main classification goal is to minimize the number of pixels wrongly classified, the mean texture parameter should be used, whereas if the main classification goal is to minimize the unclassified pixels the angular second moment texture parameter should be used. On the whole, both QuickBird and IKONOS images offered promising results in classifying plastic greenhouses.

Parameter identification using optimization techniques in open-channel inverse problems

Adverse socio-economic impacts of recent floods both in Europe and other continents emphasize the need for accurate flood forecasting capabilities towards improved flood risk management services. Flood forecasting models are often data-intensive. These models are inherited with (i) conceptual parameters that often cannot be assessed by field measurements, as in conceptual models; and/or (ii) empirical parameters that their direct measurements are either difficult, for example, roughness coefficient or costly, for example, survey data. There is also a category of practical problems, where modelling is required but gauged data are not available. Models, other than purely theoretical ones, for example, Large Eddy Simulation models, need calibration and the problem is even more pronounced in the case of ungauged rivers. Optimal values of these parameters in a mathematical sense can be identified by a number of techniques as discussed and applied in this paper. New generations of satellites are now able to provide observation data that can be useful to implement these techniques. This paper presents the results of synthesized flood data emulating data obtained from remote sensing. A one-dimensional, steady-state flow in a channel of simple geometry is studied. The paper uses optimization methods and the Extended Kalman Filter to ascertain/improve the values of the parameters.

Dimensioning and Effective Handling of Signalling Channels in a Multimedia GEO Satellite Platform

The deployment of highly powerful and sophisticated new-generation satellite broadband systems implies that a large portion of their bandwidth on the radio interface has to be devoted to conveying signalling information. Adequately dimensioning such a signalling bandwidth is an important design objective allowing the effective exploitation of the overall system resources and the cost-effective provision of a target quality of service to multimedia traffic. The performance of two basic techniques for accessing the signalling channels in a reference multimedia geostationary platform is investigated in this paper: random (slotted Aloha) and dedicated access. It is demonstrated here that dedicated access, despite rational appearances, allows 50% saving of signalling bandwidth while satisfying both the system and user constraints in terms of grade and quality of service respectively. This is accomplished by providing a statistical centralized connection admission control on Earth and an intelligent scheduling of the resource requests on board the satellite.

Information Content of Infrared Satellite Sounding Measurements with Respect to CO2

Information theory is used to study the capabilities of the new-generation satellite infrared sounders [Atmospheric Infrared Sounder (AIRS) and Infrared Atmospheric Sounding Interferometer (IASI)] for retrieving atmospheric carbon dioxide (CO2) and for contrasting these new instruments with the current system of infrared sounders [Television and Infrared Observation Satellite (TIROS) Operational Vertical Sounder/High-Resolution Infrared Radiation Sounder (TOVS/HIRS)]. It is shown that instruments like AIRS and IASI will be able to retrieve column-averaged CO2 mixing ratios with high enough accuracy (order of 1–2 ppmv) to be useful for atmospheric CO2 inversion studies that try to estimate sources and sinks of CO2. On the other hand, the TOVS/HIRS system is only able to retrieve column-averaged CO2 mixing ratios with an accuracy of the same order as the seasonal amplitude of atmospheric CO2 variations (order of 10 ppmv). It is also shown that the constraining a priori covariance matrix has an important effect on what information can be extracted from the observations.

Crustal thickness in Antarctica from CHAMP gravimetry

CHAMP, flying at an altitude of about 400 km, is the first of a new generation of satellites dedicated to Earth gravity field observation. The high-quality data have generated new gravity field models: EIGEN-1S in 2001, and EIGEN-2S more recently. The gravitational potential is decomposed into spherical harmonic coefficients and in this study we use the free air gravity anomalies reconstituted up to degree 60, at zero altitude. The anomalies for the Antarctic continent range from −57 to 65 mGal. We have modeled the gravity effect from the ice, the ocean and the bedrock, using a 666 km cut-off filter to simulate the resolution obtained by CHAMP. Computing the differences between this terrain effect and the CHAMP map provides a map of the Bouguer anomalies. Because of the dominant influence of the crust, we first used a crustal thickness model from seismology. This gives a map of the mantle Bouguer anomalies, the range of which is still large (between −255 and 216 mGal) indicating imperfections in the crust model. By appealing to isostasy we then imposed the condition that this mantle Bouguer anomaly should vanish and therefore solve for a new resulting crustal thickness. This gravity-based crust model gives thicknesses from 8.5 to 42.6 km in the zone of interest. There is a good general agreement with seismological models, but our models shows more detail, particularly in the western part of the continent. These details are in agreement with geological studies.