International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, Nevada / The United States Government, through the Integrated Program Office (IPO), currently operates a converged polar orbiting constellation of POES and DMSP satellites to acquire, process and disseminate meteorological and environmental data on a global scale. Because of the increasing need for more precise and timely meteorological data, the IPO is developing the follow on system known as the National Polar-orbiting Operational Environmental Satellite System (NPOESS). The NPOESS system is expected to use a modernized, CCSDS compatible data acquisition and distribution network, and will provide more timely data than for the current POES/DMSP satellites. The NPOESS satellite system will also continue the collection of long-term environmental data as a follow on to NASA’s Earth Observation System (EOS). The continuation of NASA’s EOS system will begin with a risk reduction effort in support of NPOESS, known as the NPOESS Preparatory Project (NPP). This paper will describe the CCSDS implementation that both the NPP and NPOESS satellites are expected to use beginning with the launch of the NPP spacecraft in 2006. The launch of the first NPOESS satellite is anticipated in 2009.

No description available.

International Telemetering Conference Proceedings / October 22-25, 2001 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Telemetry for Earth-Observation missions is characterized by very high data rates and stringent requirements. Channel codes both power and bandwidth efficient must be used to improve downlink performance and to achieve the very low values of error rates needed at the received side. In this paper, we review and analyzed three codes of possible interest for these applications: turbo codes, serial turbo codes and product codes. These schemes are evaluated and compared both by simulation and analytical techniques. A particular attention is devoted to complexity, a key issue for practical implementation at high data rates.

The overarching theme of my thesis is understanding observed variations of northern hemisphere atmospheric carbon dioxide (CO2) and methane (CH4) concentrations. I focus my analysis on high-latitude observations of these gases, as there are large stores of carbon in boreal vegetation and tundra which are vulnerable to rapid warming in the Arctic. My thesis is split into two parts. First, I use the wavelet transform to spectrally decompose observed multi-decadal timeseries for CO2 and CH4. I perform a series of numerical experiments based on synthetic data in order to characterise the errors associated with the analysis. For CO2, I analyse the phase and amplitude of the detrended seasonal cycle of CO2 to infer changes about carbon uptake by northern vegetation. I do not find a long-term change in the length of the carbon uptake period despite significant changes in the spring and autumn phase. I do find an increase in the rate of peak uptake which coincides with the observed increase in seasonal amplitude. These results suggest that the carbon uptake period of boreal vegetation has become more intense but has not changed in length, which provides evidence for an increase in net uptake of CO2 in the high latitudes. For CH4, I test the hypothesis that an increase in Arctic wetland emissions could result in a decrease in the seasonal amplitude of CH4 in the high latitudes. This hypothesis is based on the fact that the seasonal minima of CH4 roughly coincides with the peak of high latitude wetland CH4 emissions. I find that the CH4 seasonal amplitude has significantly decreased at a number of high-latitude sites. However I also find that atmospheric transport appears to drive much of the variability in high-latitude CH4 and that transport could also be responsible for the observed changes in amplitude. I show that an increase in wetland emissions is likely to have a more pronounced effect on the high-latitude CH4 seasonal cycle in the future. In the second section of my thesis, I describe a series of experiments in collaboration with the UK Astronomy Technology Centre, in which I characterise a new instrument technology for satellite applications to observe changes in CO2 from low-Earth orbit. The proof of concepts experiments were performed with a bench top hyperspectral imager. I show that the instrument is able to capture clean spectra at the wavelengths required for CO2 with low levels of scattered light between spectra.

In this thesis, we introduce a new class of problems, which we call Optimal Areal Positioning (OAP), and study a special form of these problems. OAPs have important applications in earth observation satellite management, tele-robotics, multi-camera control, and surveillance. In OAP, we would like to find the optimal position of a set of floating geometric objects (targets) on a two-dimensional plane to (partially) cover another set of fixed geometric objects (requests) in order to maximize the total reward obtained from covered parts of requests. In this thesis, we consider the special form of OAP in which targets and requests are parallel axes rectangles and targets are of equal size. A predetermined reward is associated with covering an area unit of each request. Based on the number of target rectangles, we classify rectangular OAP into two categories: Single Target Problem (STP) and Multi-Target Problem (MTP). The structure of MTP can be compared to the planar p-center which is NP-complete, if p is part of the input. In fact, we conjecture that MTP is NP-complete. The existing literature does not contain any work on MTP. The research contributions of this thesis are as follows: We develop new theoretical properties for the solution of STP and devised a new solution approach for it. This approach is based on a novel branch-and-bound (BB) algorithm devised over a reduced solution space. Branching is done using a clustering scheme. Our computational results show that in many cases our approach significantly outperforms the existing Plateau Vertex Traversal and brute force algorithms, especially for problems with many requests appearing in clusters over a large region. We perform a theoretical study of MTP for the first time and prove several theoretical properties for its solution. We have introduced a reduced solution space using these properties. We present the first exact algorithm to solve MTP. This algorithm has a branch-and-bound framework. The reduced solution space calls for a novel branching strategy for MTP. The algorithm has a main branch-and-bound tree with a special structure along with two trees (one for each axis) to store the information required for branching in the main tree in an efficient format. Branching is done using a clustering scheme. We perform computational experiments to evaluate the performance of our algorithm. Our algorithm solves relatively large instances of MTP in a short time.

ITC/USA 2013 Conference Proceedings / The Forty-Ninth Annual International Telemetering Conference and Technical Exhibition / October 21-24, 2013 / Bally's Hotel & Convention Center, Las Vegas, NV / The need for increased downlink data rates and bandwidth for Earth Observation (EO) missions is driving mission planners to consider Ka-Band (25.5 to 27.0 GHz) downlinks to replace or augment the existing X-Band (8.025 to 8.400 GHz) services. Future ground stations will be required to support both bands as well as S-Band (2.0-2.3) GHz telemetry and command functions. This paper discusses the inherent tradeoffs in such a design, and proposes an implementation which permits simultaneous data reception in X-Band and Ka-Band, while providing TT&C functionality at S-Band. Analytical and measured data for the implementation are provided.

Thesis (MEng)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: The ability of satellites to actively control their attitude has changed the way we live. Navigation systems, satellite television, and weather forecasting, for example, all rely on satellites which are able to determine and control their attitude accurately. This project was aimed at designing and analysing an attitude determination and control system (ADCS) for a 20 kg Earth observation satellite by means of simulation. A realistic simulation toolset, which includes the space environment, sensor, and actuator models, was created using MATLAB and Simulink. An ADCS hardware suite was selected for the satellite based on a given set of pointing and stability requirements, as well as current trends in the small satellite industry. The hardware suite consists of among others a star tracker and three reaction wheels. A variety of estimators and controllers were investigated, after which an application specific ADCS state machine was defined. The state machine included a Safe Mode for de-tumbling, a Nominal Mode for normal operation, a Forward Motion Compensation (FMC) Imaging Mode for Earth observation, and a Target Tracking Mode for ground station tracking. Simulation results indicated that de-tumbling, coarse and fine sun tracking, FMC factor 4 imaging, and target tracking were successfully implemented. Lastly, the satellite’s pointing error and stability were determined to be less than 70 arcseconds and 7 arcseconds per second respectively, both values well within the given requirements. / AFRIKAANSE OPSOMMING: Satelliete se vermoë om hul oriëntasie aktief te beheer, het die manier waarop ons lewe, verander. Navigasiestelsels, satelliettelevisie en weervoorspelling, byvoorbeeld, maak staat op satelliete wat hul oriëntasie akkuraat kan bepaal en beheer. Die mikpunt van hierdie projek was die ontwerp en analise van ’n oriëntasiebepaling- en -beheerstelsel (ADCS) vir ’n 20 kg aardwaarnemingsatelliet deur middel van simulasie. ’n Realistiese simulasieopstelling, wat modelle van die ruimteomgewing, sensore en aktueerders insluit, was ontwikkel deur gebruik te maak van MATLAB en Simulink. ’n ADCS hardewarestel was gekies vir die satelliet op grond van ’n stel rig- en stabiliteitsvereistes, sowel as die huidige tendense in die klein-satellietbedryf. Die hardewarestel bestaan onder andere uit ’n stervolger en drie reaksiewiele. Nadat verskeie afskatters en beheerders ondersoek was, was ’n toepassingspesifieke ADCS toestandmasjien gedefinieer. Die toestandmasjien het ’n Veilige Modus vir onttuimelling, ’n Nominale Modus vir normale operasie, ’n Vorentoe-bewegingskompensering (FMC) Beeldskandeermodus vir aardwaarneming en ’n Teikenvolgmodus vir grondstasie volging ingesluit. Simulasieresultate het aangedui dat onttuimeling, growwe- en fyn sonvolging, FMC faktor 4 beeldskandering en teikenvolging suksesvol geïmplementeer was. Laastens was die satelliet se rigfout en stabiliteit bepaal as minder as 70 boogsekondes en 7 boogsekondes per sekonde onderskeidelik, albei waardes gemaklik binne die vereistes.

>Magister Scientiae - MSc / There have been increasing calls to monitor Groundwater-Dependent Ecosystems (GDEs) more effectively, since they are biodiversity hotspots that provide several ecosystem services. The accurate monitoring of GDEs is an indispensable under Sustainable Development Goal (SDG) 15, because it promotes the existence of phreatophytes. It is imperative to monitoring GDEs, since their ecological significance (e.g., as biodiversity hotspots) is not well understood in most environments they exist. For example, vegetation diversity in GDEs requires routine monitoring, to conserve their biodiversity status and to preserve the ecosystem services in these environments. Such monitoring requires robust measures and techniques, particularly in arid environments threatened by groundwater over–abstraction, landcover and climate change. Although in–situ methods are reliable, they are challenging to use in extensive transboundary groundwater resources such as the Khakea-Bray Transboundary Aquifer.

The aim of this thesis is to evaluate the capability of radio detection and ranging (radar) data collected by the Advanced Land Observing Satellite (ALOS) Phased Array type L-band Synthetic Aperture radar (PALSAR), supported by field measurements obtained through ground survey, to predict and map Above Ground Woody Biomass (AGWB) in the tropical savannas of the developing country of Belize, and to understand how the forest structure may influence the backscatter observed. Firstly, an extensive inventory of the woody vegetation of the tropical savannas of Belize was created by measuring the diameter at breast height (dbh), the total height (ht) and the location of 6547 trees in plots covering a total woodland area of 30.8 hectares, located within four protected areas (the Rio Bravo Conservation and Management Area (11×1ha), Deep River (108×0.1ha) and Manatee Forest Reserve (1ha) and the Bladen Nature Reserve (1ha) and also from plots located in unprotected areas (7×1ha). These measurements of forest structure, when combined with information about forest management practices obtained from local organisations revealed that different forms of protection and management may lead to the development of pine woodlands with different structural characteristics in these savannas. Secondly, a case-study was conducted to establish the sensitivity of the ALOS PALSAR backscatter data to AGWB and determine the effect of sample plot size to their relationship. The findings of this case-study show that the L-band backscatter in these low density pine woodlands is a possible predictor of AGWB and confirm that the appropriate sample plot size for predicting AGWB is one hectare; while the sensitivity degrades significantly with decreasing sample plot size. Taken together, the findings described above were combined to assess the capability of ALOS PALSAR backscatter to predict AGWB in these woodlands. A semi-empirical Water Cloud Model (WCM) describing the interaction between the backscatter and vegetation was re-arranged to enable the prediction of AGWB. Non-linear regression analysis revealed that the ALOS PALSAR backscatter predicted AGWB with an R2=0.92; an external validation conducted with additional ground reference data estimated this AGWB prediction to have an RMSE ~13 t/ha. The form of the regression model linking backscatter to AGWB appears to be particularly influenced by sample plots with higher tree numbers and by plots in which the trees were more homogeneous. The presence of many similar sized individuals within some plots is postulated as one explanation for the elevated saturation level for predictions in this study (> 100 t/ha) compared to other models. The model developed here predicts complete saturation in the backscatter - AGWB relationship to occur primarily as a result of increases in the tree number density and often concurrently in basal area, two parameters which are usually strongly correlated with AGWB in these woodlands. Thirdly, the locally validated relationship between ALOS PALSAR backscatter and AGWB is used to map AGWB for the lowland pine savannas of Belize at a spatial resolution of 100m. The mapping estimates that over 90% of these pine woodlands have an AGWB below 60 t/ha, with the average woody biomass estimated at 23.5 t/ha. When these new predictions are mapped and aggregated over the extents of two protected areas (Rio Bravo and Deep River), the totals obtained agree closely (error ≤20%) with previous estimates of AGWB obtained from ground data and previous research. The combined evidence suggests that woodland protection may produce a small, positive effect upon AGWB, with the mean of the AGWB/ha predictions higher in areas that are protected and managed for biodiversity (29.55 ± 0.84 t/ha) than in other areas that are not protected (23.29 ± 0.19 t/ha). When the fine scale local AGWB mapping produced using ALOS PALSAR is compared cell-by-cell with global biomass products at coarser spatial resolutions (500m and 1000m), the AGWB differences observed range from 115-120%. When the coarser AGWB estimates are aggregated over the extents of Deep River and Rio Bravo, the AGWB totals obtained differ significantly (~280 – 300%) from AGWB estimates from ground data and previous research. Overall, these findings suggest that where sufficient ground data exists to build a reliable local relationship to radar backscatter, more detailed biomass mapping can be produced from ALOS and similar satellite sensor data at resolutions of ~100m. This more accurate and spatially detailed information about the distribution of woody biomass within tropical lowland savannas is more appropriate for monitoring local changes in forest cover and for supporting management decisions for forested areas of around ~10,000ha than estimates based upon previously available, but coarser scale, global biomass products.

La humedad del suelo es la variable que regula los intercambios de agua, energía, y carbono entre la tierra y la atmósfera. Mediciones precisas de humedad son necesarias para una gestión sostenible de los recursos hídricos, para mejorar las predicciones meteorológicas y climáticas, y para la detección y monitorización de sequías e inundaciones. Esta tesis se centra en la medición de la humedad superficial de la Tierra desde el espacio, a escalas global y regional. Estudios teóricos y experimentales han demostrado que la teledetección pasiva de microondas en banda L es optima para la medición de humedad del suelo, debido a que la atmósfera es transparente a estas frecuencias, y a la relación directa de la emisividad del suelo con su contenido de agua. Sin embargo, el uso de la teledetección pasiva en banda L ha sido cuestionado en las últimas décadas, pues para conseguir la resolución temporal y espacial requeridas, un radiómetro convencional necesitaría una gran antena rotatoria, difícil de implementar en un satélite. Actualmente, hay tres principales propuestas para abordar este problema: (i) el uso de un radiómetro de apertura sintética, que es la solución implementada en la misión Soil Moisture and Ocean Salinity (SMOS) de la ESA, en órbita desde noviembre del 2009; (ii) el uso de un radiómetro ligero de grandes dimensiones y un rádar operando en banda L, que es la solución que ha adoptado la misión Soil Moisture Active Passive (SMAP) de la NASA, con lanzamiento previsto en 2014; (iii) el desarrollo de técnicas de desagregación de píxel que permitan mejorar la resolución espacial de las observaciones. La primera parte de la tesis se centra en el estudio del algoritmo de recuperación de humedad del suelo a partir de datos SMOS, que es esencial para obtener estimaciones de humedad con alta precisión. Se analizan diferentes configuraciones con datos simulados, considerando (i) la opción de añadir información a priori de los parámetros que dominan la emisión del suelo en banda L —humedad, rugosidad, temperatura del suelo, albedo y opacidad de la vegetación— con diferentes incertidumbres asociadas, y (ii) el uso de la polarización vertical y horizontal por separado, o del primer parámetro de Stokes. Se propone una configuración de recuperación de humedad óptima para SMOS. La resolución espacial de los radiómetros de SMOS y SMAP (40-50 km) es adecuada para aplicaciones globales, pero limita la aplicación de los datos en estudios regionales, donde se requiere una resolución de 1-10 km. La segunda parte de esta tesis contiene tres novedosas propuestas de mejora de resolución espacial de estos datos: • Se ha desarrollado un algoritmo basado en la deconvolución de los datos SMOS que permite mejorar la resolución espacial de las medidas. Los resultados de su aplicación a datos simulados y a datos obtenidos con un radiómetro aerotransportado muestran que es posible mejorar el producto de resolución espacial y resolución radiométrica de los datos. • Se presenta un algoritmo para mejorar la resolución espacial de las estimaciones de humedad de SMOS utilizando datos MODIS en el visible/infrarrojo. Los resultados de su aplicación a algunas de las primeras imágenes de SMOS indican que la variabilidad espacial de la humedad del suelo se puede capturar a 32, 16 y 8 km. • Un algoritmo basado en detección de cambios para combinar los datos del radiómetro y el rádar de SMAP en un producto de humedad a 10 km ha sido desarrollado y validado utilizando datos simulados y datos experimentales aerotransportados. Este trabajo se ha desarrollado en el marco de las actividades preparatorias de SMOS y SMAP, los dos primeros satélites dedicados a la monitorización de la variación temporal y espacial de la humedad de la Tierra. Los resultados presentados contribuyen a la obtención de estimaciones de humedad del suelo con la precisión y la resolución espacial necesarias para un mejor conocimiento del ciclo del agua y una mejor gestión de los recursos hídricos. / Soil moisture is a key state variable of the Earth's system; it is the main variable that links the Earth's water, energy and carbon cycles. Accurate observations of the Earth's changing soil moisture are needed to achieve sustainable land and water management, and to enhance weather and climate forecasting skill, flood prediction and drought monitoring. This Thesis focuses on measuring the Earth's surface soil moisture from space at global and regional scales. Theoretical and experimental studies have proven that L-band passive remote sensing is optimal for soil moisture sensing due to its all-weather capabilities and the direct relationship between soil emissivity and soil water content under most vegetation covers. However, achieving a temporal and spatial resolution that could satisfy land applications has been a challenge to passive microwave remote sensing in the last decades, since real aperture radiometers would need a large rotating antenna, which is difficult to implement on a spacecraft. Currently, there are three main approaches to solving this problem: (i) the use of an L-band synthetic aperture radiometer, which is the solution implemented in the ESA Soil Moisture and Ocean Salinity (SMOS) mission, launched in November 2009; (ii) the use of a large lightweight radiometer and a radar operating at L-band, which is the solution adopted by the NASA Soil Moisture Active Passive (SMAP) mission, scheduled for launch in 2014; (iii) the development of pixel disaggregation techniques that could enhance the spatial resolution of the radiometric observations. The first part of this work focuses on the analysis of the SMOS soil moisture inversion algorithm, which is crucial to retrieve accurate soil moisture estimations from SMOS measurements. Different retrieval configurations have been examined using simulated SMOS data, considering (i) the option of adding a priori information from parameters dominating the land emission at L-band —soil moisture, roughness, and temperature, vegetation albedo and opacity— with different associated uncertainties and (ii) the use of vertical and horizontal polarizations separately, or the first Stokes parameter. An optimal retrieval configuration for SMOS is suggested. The spatial resolution of SMOS and SMAP radiometers (~ 40-50 km) is adequate for global applications, but is a limiting factor to its application in regional studies, where a resolution of 1-10 km is needed. The second part of this Thesis contains three novel downscaling approaches for SMOS and SMAP: • A deconvolution scheme for the improvement of the spatial resolution of SMOS observations has been developed, and results of its application to simulated SMOS data and airborne field experimental data show that it is feasible to improve the product of the spatial resolution and the radiometric sensitivity of the observations by 49% over land pixels and by 30% over sea pixels. • A downscaling algorithm for improving the spatial resolution of SMOS-derived soil moisture estimates using higher resolution MODIS visible/infrared data is presented. Results of its application to some of the first SMOS images show the spatial variability of SMOS-derived soil moisture observations is effectively captured at the spatial resolutions of 32, 16, and 8 km. • A change detection approach for combining SMAP radar and radiometer observations into a 10 km soil moisture product has been developed and validated using SMAP-like observations and airborne field experimental data. This work has been developed within the preparatory activities of SMOS and SMAP, the two first-ever satellites dedicated to monitoring the temporal and spatial variation on the Earth's soil moisture. The results presented contribute to get the most out of these vital observations, that will further our understanding of the Earth's water cycle, and will lead to a better water resources management.