Remote Sensing Of The Cryosphere In High Mountain Asia

High Mountain Asia (HMA), often referred to as the "third pole" of the world because its high elevation glaciers, contains the largest amount of fresh water outside the polar ice sheets. The region's hydrology is strongly controlled by variations in the timing and distribution of runoff from snow and glacier melt. Recent improvements in remote sensing technologies and atmospheric / land surface models provides new approaches for assessing the HMA cryosphere. A recently-funded NASA program aims to apply these tools to advance understanding of HMA cryospheric processes. Here we present an overview of planned team activities during the three-year project

A multiscale approach for detection and mapping differential subsidence using multi-platform InSAR products

Detecting and mapping subsidence is currently supported by interferometric synthetic aperture radar (InSAR) products. However, several factors, such as band-dependent processing, noise presence, and strong subsidence limit the use of InSAR for assessing differential subsidence, which can lead to ground instability and damage to infrastructure. In this work, we propose an approach for measuring and mapping differential subsidence using InSAR products. We consider synthetic aperture radar (SAR) data availability, data coverage over time and space, and the region\u27s subsidence rates to evaluate the need of post-processing, and only then we interpret the results. We illustrate our approach with two case-examples in Central Mexico, where we process SAR data from the Japanese ALOS (L-band), the German TerraSAR-X (X-band), the Italian COSMO-SkyMed (X-band) and the European Sentinel-1 (C-band) satellites. We find good agreement between our results on differential subsidence and field data of existing faulting and find potential to map yet-to-develop faults

Optical Time-Transfer for Bistatic SAR Small Spacecraft

A spacecraft-to-spacecraft optical time-transfer simulation has been developed as a tool for informing NASA’s Surface Deformation and Change (SDC) mission architecture. The SDC mission will combine radar images from multiple spacecraft to improve understanding of the Earth’s sea-level and landscape changes. Spacecraft must be precisely synchronized in order to create sharp and phase accurate radar images. Simulation of multiple spacecraft time-synchronizing via laser communication can inform technology choices of a mission by providing sub-nanosecond precision estimates of clock error. This timing and ranging simulation has been combined with a radar system performance analysis pipeline. The simulated timing errors are used in a radar simulation to predict performance of bistatic SAR systems in the presence of oscillator noise and time synchronization inaccuracy. Precision time-transfer techniques facilitate the accurate synchronization of clocks between any combination of terminals. Most time-transfer technology for comparing two clocks at different terminals use radio frequencies (RF) to measure the time delay between the sending and receiving of signals. Laser technology offers the capability to transmit high data rates with systems that are of smaller size and lower power than comparable RF systems. The clocks on independent spacecraft will have some phase and frequency errors between them that result in clock drift. The two clock models that are included in this bi-directional MATLAB simulation are a Microchip Microsemi cesium-based Chip-Scale Atomic Clock (CSAC) and a Microchip Microsemi rubidium-based Miniature Atomic Clock (MAC). The CSAC has flown as hardware for small satellite missions such as the University of Florida’s CHOMPTT mission. A study of an example orbit, based on previous satellite laser ranging (SLR) missions and lasing rates demonstrate the impact of flight configuration parameters on the synchronization error between two spacecraft. The MATLAB timing simulation uses a Runge-Kutta 4th-order method to propagate spacecraft orbits and computes the light-travel time estimate between them. The simulation outputs the estimated clock error based on a user-defined spacecraft cluster configuration. The radar simulation is applied to evaluate a potential future bistatic SAR constellation architecture. In the proposed architecture, satellites follow each other in the same orbit at 500 km altitude, with a 250 km baseline direct line-of-sight between satellites. We also baseline the CSAC as a stable oscillator. We use NASA’s NISAR for baseline radar system parameters, but scale down the simulated antenna and radar power to represent a possible small-satellite platform. We compute a clock-system introduced phase error of 0.17 degrees with our simulated time-transfer architecture. This analysis technique could be extended or modified to evaluate the timing requirements of other geometries for other future multistatic SAR missions, or other interferometric satellite missions

Earth Observations and Integrative Models in Support of Food and Water Security

Global food production depends upon many factors that Earth observing satellites routinely measure about water, energy, weather, and ecosystems. Increasingly sophisticated, publicly-available satellite data products can improve efficiencies in resource management and provide earlier indication of environmental disruption. Satellite remote sensing provides a consistent, long-term record that can be used effectively to detect large-scale features over time, such as a developing drought. Accuracy and capabilities have increased along with the range of Earth observations and derived products that can support food security decisions with actionable information. This paper highlights major capabilities facilitated by satellite observations and physical models that have been developed and validated using remotely-sensed observations. Although we primarily focus on variables relevant to agriculture, we also include a brief description of the growing use of Earth observations in support of aquaculture and fisheries

Land subsidence hazard in iran revealed by country-scale analysis of sentinel-1 insar

Many areas across Iran are subject to land subsidence, a sign of exceeding stress due to the over-extraction of groundwater during the past decades. This paper uses a huge dataset of Sentinel-1, acquired since 2014 in 66 image frames of 250×250km, to identify and monitor land subsidence across Iran. Using a two-step time series analysis, we first identify subsidence zones at a medium scale of 100m across the country. For the first time, our results provide a comprehensive nationwide map of subsidence in Iran and recognize its spatial distribution and magnitude. Then, in the second step of analysis, we quantify the deformation time series at the highest possible resolution to study its impact on civil infrastructure. The results spots the hazard posed by land subsidence to different infrastructure. Examples of road and railways affected by land subsidence hazard in Tehran and Mashhad, two of the most populated cities in Iran, are presented in this study

Exploring cloud-based platforms for rapid insar time series analysis

The idea of near real-time deformation analysis using Synthetic Aperture Radar (SAR) data as a response to natural and anthropogenic disasters has been an interesting topic in the last years. A major limiting factor for this purpose has been the non-availability of both spatially and temporally homogeneous SAR datasets. This has now been resolved thanks to the SAR data provided by the Sentinel-1A/B missions, freely available at a global scale via the Copernicus program of the European Space Agency (ESA). Efficient InSAR analysis in the era of Sentinel demands working with cloud-based platforms to tackle problems posed by large volumes of data. In this study, we explore a variety of existing cloud-based platforms for Multioral Interferometric SAR (MTI) analysis and discuss their opportunities and limitations

Towards Blockchain-Based Identity and Access Management for Internet of Things in Enterprises

With the Internet of Things (IoT) evolving more and more, companies active within this area face new challenges for their Identity and Access Management (IAM). Namely, general security, resource constraint devices, interoperability, and scalability cannot be addressed anymore with traditional measures. Blockchain technology, however, may act as an enabler to overcome those challenges. In this paper, general application areas for blockchain in IAM are described based on recent research work. On this basis, it is discussed how blockchain can address IAM challenges presented by IoT. Finally, a corporate scenario utilizing blockchain-based IAM for IoT is outlined to assess the applicability in practice. The paper shows that private blockchains can be leveraged to design tamper-proof IAM functionality while maintaining scalability regarding the number of clients and transactions. This could be useful for enterprises to prevent single-point-of-failures as well as to enable transparent and secure auditing & monitoring of security-relevant events

Isolated perianal tuberculosis

PubMed ID: 15813425Perianal tuberculosis, without the presence of any previous or active pulmonary infection, is extremely rare. A case of isolated perianal tuberculosis without gastrointestinal or pulmonary spread will be discussed here with an evaluation of the clinical features. © 2005 Van Zuiden Communications B.V. All rights reserved