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Ionospheric Slant TEC Analysis Using GNSS-Based Estimation (IonoSTAGE)

At the time of this reporting, IonoSTAGE has been operated successfully under both UNIX and Macintosh operating systems. NASA’s Jet Propulsion Laboratory, Pasadena, California As signals emitted by global navigation satellite systems (GNSS) propagate toward users on or near the surface of the Earth, they experience delay due to the presence of charged particles in the ionosphere. Currently, ionospheric delay is the largest source of GNSS positioning error. To guarantee the safety of airline navigation based upon GNSS signals, satellite-based augmentation systems have been developed to ensure the accuracy, integrity, availability, and continuity of user position estimates derived from GNSS measurements.

Posted in: Briefs, TSP, Electronics & Computers

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Implementation of a Terrain Radiometric Correction for UAVSAR

A paper discusses a calibration method suited to correct variations of UAVSAR (unmanned aerial vehicle synthetic aperture radar) backscatter with topography. To use radar backscatter to estimate forest biomass on terrain with slopes, it is necessary to remove the effect of topography. The remaining signal should be related to biomass. The hybrid approach uses the radar line of sight to project an oversampled version of the Digital Elevation Model into radar coordinates for summation. Terrain topography has a major impact on the radar backscatter. Slopes facing the radar appear very bright while slopes facing away appear darker.

Posted in: Briefs, TSP, Electronics & Computers

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Picoradian Staring Astrometry Using a Simple Staring Telescope

A document describes solutions to problems of astrometry at the microarc-second (picoradian) level using a simple staring telescope. The problems include field-dependent beam-walk on the telescope’s mirrors, pixel position irregularity and distortion over time, non-flat intra-pixel quantum efficiency, and systematic errors inherent in the most common image centroiding algorithms (imperfect knowledge of the point spread function).

Posted in: Briefs, TSP, Electronics & Computers

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Missing Value Imputation in Astronomical Time-Series Data

A document describes a solution to missing flux values in time-domain optical and radio astronomical survey data that form “light curves.” The technique incorporates a priori astronomical knowledge into a missing value imputation technique. It is assumed that missing values in astronomical time series are either Missing At Random (MAR), or missing due to the flux of the source falling below the instrument’s sensitivity threshold, termed Threshold Removed Observations (TRO).

Posted in: Briefs, TSP, Electronics & Computers

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Automatic Lunar Rock Detection and Mapping

NASA’s Jet Propulsion Laboratory, Pasadena, California Safe spacecraft landing on planetary and small body surfaces is of primary concern. Estimation of landing risk is a critical task when evaluating and certifying potential landing sites. Such analyses require the detection and mapping of all potential landing hazards such as rocks and boulders, craters, slopes, and terrain roughness.

Posted in: Imaging, Briefs, TSP, Electronics & Computers

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Technique for Finding the Center of an Image of a Rising or Setting Sun Based on Simulated Images

NASA’s Jet Propulsion Laboratory, Pasadena, California A new JPL project requires that the center of the images of a rising or setting Sun be determined with certain accuracy — for example, within 1 km — when the Sun is observed from the International Space Station (ISS). This center-finding technique can be used in applications such as a Sun-Tracker. To meet such needs, a simulation tool was developed for the generation of Sun images observed either on the ground or from space. The new technique enables one to find the center of a Sun image based on simulated images. The technique does not rely on ellipse-fitting to the boundary of a Sun image or other calibration techniques, so the accuracy is not affected by the distortion of Sun images.

Posted in: Imaging, Briefs, TSP, Electronics & Computers

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Modeling Lunar Surface Systems Concepts of Operations

The plans that are generated can be optimized for a specific set of goals, such as maximizing science data or minimizing power consumption. NASA’s Jet Propulsion Laboratory, Pasadena, California The goal of this work was to model lunar surface systems using a declarative planning system (ASPEN — Activity Scheduling/Planning Environment), provide a parameterizable Excel document to aid in the model generation, and deliver both Mac and PC versions. An adaptation of Microsoft Excel and ASPEN for Lunar Surface System concepts of operations was used. The goal of the system is to enable searching through several concepts of operations. A concept of operations consists of a proposed schedule of high-level activities and parameterization of resources (e.g., power, communications, oxygen, water, etc.) where three distinct phases of development occurred: (1) initial system development for Lunar, (2) planning system development for Lunar, and (3) planning system development for NASA’s 13th Desert Research and Technology Studies (Desert RATS) live trial.

Posted in: Briefs, TSP, Electronics & Computers

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