News Article | November 2, 2015
"Not quite, scientists say. But new study results show the fallibility of current measuring tools and challenges current theories about the causes of sea level rise." "A new NASA study found that Antarctica has been adding more ice than it's been losing, challenging other research, including that of the UN's Intergovernmental Panel on Climate Change, that concludes that Earth’s southern continent is losing land ice overall. In a paper published in the Journal of Glaciology on Friday, researchers from NASA's Goddard Space Flight Center, the University of Maryland in College Park, and the engineering firm Sigma Space Corporation offer a new analysis of satellite data that show a net gain of 112 billion tons of ice a year from 1992 to 2001 in the Antarctic ice sheet. That gain slowed to 82 billion tons of ice per year between 2003 and 2008."
Chang T.,Sigma Space Corporation |
IEEE Transactions on Geoscience and Remote Sensing | Year: 2011
Sixteen Moderate Resolution Imaging Spectroradiometer thermal emissive bands (TEBs) cover the wavelength from 3.75 to 14.24 μ. TEB calibration uses data collected from the detector responses to the onboard blackbody (BB) and space view. The BB was designed to operate either at a constant temperature for detector linear gain calibration or at temperatures varying from ambient ( ∼270 K) to 315 K for on-orbit characterization of nonlinear coefficients. In this paper, we assess TEB on-orbit calibration performance in two aspects: One is to review the calibration trending on the orbital, daily, and multiyear timescales, and the other is to analyze the on-orbit calibration radiance uncertainty and its impact on the calibration. The calibration trending confirms the detector response dependence on the instrument temperature. The temperature trending and prelaunch characterization provide the basis for determining the calibration radiance source temperature range and uncertainties. An analytical approach was used to assess the impacts of onboard radiance uncertainties. The BB emission uncertainty, resulting from the temperature measurement error and emissivity uncertainty, causes a calibration uncertainty up to 0.3%, a value decreasing with the band wavelength. The BB nonblackness effect is analyzed and found to be insignificant. For the band with the lowest BB emissivity, the nonblackness affects the calibration radiance by less than 0.08%. The cavity emission uncertainty and the scan-mirror emission uncertainty both cause a less than 0.1% calibration uncertainty. The analysis of the nonlinear calibration coefficient uncertainty shows that its effect on the low Earth-view brightness-temperature range varies by band and is generally insignificant. © 2011 IEEE.
Sigma Space Corporation | Date: 2010-01-25
A polarization switching lidar device is arranged for remote detection and characterization of airborne aggregations of particulates. It includes a pulsed laser, a mirror, a polarizing beam splitter, an actively controlled retarder arranged to be controllably alternated between a zero retardation state and a quarter-wave retardation state such that the transmitted portion of the exiting laser light beam is linearly polarized in a predetermined direction when the actively controlled retarder is in the zero retardation state, while being circularly polarized in a predetermined rotational sense when the actively controlled retarder is in the quarter-wave retardation state. A directable telescoping assembly is arranged to collect photons backscattered by the airborne aggregations of particulates and to redirect the collected portion of depolarized backscattered photons onto the polarizing beam splitter. A photodetector is arranged to generate at least one electronic signal proportional to the collected portion of depolarized backscattered photons.
Ranson K.J.,NASA |
Montesano P.M.,Sigma Space Corporation |
Remote Sensing of Environment | Year: 2011
The circumpolar taiga-tundra ecotone was delineated using an image-segmentation-based mapping approach with multi-annual MODIS Vegetation Continuous Fields (VCF) tree cover data. Circumpolar tree canopy cover (TCC) throughout the ecotone was derived by averaging MODIS VCF data from 2000 to 2005 and adjusting the averaged values using linear equations relating MODIS TCC to Quickbird-derived tree cover estimates. The adjustment helped mitigate VCF's overestimation of tree cover in lightly forested regions. An image segmentation procedure was used to group pixels representing similar tree cover into polygonal features (segmentation objects) that form the map of the transition zone. Each polygon represents an area much larger than the 500. m MODIS pixel and characterizes the patterns of sparse forest patches on a regional scale. Those polygons near the boreal/tundra interface with either (1) mean adjusted TCC values from 5 to 20%, or (2) mean adjusted TCC values < 5% but with a standard deviation > 5% were used to identify the ecotone. Comparisons of the adjusted average tree cover data were made with (1) two existing tree line definitions aggregated for each 1° longitudinal interval in North America and Eurasia, (2) Landsat-derived Canadian proportion of forest cover for Canada, and (3) with canopy cover estimates extracted from airborne profiling lidar data that transected 1238 of the TCC polygons. The adjusted TCC from MODIS VCF shows, on average, < 12% TCC for all but one regional zone at the intersection with independently delineated tree lines. Adjusted values track closely with Canadian proportion of forest cover data in areas of low tree cover. A comparison of the 1238 TCC polygons with profiling lidar measurements yielded an overall accuracy of 67.7%. © 2011.
Sigma Space Corporation | Date: 2010-08-09
A method of locking of and a directionally adjustable mount including a first plate arranged to stabilize an anisotropic device, a second plate arranged to engage the first plate and provide a support, a second supporting member arranged to engage the second plate and to rollably support the first plate so as to define a local spacing between the plates, and a first supporting member arranged to have a first axis of symmetry and to contact the first plate and engage the second supporting member. In a locked position, the supporting members are arranged coaxially regarding the axis of symmetry, such that a sum of a positioning force applied by the first supporting member and a locking force applied by the second supporting member upon the first plate substantially vanishes, so that a resulting local moment of force oriented to deform the at least one first plate also substantially vanishes.
Sigma Space Corporation | Date: 2011-12-06
A method for monitoring of traffic patterns and securely processing events of violations of traffic regulations on at least one designated surface incorporating steps of positioning at least one mobile traffic monitoring and recording module arranged to monitor traffic on at least one designated surface, to detect events of potential violations of traffic regulations, to store information pertinent to the monitored traffic and detected events of potential violations of traffic regulations, and to transmit, using a secure wireless method, at least a portion of the stored information for further processing. The method also include establishing at least one traffic information processing center arranged to securely receive and process transmitted portion of the stored information, to process received portion of the stored information pertinent to traffic regulations violations, and to generate actionable portfolio of documents for communication to subjects having interest in the processed traffic regulations violations.
Sigma Space Corporation | Date: 2016-04-27
The present invention is directed to a self consistent system for generation and adaptive implementation of overflying multi sensor measurements and derivation of actionable aggregants pertinent to determination of status and proactive management models of distributed resource. The system includes at least one set of calibrated overflying multisensor detectors arranged for detecting signals from electromagnetic radiation redirected by a plurality of underlying structures having a combination of features having variable scale lengths.
Sigma Space Corporation | Date: 2011-09-21
A polarization switching lidar device, arranged for remote detection and characterization of airborne aggregations of particulates, includes a pulsed laser, a mirror, a polarizing beam splitter, an actively controlled retarder arranged to be controllably alternated between a zero retardation state and a quarter-wave retardation state such that the transmitted portion of the exiting laser light beam is linearly polarized in a predetermined direction when the actively controlled retarder is in the zero retardation state, while being circularly polarized in a predetermined rotational sense when the actively controlled retarder is in the quarter-wave retardation state. A directable telescoping assembly is arranged to collect photons backscattered by the airborne aggregations of particulates and to redirect the collected portion of depolarized backscattered photons onto the polarizing beam splitter. A photodetector is arranged to generate at least one electronic signal proportional to the collected portion of depolarized backscattered photons.
Agency: Department of Defense | Branch: Navy | Program: SBIR | Phase: Phase I | Award Amount: 69.12K | Year: 2010
Sigma has developed a highly successful, airborne, 100 beam, photon-counting, 3D imaging lidar which operates at a laser repetition rate of 22 Khz and is therefore capable of an unprecedented 2.2 Megapixel per second data rate in topographic mode. The system uses a single passively Q-switched microchip laser operating at 532 nm (near the transmission peak of water) and was designed to fit into the nose cone of an Aerostar mini-UAV. It has successfully performed high resolution (15 cm horizontal, 6 cm vertical) surface topography over wide swaths (up to 524 m) from a nominal operating altitude of 1 km. The mass and weight of the Sigma lidar is roughly an order of magnitude less than the operational SHOALS-3000 lidar We propose to modify the lidar design to provide (in addition to the current topographic mode) one or more software-selectable hydrographic modes of operation, permitting trades between depth penetration and horizontal spatial resolution during bathymetry operations. The active lidar will also be mated with an optically coregistered passive hyperspectral camera which best duplicates the performance of the operational CASI-1500 and the final package will be configured to fit in one of the larger Naval Tier II UAVs, the RQ-Pioneer.
Agency: National Aeronautics and Space Administration | Branch: | Program: SBIR | Phase: Phase I | Award Amount: 124.69K | Year: 2015
The proposal describes a next generation 3D imaging lidar (IML) suitable for a uniquely wide range of space applications - from orbital mapping and proximity operations of small bodies such as asteroid and comets, to full scale entry, decent and landing operations on other planetary bodies. Low Earth Orbit operations such as rendezvous and docking between spacecraft, and space debris search and collection can also be accommodated. Such versatility is made possible system by a system architecture which merges the architectures of two high performance imaging lidars - the Sigma Space 3D Imaging Lidar and the Imaging Lidar for planetary landing developed by the European Space Agency. The result is a highly modular architecture that is scalable and "open" in terms of future development of the underlying technologies thus providing a path for reusable NASA investment. The design combines several advanced technologies which have matured independently of each other into a state-of-the-art system with performance parameters and flexibility greatly exceeding those of the existing instruments. Its key advantage is the operation at the ultimate single photon sensitivity level which minimizes instrument Size, Weight, and Power (SWAP). It is combined with other useful features such as high spatial and range resolution, wide FOV, highly flexible scanning with variable field of regard (FOR), autonomous target acquisition and tracking, and programmable surface measurement rates up to several 3D Megapixels per second (Mpix/s) during orbital mapping and spacecraft entry, descent and landing operations. It advances the state of the art by extending the range of 3D measurements from 10m to 10km, improving the measurement accuracy and the spatial resolution and significantly reducing the impact of incorporating such sensors on the spacecraft in terms of SWAP, spacecraft accommodation complexity, and cost.