Martin S.R.,Jet Propulsion Laboratory |
Booth A.J.,Sigma Space Corporation
Astronomy and Astrophysics | Year: 2010
Context.Technology is being developed for the characterization and detection of small, Earth-size exoplanets by nulling interferometry in the mid-infrared waveband. While high-performance nulling experiments have shown the possibility of using the technique, to achieve these goals, nulling has to be done on multiple beams, with high stability over periods of hours. To address the issues of the perceived complexity and difficulty of the method, a testbed was developed for the Terrestrial Planet Finder Interferometer (TPF-I) project which would demonstrate four beam nulling and faint exoplanet signal extraction at levels traceable to flight requirements. Containing star and planet sources, the testbed would demonstrate the principal functional processes of the TPF-I beam-combiner by generating four input beams of star and planet light, and recovering the planet signature at the output. Aims. Here we report on experiments designed with traceability to a flight system, showing faint exoplanet signal detection in the presence of strong starlight. The experiments were designed to show nulling at the flight level of ≈10 -5, starlight suppression of 10 -7 or better, and detection of an exoplanet at a contrast of 10 -6 compared to the star. This performance level meets the flight requirements for the parts of the detection process that can be demonstrated using a monochromatic source. To achieve these results, the testbed would have to operate stably for several hours, showing control of disturbances at levels equivalent to the flight requirements. Methods.A test process was designed which would show that the necessary performance could be achieved. To show reproducibility, the tests were run on three separate occasions, separated by several days. The tests were divided into three main parts which would show first, starlight suppression, second, a realistic faint exoplanet signal production, and finally, exoplanet signal detection in the presence of the starlight. Results. A number of data sets were acquired showing the achievement of the required performance. The data reported here show nulling at levels between about 5.5 and 8.5 × 10 -6, starlight suppression between 8.4 × 10 -9 and 1.4 × 10 -8, and detection of planet signals with contrast to the star between 3.8× 10 -7 and 4.4× 10 -7. The signal to noise ratios for the detections were between 14.0 and 26.9. These data met all the criteria of the demonstration, showing reproducible stable performance over several hours of operation. Conclusions. These data show the successful execution, at flight-like performance levels, of almost the whole exoplanet detection process using a four beam, nulling beam-combiner. © ESO 2010.
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.
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.
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.