Improved Two-Step Replication Process for Producing Precision Optical Mirrors

Production of precision optical mirrors by replication requires molds or mandrels of the complementary shape. For example, replicating a concave mirror requires a convex mandrel. Convex shapes are difficult to fabricate and test since they do not focus light. Convex mandrels are therefore costly when they are available. Their sizes are limited to 1-2 meters. Two-step or double replication is well known in the art. In the traditional method, a specific polymer resin system with fillers is used to replicate an existing concave mirror (designated as “mother”) to produce a convex intermediate designated as “daughter.” The same material is then used to replicate the daughter, creating a third-generation concave that is designated as “granddaughter.”

Posted in: Briefs, Optics


System and Method for Generating a Frequency-Modulated Linear Laser Waveform

Applications include manufacturing equipment, robotics, surveillance and security, military imaging, and spectroscopy.NASA’s Langley Research Center has made a breakthrough improvement in laser frequency modulation. Frequency modulation technology has been used for surface mapping and measurement in sonar, radar, and time-of-flight laser technologies for decades. Although adequate, the accuracy of distance measurements made by these technologies can be improved by using a high-frequency triangular-waveform laser instead of a sine waveform or lower-frequency radio or microwaves. This new system generates a triangular modulation waveform with improved linearity that makes possible precision laser radar [light detection and ranging (lidar)] for a variety of applications.

Posted in: Briefs, Lasers & Laser Systems, Optics, Photonics


Characterizing Richness of Previously Unmapped Terrain and Estimating its Impact on Navigation Performance using 3D Range Sensors in Flight

NASA’s Jet Propulsion Laboratory, Pasadena, California Landers to large planetary bodies such as Mars typically use a secondary reconnaissance spacecraft to generate high-fidelity 3D terrain maps that are subsequently used for landing site selection and creating onboard maps for terrain-relative navigation systems. This luxury does not exist with small primitive bodies such as comets and asteroids. For these bodies, the landing spacecraft has to perform the 3D mapping and, with possible help from ground control, choose a feasible landing site. To enable this operation, the spacecraft would need to carry a 3D ranging sensor system such as a LIDAR. With the spacecraft placed in extended mapping orbits, 3D range measurement data is then used to create a shape model of the object. Terrain-based navigation schemes that employ cameras could then be used to image, detect, match, and track features against the map database to provide a 6-degrees-of-freedom (DOF) navigation solution during descent. Camera-based systems, however, are not robust to lighting variations, and do not provide a direct 3D position/range feedback.

Posted in: Briefs, Optics, Photonics


Continental-Scale Mapping of Adélie Penguin Colonies from Landsat Imagery

Remote sensing is used for biological conservation. Goddard Space Flight Center, Greenbelt, Maryland The Adélie penguin has a circum-Antarctic distribution and is widely considered a useful indicator of status and change in the Antarctic and Southern Ocean ecosystems. Breeding distribution of the Adélie penguin was surveyed with Landsat-7 Enhanced Thematic Mapper Plus (ETM+) over the entire continent of Antarctica. An algorithm was designed to minimize radiometric noise and to retrieve Adélie penguin colony location and spatial extent from the ETM+ data. In all, 259 ETM+ scenes were selected from the Lansdat archive from the 1999–2003 era and were used in the retrieval. Pixel clustering identified a total of 244 individual Adélie penguin colonies, ranging in size from a single pixel (900 m2) to a maximum of 875 pixels (0.788 km2). The Landsat retrievals successfully located Adélie penguin colonies that accounted for ≈96 to 97% of the regional population used as ground truth, with errors of omission and commission on the order of only 1 to 2%.

Posted in: Briefs, Tech Briefs, Environmental Monitoring, Imaging, Photonics


Photogrammetric-Based Pose Initialization and Propagation for Inertial Navigation Systems

NASA’s Jet Propulsion Laboratory, Pasadena, California The purpose of the Pose Initialization and Propagation (PIP) system is to provide an absolute navigational solution (position, velocity, and attitude) to a moving vehicle without using GPS. This was developed as a navigation system for rocket launches in a GPS-denied environment, but it is applicable to a variety of moving vehicles. It was designed to be integrated with JPL’s Terrain Relative Navigation system as a test of the Mars Entry, Descent, and Landing (EDL) system. It was successfully used by JPL on Masten Space Systems’ Xombie vehicle in 2014.

Posted in: Briefs, Tech Briefs, Imaging, Photonics


Multi-Channel Laser Absorption Spectrometer for Combustion Product Monitoring

This instrument can detect fires associated with electrical wiring and electronics packaging materials. NASA’s Jet Propulsion Laboratory, Pasadena, California Tunable laser absorption spectrometer (TLAS) sensors enable gas monitoring with high accuracy and gas specificity, and can be optimized for continuous, maintenance-free operation on long-duration manned spacecraft missions. This innovation is a portable, five-channel TLAS instrument designed to continuously monitor ambient concentrations of carbon monoxide, hydrogen chloride, hydrogen cyanide, hydrogen fluoride, and carbon dioxide, with low-level detection limits below the standard spacecraft maximum allowable concentrations. Monitoring of these particular hazardous compounds allows tracking of ambient conditions and enables detection of fires associated with electrical wiring and electronics packaging materials.

Posted in: Briefs, TSP, Tech Briefs, Imaging, Photonics


Disturbance-Free, High-Resolution Imaging from Space

Telecommunication satellites, astrophysical imaging, remote sensing, surveillance, and reconnaissance from space could all benefit from this innovation.All imaging systems from space are affected by disturbances originating in the spacecraft in the form of mechanical noise from thruster and reaction/momentum wheels, and sensor noise. A drag-free system is truly unaffected by any disturbances, as it is in pure freefall. Hence, leveraging drag-free technology can provide a quantum leap in improvement for spaceborne imaging systems.

Posted in: Briefs, Tech Briefs, Imaging, Photonics


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