electrical and electronics
Smooth-Walled Feed Horn
The technology is a monotonically-profiled, smooth-walled scalar feed horn optimized between 33 and 45 GHz. The phase center for this horn is near the aperture and is stable in frequency. The feed horns monotonic profile is compatible with machining by progressive plunge milling in which successively more accurate tools are used to realize the feed profile. This technique has been used for individual feeds and is potentially useful for fabricating large arrays of feed horns, such as multimode Winston concentrators, direct-machined smooth-walled conical feed horns, and for dual-mode feed horns.
Low Frequency Wideband Step Frequency Inverse Synthetic Aperture Radar
This technology is a low frequency (25~100 MHz) wide band (75 MHz) subsurface imaging ISAR. Use of low frequencies allows the electromagnetic energy to penetrate to a greater depth, enabling observation of the interior of a solid object to a higher resolution than can be achieved with alternate technologies. Higher bandwidth has been used in earlier ISAR systems; however these require expensive high bandwidth RF components, and also higher speed data processing units. The new ISAR system uses a novel step frequency technique which eliminates both these requirements. The step frequency approach keeps the local bandwidth very small; enabling data processing at much lower speed. And by stepping through the frequencies, this ISAR achieves much higher overall bandwidth and consequently very high range resolution.
Solid-State Microwave Power Module
Typically, microwave power modules (MPMs) are useful only for radar and navigation purposes because they lack the linearity and efficiency required for communications. In standard configurations, conventional MPMs require both a solid-state amplifier at the front end and a microwave vacuum electronics amplifier at the back end. By contrast, Glenn's design features a wideband multi-stage distributed amplifier system. The low-power stage is a high-efficiency gallium arsenide (GaAs) pseudomorphic high-electron-mobility transistor (pHEMT)-based monolithic microwave integrated circuit (MMIC) distributed amplifier. The medium-power stage is configured to pick up and amplify the low-power signal. This stage can be either another high-efficiency GaAs pHEMT or a gallium nitride (GaN) HEMT-based MMIC distributed amplifier, depending on the need. The high-power stage, configured to pick up the signal from the second amplifier, is a high-efficiency GaN HEMT-based MMIC distributed amplifier, which supplants the traveling-wave tube amplifier found in most microwave power modules. In Glenn's novel MPM, the radar functions as a scatterometer, radiometer, and synthetic aperture imager. The high-speed communications system down-links science data acquired by Earth-observing instruments. The navigation system functions like a transponder for autonomous rendezvous and docking, and estimates the range information. Glenn's MPM gives systems the versatility to use a single power module to drive not only radar and navigation but also communications systems.
Low Frequency Portable Acoustic Measurement System
Langley has developed various technologies to enable the portable detection system, including: - 3-inch electret condenser microphone - unprecedented sensitivity of -45 dB/Hz - compact nonporous windscreen - suitable for replacing spatially demanding soaker hoses in current use - infrasonic calibrator for field use - piston phone with a test signal of 110 dB at 14Hz. - laboratory calibration apparatus - to very low frequencies - vacuum isolation vessel - sufficiently anechoic to permit measurement of background noise in microphones at frequencies down to a few Hz - mobile source for reference - a Helmholtz resonator that provides pure tone at 19 Hz The NASA system uses a three-element array in the field to locate sources of infrasound and their direction. This information has been correlated with PIREPs available in real time via the Internet, with 10 examples of good correlation.
Infrasound Sensor Technology
Large aircraft can generate air vortices in their wake, turbulence that can prove hazardous to aircraft that follow too closely. Because wake vortices are invisible, all takeoffs at busy airports are spaced several minutes apart. This separation gives the vortices time to dissipate, even though they only occur 10% of the time, with resulting loss of operational efficiency. Similarly, clear air turbulence is invisible and can also be hazardous to aircraft. By detecting such disturbances through their infrasound emissions, precautions can be taken to avoid them. Other phenomena can be detected through infrasound, including tornadoes, helicopters on the other side of mountains, underground nuclear explosions and digging tunnels. Through the unique properties of infrasound, many of these can be detected from hundreds of miles away. NASA's infrasound sensor is a highly refined microphone that is capable of detecting acoustic waves from 20 Hz down to dc, the infrasound range. The design is robust and compact, eliminating the bulk and weight found in other technologies. Where most alternative methods are restricted to certain weather conditions and locations, the NASA sensor filters noise from wind and other sources, allowing its use under any weather or geographic conditions.
Super Resolution 3D Flash LIDAR
This suite of technologies includes a method, algorithms, and computer processing techniques to provide for image photometric correction and resolution enhancement at video rates (30 frames per second). This 3D (2D spatial and range) resolution enhancement uses the spatial and range information contained in each image frame, in conjunction with a sequence of overlapping or persistent images, to simultaneously enhance the spatial resolution and range and photometric accuracies. In other words, the technologies allows for generating an elevation (3D) map of a targeted area (e.g., terrain) with much enhanced resolution by blending consecutive camera image frames. The degree of image resolution enhancement increases with the number of acquired frames.