High Altitude UAV for Monitoring Meteorological Parameters

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.

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.

The extreme low frequency hydrophone boasts unprecedented capability for precise detection as proven in testing, where it sensed wave range between surface waves and tidal surges with periods between .3 and 30 seconds, or 3 to .033 Hz. The technology uses a back-electret microphone, inherently reducing noise, in a stainless steel body. The stainless steel diaphragm conducts infrasound well and the materials robust nature and internal configuration facilitates sub-freezing and deeply submerged sensing of sound down to .0001 Hz. With an appropriately spaced array of three hydrophones it is possible to determine the direction of origin of a submerged infrasonic source, the addition of one more in another location will also enable determination of the precise location of origin. The oil industry uses existing infrasound systems to locate undersea oil deposits and this technology could potentially improve the accuracy or reliability of current practices. It could also be used to give tsunami and earthquake warnings, monitor ships, and to generate electrical energy from infrasound. This technology has potential to unlock new industry uses not currently understood due to the unprecedented nature of its capabilities.

The Vortex Radiometer (VR) creates concentric, annular antenna beam patterns that measure sky-noise temperature. Annular antenna patterns are created by imparting orbital angular momentum into the electric field received by the antenna using spiral phase plates placed in front of the antenna aperture, generating multiple radiometer channels. Data points are then collected by plotting the measured noise temperature of each radiometer channel as a function of time. Noise temperature increases as a noise source (e.g., weather-related noise, signal interference, etc.) traverses the antenna beam patterns. An algorithm is then used to correlate noise temperature peaks in adjacent beams and to determine when a fade will occur, how long the fade will last, and how intense the fade will be. With this information, effective and efficient strategies can be implemented using cognitive communication and antenna systems to autonomously select the optimum fade-mitigation technique and parameter (e.g., increasing the transmission power, adjusting the modulation and/or coding scheme, etc.). NASA's VR system has been prototyped, including the radiometer device and the algorithm for characterizing noise sources based on VR data. Simulations have shown that a VR system can instruct an existing cognitive antenna to switch between Ka- and X-Band communications in order to avert interference from small diameter noise sources. Any high-performance communication systems operating in RF or optical frequencies may benefit from NASA's VR capabilities.

The Space Weather DONKI builds a catalog of past, present, ongoing, and expected Space Weather events. The catalog contains both forecaster logs and notifications. DONKI version 2.0 of has a comprehensive web-service API access for users to obtain space weather events stored in the database. The database consists of a backend and a web application. The database uses a framework that allows modularization of code and promotes code reuse. DONKI is the first application to allow space weather scientists to store all space weather events in one centralized data center. The comprehensive database provides search capability to support scientists allowing them to look into linkages, relationships, and cause-and-effects between space weather activities.