weather

optics
Hubble Peers at a Distinctly Disorganized Dwarf Galaxy
Image Credit: ESA/Hubble and NASA; Acknowledgement: Judy Schmidt
Laser Beam Expander with Adjustable Collimation
The usual approach to adjusting divergence and convergence is to manipulate the focal setting to the output telescope usually done by adjusting the spacing between the negative and positive focal length lenses by a large degree (~0.25mm for the FLARE beam expander). The optimization to this system enables a wide range of focal settings while only requiring minimal adjustments to the lens. By changing the spacing between the input lens and output lenses, we can adjust the output telescope collimation and the divergence of the output laser beam. The amount of required lens motion is reduced by an order of magnitude by splitting the input lens in two and adjusting the small remaining air gaps between lenses. The enhancements are dependent on the material selection and the curvature of the new interface within the two-part negative lens. This approach makes the system more efficient and compatible with thermal adjustment methods.
sensors
Punta Santa Domingo, Mexico
Sodium LIDAR for Spaceborne Missions
The instrument consists of a high-energy laser transmitter at 589 nm and highly sensitive photon counting detector that allows for range-resolved atmospheric-sodium-temperature profiles. The atmospheric temperature is deduced from the linewidth of the resonant fluorescence from the atomic sodium vapor D2 line as measured by the tunable laser. A high power energy laser allows for some daytime sodium LIDAR observations when used with a narrow bandpass filter based on etalon or atomic sodium Faraday filters with ~5 to 10 pm optical bandwidth.
sensors
A powerful cold front moving from the central United States to the East Coast.
Frequency Diversity Pulse Pair Algorithm for Mitigation of Radar Range-Doppler Ambiguity
This technology mitigates the Doppler ambiguity by creating an innovative frequency. This frequency diversity technique takes advantage of the recent development in digital waveform generation and digital receiver technologies by transmitting a pair of pulses (or more pulses) with slightly shifted center frequencies in each pulse repetition period. Radar return signals from these pulses can be separated by the digital filters implemented in the digital receiver. In Doppler radar operation, the maximum unambiguous range is determined by the radar transmission pulse repetition time. This unique frequency diversity technique is implemented by alternating the order of the pulse pair with center frequencies as f1, f2, and f2, f1, then integrate the phase estimates of f1/f2 pulse pair and f2/f1 pulse pair in equal numbers. This approach will cancel the phase shift as a function of range between the pulses to enable the retrieval of Doppler phase. Although this method is more advanced, it also has its inherent limits, such as increased phase error and increased complexity in radar hardware to transmit and receive dual polarized signals. Despite its faults, it is a step forward in the evolution of the Doppler radar and its growing applications.
electrical and electronics
Spain
Using the Power Grid for Geophysical Imaging
This technology utilizes the U.S. high-voltage power transmission grid system as an extremely large antenna to extract unprecedented spatiotemporal space physical and geological information from distributed GIC observations. GICs are measured using differential a magnetometer technique involving one fluxgate magnetometer under the transmission line and another reference magnetometer station nearby. The reference station allows subtraction of the natural field from the line measurement, leaving only the GIC-related Biot-Savart field. This allows inversion of the GIC amplitude. The magnetometer stations are designed to operate autonomously. They are low-cost, enabling large scale application with a large number of measurement locations.
electrical and electronics
Radio Waves
Dynamic Range Enhancement of High-Speed Data Acquisition Systems
Electronic waveforms exist that exceed the capabilities of state-of-the-art data acquisition hardware that is commonly available. The electronic waveforms that need to be measured simultaneously contain wide bandwidth, high frequency content, a DC reference, high dynamic range, and a high crest factor. The NASA Glenn high-speed data acquisition system creates a voltage compression effect with a custom transfer function that is adapted to the voltage range, frequency bandwidth, and electrical impedance of both the test article and data acquisition device. The compression transfer function is later reversed (or decompressed) with a software algorithm to restore the original signal's voltage from the acquired data. The data is thus improved via better signal-to-noise ratio, better low-amplitude accuracy, better resolution, and preservation of high-frequency spectral content. The circuit can be realized with either passive components or both active and passive components. Either realization is specialized for the test article and data acquisition hardware. This is an early-stage technology requiring additional development. Glenn welcomes co-development opportunities.
optics
Video Acuity Measurement System
Video Acuity Measurement System
The Video Acuity metric is designed to provide a unique and meaningful measurement of the quality of a video system. The automated system for measuring video acuity is based on a model of human letter recognition. The Video Acuity measurement system is comprised of a camera and associated optics and sensor, processing elements including digital compression, transmission over an electronic network, and an electronic display for viewing of the display by a human viewer. The quality of a video system impacts the ability of the human viewer to perform public safety tasks, such as reading of automobile license plates, recognition of faces, and recognition of handheld weapons. The Video Acuity metric can accurately measure the effects of sampling, blur, noise, quantization, compression, geometric distortion, and other effects. This is because it does not rely on any particular theoretical model of imaging, but simply measures the performance in a task that incorporates essential aspects of human use of video, notably recognition of patterns and objects. Because the metric is structurally identical to human visual acuity, the numbers that it yields have immediate and concrete meaning. Furthermore, they can be related to the human visual acuity needed to do the task. The Video Acuity measurement system uses different sets of optotypes and uses automated letter recognition to simulate the human observer.
communications
Front Image
Tunable Multi-Tone, Multi-Band, High-Frequency Synthesizer
Glenn's revolutionary new multi-tone, high-frequency synthesizer can enable a major upgrade in the design of high data rate, wide-band satellite communications links, in addition to the study of atmospheric effects. Conventional single-frequency beacon transmitters have a major limitation: they must assume that atmospheric attenuation and group delay effects are constant at all frequencies across the band of interest. Glenn's synthesizer overcomes this limitation by enabling measurements to be made at multiple frequencies across the entire multi-GHz wide frequency, providing much more accurate and actionable readings. This novel synthesizer consists of a solid-state frequency comb or harmonic generator that uses step-recovery semiconductor diodes to generate a broad range of evenly spaced harmonic frequencies, which are coherent and tunable over a wide frequency range. These harmonics are then filtered by a tunable bandpass filter and amplified to the necessary power level by a tunable millimeter-wave power amplifier. Next, the amplified signals are transmitted as beacon signals from a satellite to a ground receiving station. By measuring the relative signal strength and phase at ground sites the atmospheric induced effects can be determined, enabling scientists to gather essential climate data on hurricanes and climate change. In addition, the synthesizer can serve as a wideband source in place of a satellite transponder, making it easier to downlink high volumes of collected data to the scientific community. Glenn's synthesizer enables a beacon transmitter that, from the economical CubeSat platform, offers simultaneous, fast, and more accurate wideband transmission from space through the Earth's atmosphere than has ever been possible before.
communications
Rendition of NASA's FASTSAT in orbit.
High-Speed, Low-Cost Telemetry Access from Space
NASA's SDR uses Field-Programmable Gate Array (FPGA) technology to enable flexible performance on orbit. A first-generation FM-modulated transceiver is capable of operating at up to 1 Mbps downlink and 50 kbps uplink, full duplex. An FPGA performs Reed-Solomon (255,223) encoding, decoding, and bit synchronization, providing Consultative Committee for Space Data Systems (CCSDS) and Near Earth Network (NEN) telemetry protocol compatibility. The transceiver accepts data from the onboard flight computer via a source synchronous RS422 interface. NASA's second-generation full duplex SDR, known as PULSAR (programmable ultra-lightweight system-adaptable radio, Figures 1 and 2 below) incorporates command receiver and telemetry transmitters, as well as updated processing and power capabilities. An S-band command receiver offers a max uplink data rate of 300 Kbps and built-in QPSK demodulation. X- and S-Band telemetry transmitters offer a max downlink data rate of 150 Mbps and flexible forward-error correction (FEC) using Reed-Solomon encoding (LDPC rate 7/8 and 1/2 convolution in development), and it uses QPSK modulation. The use of FEC adds an order of magnitude increase in telemetry throughput due to an improved coding gain. An onboard FPGA uses high-speed logic for uplink/downlink and encoding/decoding processes. Balloon flight testing has been conducted and is ongoing for PULSAR.
information technology and software
The Yellow Sea
MERRA/AS and Climate Analytics-as-a-Service (CAaaS)
NASA Goddard Space Flight Center now offers a new capability for meeting this Big Data challenge: MERRA Analytic Services (MERRA/AS). MERRA/AS combines the power of high-performance computing, storage-side analytics, and web APIs to dramatically improve customer access to MERRA data. It represents NASAs first effort to provide Climate Analytics-as-a-Service. Retrospective analyses (or reanalyses) such as MERRA have long been important to scientists doing climate change research. MERRA is produced by NASAs Global Modeling and Assimilation Office (GMAO), which is a component of the Earth Sciences Division in Goddards Sciences and Exploration Directorate. GMAOs research and development activities aim to maximize the impact of satellite observations in climate, weather, atmospheric, and land prediction using global models and data assimilation. These products are becoming increasingly important to application areas beyond traditional climate science. MERRA/AS provides a new cloud-based approach to storing and accessing the MERRA dataset. By combining high-performance computing, MapReduce analytics, and NASAs Climate Data Services API (CDS API), MERRA/AS moves much of the work traditionally done on the client side to the server side, close to the data and close to large compute power. This reduces the need for large data transfers and provides a platform to support complex server-side data analysesit enables Climate Analytics-as-a-Service. MERRA/AS currently implements a set of commonly used operations (such as avg, min, and max) over all the MERRA variables. Of particular interest to many applications is a core collection of about two dozen MERRA land variables (such as humidity, precipitation, evaporation, and temperature). Using the RESTful services of the Climate Data Services API, it is now easy to extract basic historical climatology information about places and time spans of interest anywhere in the world. Since the CDS API is extensible, the community can participate in MERRA/ASs development by contributing new and more complex analytics to the MERRA/AS service. MERRA/AS demonstrates the power of CAaaS and advances NASAs ability to connect data, science, computational resources, and expertise to the many customers and applications it serves.
optics
Tin Bider Crater, Algeria
High Output Maximum Efficiency Resonator (HOMER)
NASAs high performance laser has been extensively tested and analyzed to complete space-worthy Technology Readiness Level 6 (TRL-6). These tests include thermal vacuum test, vibration tests, and laser life testing. The HOMER enclosure is a pressurized vessel with sealed window and electrical feedthroughs for space. HOMERs design factors render the degradation rate to be remarkably low 100 uJ/B. These design factors being the heavy derating of the LDA drive parameters beginning of life (BOL) set point of 50 A, and 65 us in width. The other factor is the cavitys inherent large beam area, thus keeping longitudinal mode beating to a minimum, and thus peak temporal intensity spikes that can slowly pit coatings to an absolute minimum. HOMER is an oscillator only design that features an actively Q-switched cavity with an 808nm side pump Nd:YAG zig-ag slab, employing a positive branch unstable resonator and a Gaussian reflective output coupler for TEM00 far field beam quality. These cavities allow high pulse energies with beam quality and high efficiency without the need for intracavity aperture which can cause small scale self-focusing and degrading optical diffractive effects. Approximately 2-3 times the optics are typically required for an equivalent MOPA system. This important factor is critical in the instrument design phase of a flight project, when formulating the missions cost, mass, and overall hardware complexity.
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