Engineering Papers⌕ Search

Engineering topics

Singh, Upendra N.

Publications and source records attributed to Singh, Upendra N..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2019

Laser Energy Monitor for Triple-Pulse 2-μm IPDA Lidar Application

Integrated path differential absorption (IPDA) lidar is an active remote sensing technique for monitoring different atmospheric species. The technique relies on wavelength differentiation between strong and weak absorbing features normalized to the transmitted energy. An advanced 2-μm triple-pulse IPDA lidar was developed at NASA Langley Research Center for active sensing of carbon dioxide and water vapor simultaneously. The IPDA transmitter produces three successive laser pulses separated by a short interval (200 μs) with a repetition rate of 50Hz. Measurement of laser pulse energy accurately is a prerequisite for the retrieval of gas mixing ratios from IPDA. The design and calibration of a 2-μm triple-pulse laser energy monitor are presented. Due to the short interval between the three transmitted pulses, conventional thermal energy monitors underestimate the total transmitted energy. The design is based on a high speed, extended range InGaAs pin quantum detector suitable for separating the three pulse events. Pulse integration is applied for converting the detected pulse power into energy. The results obtained from the laser energy monitor were compared to an ultra-fast energy-meter reference for energy scaling and verification. High correlations between the pin energy monitor and the total transmitted energy were obtained. The objective of this development is to reduce measurement biases and errors using the triple-pulse IPDA technique.

Refaat, Tamer F.↗
NASA NTRS2019

Active Optical Remote Sensing Sensors and Instrumentation for NASA’s Future Earth and Space Science Measurements/Missions

Abstract—Active optical (Laser/Lidar) measurement techniques are critical for the future National Aeronautics and Space Administration (NASA) Earth, Planetary Science, Exploration, and Aeronautics measurements. The latest science decadal surveys recommend a number of missions requiring active optical systems to meet the science measurement objectives and the aeronautics community continues to use Laser/Lidar technologies to meet the aeronautics measurement objectives. This presentation will provide an overview of NASA efforts in developing and maturing state-of-the-art advanced solid-state flight laser/lidar systems for airborne and space-borne remote sensing measurements. The presentation will also provide details of a strategic approach for active optical technologies and techniques to meet the NASA’s future Earth and Space Science measurement ments for space-based applications.

Singh, Upendra N.↗
NASA NTRS2019

Frequency Control of Multi-Pulse 2-micron Laser Transmitter for Atmospheric Carbon Dioxide Measurement

Laser sources with highly stabilized emission wavelength is of paramount importance for a long term atmospheric carbon dioxide (CO2) measurement from a space platform. Integrated Path Differential Absorption (IPDA) lidar is a promising instrument for such a task. The design of a laser transmitter, with emphasis on the method used to control and select several wavelengths, is presented. This multi-pulsed, injection seeded, 2-μm transmitter uses a Ho:Tm:YLF laser crystal which has matching emission to the absorption of CO2 in the R30 spectroscopic area. The injection seeded laser produces triple single longitudinal mode transform limited line width pulses with a total of 80 mJ at a repetition rate of 50 Hz.

Petros, Mulugeta↗
NASA NTRS2019

Ground Testing of 2-µm Triple-Pulse IPDA Lidar for Carbon Dioxide and Water Vapor Measuremets

A triple-pulse, 2-µm, Integrated Path Differential Absorption (IPDA) lidar was developed at NASA Langley Research Center. This active remote sensing instrument provides a technique for measuring atmospheric carbon dioxide and water vapor simultaneously and independently. A 2-µm high-energy pulsed laser is incorporated for the IPDA transmitter, which provides high signal-to-noise ratio measurements using a commercial direct detection system. This results in a high-precision measurement capability for the low troposphere weighted-average column dry-air volume mixing ratio of the gases. Recent IPDA ground testing indicated carbon dioxide and water vapor measurements sensitivities of 8% and 14%, respectively and biases of 0.1%. However, using the R30 centerline position for the on-line enhances the CO2 measurement sensitivity to 0.6%.

Refaat, Tamer F.↗
NASA NTRS2018

MCT Avalanche Photodiode Detector for Two-Micron Active Remote Sensing Applications

Mercury Cadmium Telluride electron initiated avalanche photodiodes demonstrated a breakthrough in lidar active remote sensing technology. A lidar detection system, based on an array of these devices, was integrated and characterized for 2-μm applications. Characterization experiments were focused on evaluating the dark current, gain and responsivity variations with bias voltage. Quantum efficiency and input dynamic range including noise-equivalent-power and maximum detectable power, were calculated from these results. Operating the detection system using four pixels at 77.6 K, 12 V bias resulted in a current responsivity of 615.8 A/W and a voltage responsivity of 1.45 GV/W. Minimum detectable power of 14 pW was obtained, which is equivalent to 5.7 fW/Hz(exp 1/2) noise-equivalent-power, indicating an average noise-equivalent-power of 1.4 fW/Hz(exp 1/2) per pixel. Work is in progress to integrate and validate this detection system using a newly developed triple-pulse integrated path differential absorption lidar for simultaneous and independent atmospheric measurements of water vapor and carbon dioxide.

Refaat, Tamer F.↗
NASA NTRS2018

Water Vapor Column Measurements with Infrared Active Optical IPDA Lidar

Development of a novel triple-pulsed 2-μm direct detection Integrated Path Differential Absorption (IPDA) lidar to measure column average carbon dioxide (XCO2) and water vapor (XH2O) from an airborne platform provides a new tool to advance atmospheric science studies. Column water vapor measurements are used in global mapping of weather fronts, weather forecast, and in studies of atmospheric transport, radiation, clouds and climate. Water vapor interference is source of biases in XCO2 measurements due to overlap in absorption, line broadening, and retrieval of dry air mixing of carbon dioxide. Model calculations show a XH2O measurement capability of 0.5% accuracy over 1.0 km spatial scales from the NASA B-200 aircraft. Ground testing of the integrated IPDA was in progress during December 2017-January 2018, and airborne measurements and validation of XH2O measurements over land and ocean are planned during January-February 2018. Technology developments in the measurement of XH2O are presented along with performance projections, and results from ground and airborne testing and validations in this paper.

Singh, Upendra N.↗
NASA NTRS2018

Airborne, Direct-Detection, 2-μm Triple-Pulse IPDA Lidar for Simultaneous and Independent Atmospheric Water Vapor and Carbon Dioxide Active Remote Sensing

Atmospheric water vapor and carbon dioxide are important greenhouse gases that significantly contribute to the global radiation budget on Earth. A 2-micron triple-pulse, Integrated Path Differential Absorption (IPDA) lidar instrument for ground and airborne atmospheric carbon dioxide and water vapor concentration measurements using direct detection was developed at NASA Langley Research Center. This active remote sensing instrument provides an alternate approach with significant advantages for measuring atmospheric concentrations of the gases. A high energy pulsed laser transmitter approach coupled with sensitive receiver detection provides a high-precision measurement capability by having a high signal-to-noise ratio. This paper presents the concept, development, integration and testing of the 2-micron triple-pulse IPDA. The integration includes the various IPDA transmitter, receiver and data acquisition subsystems and components. Ground and airborne testing indicated successful operation of the IPDA lidar.

Refaat, Tamer F.↗
NASA NTRS2018

Evaluation of 2-μm Pulsed Integrated Path Differential Absorption Lidar for Carbon Dioxide Measurement—Technology Developments, Measurements, and Path to Space

The societal benefits of understanding climate change through the identification of global carbon dioxide sources and sinks led to the recommendation for NASA's Active Sensing of Carbon Dioxide Emissions over Nights, Days, and Seasons space-based mission for global carbon dioxide measurements. For more than 15 years, the NASA Langley Research Center has developed several carbon dioxide active remote sensors using the differential absorption lidar technique operating at 2-μm wavelength. Recently, an airborne double-pulsed integrated path differential absorption lidar was developed, tested, and validated for atmospheric carbon dioxide measurement. Results indicated 1.02% column carbon dioxide measurement uncertainty and 0.28% bias over the ocean. Currently, this technology is progressing toward triple-pulse operation targeting both atmospheric carbon dioxide and water vapor-the dominant interfering molecule on carbon dioxide remote sensing. Measurements from the double-pulse lidar and the advancement of the triple-pulse lidar development are presented. In addition, measurement simulations with a space-based IPDA lidar, incorporating new technologies, are also presented to assess feasibility of carbon dioxide measurements from space.

Singh, Upendra N.↗
NASA NTRS2017

Triple-Pulse Integrated Path Differential Absorption Lidar for Carbon Dioxide Measurement - Novel Lidar Technologies and Techniques with Path to Space

The societal benefits of understanding climate change through identification of global carbon dioxide sources and sinks led to the desired NASA's active sensing of carbon dioxide emissions over nights, days, and seasons (ASCENDS) space-based missions of global carbon dioxide measurements. For more than 15 years, NASA Langley Research Center (LaRC) have developed several carbon dioxide active remote sensors using the differential absorption lidar (DIAL) technique operating at the two-micron wavelength. Currently, an airborne two-micron triple-pulse integrated path differential absorption (IPDA) lidar is under development. This IPDA lidar measures carbon dioxide as well as water vapor, the dominant interfering molecule on carbon dioxide remote sensing. Advancement of this triple-pulse IPDA lidar development is presented.

Singh, Upendra N.↗
NASA NTRS2017

Novel Technique and Technologies for Active Optical Remote Sensing of Greenhouse Gases

The societal benefits of understanding climate change through identification of global carbon dioxide sources and sinks led to the desired NASA's active sensing of carbon dioxide emissions over nights, days, and seasons (ASCENDS) space-based missions of global carbon dioxide measurements. For more than 15 years, NASA Langley Research Center (LaRC) have developed several carbon dioxide active remote sensors using the differential absorption lidar (DIAL) technique operating at the two-micron wavelength. Currently, an airborne two-micron triple-pulse integrated path differential absorption (IPDA) lidar is under development. This IPDA lidar measures carbon dioxide as well as water vapor, the dominant interfering molecule on carbon dioxide remote sensing. Advancement of this triple-pulse IPDA lidar development is presented.

Singh, Upendra N.↗
NASA NTRS2016

Airborne Lidar for Simultaneous Measurement of Column CO2 and Water Vapor in the Atmosphere

The 2-micron wavelength region is suitable for atmospheric carbon dioxide (CO2) measurements due to the existence of distinct absorption feathers for the gas at this particular wavelength. For more than 20 years, researchers at NASA Langley Research Center (LaRC) have developed several high-energy and high repetition rate 2-micron pulsed lasers. This paper will provide status and details of an airborne 2-micron triple-pulse integrated path differential absorption (IPDA) lidar. The development of this active optical remote sensing IPDA instrument is targeted for measuring both CO2 and water vapor (H2O) in the atmosphere from an airborne platform. This presentation will focus on the advancement of the 2-micron triple-pulse IPDA lidar development. Updates on the state-of-the-art triple-pulse laser transmitter will be presented including the status of seed laser locking, wavelength control, receiver telescope, detection system and data acquisition. Future plans for the IPDA lidar system for ground integration, testing and flight validation will also be presented.

Singh, Upendra N.↗
NASA NTRS2016

Development of an Airborne Triple-Pulse 2-Micron Integrated Path Differential Absorption Lidar (IPDA) for Simultaneous Airborne Column Measurements of Carbon Dioxide and Water Vapor in the Atmosphere

This presentation will provide status and details of an airborne 2-micron triple-pulse integrated path differential absorption (IPDA) lidar being developed at NASA Langley Research Center with support from NASA ESTO Instrument Incubator Program. The development of this active optical remote sensing IPDA instrument is targeted for measuring both atmospheric carbon dioxide and water vapor in the atmosphere from an airborne platform. This presentation will focus on the advancement of the 2-micron triple-pulse IPDA lidar development. Updates on the state-of-the-art triple-pulse laser transmitter will be presented including the status of seed laser locking, wavelength control, receiver and detector upgrades, laser packaging and lidar integration. Future plan for IPDA lidar system for ground integration, testing and flight validation will also be presented.

Singh, Upendra N.↗
NASA NTRS2016

Wavelength Locking to CO2 Absorption Line-Center for 2-Micron Pulsed IPDA Lidar Application

An airborne 2-micron triple-pulse integrated path differential absorption (IPDA) lidar is currently under development at NASA Langley Research Center (LaRC). This IPDA lidar system targets both atmospheric carbon dioxide (CO2) and water vapor (H2O) column measurements. Independent wavelength control of each of the transmitted laser pulses is a key feature for the success of this instrument. The wavelength control unit provides switching, tuning and locking for each pulse in reference to a 2-micron CW (Continuous Wave) laser source locked to CO2 line-center. Targeting the CO2 R30 line center, at 2050.967 nanometers, a wavelength locking unit has been integrated using semiconductor laser diode. The CO2 center-line locking unit includes a laser diode current driver, temperature controller, center-line locking controller and CO2 absorption cell. This paper presents the CO2 center-line locking unit architecture, characterization procedure and results. Assessment of wavelength jitter on the IPDA measurement error will also be addressed by comparison to the system design.

Refaat, Tamer F.↗
NASA NTRS2016

2-Micron Triple-Pulse Integrated Path Differential Absorption Lidar Development for Simultaneous Airborne Column Measurements of Carbon Dioxide and Water Vapor in the Atmosphere

For more than 15 years, NASA Langley Research Center (LaRC) has contributed in developing several 2-micron carbon dioxide active remote sensors using the DIAL technique. Currently, an airborne 2-micron triple-pulse integrated path differential absorption (IPDA) lidar is under development at NASA LaRC. This paper focuses on the advancement of the 2-micron triple-pulse IPDA lidar development. Updates on the state-of-the-art triple-pulse laser transmitter will be presented including the status of wavelength control, packaging and lidar integration. In addition, receiver development updates will also be presented, including telescope integration, detection systems and data acquisition electronics. Future plan for IPDA lidar system for ground integration, testing and flight validation will be presented.

Singh, Upendra N.↗
NASA NTRS2015

Double-Pulsed 2-Micrometer Lidar Validation for Atmospheric CO2 Measurements

A double-pulsed, 2-micron Integrated Path Differential Absorption (IPDA) lidar instrument for atmospheric carbon dioxide (CO2) measurements is successfully developed at NASA Langley Research Center (LaRC). Based on direct detection technique, the instrument can be operated on ground or onboard a small aircraft. Key features of this compact, rugged and reliable IPDA lidar includes high transmitted laser energy, wavelength tuning, switching and locking, and sensitive detection. As a proof of concept, the IPDA ground and airborne CO2 measurement and validation will be presented. IPDA lidar CO2 measurements ground validation were conducted at NASA LaRC using hard targets and a calibrated in-situ sensor. Airborne validation, conducted onboard the NASA B-200 aircraft, included CO2 plum detection from power stations incinerators, comparison to in-flight CO2 in-situ sensor and comparison to air sampling at different altitude conducted by NOAA at the same site. Airborne measurements, spanning for 20 hours, were obtained from different target conditions. Ground targets included soil, vegetation, sand, snow and ocean. In addition, cloud slicing was examined over the ocean. These flight validations were conducted at different altitudes, up to 7 km, with different wavelength controlled weighing functions. CO2 measurement results agree with modeling conducted through the different sensors, as will be discussed.

Singh, Upendra N.↗
NASA NTRS2015

Self-Calibration and Laser Energy Monitor Validations for a Double-Pulsed 2-Micron CO2 Integrated Path Differential Absorption Lidar Application

Double-pulsed 2-micron integrated path differential absorption (IPDA) lidar is well suited for atmospheric CO2 remote sensing. The IPDA lidar technique relies on wavelength differentiation between strong and weak absorbing features of the gas normalized to the transmitted energy. In the double-pulse case, each shot of the transmitter produces two successive laser pulses separated by a short interval. Calibration of the transmitted pulse energies is required for accurate CO2 measurement. Design and calibration of a 2-micron double-pulse laser energy monitor is presented. The design is based on an InGaAs pin quantum detector. A high-speed photo-electromagnetic quantum detector was used for laser-pulse profile verification. Both quantum detectors were calibrated using a reference pyroelectric thermal detector. Calibration included comparing the three detection technologies in the single-pulsed mode, then comparing the quantum detectors in the double-pulsed mode. In addition, a self-calibration feature of the 2-micron IPDA lidar is presented. This feature allows one to monitor the transmitted laser energy, through residual scattering, with a single detection channel. This reduces the CO2 measurement uncertainty. IPDA lidar ground validation for CO2 measurement is presented for both calibrated energy monitor and self-calibration options. The calibrated energy monitor resulted in a lower CO2 measurement bias, while self-calibration resulted in a better CO2 temporal profiling when compared to the in situ sensor.

Refaat, Tamer F.↗