With internal research and development (IRAD) and NASA Earth Science Technology Office (ESTO) funding, Ball Aerospace has developed the HSRL (high spectral resolution lidar) for Aerosols Winds and Clouds using the Optical Autocovariance Wind Lidar (HAWC-OAWL) – a Doppler wind lidar system to measure winds and aerosol levels from aerosol backscatter. The Doppler receiver uses a Quadrature Mach Zehnder Interferometer (QMZI) receiver that measures changes in fringe phase (e.g. Doppler induced changes in laser frequency) and fringe amplitude (illumination coherence length). Airborne flight tests in 2016 demonstrated the performance of a two-look version of the system in making line-of-sight (LOS) wind measurements and in retrieving horizontal vector wind estimates from aircraft. Subsequently, ground-tests alongside NCAR’s HSRL system providing known aerosol profiles demonstrated that the instrument performance model accurately predicts the measurement uncertainty. The system has since been reconfigured for the DC-8 aircraft to include two-looks, two-wavelengths and depolarization measurements. Current ground-based studies at Ball Aerospace are focused on demonstrating HSRL measurements with HAWC-OAWL using the QMZI ability to measure fringe amplitude as well as phase. The combined HSRL and winds measurement enables studies of aerosol transport as well as impacts of winds on cloud formations. We will review the QMZI theory and present preliminary results of HSRL data products from ground-based measurements.
We are investigating the potential of the “vortex” laser beam to provide additional information of natural scenes from aircraft and space-based lidars. This type of beam has a spatial wavefront with a helical twist that creates an optical singularity on axis, and carries orbital angular momentum. We will report on preliminary results for differences in Rayleigh-Mie scattering, and scattering from rough surfaces, and plans for future studies.
CALIPSO is a joint NASA – CNES satellite currently in its third year of operation in low earth orbit. The satellite is making optical measurements of the Earth’s atmosphere to help quantify the impact of aerosols and clouds on the Earth’s radiation budget. To do this, it carries three instruments: CALIOP, a two-wavelength polarization-sensitive elastic backscatter lidar; the IIR a three band thermal imaging radiometer; and the WFC a visible single-band imager. CALIOP utilizes a Nd:YAG laser which incorporates a harmonic crystal to provide laser light at both 1064 nm and 532 nm. This beam is expanded and transmitted into the atmosphere at near nadir. The laser light scattered from clouds and aerosols back to the satellite, along with any solar background light, is collected by a one meter diameter beryllium telescope. The captured light is separated into its two wavelengths and optically filtered. The 1064 nm component is detected with an avalanche photodiode, while the 532 nm component is further resolved into two linear polarization components which are then detected by matching photomultiplier tubes. This presentation will describe the lidar and give examples of its on-orbit performance.
Methane emissions from natural gas production, storage, and transportation are potential sources of greenhouse gas emissions. Methane leaks also constitute revenue loss potential from operations. Since 2013, Ball Aerospace has been developing advanced airborne sensors using integrated path differential absorption (IPDA) LIDAR instrumentation to identify methane, propane, and longer-chain alkanes in the lowest region of the atmosphere. Additional funding has come from the U.S. Department of Transportation, Pipeline and Hazardous Materials Administration (PHMSA) to upgrade instrumentation to a broader swath coverage of up to 400 meters while maintaining high spatial sampling resolution and geolocation accuracy. Wide area coverage allows efficient mapping of emissions from gathering and distribution networks, processing facilities, landfills, natural seeps, and other distributed methane sources. This paper summarizes the benefits of advanced instrumentation for aerial methane emission mapping, describes the operating characteristics and design of this upgraded IPDA instrumentation, and reviews technical challenges encountered during development and deployment.
To address mission risk and cost limitations the US has faced in putting a much needed Doppler wind lidar into space, Ball Aerospace and Technologies Corp, with support from NASA’s Earth Science Technology Office (ESTO), has developed the Optical Autocovariance Wind Lidar (OAWL), designed to measure winds from aerosol backscatter at the 355 nm or 532 nm wavelengths. Preliminary proof of concept hardware efforts started at Ball back in 2004. From 2008 to 2012, under an ESTO-funded Instrument Incubator Program, Ball incorporated the Optical Autocovariance (OA) interferometer receiver into a prototype breadboard lidar system by adding a laser, telescope, and COTS-based data system for operation at the 355 nm wavelength. In 2011, the prototype system underwent ground-based validation testing, and three months later, after hardware and software modifications to ensure autonomous operation and aircraft safety, it was flown on the NASA WB-57 aircraft. The history of the 2011 test flights are reviewed, including efforts to get the system qualified for aircraft flights, modifications made during the flight test period, and the final flight data results. We also present lessons learned and plans for the new, robust, two-wavelength, aircraft system with flight demonstrations planned for Spring 2016.
metrology, spectroscopy, atomic clocks and geodesy. This technology will be a key enabler to several proposed NASA science missions. Although lasers such as Q-switched Nd-YAG are now commonly used in space, other types of lasers - especially those with narrow linewidth - are still few in number and more development is required to advance their technology readiness. In this paper we discuss a reconfigurable laser frequency stabilization testbed, and end-to-end modeling to support system development. Two important features enabling testbed flexibility are that the controller, signal processing and interfaces are hosted on a field programmable gate array (FPGA) which has spacequalified equivalent parts, and secondly, fiber optic relay of the beam paths. Given the nonlinear behavior of lasers, FPGA implementation is a key system reliability aspect allowing on-orbit retuning of the control system and initial frequency acquisition. The testbed features a dual sensor system, one based upon a high finesse resonator cavity which provides relative stability through Pound-Drever-Hall (PDH) modulation and secondly an absolute frequency reference by dither locking to an acetylene gas cell (GC). To provide for differences between ground and space implementation, we have developed an end-to-end Simulink/ Matlab®-based control system model of the testbed components including the important noise sources. This model is in the process of being correlated to the testbed data which then can be used for trade studies, and estimation of space-based performance and sensitivities. A 1530 nm wavelength semiconductor laser is used for this initial work.
Analysis of data measured by the NASA Langley airborne High Spectral Resolution Lidar is presented focusing on
measurements over the ocean. The HSRL is a dual wavelength polarized system (1064 and 532 nm) with the inclusion of
a molecular backscatter channel at 532 nm. Data from aircraft flights over the Pamlico Sound out to the Atlantic Ocean,
over the Caribbean west of Barbados, and off the coast of Barrow, Alaska are evaluated. Analysis of the data
demonstrates that the molecular channel detects the presence of water due to its ability to differentiate the Brillouin-
Mandelshtam spectrum, i.e. the scattering spectrum of water, from the Rayleigh/Mie spectrum. The characteristics of the
lidar measurements over water, land, ice, and mixed ice/water surfaces are examined. Correlations of the molecular
channel lidar signals with bathymetry (ocean depth) and extraction of attenuation from the HSRL lidar measurements are
presented and contrasted with ocean color data.
Laser remote sensing of the Earth from space offers many unique capabilities stemming from the unique properties of
lasers. Lidars make possible three-dimensional characterizations that enable new scientific understanding of the natural
processes that shape the planet's oceans, surface, and atmosphere. However, the challenges to further expand on these
successes remain complex. Operation of lidars from space is limited in part by the relatively low power available to the
lasers, the low signal scattered back to the instrument because of the large distance to the surface, and the need for
reliable and autonomous operation because of the significant investment required for satellites. The instrument
complexities are compounded by the diversity in the Earth scenes as well as the variability in albedo from cloud, ice,
vegetation, desert, or ocean, combined with the highly variable transmission of the laser beam through clouds, forest
canopy, or ocean surface and near-surface. This paper will discuss the development of a new approach to space-based
lidars that uses adaptive instrument techniques to dramatically enhance the capability of space-based lidars.
The Topographic Mapping Flash Lidar (TMFL) developed at Ball Aerospace combines a pushbroom format transmitter
at 1064 nm with a flash focal plane receiver. The wide 20 degree field of view of the instrument enables broad swath
coverage from a single laser pulse without the need for a scanning mechanism. These features make the TMFL design
particularly well-suited for space flight. TMFL has been demonstrated during an airborne flight where data were
gathered over a forest plot to measure tree waveforms. Topographic maps were assembled of river beds and geologic
areas of high relief. The TMFL has also been used to observe multiple-scattering phenomena in clouds by illuminating a
steam plume from the aircraft above. Signal was recorded off-axis from the illuminated laser line by as much as 1
degree. The TMFL study of multiple-scattering is valuable as it provides a unique way to significantly improve the
calibration of measured backscatter for space lidars. Lidar backscatter was also measured from water surface and was
shown to correlate with models of water surface roughness.
Validated models describing on-orbit performance of Earth sensing instruments provide understanding of the calibration
of the instrument and insight that can be used to guide design choices for future missions. The success of the Cloud
Aerosol Lidar with Orthogonal Polarization (CALIOP) launched as part of the CALIPSO instrument suite provides an
opportunity to develop validated radiometric and integrated models of the instrument. We present validation of these
models with on-orbit data and describe how these models can be used to help define instrument requirements for future
active sensing missions that hope to capture both atmospheric and oceanographic properties. While designed for
atmospheric returns, CALIOP data includes backscatter from land, ice, and ocean surface and from beneath the ocean
surface. A radiometric model describing atmospheric returns that has been validated against CALIOP performance is
extended to include ocean subsurface returns. The model output is compared with CALIOP, aircraft lidar measurements,
and space-based ocean color measurements. This provides an opportunity to explore the value of space-based lidar
measurements to ocean measurements and to identify the impact of laser and detector design choices on the returned
lidar signal from the ocean as part of an ongoing effort to investigate oceanographic lidars.
LIDAR systems are becoming an important tool in many areas of remote data collection. Recently, BATC has applied their integrated modeling toolset, EOSyM (End-to-end Optical System Model), to development of a LIDAR system model. With the recent successful launch and deployment of the Calipso remote sensing instrument, an additional opportunity was present to develop a partially validated model from combined test data and measureables from the flight. The concept was to validate the CALIPSO system model and then use this tool to facilitate the system engineering process for future space-based designs. The system model includes the important physics of a laser, the CALIPSO optical prescription for the transmitter and receiver, thermoelastic disturbances, a simple atmospheric model, detection and signal processing of the data. This paper describes the model development process using EOSyM, some initial results with comparison to flight data and proposed future developments to expand it's use for future missions.
The CALIPSO satellite launched on April 28, 2006. It successfully entered into the Aqua (A) -train of Earth observing
satellites along with its co-manifested CloudSat satellite. CALIPSO includes a Payload built for NASA by Ball
Aerospace & Technologies Corp. The Payload includes three instruments for earth remote sensing: A two-wavelength
polarization-sensitive lidar, a visible wide-field camera (WFC), and an infrared imaging radiometer (IIR). The
commissioning and performance assessment of the satellite were successfully completed in the first ninety days after
launch. This paper highlights some of the key instrument performance measured during commissioning, focusing on the
lidar and wide-field camera.
The CALIPSO LIDAR utilizes a receiver telescope with a narrow Field-of-View (FOV) to reject background light and meet SNR requirements - FOV ≈ 130 μrad. To maximize SNR the laser is collimated (divergence ≈100 μrad) and must be aligned to the receiver telescope FOV to within +/- 12 μrad (allocated). To make accurate LIDAR measurements the receiver/laser alignment must not vary by more than +/- 10 μrad (allocated) over an orbit. To make accurate depolarization measurements of clouds, the polarization axis of the laser must be aligned to within +/- 0.5 degrees (allocated) relative to the aft optical bench polarization axis and maintain alignment throughout the motion of the boresight adjustment range. The Active Boresight Mechanism provides a means of re-aligning the laser to the telescope on-orbit. A comprehensive performance testing campaign demonstrated that the Active Boresight Mechanism met or exceeded requirements. On-orbit performance results are imminent, as CALIPSO is scheduled for launch this Fall.
IN 2005 a lidar instrument will be launched aboard the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellite for measuring the three dimensional distribution of atmospheric clouds and aerosols. A key part of the lidar instrument is a 532 nm tunable etalon, which allows daytime operation. The design rationale and measured optical performance of the etalon and its mounting sytem during assembly and integration are presented.
The CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) mission is designed to study the impact of clouds and aerosols on the Earth's radiation budget. Three instruments and their infrastructure make up the payload. They are a two-wavelength, polarization-sensitive lidar, a wide-field camera (WFC) operating at 645 nm, and a three-channel, infrared (IR), imaging radiometer (IIR) built by Sodern in France. The lidar is a follow-on to the short-duration LITE mission that flew on the shuttle.1 The lidar and WFC, built by Ball Aerospace under contract to NASA Langley Research Center, has completed its environmental and performance testing and is being integrated to the spacecraft in preparation for an April 2005 launch. This paper gives an overview of the testing and performance of this payload while being built and integrated at Ball Aerospace.
Conventional immersion aircraft thermometers suffer significant performance limitations, particularly for high- speed aircraft and at high angles-of-attack and side-slip. Moreover, immersion thermometers cannot perform through hot thick aircraft boundary layers and greatly increase the radar cross section of low observable aircraft. OPHIR Corporation has developed passive, remote-sensing thermometers which overcome these significant limitations. In addition, we have developed range-resolved radiometers to provide temperature profiles. Range resolved temperature profiles may enable Clear Air Turbulence, air density fluctuations and other flight hazards to be detected well ahead of the aircraft. A review of OPHIR's radiometer technology is presented. The fundamentals of radiant gas thermometry are introduced. Single wavelength 4.255 micrometer and 15 micrometer radiometers and range- resolved 15 micrometer radiometers are discussed as are data collected from numerous fight test programs. Finally, a laboratory demonstration of the multi-range capabilities of radiometers is discussed.
Many trace atmospheric gas constituents have optical absorption bands in the 2 - 5 micrometers atmospheric transmission window. Remote sensing of these compounds is possible with an appropriate laser source. We use stimulated Raman scattering in hydrogen to shift pulsed, Cr:LiSAF laser emission from the near infrared to this mid-infrared band. Injection seeding the oscillator with a spectrally narrow, low-power diode laser produces a tunable, spectroscopic grade source. We have combined this laser source with transmitting and receiving optics in order to make double- ended, long-path DIAL measurements. For example, we are able to detect ambient levels of water and methane and trace levels of ethane over a two mile, round-trip path. Spectral control is critical for making these measurements for several reasons. First, the DIAL technique requires a spectrally narrow source to tune across the narrow absorption bands of molecules with absorption features in the 2 - 5 micrometers band. Second, good spectral control allows species-specific detection when there are target species with closely spaced absorption features. Third, strong water vapor and CO2 absorption bands are common throughout the 2 - 5 micrometers band causing large fluctuations in the background transmission. Good spectral control enables species specific detection within this highly variable transmission background.
The increase low-frequency amplitude noise on several extended cavity diode lasers was measured when frequency of phase lock servos were applied using the injection current as the feedback channel. The AM noise increase inside the FM servo bandwidth is approximately that expected from the suppression of frequency noise uncorrelated with the inherent amplitude noise of the laser.
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