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NASA NTRS2014

Self-Raman Nd:YVO4 Laser and Electro-Optic Technology for Space-Based Sodium Lidar Instrument

We are developing a laser and electro-optic technology to remotely measure Sodium (Na) by adapting existing lidar technology with space flight heritage. The developed instrumentation will serve as the core for the planning of an Heliophysics mission targeted to study the composition and dynamics of Earth's mesosphere based on a spaceborne lidar that will measure the mesospheric Na layer. We present performance results from our diode-pumped tunable Q-switched self-Raman c-cut Nd:YVO4 laser with intra-cavity frequency doubling that produces multi-watt 589 nm wavelength output. The c-cut Nd:YVO4 laser has a fundamental wavelength that is tunable from 1063-1067 nanometers. A CW (Continuous Wave) External Cavity diode laser is used as a injection seeder to provide single-frequency grating tunable output around 1066 nanometers. The injection-seeded self-Raman shifted Nd:VO4 laser is tuned across the sodium vapor D2 line at 589 nanometers. We will review technologies that provide strong leverage for the sodium lidar laser system with strong heritage from the Ice Cloud and Land Elevation Satellite-2 (ICESat-2) Advanced Topographic Laser Altimeter System (ATLAS). These include a space-qualified frequency-doubled 9 watts-at-532-nanometer wavelength Nd:YVO4 laser, a tandem interference filter temperature-stabilized fused-silica-etalon receiver and high-bandwidth photon-counting detectors.

Krainak, Michael A.↗

NASA NTRS2014

Self-Raman Nd:YVO4 Laser and Electro-Optic Technology for Space-Based Sodium Lidar Instrument

Krainak, Michael A.↗

NASA NTRS2016

The Lick AGN Monitoring Project 2011: Spectroscopic Campaign and Emission-line Light Curves

In the Spring of 2011 we carried out a 2.5 month reverberation mapping campaign using the 3 m Shane telescope at Lick Observatory, monitoring 15 low-redshift Seyfert 1 galaxies. This paper describes the observations, reductions and measurements, and data products from the spectroscopic campaign. The reduced spectra were fitted with a multicomponent model in order to isolate the contributions of various continuum and emission-line components. We present light curves of broad emission lines and the active galactic nucleus (AGN) continuum, and measurements of the broad Hβ line widths in mean and rms spectra. For the most highly variable AGNs we also measured broad H beta line widths and velocity centroids from the nightly spectra. In four AGNs exhibiting the highest variability amplitudes, we detect anticorrelations between broad H beta width and luminosity, demonstrating that the broad-line region "breathes" on short timescales of days to weeks in response to continuum variations. We also find that broad H beta velocity centroids can undergo substantial changes in response to continuum variations; in NGC 4593, the broad H beta velocity shifted by approximately 250 km s(exp -1) over a 1 month period. This reverberation-induced velocity shift effect is likely to contribute a significant source of confusion noise to binary black hole searches that use multi-epoch quasar spectroscopy to detect binary orbital motion. We also present results from simulations that examine biases that can occur in measurement of broad-line widths from rms spectra due to the contributions of continuum variations and photon-counting noise.

galaxies: Seyfert↗

NASA NTRS2015

NGSLR Safety Handbook

NASA's Next Generation Satellite Laser Ranging (NGSLR) station is the prototype for NASA's Satellite Laser Ranging (SLR) systems which will be deployed around the world in the coming decade. The NGSLR system will be an autonomous, photon-counting SLR station with an expected absolute range accuracy of better than one centimeter and a normal point (time-averaged) range precision better than one millimeter. The system provides continuous (weather permitting), 24 hour tracking coverage to an existing constellation of approximately two dozen artificial satellites equipped with passive retroreflector arrays, using pulsed, 532 nm, class IV laser systems. Current details on the approved laser systems can be found in the Appendix 1 of this document. This safety plan addresses the potential hazards to emitted laser radiation, which can occur both inside and outside the shelter. Hazards within the shelter are mitigated through posted warning signs, activated warning lights, procedural controls, personal protective equipment (PPE), laser curtains, beam blocking systems, interlock controls, pre-configured laser control settings, and other controls discussed in this document. Since the NGSLR is a satellite tracking system, laser hazards exist outside the shelter to personnel on the shelter roof and to passing aircraft. Potential exposure to personnel outside the system is mitigated through the use of posted warning signs, access control, procedural controls, a stairwell interlock, beam attenuation/blocking devices, and a radar based aircraft detection system.

satellite laser ranging↗

NASA NTRS2015

SIMPL/AVIRIS-NG Greenland 2015: Flight Report

In August 2015, NASA conducted a two-aircraft, coordinated campaign based out of Thule Air Base, Greenland, in support of Ice, Cloud, and land Elevation Satellite‐2 (ICESat-2) algorithm development. The survey targeted the Greenland Ice Sheet and sea ice in the Arctic Ocean during the summer melt season. The survey was conducted with a photon-counting laser altimeter in one aircraft and an imaging spectrometer in the second aircraft. Ultimately, the mission, SIMPL/AVIRIS-NG Greenland 2015, conducted nine coordinated science flights, for a total of 37 flight hours over the ice sheet and sea ice.

Ice Sheet↗

NASA NTRS2015

Quantum Dots Microstructured Optical Fiber for X-Ray Detection

A novel concept for the detection of x-rays with microstructured optical fibers containing quantum dots scintillation material comprised of zinc sulfide nanocrystals doped with magnesium sulfide is presented. These quantum dots are applied inside the microstructured optical fibers using capillary action. The x-ray photon counts of these fibers are compared to the output of a collimated CdTe solid state detector over an energy range from 10 to 40 keV. The results of the fiber light output and associated effects of an acrylate coating and the quantum dots application technique are discussed.

DeHaven, S. L.↗

NASA NTRS2016

Imaging Analysis of the Hard X-Ray Telescope ProtoEXIST2 and New Techniques for High-Resolution Coded-Aperture Telescopes

Wide-field (greater than or approximately equal to 100 degrees squared) hard X-ray coded-aperture telescopes with high angular resolution (greater than or approximately equal to 2 minutes) will enable a wide range of time domain astrophysics. For instance, transient sources such as gamma-ray bursts can be precisely localized without the assistance of secondary focusing X-ray telescopes to enable rapid followup studies. On the other hand, high angular resolution in coded-aperture imaging introduces a new challenge in handling the systematic uncertainty: the average photon count per pixel is often too small to establish a proper background pattern or model the systematic uncertainty in a timescale where the model remains invariant. We introduce two new techniques to improve detection sensitivity, which are designed for, but not limited to, a high-resolution coded-aperture system: a self-background modeling scheme which utilizes continuous scan or dithering operations, and a Poisson-statistics based probabilistic approach to evaluate the significance of source detection without subtraction in handling the background. We illustrate these new imaging analysis techniques in high resolution coded-aperture telescope using the data acquired by the wide-field hard X-ray telescope ProtoEXIST2 during a high-altitude balloon flight in fall 2012. We review the imaging sensitivity of ProtoEXIST2 during the flight, and demonstrate the performance of the new techniques using our balloon flight data in comparison with a simulated ideal Poisson background.

balloons - instrumentation: detectors - techniques↗

NASA NTRS2017

Radiation and Temperature Hard Multi-Pixel Avalanche Photodiodes

The structure and method of fabricating a radiation and temperature hard avalanche photodiode with integrated radiation and temperature hard readout circuit, comprising a substrate, an avalanche region, an absorption region, and a plurality of Ohmic contacts are presented. The present disclosure provides for tuning of spectral sensitivity and high device efficiency, resulting in photon counting capability with decreased crosstalk and reduced dark current.

Bensaoula, Abdelhak↗

NASA NTRS2017

Langley Mobile Ozone Lidar: Ozone and Aerosol Atmospheric Profiling for Air Quality Research

The Langley mobile ozone lidar (LMOL) is a mobile ground-based ozone lidar system that consists of a pulsed UV laser producing two UV wavelengths of 286 and 291 nm with energy of approximately 0.2 mJ/pulse 0.2 mJ/pulse and repetition rate of 1 kHz. The 527 nm pump laser is also transmitted for aerosol measurements. The receiver consists of a 40 cm parabolic telescope, which is used for both backscattered analog and photon counting. The lidar is very compact and highly mobile. This demonstrates the utility of very small lidar systems eventually leading to space-based ozone lidars. The lidar has been validated by numerous ozonesonde launches and has provided ozone curtain profiles from ground to approximately 4 km in support of air quality field missions.

De Young, Russell↗

NASA NTRS2018

Superconducting Sensors for Microwave and Optical Photon-Starved Communications (Plenary)

NASA mission modeling indicates a desire for approximately a tenfold data improvement per decade from the Deep Space Network through the year 2040. Some of this improvement will come from aperture enhancement and antenna arraying, increased use of Ka-band over X-band, and high performance optical terminals (e.g. 12 m ground telescope). The remainder will depend on "disruptive" technologies. Deep-space communications differs from near earth communications. One way light travel times are measured in minutes rather than seconds and distances involved are large enough such that optical signals are photon limited and microwave signals have extremely low flux density. High frequency SQIF receivers and single photon detectors for optical communications will be described. Specifically, progress towards a "noiseless" receiver based on arrays of incommensurate area SQUIDs, and single photon counting detectors based on superconducting nanowires and kinetic inductance effects, will be discussed. Finally, the design of an optimal array of optical telescopes to emulate performance of a monolithic 12 m telescope will be outlined. In this case, optimal means minimizing the initial capital investment and operational cost while maintaining performance requirements of the deep-space link.

Romanofsky, Bob↗

NASA NTRS2018

Development of a Mars Lidar (MARLI) for Measuring Wind and Aerosol Profiles from Orbit

Our understanding of the Mars atmosphere and the coupled atmospheric processes that drive its seasonal cycles is limited by a lack of observation data, particularly measurements that capture diurnal and seasonal variations on a global scale. As outlined in the 2011 Planetary Science Decadal Survey and the recent Mars Exploration Program Analysis Group(MEPAG) Goals Document, near-polar-orbital measurements of height-resolved aerosol backscatter and wind profiles area high-priority for the scientific community and would be valuable science products as part of a next-generation orbital science package. To address these needs, we have designed and tested a breadboard version of a direct detection atmospheric wind lidar for Mars orbit. It uses a single-frequency, seeded Nd:YAG laser ring oscillator operating at 1064nm (4 kHz repetition rate), with a 30-ns pulse duration amplified to 4 mJ pulse energy. The receiver uses a Fabry-Perotetalon as part of a dual-edge optical discrimination technique to isolate the Doppler-induced frequency shift of the back scattered photons. To detect weak aerosol backscatter profiles, the instrument uses a 4x4 photon-counting HgCdTeAPD detector with a 7 MHz bandwidth and < 0.4 fW/Hz(exp 1/2) noise equivalent power. With the MARLI lidar breadboard instrument, we were able to measure Doppler shifts continuously between 1 and 30 m/s by using a rotating chopper wheel to impart a Doppler shift to incident laser pulses. We then coupled the transmitter and receiver systems to a laser ranging telescope at the Goddard Geophysical and Astronomical Observatory (GGAO) to measure backscatter and Doppler wind profiles in the atmosphere from the ground. We measured a 5.3 ± 0.8 m/s wind speed from clouds in the planetary boundary layer at a range of 4 to 6 km. This measurement was confirmed with a range-over-time measurement to the same clouds as well as compared to EMC meteorological models. Here we describe the lidar approach and the breadboard instrument, and report some early results from ongoing field experiments.

Cremons, Daniel R.↗

NASA NTRS2018

WFIRST CGI Integral Field Spectrograph Performance and Post-Processing in the OS6 Observing Scenario

The WFIRST coronagraph instrument (CGI) will have an integral field spectrograph (IFS) backend to disperse the entire field of view at once and obtain spatially-resolved, low-resolution spectra of the speckles and science scene. The IFS will be key to understanding the spectral nature of the speckles, obtain science spectra of planets and disks, and will be used for broadband wavefront control. In order to characterize, predict, and optimize the performance of the instrument, we present a detailed model of the IFS in the context of the new OS6 observing scenario. The simulation includes spatial, spectral, and temporal variations of the speckle field on the IFS detector plane, which allows us to explore several post-processing methods and assess what gains can be expected. The simulator includes the latest models of the detector behavior when operating in photon-counting mode.

WFIRST coronagraph instrument (CGI)↗

NASA NTRS2019

ATLAS Flight Science Receiver Algorithms

This is the basis document for the ATLAS Receiver Algorithms. ATLAS is the single instrument on the ICESat-2 mission. The Receiver (Rx) Algorithms select the signal location in real-time and instruct the hardware to telemeter a vertical band of received time-tags about this signal location. The algorithms are implemented in the Flight Software (FSW) and in the hardware of the Photon Counting Electronics (PCE) cards. The sole purpose of the algorithms is to reduce the telemetry data volume to fit within the downlink constraint while maximizing the probability of downlinking surface signal. All versions of the Receiver Algorithms from version 2.8 onward incorporate our best knowledge of the ATLAS hardware at this time. It presents algorithms that, based on current Simulator testing, satisfy all of the requirements for the Rx Algorithms. Testing during ATLAS Instrument Integration and Testing with the hardware and software implementation of the Rx Algorithms revealed characteristics and responses that required changes to the Rx Algorithms and this document, which are captured in the change record below.All relevant documentation for the Receiver Algorithms can be found on the ICESat-2 Technical Data Management System (TDMS) under the ATLAS Algorithms subsystem.The launch version of the FSW (version 3.1.0) is based upon version 3.7c of this document.

Mcgarry, Jan L.↗

NASA NTRS2019

Optical Array Versus Monolithic Telescope Ground Station Cost Assessment

The purpose of this study is to outline the design of an optimal array of optical telescopes to emulate performance of a monolithic 12 m telescope in support of deep-space communications. In this case, optimal means minimizing the initial capital investment and operational cost while maintaining performance requirements of the deep-space link. The design is approached from a practical, engineering perspective. Pulse position modulation (PPM) signal formatting and photon counting detectors are assumed at each telescope in the array. That is, the telescopes function as so-called light buckets, so direct detection (as opposed to coherent reception) of the received signals is assumed, and there is no intention to consider active compensation for atmospheric turbulence-induced phase fluctuations. A parametric analysis among aperture size, detector size, and primary mirror surface quality, in the context of field-of-view expansion, is presented to minimize the cost function.

Romanofsky, Robert R.↗

NASA NTRS2020

The Atmospheric Measurements of ICESat-2

ICESat-2 is an exciting new multi-beam, photon-counting, satellite lidar designed to acquire simultaneous high-resolution measurements of the earth's surface and atmospheric structure. Launched in September, 2018 the Advanced Topographic Lidar Altimeter System (ATLAS) on board ICESat-2 has been acquiring data continuously for nearly 1 year. The 3 laser beams comprising the atmospheric channel are providing excellent back scatter measurements that enable the retrieval of global cloud fraction, cloud and aerosol layer height, column optical depth, and blowing snow properties. Public release of the data products began with version 1in May, 2019 and continues with a significantly improved version 2 in October, 2019. This presentation will give an overview of the ICESat-2 atmospheric channel and show examples of cloud, aerosol and blowings now properties as well as comparisons of ATLAS and CALIOP measurements.

Palm, Stephen↗

NASA NTRSDate not supplied

The ICESat-2 Mission: Land, Ocean, and Inland Water Data Products for Middle and Low Latitude Science and Applications

NASA’s Ice, Cloud, and Land Elevation Satellite (ICESat-2) is a polar orbiting mission, launched on September 15, 2018, with over two years of nearly continuous observations. The sole instrument onboard is the Advanced Topographic Laser Altimeter System (ATLAS), a micropulse, high repetition rate, six-beam, 532 nm Lidar with photon-counting technology. Although designed primarily for detecting height changes in ice caps and sea ice in the high latitudes, it continuously observes all terrain in its track including middle and low latitude regions as well, during approximately 15 orbits per day. The official ICESat-2 products include not only cryosphere data but also global high resolution parameters associated with tree canopies, land surface, oceans, and over 1.5 million inland water bodies consisting of lakes, rivers and coastal waters. This presentation provides an overview and the status of the ICESat-2 mission including: i) a summary of the salient technological features and orbit design, ii) the official ICESat-2 science data products for ice, vegetation canopy, ocean sea level, and inland water including several examples in the middle and low latitudes, iii) a list of NASA sponsored software tools for globally browsing the two year archive and for processing both the raw data and the official ICESat-2 geophysical data products, and iv) avenues for interested users to connect with the ICESat-2 Applications Program for answering questions and assistance in possibly using ICESat-2 data in your particular science or application. The overall goal is to facilitate the use of ICESat-2 data not only for science investigations but also for improved decision support applications with societal benefit. Additional ICESat-2 information, documentation and data products are publicly available at https://nsidc.org/data/icesat-2

ICESat-2↗

NASA NTRS2002

Superconducting kinetic inductance photon detectors.

We are investigating a novel superconducting detector and readout method that could lead to photon counting, energy resolving focal plane arrays. This concept is intrinsically different from STJ and TES detectors, and in principle could deliver large pixel counts, high sensitivity, and Fano-limited spectral resolution in the ptical/UV/X-ray bands. The readout uses the monotonic relation between the kinetic surface inductance L***subs***, of a superconductor and the density of quasiparticles n, which holds even at temperatures far below T***subc***. This allows a sensitive readout of the number of excess quasiparticles in the detector by monitoring the transmission phase of a resonant circuit. The most intriguing aspect of this concept is that passive frequency multiplexing could be used to read out ~ l0***super4*** detectors with a single HEMT amplifier. Single x-ray events have been observed in prototype detectors.

kinetic↗

NASA NTRS2017

ExEP Yield Modeling Tool and Validation Test Results

EXOSIMS is an open-source simulation tool for parametric modeling of the detection yield and characterization of exoplanets. EXOSIMS has been adopted by the Exoplanet Exploration Programs Standards De nition and Evaluation Team (ExSDET) as a common mechanism for comparison of exoplanet mission concept studies. To ensure trustworthiness of the tool, we developed a validation test plan that leverages the Python-language unit-test framework, utilizes integration tests for selected module interactions, and performs end-to-end cross- validation with other yield tools. This paper presents the test methods and results, with the physics-based tests such as photometry and integration time calculation treated in detail and the functional tests treated summarily. The test case utilized a 4m unobscured telescope with an idealized coronagraph and an exoplanet population from the IPAC radial velocity (RV) exoplanet catalog. The known RV planets were set at quadrature to allow deterministic validation of the calculation of physical parameters, such as working angle, photon counts and integration time. The observing keepout region was tested by generating plots and movies of the targets and the keepout zone over a year. Although the keepout integration test required the interpretation of a user, the test revealed problems in the L2 halo orbit and the parameterization of keepout applied to some solar system bodies, which the development team was able to address. The validation testing of EXOSIMS was performed iteratively with the developers of EXOSIMS and resulted in a more robust, stable, and trustworthy tool that the exoplanet community can use to simulate exoplanet direct-detection missions from probe class, to WFIRST, up to large mission concepts such as HabEx and LUVOIR.

Nunez, Paul↗