2017 ACT Projects Announced
12 Projects Awarded Funding Under the Advanced Component Technology (ACT) Program (2017 ROSES A.48 Solicitation NNH17ZDA001N-ACT Research Opportunities in Space and Earth Sciences)
10/19/2017 – NASA’s Science Mission Directorate, NASA Headquarters, Washington, DC, has selected proposals for the Advanced Component Technology Program (ACT-17) in support of the Earth Science Division (ESD). The ACT-17 supports the development of instrument component and subsystem technologies addressing any of the science focus areas in NASA’s Earth Science program.
The ESD is awarding 12 proposals, for a total dollar value over a three-year period of approximately $14 million, through the Earth Science Technology Office located at NASA Goddard Space Flight Center, Greenbelt, MD.
The Advanced Component Technology (ACT) program seeks proposals for technology development activities leading to new component and subsystem-level airborne and space-based measurement techniques to be developed in support of the Science Mission Directorate’s Earth Science Division. The objectives of the ACT program are to research, develop, and demonstrate component- and subsystem-level technology development that:
- Enable new Earth observation measurements.
- Reduce the risk, cost, size, volume, mass, and development time of Earth observing instruments.
The ACT program brings instrument components to a maturity level that allows their integration into other NASA technology programs such as the Instrument Incubator Program. Some of these components are directly infused into mission designs by NASA flight projects and others “graduate” to other technology development programs for further development.
Eighty-Eight ACT-17 proposals were evaluated of which 12 have been selected for award. The awards are as follows (names link to project abstracts):
| Christopher Beaudoin, University of Massachusetts, Lowell Geodetic Reference Instrument Transponder for Small Satellites (GRITSS) |
| Igor Bendoym, Phoebus Optoelectronics Metamaterial-Based, Low SWaP, Robust and High Performance Hyperspectral Sensor for Land and Atmospheric Remote Sensing |
| Nacer Chahat, Jet Propulsion Laboratory Planar Metasurface Reconfigurable W-Band Antenna for Beam Steering |
| William Deal, Northrop Grumman Systems Corporation Integrated Receiver and Switch Technology (IRaST) |
| Tso Yee Fan, Massachusetts Institute of Technology/Lincoln Laboratory Laser Transmitter for Space-Based Water Vapor Lidar |
| James Garrison, Purdue University P/I Band Multi-Frequency Reflectometry Antenna for a U-Class Constellation |
| Sarath Gunapala, Jet Propulsion Laboratory Very Long Wavelength Infrared Focal Plane Arrays for Earth Science Applications |
| Jonathan Klamkin, University of California, Santa Barbara IMPRESS Lidar: Integrated Micro-Photonics for Remote Earth Science Sensing Lidar |
| Adam Milstein, Massachusetts Institute of Technology/Lincoln Laboratory Computational Reconfigurable Imaging Spectrometer (CRISP) |
| Jeffrey Piepmeier, Goddard Space Flight Center Correlator Array-Fed Microwave Radiometer Component Technologies |
| John Smith, Langley Research Center Advanced Photon-Counting Detector Subsystem for Spaceborne Lidar Applications |
| Michelle Stephens, National Institute of Standards & Technology A Black Array of Broadband Absolute Radiometers (BABAR) for Spectral Measurements of the Earth |
Christopher Beaudoin, University of Massachusetts, Lowell
Geodetic Reference Instrument Transponder for Small Satellites (GRITSS)
Background: In support of NASA’s Earth Surface and Interior (ESI) focus area, the Terrestrial Reference Frame (TRF) is the foundation for virtually all airborne, space- based, and ground-based Earth observations. This frame is developed by combining the observations from Satellite Laser Ranging (SLR), Very Long Baseline Interferometry (VLBI), the Global Navigation Satellite System (GNSS), and Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) stations, and is realized as an international standard through the International Terrestrial Reference Frame (ITRF). Combining the different measurement techniques is only possible with accurate knowledge of the relative measurement reference points between co-located systems, and doing so is essential to take full advantage of the strengths of each technique. Currently, the ITRF is limited in accuracy by systematic errors in tying together the contributions from the different geodetic techniques. Since standard ground-based surveys providing ties between geodetic techniques have reached the limit of their capabilities, a new approach is required that extends technique ties into space.
Major goals: We propose to develop a new space flight instrument and verify a measurement concept that enables the determination of systematic errors between the VLBI, GNSS, and SLR independent measurement techniques by extending surveying techniques out to spaceflight assets. The proposed instrument, functioning as a GNSS L- to-X-band transponder, establishes frequency compatibility between VLBI and GNSS, thereby facilitating a direct space-based geodetic tie between these two radio-based techniques in post-processing. Separate laser retro-reflectors flown concurrently with GRITSS would provide additional connection to the SLR network. Because the measurement concept by which the VLBI/GNSS systematic errors will be determined only requires one VLBI station to observe the space vehicle, the space vehicle may be in Low-Earth Orbit. This is advantageous as it opens up the possibility of using inexpensive CubeSats or other small satellites, making it possible to implement a cost-effective constellation of spacecraft to provide better global coverage and further improve the accuracy of the geodetic site ties.
Specific tasks:
1) Develop modified version of an existing space flight GNSS receiver to support GNSS relaying functionality
Procure commercial space flight UHF (low data rate), S, and X-band (high data rate) digital data transmitters.
2) Design and fabricate a fit-form-function instrument capable of being implemented within a Cubesat/Small Satellite.
3) Bench test breadboard concept of GNSS-to-VLBI transponder with GNSS synthetic signal generators and space vehicle GNSS receivers.
4) Bench test breadboard concept of GNSS-to-VLBI transponder with GNSS synthetic signal generators and space vehicle GNSS receivers.
5) On sight ground test of GNSS-to-VLBI transponder at Goddard Geophysical Astronomical Observatory.
6) Airborne flight test evaluation of GNSS-to-VLBI transponder at Goddard Geophysical Astronomical Observatory.
Igor Bendoym, Phoebus Optoelectronics
Metamaterial-Based, Low SWaP, Robust and High Performance Hyperspectral Sensor for Land and Atmospheric Remote Sensing
Our primary objective is to develop a hyperspectral imaging technology, the Metamaterial Spectrometer (MS), which minimizes the tradeoffs between performance and the size, weight, and power (SWaP). Our MS technology provides a competitive advantage over conventional optical systems, by enabling the sensor to be more narrowly targeted the spectral bands of interest for measuring trace gases and aerosols in the earth’s atmosphere. Additional objectives that will be met are:
1. Demonstrate a SWaP reduction relative to current hyperspectral systems.
2. Demonstrate improved spectroscopic performance relative to current systems.
3. Produce sensor datasets to quantify atmospheric constituents, or spectral indices for land and vegetation characterization.
4. Produce sensor datasets of gases relevant to earth science measurements of the atmosphere.
5. Minimize the total cost of the hyperspectral sensing system, while maintaining state-of-the-art performance.
6. Demonstrate reduction in data processing times, as a result of spectral channel optimization and bandwidth performance of the metamaterial.
7. Provide a framework and testing platform, to tailor future iterations of the technology to specific sensing missions.
8. Develop the fundamental concepts of the technology to expand it to other spectral bands, from the visible to the LWIR.
The anticipated benefits of the proposed technology are:
1. Incorporating many pixel-scale filters eliminates the need for a dispersive element within the system.
2. Selectable channels with varying passbands measure only desired channels, shrinking detector, electronics, and data rate needs.
3. Compatibility with fast optical systems makes best use of available signal, minimizing aperture size for a given measurement performance.
4. Enable hyperspectral filtering technology to be used with miniature space platforms such as CubeSats.
5. Provide a flexible and cost-minded hyperspectral imaging platform for a variety of spectral bands.
6. Extend the MS technology for use in space-based applications such as long-range laser communication.
The outline for the proposed work and methodology is as follows:
1. Simulate the MS filter design, from the unit cell to the finite scale structures, using industry standard electromagnetic simulation software, to optimize in-band transmission and out-of-band rejection.
2. Fabricate optimized designs using standard CMOS micro-fabrication technologies.
3. Optically characterize fabricated test structures, and compare performance to simulated predictions.
4. Use optical characterization data to refine simulations, optimize designs, fabricate improved test structures, and repeat optical tests.
5. Iterate step 4 until test structures demonstrate performance required for a prototype level device.
6. Fabricate and optically characterize the full prototype filter as a standalone device.
7. Integrate the MS filter into a complete optical system for more in-depth, system- level testing (to be performed by our industry partner.)
8. Quantify relevant performance data of the prototype system, and estimate the improvement to earth science measurements.
Period of performance: 3 years; Entry TRL 2, Exit TRL 5
Nacer Chahat, Jet Propulsion Laboratory
Planar Metasurface Reconfigurable W-Band Antenna for Beam Steering
In general, radar and radiometer instruments for Earth Science measurements need a scanning antenna capability. Mechanical conical scanning is suitable for certain applications, but not cloud and precipitation vertical profiling. At W-band technologies to achieve electronic scanning are being developed but require a phased array feed + reflector solution which is not well suited for very small platforms where it is necessary to launch with a stowed configuration and deploy in space. We propose to develop Planar Metasurface Reconfigurable Antenna with electronic beam Steering capability (PMRSA). PMRSA do not require the use of a feed at the focal point; they are compact and flat, the feed point is in the middle of a very thin planar surface. They are therefore ideally shaped for panel-folding in Cubesats. For proof-of-concept demonstration, we will design and develop a W-band PMRSA and show its scanning capabilities over a wide range of scanning angles.
William Deal, Northrop Grumman Systems Corporation
Integrated Receiver and Switch Technology (IRaST)
Northrop Grumman Corporation (NGC) with the Jet Propulsion Laboratory (JPL) propose development in two technical areas for this ACT – Integrated Receiver and Switch Technology (IRaST):
1) A highly integrated heterodyne receiver capable of simultaneously observing the 424 GHz oxygen band and the 448 GHz water vapor band
2) Submillimeter wave switch technology using InP HEMT to allow 1/f noise reduction in front-end Low Noise Amplifiers (LNAs) integrated onto the same integrated circuit (IC)
Both developments will be done on NGC InP 25nm HEMT technology by designing and processing a dedicated foundry run for this project. NGC and JPL will work closely on the design of the components, packaging and testing, and analysis of the radiometric characteristics.
IRaST is expected to have significant benefits for atmospheric science. The integrated receiver for temperature and water vapor profiling of the upper atmosphere will provide detailed information of the atmosphere between 6 to 16 km in tropical atmosphere and will increase nadir resolution and will reduce aperture size when used for limb sounding. The integrated switch technology will improve cloud ice measurements by reducing the 1/f noise contribution in low DC power direct detection receivers being developed on TWICE and intended for application to ENTICE.
Application of 25 nm InP HEMT technology to both of these problems will provide a scientific solution with considerable benefits over existing technologies in terms of Size, Weight, and Power (SWaP) enabled both by the high level of integration which is bought by MMIC technology and DC power savings. We estimate the upper atmosphere temperature and water vapor profiling receiver to consume approximately 1 W of DC power excluding the X-Band LO. 660 GHz direct detection receivers consume approximately 120 mW, compared to 6-10 W of DC power consumed by a heterodyne receiver in GaAs Schottky technology. Therefore, both of these technologies are ideal CubeSat applications.
The upper atmospheric temperature and humidity sounding receiver will be developed by JPL using proven models for 25 nm InP HEMT provided by NGC. Two full design iterations will be completed by JPL, along with corresponding design, layout, component measurements, and receiver validation. Development will start from LNA’s developed on IRAD. The LNA will be integrated with an I-Q mixer which will allow separation of both the 424 GHz oxygen line and the 448 GHz water vapor line.
The integrated Dicke switches will be developed by NGC using IRAD designs which have already been analyzed and layouts created. NGCs second design iteration will be aided by device modeling. The Dicke switches will be combined with existing direct detection receivers and radiometric performance will be evaluated. Impact to receiver sensitivity will be managed by placing an additional balanced LNA in front of the Dicke switch. This technique has been proven at W-Band and reduces the 1/f noise contribution of the additional LNA. Two MMIC design iterations are budgeted in NGC’s 25 nm InP HEMT process.
The Period of Performance (PoP) for IRaST is 24 months. This allows time for the two full design iterations, wafer processing, and receiver validation.
With the underlying semiconductor technology already in existence, and models showing the feasibility of the proposed IRaST tasks, entry TRL level is TRL2. IRaST will complete with packaged receiver measurements in a laboratory environment. Therefore, exit TRL is TRL4. This represents a two level TRL increase over a two year period.
Tso Yee Fan, Massachusetts Institute of Technology/Lincoln Laboratory
Laser Transmitter for Space-Based Water Vapor Lidar
Water vapor (WV) lies at the heart of most key atmospheric processes. Humidity is essential for the development of severe weather, it influences, directly and indirectly through cloud formation, the planetary radiative balance, and it influences atmospheric dynamics, surface fluxes and soil moisture. Despite its central importance, research to date has not led to a universally accepted picture of the factors controlling WV amount, a solid understanding of the mechanisms by which it influences atmospheric processes, or even precise knowledge of its concentrations in many parts of the atmosphere.
A future satellite-based WV Differential Absorption Lidar (DIAL) would revolutionize weather and climate research by providing high-resolution and accurate WV profiles with global coverage. Passive microwave and IR measurements are the backbone of weather and climate research but have significant limitations. Passive measurements are weighted toward the upper troposphere and hence have very little sensitivity near the surface where the majority of WV and its largest spatial and temporal gradients reside. Passive sounders also suffer from coarse vertical resolution and unknown biases resulting from aerosol and cloud contamination. The DIAL approach is self-calibrating, and its measurement uncertainties can be precisely quantified and traded by adapting the spatial resolution to the defined scientific objective. Furthermore, the DIAL approach can overcome one of the largest shortcomings of current passive measurements by adjusting the measurement sensitivity to near-surface atmosphere to capture the moisture variability above and through the boundary layer, in the presence of intervening cloud and aerosol layers in order to improve our understanding of fundamental mechanisms driving convection and cloud microphysics.
Conventional WV DIAL lasers are inadequate for space-based operation as they are inefficient, complex, and have low average power, which limits precision and spatial resolution. We propose to build a WV DIAL laser transmitter to enable WV DIAL measurements throughout the troposphere from a space-based platform. The transmitter will probe an atmospheric WV absorption line near 816 nm, allowing for profile measurements of WV number density using the DIAL technique, and aerosol and cloud profiles using the backscatter lidar approach. As part of this effort, we will advance the TRL of the laser transmitter to lower the development time, risk, and cost of a future WV DIAL satellite instrument.
The proposed laser will utilize thulium-based solid-state laser crystals, which offer the prospect of greatly improved efficiency, simplicity, and average-power scalability compared to conventional methods. Recent proof-of-principle demonstrations of Tm:LiYF4 (YLF) lasers highlight the promise of the proposed approach, provide laser physics understanding, and set a clear development path. The objective of this proposal is to develop Tm:YLF lasers with the energy per pulse (≥100 mJ), average power (≥10 W, 50 Hz double pulsed), efficiency (≥5%), and spectral control (≥ 99.9% spectral purity) needed for a space-based WV DIAL. The period of performance for the proposed effort is 3 years. Years 1 and 2 will focus on risk reduction where critical performance metrics will be demonstrated on a bench top breadboard. In year 3 we will design and build a brassboard laser compatible with the NASA Langley Research Center (LaRC) WV DIAL, High Altitude Lidar Observatory (HALO). We exit the program with a brassboard laser that has the performance of a space-based WV DIAL system and will be validated using HALO in a follow-on effort from high-altitude aircraft as a stepping stone to space. This technology has entry TRL-2 and a planned TRL-4 exit with a clear path to TRL-5 in a follow-on program by incorporation of the brassboard laser into HALO.
James Garrison, Purdue University
P/I Band Multi-Frequency Reflectometry Antenna for a U-Class Constellation
Soil Moisture is declared an Essential Climate Variable (ECV) by the World Meteorological Organization. Root zone soil moisture (RZSM), in particular, is critical for understanding hydrologic fluxes linking surface and subsurface processes and the interplay between the water and carbon cycles. Only near-surface (0-10 cm) soil moisture is available through current spaceborne remote sensing, with data assimilation relied upon to produce RZSM as level-4 data products. P-band SAR has the potential to measure deeper moisture from space, although radio spectrum restrictions currently prohibit transmission over Europe and North America. Signal-of-Opportunity reflectometry has emerged as a third method of spaceborne microwave remote sensing combining features of active and passive remote sensing. SoOp operates as an active remote sensing technique in a forward reflection bistatic configuration exploiting pre- existing signal sources. Spacebased sources at these frequencies include LEO text- messaging satellites (137-138 MHz) and government narrowband and broadband geosynchronous communications satellites (240-270 MHz and 360-380 MHz). On the other hand, the hardware is passive (receive only) and the measurand of forward reflectivity is linked by Kirchoff’s law and conservation of energy to emissivity. A great advantage of SoOp is that these features enable low-power instruments to meet link budgets with sufficient margin using relatively small wire-type antennas.
We propose to develop a deployable broadband antenna covering 137-380 MHz (P/I bands) with industry partner MMA Design for use in a SoOp instrument constellation. The resulting technology will be compatible with U-class satellite borne SoOp instruments. We envision a train of 6-U satellites, each with two antennas and tri-band SoOp receivers in high-inclination low-Earth orbit for measuring surface reflectivity for retrieving soil moisture and other surface parameters. The deployable antenna uses innovative printed-circuit membrane technology to achieve 1-U stowed volume. We will investigate two antenna types: Broadband Crossed Dipole Membrane Antenna (BCMA) and Log-Periodic Dipole Array (LPDA). Following downselect, a sub-scale model will be built and tested, to validate the design of both the electromagnetic (EM) properties of the antenna and mechanical design of the deployment mechanism.
We will enter at TRL 2, mature the technology during a two-year period of performance (Jan. 2018 to Dec. 2019), and exit at TRL 4.
Sarath Gunapala, Jet Propulsion Laboratory
Very Long Wavelength Infrared Focal Plane Arrays for Earth Science Applications
Very long-wavelength infrared (VLWIR) focal plane arrays (FPAs) needed for Earth Science imaging, spectral imaging, and sounding applications have always been among the most challenging in infrared photodetector technology due to the rigorous material growth, device design and fabrication demands. Future Small Satellite missions will present even more challenges for VLWIR FPAs, as operating temperature must be increased so that cooler (and radiator) volume, mass, and power can be reduced. By combining recent advances in type-II superlattice (T2SL) barrier infrared detector (BIRD), light-trapping resonator pixel concept, and high dynamic range (HDR) 3D Readout IC (3D-ROIC), we will demonstrate a cost-effective, high-performance breakthrough VLWIR FPA technology with significantly higher operating temperature and sensitivity than previously attainable, and with the flexibility to meet a variety of Earth Science thermal infrared (TIR) measurement needs, particularly the special requirements of Small Satellite missions.
Jonathan Klamkin, University of California, Santa Barbara
IMPRESS Lidar: Integrated Micro-Photonics for Remote Earth Science Sensing Lidar
This investigation will demonstrate ultra-low size, weight, and power (SWaP) Lidar photonic integrated circuits (PICs) for Earth science sensing applications for measuring atmospheric constituents such as carbon dioxide (CO2). The extreme reduction in SWaP will enable significantly more science measurements at lower cost. This technology development is applicable to current and planned applications like lab demonstrations, heavy-lift aircraft (e.g. DC8) measurements, and satellite missions such as ASCENDS, but it is particularly enabling for limited-resource platforms like cubesats and unmanned aircraft (e.g. Ikhana).
The integrated Lidar PIC will enable spectroscopic measurements of the Earth’s atmosphere with increased sensitivity while significantly reducing SWaP. It will enable near infrared (NIR) multi-wavelength analysis (e.g. CO2 and greenhouse gas monitoring) with the same integrated device. The focus of this work will be to realize a fully functional system on a chip for Earth science measurements using photonic integration technology. PICs have been highly developed for the telecommunications industry; however, these PICs do not meet the needs for scientific Lidar applications. We will leverage the significant investment from the telecommunications industry and develop PICs customized for Earth science applications. The PICs will include components such as fast tuning optical sources, photodiodes, and passive waveguides. PICs will be closely integrated with electronic integrated circuits (EICs) to form sophisticated integrated optical phase-locked loop (PLL) circuits for dynamically switching and locking a seed laser module across the gas absorption line. The PICs could eventually be qualified for space, thus setting a path for insertion into future NASA missions.
The proposed technology is modular and can be transferred to other wavelengths for measurements of other species. Our objectives are to (1) significantly lower the cost and SWaP of the Lidar transmitter, (2) enable missions for multiple species not possible with prior state of the art, (3) scan multiple programmable wavelength points, and (4) improve transmitter reliability and ruggedness. Although we propose laser spectroscopy as a pathfinder demonstration, investment in this technology will have significant reach into many additional NASA science measurements that are enabled by reductions in SWaP, cost and complexity and improvements in performance.
The team comprises the University of California Santa Barbara (UCSB) and members of the Science and Engineering Directorates at NASA Goddard Space Flight Center (GSFC). These groups are experts in integrated photonics and Lidar, respectively. UCSB has pioneered PICs based on a number of materials platforms, and is also the West Coast Hub of the American Institute for Manufacturing Integrated Photonics (AIM Photonics), a federally funded Institute for Manufacturing Innovation. UCSB is currently working on two NASA grants in close collaboration with the Lasers and Electro-Optics Branch at NASA GSFC: The Early Career Faculty Space Technology Research Grant on Low SWaP Lasers for Deep Space Communications and the Early Stage Innovations Award on Integrated Photonics for Low-Earth Orbit Space Optical Communications. The group at GSFC has been working on the ASCENDS Mission and related technology development for many years and has direct knowledge of the science needs and the instrument performance requirements. The combination of device, PIC, integrated optical PLL, and electronic-photonic subsystem expertise from UCSB, with the Lidar, laser instrument, Earth science, detection, and remote sensing expertise from NASA GSFC puts our team in a strong position to achieve the objectives of this program.
The period of performance is 01/01/2018-12/31/2020. The entry TRL is 1-2 and the planned exit is 3-4.
Adam Milstein, Massachusetts Institute of Technology/Lincoln Laboratory
Computational Reconfigurable Imaging Spectrometer (CRISP)
Spaceborne infrared spectral imagers and sounders provide critical data for a wide range of Earth science applications, such as weather, climate, air quality, and land/water usage. For example, hyperspectral sounders such as Atmospheric Infrared Sounder (AIRS) and the Cross-Track Infrared Sounder (CrIS) observe the Earth’s atmosphere with dense spectral coverage, enabling significantly improved weather forecasts and unprecedented measurements of atmospheric composition. In addition, several proposed or existing multispectral imagers such as HyspIRI contain thermal infrared channels, with diverse applications, including land surface imaging. Despite the high value of such infrared imaging spectrometers, high cost and complexity have limited the number of fielded instruments, and dramatically increased the impact of losing any one instrument. Longwave instruments in particular require significant size, weight, and power (SWaP) due to the need for cryocooling, with the cost of existing instruments typically in the hundreds of millions of dollars. As a result, revisit intervals for instruments in low Earth orbit are typically no greater than 12 hours, limiting observations of dynamic phenomena such as severe weather events. As noted in the 2007 Decadal Survey, the cancelation of geostationary hyperspectral sounding from GOES-R led to a significant loss of planned spatial and temporal coverage.
To address this, we propose Computational Reconfigurable Imaging Spectrometer (CRISP), a new imaging spectrometer suitable for hyperspectral and multispectral missions. The design of this system will enable high performance from smaller and less- expensive components such as uncooled microbolometers, and thus be more suitable for small satellites that can be deployed in constellations. CRISP is a novel design that exploits platform motion, dispersive elements, and coded sensing techniques to make a time series of encoded measurements of the optical spectrum at each pixel. This encoding is inverted using specialized processing to recover the spectrum. The proposed effort will demonstrate significant sensitivity and other advantages over existing imaging spectrometer designs, enabling miniaturization and improved area coverage. Spectral and spatial resolution and coverage can be traded off with a simple configuration change to encompass multiple mission types. As a particular example, the effort will demonstrate that an uncooled CRISP system can provide longwave sensitivity and spectral resolution comparable to AIRS for relevant channels, with improved spatial resolution that may enhance boundary layer observation and complement existing midwave Cubesat sounder efforts. Multispectral applications with more demanding spatial requirements will be demonstrated as well. The goal of the proposed effort is to improve the technology readiness of CRISP by validating it in a laboratory, designing and building a brassboard, and demonstrating a brassboard in outdoor and environmental testing.
We assess CRISP to currently be at a TRL of 3, as the theory has been formulated and simulated, but, to date, only a partially functional breadboard demonstration has been instantiated in hardware. In Year 1, we propose to build a fully functional breadboard, and demonstrating the principles and theoretical sensitivity enhancement described in the main proposal text. We will also develop the processing algorithms. This system will satisfy the criteria for a TRL of 4. In year 2, we propose subject it to thermal tests, along with functional tests on an outdoor rotating platform. This system will satisfy the criteria for TRL5.
Jeffrey Piepmeier, Goddard Space Flight Center
Correlator Array-Fed Microwave Radiometer Component Technologies
Multiband passive microwave imagery in X to W Bands (e.g., 10, 18 or 19, 22 or 24, 37, 86 or 89 GHz) has a nearly 40-year history of utilization for measurement of multiple geophysical parameters. For example, quantities retrieved include precipitation rate, integrated water vapor, integrated cloud liquid water and ice, ocean surface wind speed, snow water equivalent, sea ice concentration, and land surface temperature (for evapotranspiration). Spatial resolution is limited by aperture size, and although aperture sizes have grown to 1-2 meters, current capability will not meet future science spatial resolution needs. As geophysical models have improved, the need has emerged to improve spatial resolution further to < 5 km. Improved spatial resolution in turn leads to a need to populate the antenna with additional radiometer elements to preserve noise performance (NEDT) and to provide adequate spatial sampling of Earth’s surface.
We propose to develop key building blocks of a multi-band correlator array that would feed a large reflector antenna to generate multiple radiometer beams on Earth. The envisioned system (relevancy scenario) would image Earth at 36.5 and 89.0 GHz with 2 to 3 km spatial resolution and at 10.65, 18.7 and 23.8 GHz with 5 to 10 km resolution from 700 km altitude with approximately 0.5 to 1 K NEDT. At 36.5 GHz, the proposed spatial resolution is a 10X improvement over the legacy polar-orbiting capability SSM/I and SSMIS and a 3X improvement over the modern AMSR2 radiometer. The correlator array feed will also enable a conical scanning radiometer to image with 50% overlap between footprints (complete Nyquist sampling). Today’s state-of-the-art radiometers do not provide spatial Nyquist sampling in all of these microwave bands. The key proposed development is a broadband line array covering 10-90 GHz appropriate for illuminating a large deployable reflector and will be developed by industry partner Nuvotronics Inc. A trade-study and design will be performed for integrating calibration noise coupling, frequency multiplexing, and low noise amplification into the beam forming structures. A brassboard sub-scale correlator array-fed radiometer will be developed at 36.5 GHz and elevation scanning of the main beam will be demonstrated. We will enter at TRL 2, mature the technology during a two-year period of performance (Jan. 2018 to Dec. 2019), and exit at TRL 3.
John Smith, Langley Research Center
Advanced Photon-Counting Detector Subsystem for Spaceborne Lidar Applications
We propose to develop low-noise, high-efficiency, and high-dynamic-range lidar detector technology that will significantly enhance the performance of lidars designed for aerosol, cloud, and ocean profiling. The requirements for our project are derived from a spaceborne lidar concept developed in response to the 2007 Decadal Survey for Earth Science and Applications from Space and a current international spaceborne lidar concept study. The new detector technology will enable the first-ever ocean profiling lidar from space and advanced retrievals of dense cloud properties. The driving requirements concern the large dynamic range, high vertical resolution, and fast transient recovery required of the detection system for ocean and cloud profiling. Our approach involves the use of an array of mature silicon photomultiplier detectors and development of a custom Read-Out Integrated Circuit (ROIC) that records photo-electron events at 10-ns resolution from each detector in the array and sums those values for each time bin to produce a single profile. This approach achieves (1) a dynamic range that is orders of magnitude higher than current photon counting schemes (2) provides the temporal resolution to achieve < 2-m vertical resolution, and (3) and has transient recovery characteristics required to accurately profile clouds and the near-surface ocean for which the measured signals attenuate extremely rapidly with depth. Moreover, this technology is also broadly applicable to ground-, aircraft-, and space-based direct detection lidars operating in the 355-900 nm wavelength range, including differential absorption lidars and direct detection wind lidars.
Michelle Stephens, National Institute of Standards & Technology
A Black Array of Broadband Absolute Radiometers (BABAR) for Spectral Measurements of the Earth
Spectral measurements from space are utilized in many areas, for example solar irradiance monitoring, urban land-use and population growth, water quality assessment, fire detection and monitoring, natural disaster damage assessment, soil and vegetation monitoring, and weather prediction and monitoring. For moderate- to low- resolution applications in the mid-wave infrared (MWIR) and long-wave infrared (LWIR) wavelengths, uncooled microbolometer linear arrays provide a solution that can be incorporated onto SmallSats and CubeSats. Existing arrays typically have a five micron spectral response range and require calibration with external, on-board blackbodies.
We propose a three-year technology development effort that will demonstrate a MEMS uncooled microbolometer linear array with spectral response from the visible through the LWIR and with integrated electronics that incorporate electrical substitution calibration on-chip. A vertically aligned carbon nanotube (VACNT) absorber will be integrated onto each element’s thermistor, and existing flight-proven electrical substitution electronics will be adapted for use in an array. The near-unity absorption and wide spectral range of the carbon nanotube absorber enable the replacement of the resonant optical cavity typically used in existing microbolometer arrays to enable a broadband detector with higher sensitivity than is currently available. By including electrical substitution capabilities, each individual microbolometer element can be absolutely calibrated without the need for an on-board blackbody. Closed-loop operation of the electrical substitution circuitry will provide excellent linearity and a large dynamic range. A new concept for monitoring the voltage drift of an on-orbit electrical substitution radiometer (ESR) by comparing the voltage reference of the microbolometer thermistor bridge to the existing satellite ultra-stable GPS signal through a voltage-controlled oscillator will be demonstrated.
The two greatest technical challenges of this effort are the development of thermistors for microbolometer arrays that can withstand the high temperature of carbon nanotube growth and adaptation of existing thermistor bridge and electrical substitution electronics developed for single bolometers to linear arrays. We propose to work on both challenges simultaneously, with the first year dedicated to choosing and testing thermistor materials and identifying appropriate electronic components, the second year dedicated to demonstrating a linear microbolometer array and electronics performance, and the third year dedicated to integrating the linear microbolometer array with the electronics.
The proposed work will reduce size, weight, and power (SWAP) requirement for IR imaging instruments by removing the need for a blackbody on-orbit while maintaining calibration and linearity. The incorporation of carbon nanotube absorbers increases the achievable spectral bandwidth. Such a detector will find use in a wide variety of Earth- imaging applications.
The existing technology is currently at Technology Readiness Level (TRL) of 2. We anticipate a TRL of 4 upon completion of the work.