19 Projects Awarded Funding Under the Instrument Incubator Program (IIP)
2019 ROSES A.49 Solicitation NNH19ZDA001N-IIP Research Opportunities in Space and Earth Sciences
10/30/2019 - NASA's Science Mission Directorate, NASA Headquarters, Washington, DC, has selected proposals, for the Instrument Incubator Program (IIP-19) in support of the Earth Science Division (ESD). The IIP-19will provide instruments and instrument subsystems technology developments that will enable future Earth science measurements and visionary Earth-observing concepts. The ESD is awarding 19 proposals, for a total dollar value over a three-year period of approximately $59 million, through the Earth Science Technology Office (ESTO).
The goals of the IIP are to research, develop, and demonstrate new measurement technologies that:
- Enable new or greatly enhance Earth observation measurements, and
- Reduce the risk, cost, size, volume, mass, and development time of Earth observing instruments.
The IIP is designed to reduce the risk of new innovative instrument systems so that they can be successfully accepted by future science solicitations. The program is designed to be flexible enough to accept technology developments at various stages of maturity, and through appropriate risk reduction activities (such as instrument design, laboratory breadboards, engineering models, laboratory and/or field demonstrations) advance the technology readiness of the instrument or instrument subsystem for infusion into futureNASA science missions.
70 IIP-19 proposals were evaluated of which 19 have been selected for award. The awards are as follows (links go to abstracts below):
| Anum Ashraf, Langley Research Center DEMETER: DEMonstrating the Emerging Technology for measuring the Earth's Radiation |
| Federico Capasso, Harvard University Metasurfaces for Compact, Next-Generation Polarimetric Remote Sensing of Aerosols and Clouds |
| Odele Coddington, University of Colorado Boulder Black Array of Broadband Absolute Radiometers for Imaging Earth Radiation |
| John Conklin, University of Florida Integrated Inertial Sensors and Laser Ranging Instruments for Small Satellite Earth Geodesy Constellations |
| Kevin Cossel, National Institute of Standards and Technology Frequency Comb Spectrometer for Satellite Atmospheric Remote Sensing |
| William Deal, Northrop Grumman Corporation Smart Ice Cloud Sensing |
| Thomas Hanisco, Goddard Space Flight Center Formaldehyde Integrated Path Differential Absorption LIDAR |
| Marco Lavalle, Jet Propulsion Laboratory Distributed Aperture Radar Tomographic Sensors (DARTS) to Map Three-Dimensional Vegetation Structure and Surface Topography |
| Nathaniel Livesey, Jet Propulsion Laboratory MLSCube – A Microwave Limb Sounder for continuity of stratospheric observations in a 6U-CubeSat form factor |
| David Long, Brigham Young University Global L-band Active/Passive Observatory for Water Cycle Studies (GLOWS) |
| Hans-Peter Marshall, Boise State University Digitally Enhanced Meta-surface Radar/Radiometer for Snow Remote Sensing |
| Kevin Maschhoff, BAE Systems SToRM SAR |
| Amin Nehrir, Langley Research Center Atmospheric Boundary-Layer Lidar PathfindEr (ABLE) |
| Raquel Rodriguez Monje, Jet Propulsion Laboratory CloudCube |
| Mark Stephen, Goddard Space Flight Center Breakthrough Technologies Enabling ESPA-Class SmallSat Implementation of Earth Science LIDAR Missions |
| William Swartz, Johns Hopkins University Applied Physics Laboratory Compact Hyperspectral Air Pollution Sensor-Demonstrator (CHAPS-D) |
| Guangning Yang, Goddard Space Flight Center Concurrent Artificially-intelligent Spectrometry and Adaptive Lidar System (CASALS) |
| Ben Yoo, University of California, Davis Multi-Spectral, Low-Mass, High-Resolution, Planar Integrated Photonic Imagers |
| Simon Yueh, Jet Propulsion Laboratory Signals of Opportunity Synthetic Aperture Radar for High Resolution Remote Sensing of Land Surfaces |
DEMETER: DEMonstrating the Emerging Technology for measuring the Earth's Radiation
Anum Ashraf, Langley Research Center
DEMETER, which stands for DEMonstrating the Emerging Technology for measuring the Earth’s Radiation, is a small sensorcraft that will demonstrate a revolutionary approach for measuring Earth’s Radiation Budget Fundamental Climate Data Record (ERB-FCDR) from Low Earth Orbit (LEO). This measurement is comprised of global Top-Of-Atmosphere (TOA) broadband radiance fields which include total reflected solar and outgoing longwave radiation. DEMETER is a sensorcraft mission solution that goes beyond preserving observational and radiometric continuity of the existing multi-decadal FCDR; it exploits new technology, integrating it with existing high TRL capability assets, and capitalizes on concurrent investments in technology demonstration flight programs from multiple agencies. This greatly expands the scientific utility of the Earth Radiation Budget Thematic Climate Data Record (ERB-TCDR). Our solution increases the spatial resolution of the measurement by a factor of 10, which enables more accurate clear-versus-cloudy sky investigations, provides in-situ data processing capability on the sensorcraft, while also reducing mass, power and cost by an order of magnitude over current approaches and brings a potentially new data set of reflected solar polarimetric observations. Reduced accommodations enable insertion of the sensorcraft into multiple orbits for more complete global diurnal sampling of the radiation fields, while providing robustness against a possible gap in the observational record.
This proposal covers a three-year period of performance (nominally January 1, 2020 to December 31, 2022) and advances the Technology Readiness Level (TRL) of the proposed sensorcraft system from 2 to 4. The result of this effort is a technology demonstration brassboard which will be tested over complete thermal regimes in the laboratory with a goal of additional testing under vacuum environments. The long-term goal is maturation the sensorcraft’s TRL to an operational system for future flight opportunities by 2025.
Current LEO ERB instruments (ERBE, CERES) that obtain global broadband coverage typically have a mass of 50-kg, require 50-W power, contain complex scanning mechanisms, and require a budget of $150M+, and integrate on large observatories (~3,000 kg) such as those in the JPSS program. This approach is expensive and introduces significant risk in the continuation of the ERB climate data record at the current level of accuracy, particularly if temporal gaps in observations were to occur. The proposed concept breaks the existing paradigm by implementing a non-scanning wide-field-angle telescope on a small free-flying sensorcraft platform.
The DEMETER team partners, NASA LaRC, Quartus Engineering Incorporated, Virginia Polytechnic Institute & State University, NovaWurks Inc. and Science Systems and Applications, Inc., provide rich heritage and experience in the areas of space-based ERB sensor design, fabrication, calibration, end-to-end numerical modeling, operations, as well as science data product generation and investigation. The team’s key members have a combined 100+ years of direct experience providing the needed expertise to pro-actively influence the design and address trades involved in this proposed effort in an integrated and intelligent manner.
ERB-TCDR is a highly assimilated Level-3B data product, therefore, a Science Advisory Group (SAG), has been established as an integral element of this proposed effort. SAG membership includes the Radiation Budget Measurement Project (RBMP) Principal Investigator and six of the project’s Working Group leads, each of whom brings unique expertise, knowledge, and perspective of the ERB-TCDR. The SAG’s charter is to advise the PI of this proposed effort, as necessary, during IIP execution regarding impacts trades/designs/tests will have on the higher level ERB-TCDR the RBMP team is responsible for producing.
Metasurfaces for Compact, Next-Generation Polarimetric Remote Sensing of Aerosols and Clouds
Federico Capasso, Harvard University
Aerosols – suspensions of solid or liquid droplets in air – present a unique challenge in atmospheric science and are, together with their interactions with clouds, key sources of uncertainty in global climate models. Light’s polarization state upon scattering from aerosols and clouds is known to carry information that can aid in determination of their mean size, droplet size uniformity, shape, and absorption properties. However, the current instrumentation for polarimetry (the measurement of light’s polarization state) is bulky and/or reliant on moving parts.
Metasurfaces – subwavelength spaced arrays of nanophotonic phase shifters, an emergent optical technology – have recently been shown to implement polarization imaging with all polarization analysis handled by a single optical element and thus hold promise for a new class of polarization instrumentation for remote sensing. To date, no past, current, or planned Earth Science airborne/spaceborne polarimeter has measured light’s circular polarization. Metasurfaces easily yield information on the circular polarization of light, therefore, the utility this seldom-measured quantity can have for aerosol and cloud remote sensing will be investigated.
The proposed IIP-ICD effort will evaluate whether metasurface-based polarimetry can achieve the accuracy mandated for cutting-edge aerosol and cloud remote sensing applications by partnering resources and personnel from Harvard University, leaders in the development of metasurfaces for polarimetric imaging, with aerosol and cloud remote sensing expertise at NASA GSFC. Our team proposes to examine the scientific feasibility of metasurfaces in this realm, whose compactness (when paired with this requisite accuracy) could enable a compact, next-generation remote sensing platform for application onboard a CubeSat. As part of this project we will fabricate several metasurface polarization camera prototypes in three wavelength bands relevant for aerosol and cloud remote sensing (550, 670, and 870 nm), characterize their accuracy, and investigate future applications of metasurfaces in polarimetry, advancing the technology from TRL 2 at entry and TRL 4 upon exit. Finally, the proposed effort will explore the utility of using new metasurface enabled observations of circular polarization for Earth Science applications; maturation of the technology has the potential to be cross-cutting with the Planetary Science community, as chirality, a potential indicator of complex biological life, contributes to the circular polarization signal.
Black Array of Broadband Absolute Radiometers for Imaging Earth Radiation
Odele Coddington, University of Colorado Boulder
We propose to develop and demonstrate a novel instrument utilizing a linear array of electrical substitution microbolometers for imaging outgoing Earth radiation with low uncertainty. Our instrument will measure in several broad bands spanning the electromagnetic spectrum from 0.2 µm to 100 µm with a 1 km spatial footprint from a low Earth orbit vantage point. Accurate measurements of outgoing broadband radiation are critical for understanding Earth’s climate. Our focus on beginning with an instrument of reduced volume, mass, and power, while enhancing spatial resolution and providing high accuracy supports key measurement objectives for use in the next generation of science missions. These objectives include broadened applicability to small satellite platforms and reduced risk from potential data record gaps.
Our instrument, the Black Array of Broadband Absolute Radiometers (BABAR) Earth Radiation Imager (BABAR-ERI), capitalizes on linear detector array technology in development under an Advanced Component Technology (ACT) award (#ACT-17-0025). BABAR is an uncooled microbolometer electrical-substitution radiometer array with Vertically Aligned Carbon Nanotubes (VACNT) as the optical absorber. Electrical-substitution radiometers are used extensively in precision radiometry, but have never been used for imaging despite their many advantages. Relative to traditional microbolometer arrays, the BABAR detector allows for faster response, higher linearity, higher accuracy, and higher long-term stability. This is achieved by using closed-loop electrical substitution techniques in conjunction with electrical substitution radiometry. The VACNTs provide spectrally flat absorptance greater than 99.8% over the range from 0.2 µm to 100 µm. The combination of electrical substitution and broadband VACNT absorption provides a path to a compact, high resolution, and high accuracy instrument because on-board calibration hardware is not required. Absolute radiometry will be verified against the Planar Bolometric Radiometer for Irradiance (PBR-I) reference standard. These properties make BABAR-ERI ideal for space-based Earth energy budget and remote sensing applications.
In order to accommodate the broad wavelength range desired for energy budget applications, an all-reflective imaging system will be implemented. A key aspect of this IIP will be generating a compact design which can fit onto a 6U CubeSat bus. This will enable a future, straightforward on-orbit demonstration as well as facilitate potential future deployment of multiple BABAR-ERI instruments on a constellation of small spacecraft.
The proposing team has a long history of instrument development and deployment of radiometers in space-based and suborbital platforms. The proposed sensors draw heritage from: the Compact Solar Spectral Irradiance Monitor (CSIM), developed under a 2013 IIP award, that has been making daily solar irradiance measurements from a 6U CubeSat platform since early 2019; the Compact Total Irradiance Monitor (CTIM), in development for the In-Space Validation of Earth Science Technologies (InVEST) program with a planned launch in 2021; and the BABAR ACT project. The BABAR linear array detector is currently at a Technology Readiness Level (TRL) of 3. We are proposing an exit TRL of 6 at the end of this three-year project.
Integrated Inertial Sensors and Laser Ranging Instruments for Small Satellite Earth Geodesy Constellations
John Conklin, University of Florida
We plan to develop a compact inertial sensor and integrated laser interferometer for low-cost small satellite Earth geodesy constellations. Our concept has the potential to be disruptive, enabling dozens of satellite pairs at a cost that is comparable to previous Earth geodesy missions. The potential science return from the higher accuracy instruments and increased satellite constellation size would help resolve questions about how the global Earth system is changing. It would improve the accuracy and resolution of gravity field measurements, increasing our understanding of climate variability and change, including critically important temporal and spatial changes in the mass of Earth’s ice cover and water.
The instrument and satellite platform will take advantage of NASA and European Space Agency investments in technology for Earth geodesy and space gravitational wave detection. The inertial sensors (IS) will have an improved acceleration noise performance relative to the ONERA sensors employed in the Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow On (GRACE-FO) missions, achieving an acceleration noise of <10^–12 m/s^2Hz^1/2, a factor of 100 improvement over the ONERA sensors. To do so, the IS design will capitalize on technologies developed for LISA Pathfinder and performance models that were validated by flight data from that mission. With these models, we will tailor the design to meet the desired performance of next-generation geodesy missions, while minimizing the size, weight, and power of the sensor. The inertial sensor will incorporate a laser interferometer port for direct interrogation, and we will develop a strategy to modify the GRACE-FO laser ranging interferometer (LRI) to allow direct integration with the IS.
An inertial sensor and spacecraft designed from the start with laser interferometry in mind will allow an LRI with a smaller mass and volume than that used on GRACE FO, for example, by eliminating components that were only needed to allow GRACE-FO to use the GRACE spacecraft and microwave ranging instrument. By integrating a compact inertial sensor and laser ranging interferometer, and eliminating the microwave ranging system used on GRACE and GRACE FO, a low-low satellite-to-satellite tracking geodesy mission could be realized on a small satellite, for example an ESPA-class platform or smaller. The reduced cost to develop and launch this small satellite and instrument would enable a larger number of pairs of satellites to be employed in future geodesy missions. Because of the higher frequency with which they observe any given location on the Earth, multi-satellite systems can increase the temporal resolution of gravity field maps. Mixed-orbit constellations can also markedly enhance observational strength, de-correlate gravity coefficient estimates, and help address the fundamental aliasing/modeling problem that exists with previous missions. The constellation approach is also scalable and could take advantage of improved technologies when they become available.
We will develop the conceptual design of the inertial sensor and laser ranging interferometer considering the size, mass, and power constraints of small satellite platforms. The performance of the inertial sensor will be based on analytical models developed for the LISA and LISA Pathfinder missions and validated using noise measurements made with the University of Florida torsion pendulum, which is capable of measuring the performance of inertial sensors down to ~10^–13 m/s^2Hz^1/2 around a few mHz. We will also evaluate the science return for an optimized set of orbits for small satellite pairs in terms of the spatial, temporal resolution and accuracy of the recovered geopotential. In this analysis, we will consider both rideshare opportunities and Venture class launches that enable launches into desired orbits for each pair of satellites at relatively low cost.
Frequency Comb Spectrometer for Satellite Atmospheric Remote Sensing
Kevin Cossel, National Institute of Standards and Technology
The dual frequency-comb spectrometer has recently emerged as a novel instrument to support precise retrievals of atmospheric trace gas column densities over long paths without systematic drifts. In this work, we propose the development of dual comb spectroscopy (DCS) for satellite measurements to 1) perform active-source integrated vertical column measurements to ground stations, which will substantially improve coverage in the high and low latitudes and provide ultrahigh-resolving-power spectra for TCCON and OCO-2 calibration and 2) perform active satellite-to-satellite occultation measurements to obtain vertical profiles of gases in the upper troposphere and stratosphere. Specifically, we propose to develop a dual-comb spectrometer in the 2.1 um region for measurements of CH4, 13CH4, CO2, C18OO, 13CO2, H2O, N2O, and O3, as well as temperature and line-of-sight wind. When incorporated into a satellite mission, this novel instrument could yield data on the integrated columns and vertical profiles of these gases and atmospheric parameters, which in turn could support global transport model validation, contribute to greenhouse gas measurements and source attribution, and finally monitor the recovery of the stratospheric ozone layer and the ozone hole. Additionally, the column measurements will enable a cross-calibration of satellite missions such as OCO-2 and GOSAT with TCCON and the WMO standard.
Our proposed instrument is designed for active vertical column DCS as well as satellite-to-satellite DCS, as highlighted in a recent Keck Institute for Space Science report. DCS rests on the Nobel-prize winning technology of frequency comb lasers, whose collimated output comprises a set of evenly spaced narrow comb “teeth” covering a very broad spectrum. In DCS, these comb teeth are transmitted through the air and the resulting absorption is “read out” on a comb tooth-by-tooth basis with high accuracy and negligible instrument lineshape. This results in a resolving power of >10,000,000 -- orders-of-magnitude higher than achievable with a Fourier Transform or grating spectrometer. The sample point spacings of ~200-MHz (0.006 cm-1) can easily fully resolve narrow molecular features at high altitudes. Moreover, unlike conventional spectrometers, this exquisitely narrow instrument lineshape is not fundamentally linked to the instrument size. In fact, the receiver consists only of a telescope and photoreceiver, so that DCS could provide precise column gas measurements in a cost-effective and scalable approach. Finally, because DCS uses an active light source, rather than the sun, it can provide information at high/low latitudes and during night, unlike nadir-looking scattered-sunlight instruments.
In this program, we will 1) develop the DCS instrument at the 2.1 um spectral region, selected to overlap with the above listed critical gas species and current technology, 2) evaluate its operation over a 35-km open-path from the Maua Loa to Mauna Kea observatory, 3) conduct a trade study of orbit and satellite system configuration, and finally 4) evaluate the feasibility of future DCS satellite missions to support Earth science applications. A satellite-based DCS system would increase NASA’s measurement capability for several Explorer-level Targeted Observables: Greenhouse Gases, and Ozone and Trace Gases. The proposed missions will allow for global and regional CO2 and methane trends over the seasonal and multi-year scales and would enable vertical profiles on the regional and global scales for the Explorer level trace gases H2O, N2O, O3, and CH4, as called for in the 2017 NASA Earth Science Decadal Survey.
We propose a period of performance of 18 months. While we have operated DCS in the field at 1.6-um band for ground-based CO2/CH4 measurements (TRL level 5), the translation to the 2.1-um region and future satellite-based measurements is a new technology with an entry TRL level of 2 and exit TRL level of 4.
Smart Ice Cloud Sensing
William Deal, Northrop Grumman Corporation
We propose an instrument optimized for Smart Ice Cloud Sensing (SMICES) that will enable both multi-angle and multi-resolution measurements of cloud ice particles size and shape within the tropospheric temperature and water vapor profile context. This will improve understanding of tropospheric events including hurricanes, tropical deep convections, tornadoes and storms. SMICE will combine an active radar, with passive multi-band radiometers and sounders using an intelligent backend and control system. SMICES will maximize the scientific outcome by performing multi-angle and multi-resolution measurements of interesting tropospheric features and optimizing the volume of collected data by using a footprint overlap high resolution mode for the radiometers, a track-and-lock algorithm for the radar, and a reconfigurable wide-band high-resolution digital spectrometer to produce sounder channel spectra. These three system characteristics enable feature-dependent and incidence angle-dependent resolutions resulting in efficient acquisition of high resolution measurements. The intelligent feature detection enabled by SMICES, including observational locking capability and the multi-angle and multi-resolution measurements, will enable the detection of ice particles at different sizes, distribution and granularity with a fine vertical resolution of 500 meters. The use of the spectrometers enable collocated temperature and water vapor profiles measurements needed for evaluating and constraining climate model simulations of ice cloud processes.
The SMICES instrument works in the following manner. During normal operation, the radiometers continuously scan the upper troposphere at 45° incidence angle. Passive instrument calibration will be performed on board, allowing for near real-time detection of tropospheric features. Once the passive sensors detect a tropospheric feature, the radar, which is nominally nadir pointed, will point towards the feature and examine the region of interest. As the satellite travels, the relative position between the feature and the instrument also changes. By locking the radar to the target, the radar will be able to obtain multi-angle data. This intelligent control of the radar enables high-resolution data for specific features of interest.
Along with combination of active and passive sensing techniques, the “smart” functionality of SMICES is a key feature. This is enabled by calibration and feature detection algorithms using neural networks. The radiometric calibration and feature detection neural networks operation will be performed on-orbit. Antenna temperature will be estimated from the radiometric voltage reading and system operating condition using a multi-layer deep-learning neural network. The calibration neural network will have the capability to on-orbit training to account for non-stationary system effects including component aging. The feature detection neural network operation will be trained on ground using multiple datasets, and can be updated to the spacecraft as necessary.
SMICES relies on significant technology to meet its mission goals. The calibration algorithm and feature detection is currently rated to be TRL 3, as well as the antenna focus and tracking. The high resolution digital spectrometer is currently TRL 4. The Sounders and radiometers operate at 240, 310, 380, 670 and GHz and are estimated to be at TRL 5 from IIP-13 TWICE and ACT-17 IRaST. Exit TRL level of the SMICES instrument will be TRL-5. TRL4 radar receiver and up-converter operate at 233 GHz and have been developed on the DARPA ViSAR program. The 233 GHz TWT will leverage work from the DARPA ViSAR program, with the magnet being changed from a fixed magnet to a PPM. We therefore rank the TWT as TRL3.
Formaldehyde Integrated Path Differential Absorption LIDAR
Thomas Hanisco, Goddard Space Flight Center
An improved understanding of the coupled chemistry-climate system is a key objective of NASA Earth Science. Central to this objective is the reactive photochemistry that controls the lifetime of greenhouse gases like methane, the production of ozone, and the growth of organic aerosols. Formaldehyde (HCHO) is a critical player in these processes: It is a key measure of the oxidative power of the atmosphere (it is produced in the oxidation of methane), an important intermediate in the production of ozone (it produces the species that make ozone), and an indicator for the abundance of the organic precursors that lead to organic aerosols (it is produced from the same organic precursors).
HCHO is an important component of existing (OMI, TROPOMI, OMPS) and planned (TEMPO, GEMS, Sentinel-4) satellite missions. Each of these instruments measures reflected sunlight in the near ultraviolet (300-350 nm) to determine the column of HCHO. The difficulty with this technique is that the high level of scattering makes the retrieval of the column abundance strongly dependent on the assumed shape of the HCHO profile. The combination of the weak absorption signal (HCHO is present at parts per billion in the atmosphere), limited light due to scattering, and the dependence on a model-derived concentration profile, make HCHO difficult to measure accurately with passive spectroscopy. Our motivation is that this accuracy is not adequate to solve emerging science goals.
Our team proposes to develop a new method to detect formaldehyde remotely with integrated path differential absorption (IPDA) LIDAR under the IIP instrument concept demonstration (ICD) call. Our concept uses a tunable narrow-linewidth fiber amplified laser to measure the absorbance of single rotational lines of the A-X transition at 339 nm. The concept will measure the column of formaldehyde in the laser path using a simple Beer’s law analysis that is largely independent of the a priori assumptions needed in passive systems, providing improved capability in sensitivity and accuracy. In addition, since this is an active system with a small footprint, it can measure at night and in scenes partially obscured by clouds and aerosol.
The challenge is to develop the experimental capability to detect the low abundances of formaldehyde in the UV where Rayleigh scattering is large. We now have the technology to meet this challenge. We will modify a new laser developed with ESTO and GSFC IRAD support to provide the laser light at 339 nm. We will demonstrate the capability to detect HCHO with a remote target on the ground using commercially available electronics for data acquisition. We will evaluate and optimize the technique and, at the conclusion of this effort, we will provide our recommendation for the best path towards an instrument design. We will advance the TRL from 2 to 3 over an 18-month period. At the conclusion of this IIP ICD, we plan to pursue the development of an airborne IPDA instrument with the instrument Development and Demonstration (IIP-IDD) or airborne instrument technology transfer (AITT) program. Our short-term (3-5 yr) goal is to demonstrate performance in an operational airborne configuration. Longer term (5-10+ yr), this concept can be applied to space-based measurements.
Distributed Aperture Radar Tomographic Sensors (DARTS) to Map Three-Dimensional Vegetation Structure and Surface Topography
Marco Lavalle, Jet Propulsion Laboratory
We propose to mature and demonstrate a set of relevant technologies that, when coupled with recent developments in miniaturized spaceborne radars, will enable formations of satellites to perform disruptive global vegetation structure and surface topography measurements. The recent report from the 2017-2027 US Decadal Survey for Earth Science and Applications from Space recommended the global mapping of surface topography and three-dimensional vegetation structure as one of the highest priority “incubator” measurements to undertake in the next decade. Despite its extremely high relevance, significant technological developments are needed to enable the implementation of a feasible and affordable space mission that can demonstrably retrieve vegetation structural characteristics, including the underlying ground topography, with the desired vertical and horizontal resolutions, accuracy and temporal sampling.
Our concept, named Distributed Aperture Radar Tomographic Sensors (DARTS), is based on multistatic tomographic SAR (TomoSAR) observations. A notional architecture for measuring vegetation structure and surface topography globally every ~10-15 days includes a formation of ~5-10 spacecraft equipped with full-polarimetric, bistatic, L-band distributed radar instruments. One or more of the spacecrafts, the hub(s), transmits the radar signal while all remaining satellites receive the echo simultaneously. The relative position, attitude, timing, and clock are synchronized between all platforms to enable coherent, multistatic SAR observations of common scenes with nominally 50 m horizontal resolution and 3-5 m vertical resolution after multi-looking. The formation’s relative orbital control requirement is <10 m but the knowledge of the relative positions is required to <1 cm to maintain coherent phase between the distributed radar receivers for tomographic reconstruction. Data from each spacecraft is transferred to the hub spacecraft(s) via inter-satellite communications for data reduction and downlink to Earth for tomographic processing and digital elevation model generation.
The objectives of our investigation are to (1) Design, build and test a distributed system to synchronized timing, clock, relative position and sensor data for all of the distributed DARTS elements; (2) Miniaturize the distributed phase-coherent radar system by leveraging recent RF system-on-chip (RFSoC) technologies and implement compact L-band radars in order to achieve time-synchronization and phase coherence across the distributed elements. (3) Design the optimal distributed system architecture given the scientific requirements for surface topography and vegetation tomographic imaging, and analyze the tomographic signals acquired by both fixed-position and mobile small Unmanned Aerial System (sUAS) synchronized radars; (4) Design a SmallSat-compatible, L-band foldable patch antenna, including the electrical backend and the mechanical structure required to enable a cost-effective formation of satellites for the distributed DARTS system.
A multistatic interferometric system enabling single-pass SAR tomography constitutes a disruptive measurement for ecosystem science because it can provide global, high-quality year-round measurements of 3D vegetation structure while being insensitive to dynamic changes in vegetation, soil and atmosphere. Coupled with fast repeat periods, such a measurement would provide a consistent 4D view of vegetation (3D in space + 1D in time) complementing and potentially overcoming the limitations of spaceborne lidar missions and other planned missions such as TANDEM-L and BIOMASS. This investigation responds directly to the Instrument Development and Demonstration sub-element of the IIP solicitation. The proposed period of performance is 3 years. The entry Technology Readiness Level (TRL) is 2, which we plan to increase by 1 every year, aiming for a TRL equal to 5 at the end of the investigation.
MLSCube – A Microwave Limb Sounder for continuity of stratospheric observations in a 6U-CubeSat form factor
Nathaniel Livesey, Jet Propulsion Laboratory
We propose to develop technologies needed for a 6U CubeSat instrument measuring profiles of the composition, humidity, and temperature of Earth’s upper troposphere, stratosphere, and mesosphere with the vertical resolution, spatial coverage, precision, and accuracy required to derive essential Earth System Data Records. The instrument will provide continuity for the Aura Microwave Limb Sounder (MLS, launched in 2004), generally considered to represent the “platinum standard” for such measurements.
The composition of the upper troposphere and stratosphere (UT/S) plays many roles in influencing and responding to changes in surface climate. Factors such as potential injection of aerosols into the stratosphere for “geoengineering” and recently identified rogue emissions of ozone-depleting CFC-11 underscore the need for a robust quantitative understanding of those roles and their future evolution, founded on a continued record of reliable observations.
Recent technology development efforts, including several funded by ESTO, have enabled dramatic reductions in mass/power/volume/cost for future such instruments. Presently, however, no viable route to making such observations from a CubeSat-class spacecraft exists, mainly because of the requirement for a large (e.g., 60cm) aperture. A CubeSat-class MLS-type instrument represents a much-needed advance, given the far more frequent opportunities that exist for CubeSat deployments compared to other mission profiles.
“MLSCube” uses phased-array techniques to synthesize a 60cm electronically-steered aperture for limb emission observations, tunable over 316–358GHz, consisting of 24 individual receiver elements, each employing piezo-electrically-driven moving silicon lenses to aid in beam steering and sidelobe reduction. A set of identical custom System on Chip (SoC) devices will provide individual synchronized phase- and frequency-tunable 108–116GHz oscillators for each element. These will then be frequency-tripled and combined with the atmospheric signals in a Schottky diode mixer. Micromechanical switches and in-waveguide targets will be used for radiometric calibration of each element, replacing traditional but bulky switching mirrors and associated optics. The Intermediate Frequency signals will be amplified and sent through programmable attenuators, then combined for beam forming and analyzed with a 3GHz bandwidth SoC 4096 channel spectrometer that will produce spectra. Various schemes for in-flight active beamforming calibration will be developed and evaluated. While some components are high-TRL, the overall concept is currently TRL-3.
The proposed three-year effort will include validation of a four-element 183GHz prototype based on devices nearing completion developed under other programs. This will be followed by fabrication of 12 of the 24 array elements needed for the 340GHz-MLSCube instrument. These will then be integrated, along with the previously developed backend spectrometer subsystem, into a 6U CubeSat form factor (leaving space for the remaining 12 elements and 2U for spacecraft components). The partial system will be extensively calibrated, and subjected to flight-like vibration, thermal vacuum, and radio frequency interference and compliance testing, followed by a re-calibration, demonstrating TRL-5.
The recent Earth science Decadal Survey identified the parameters measured by MLSCube as key targeted observables within the “Ozone and Trace Gas” opportunity in the “Explorer” line. In addition, MLSCube is ideally suited for demonstrating potential continuity measurements in any suitably-targeted “Earth Venture-Continuity” opportunity.
Global L-band Active/Passive Observatory for Water Cycle Studies (GLOWS)
David Long, Brigham Young University
The value of L-band measurements from the Soil Moisture Active Passive (SMAP) and Soil Moisture Ocean Salinity (SMOS) missions have shown the importance of L-band data record in Earth Sciences. An obstacle to this is the high cost of designing and flying the large antennas required for L-band observations. A new technique based on reflectarray antennas provides a path to smaller, lower-cost, simpler, large-aperture antennas for low frequency microwave (L-band) observation. Using this key technology, we propose the Global L-band Active/Passive Observatory for Water Cycle Studies (GLOWS) instrument. The use of a reflectarray lens antenna enables L-band measurement capability from a significantly smaller spacecraft. This proposal to the Instrument Incubator Program (IIP) is to evaluate the radiometric performance of the new antenna design concept from TRL 2-3 to TRL 4 to advance the timeline of a GLOWS flight. The technology improvements can be applied to other remote sensing missions as well.
Digitally Enhanced Meta-surface Radar/Radiometer for Snow Remote Sensing
Hans-Peter Marshall, Boise State University
We propose to develop a Ku-band active and passive (radiometer/radar) microwave wavelength instrument capable of measuring the spatial distribution of snow-water-equivalent (SWE) from a space-borne platform using CMOS radar combined with metasurface antenna technology to overcome the isolation and dynamic range challenges associated with snow sensing. Traditionally remote sensing of SWE from a space-borne is prohibitive as it demands both a large aperture (>1m diameter) to maintain resolution in terms of ground footprint, and high dynamic range radar system (beyond 60dB) to accommodate the vast difference in reflectivity between the snowpack’s top surface and the underlying ground. This dynamic range in particular requires that a radar have a very low transmit-to-receiver leakage (again beyond 60dB). Airborne remote sensing of snow addresses this leakage by employing bi-static radars where the transmitter and receiver operate using separate antennas. The separation of the two signals with separate antennas allows these systems to easily achieve the required transmit-to-receive isolation as the two are not required to share an aperture. While suitable for large airborne campaigns, the bi-static approach is prohibitive for spaceborne platforms as needing two large antennas (as opposed to a single antenna) makes the instrument prohibitively large. To overcome this we propose an instrument which employs a new metasurface antenna which enables simultaneous transmitting and receiving using the same antenna aperture and frequency, while still providing the high isolation required for sensing SWE from a spaceborne platform. This high isolation is achieved through a combination of the antenna’s native design (approx. 20dB isolation), as well as a leakage cancelling pre-distortion technique where signals leaking between the two ports are digitally cancelled to provide an additional 50dB. Using this high dynamic range, the proposed instrument can provide critical information about snowpack features (depth, density, liquid water content) used to estimate and constrain SWE, but unlike ground-based or airborne measurements, can provide global coverage as it targets a spaceborne approach. The instrument also offers a passive radiometer mode (where the radar transmitter is disabled) which is an important measurement in constraining the amount of liquid water pooled at the bottom of the snowpack. To achieve the high level of signal processing performance required to enhance the isolation of the metasurface antenna, we employ CMOS system-on-chip (SoCs) technology (the same electronics technology used in modern smartphones) for all radar and radiometer electronics. CMOS SoCs offers approximately a factor of 100X in performance over FPGA platforms implemented with the same transistor size.
SToRM SAR
Kevin Maschhoff, BAE Systems
Observations at 1km horizontal resolution are needed to resolve the fine thermodynamic phase structure present in many severe storms, and support the weather process research needed for future convection-resolving weather models. SToRM SAR is an approach developed by BAE Systems and Colorado State University for a space-based 3D multi-static precipitation radar that employs agile micro-satellites operating synchronously in a distributed configuration to provide 1km horizontal spatial resolution observations of a precipitation field using a new interferometric method. The focus of the proposed work is on next-generation space-based precipitation field observations at finer spatial scales. The horizontal resolution of the large GPM radar is 5 km-too coarse to resolve these phenomena. A real-aperture radar-scaled to pro-vide 1 km resolution at Ku band would have an aperture dimension of 15-30 meters–a funda-mentally unaffordable approach.
SToRM SAR (Satellite Tomography of Rain and Motion using Synthetic Aperture Ra-dar) directly leverages the rapid developments in small satellite technology and launch capabil-ity to provide significant new capability at a mission cost more than 10x lower than other space-borne precipitation radars- with the ability to penetrate and characterize severe mid-latitude storms at the 1-km scale from space for the first time. The approach is compatible with both X-band and Ku-band operation, enabling full profiling through intense storms using transmitter power levels consistent with miniature solid state RF amplifiers. The approach employs range-encoded pulse sequences and strategically positioned receivers to enable a sim-ultaneous interferometric measure of the vertical and cross-track structure of the precipitation field. The along-track spatial structure is observed using a scene illumination approach simi-lar that used for the spotlight-mode employed in traditional 2D SAR. Along-track structure is recovered via a tomographic re-construction method. Radar observation locations are cued by passive IR and microwave mapping micro-satellites orbiting ahead, which indicate areas of immanent or ongoing severe weather. This cueing allows the duty-cycle of the radar to be low without sacrificing observations of the key storm regions of interest, thereby keeping the ac-commodation requirements within micro-satellite resource limits. The SToRM SAR method does not rely on the Doppler Effect for observing storm structure, but uses Doppler to sense field motions- as do ground-based Doppler-weather radars.
Under a 3-year IIP-IDD, the overall mission and instrumentation risks will be reduced though detailed observing concept and instrument payload design, supported by a realistic sim-ulations of the complex 3D precipitation field observations and ground-based field demonstra-tions of the observation method. This work builds upon a successful NASA ESTO-Funded Fea-sibility Study that developed the mathematical framework. The envisioned hardware imple-mentation is TRL5. However, the overall readiness of this relatively complex observation method is currently low (TRL2-3), and improving this readiness to TRL5 through analysis, simulation, testing, and field demonstration would be a primary focus of the risk reduction work. The method is, in part, derived from methods applied by BAE Systems in RF signals in-telligence and navigation. The precipitation field modeling is based on substantial prior work by Colorado State University in reflectivity field simulation. Field tests of the interferometry method will be conducted at BAE Systems RF range and near Colorado State University’s NSF-Funded CHILL multi-band (C-band-X-band)/dual polarization precipitation radar research and development facility near Ft Collins, CO which will enable the observation of storm structure using the new method (at X-Band) to be compared with the observations of a powerful ground-based precipitation radar.
Atmospheric Boundary-Layer Lidar PathfindEr (ABLE)
Amin Nehrir, Langley Research Center
The 2017 Decadal Survey for Earth Science Applications from Space (ESAS) identifies water vapor (WV) observations as synergetic and cross-cutting over five of six ESAS science and applications priorities. High vertical resolution profiles of WV within the Planetary Boundary Layer (PBL), as well as in the free troposphere, were identified more frequently than any other geophysical observables within ESAS, and given distinction as a “Most Important Observable” across most of the science panels. WV profiling lidar, optimized for the PBL, was explicitly identified as a candidate measurement approach and recommended for continued technology advancements to be a candidate for implementation the next decadal survey. This project, through focused technology advances and a space instrument design concept, will retire the risk for a future space based WV lidar that will enable cross-cutting science across disparate NASA focus areas. This single multi-function lidar will be capable of rideshare launch on an Evolved Expendable Launch Vehicle Secondary Payload Adapter (ESPA), which drastically reduces mission costs over a dedicated launch vehicle. Technology advancement without context of the final implementation can be misguided, resulting in costly iterations to adapt to designs to a future instrument or mission. Our proposed approach integrates technology advancement with mission design to avoid costly adaptation for final implementation. We propose to advance technologies and develop a space instrument/mission concept to enable the world’s first space-based WV DIAL optimized for PBL profiling with multi-function capability and cross-cutting application that is affordable within future EVI and EVM cost caps. A future satellite lidar based on these innovate technologies would revolutionize weather and climate research by providing three-dimensional distributions of water vapor profiles capable of delineating PBL from free tropospheric variations, estimates of total precipitable water vapor, distributions of PBL heights, profiles of aerosols and clouds, and high spatial resolution maps of methane columns.
We propose to advance the TRL of pulsed Er:YAG solid state lasers, pump laser diodes, and photonic integrated circuit (PIC) seed lasers to TRL-5. We look to execute this project by partnering with our industry collaborators, in which we have ongoing SBIR development efforts, to cost-share and maximize the TRL advancements of new innovative technologies that will further enable new and more affordable DIAL missions. Under this IIP we will leverage the work performed over multiple NASA SBIR’s (summing to >$1.3M) as well as through ongoing Department of Defense programs for the development of a space-qualifiable TRL-5 Er:YAG single-frequency laser compatible with operation on a SmallSat. The second key objective of this IIP is to substantially improve the electrical efficiency of 1532 nm pump laser diodes from the current <25% to >40% electrical efficiency. The proposed advance in pump diode efficiency is the single largest improvement to the overall lidar efficiency and enables operation on a SmallSat platform. The final objective of our IIP is to leverage an additional >$2M in SBIR and Game-Changing Technology funding to adapt existing high TRL seed laser technologies into a PIC to substantially reduce size, weight, complexity and power and enable operation on a SmallSat. The technology development is bracketed with a series of engineering design sessions between NASA Langley and ESPA SmallSat vendors to develop a high fidelity instrument design integrated on a SmallSat bus. We will conclude the program by leveraging our science collaborators respective areas of expertise to develop intelligent mission designs that integrate with existing missions and help inform the development of future observing systems. The period of performance is 36 months and the entry and exit TRL for the airborne laser subsystem is 3 and 5, respectively.
CloudCube
Raquel Rodriguez Monje, Jet Propulsion Laboratory
We propose to develop a multi-frequency millimeter-wave radar system, named CloudCube, using a minimalistic architecture that vastly reduces mass, power, size, development time and recurring costs. The instrument will enable unprecedented mission concepts that would fill existing gaps in the observation of a variety of cloud and precipitation processes. Mission concepts include, but are not limited to, low-cost radar measurements from small spacecraft platforms relevant to observation of cloud, convection and precipitation processes, global monitoring of atmospheric winds and observations of critical elements of the planetary boundary layer. For the first time, CloudCube combines Ka-, W- and G-band (35/94/238 GHz, respectively) radar backscatter with Doppler velocity measurement capability at Ka-band to simultaneously observes key components of a variety of atmospheric processes; however, the CloudCube design is modular allowing for selection of different subsets of the radar frequencies to meet targeted mission observables from a resource-limited platform. This new radar instrument provides flexible and timely capabilities to complement other instruments (e.g. lidar/spectrometer/microwave radiometer) in the Cloud Convection and Precipitation (CCP) architecture and expands the science return for other mission concepts not primarily hinged on radar observations. The concept has an entry level TRL of 3, with many critical components and subsystems at higher TRL. We will raise to TRL 6 over a three-year effort.
The instrument is designed and built from extensive heritage of JPL technology development for NASA. Some of the enabling technologies are: 1) a compact radar architecture utilizing offset I/Q with pulse compression which was demonstrated with RainCube (Radar In a Cube, NASA InVEST-15), 2) high-efficient Schottky diode frequency-multipliers, 3) a low-power, on-board digital processor and 4) the Displaced Phase Center Antenna (DPCA) approach to enable coherent measurements with small aperture antennas. The radar electronics will be developed under this project and consist of three transceivers that integrate all-solid-state transmit and receive devices inside compact modules. The transmit sources use waveguide power combining geometry with Schottky diodes at G-band and low voltage power amplifiers at both Ka- and W-bands to achieve the required transmitter power, which is kept at or below 10 W to avoid any complications from multipaction, breakdown, arcing and thermal dissipation. For the radar receivers, GaAs and InP low-noise amplifiers are used which have state-of-the-art noise temperatures. The CloudCube electronics are compatible with a number of specific antenna solutions and mission architectures to maximize its reconfigurability and tailor its resources to specific sets of science requirements.
Breakthrough Technologies Enabling ESPA-Class SmallSat Implementation of Earth Science LIDAR Missions
Mark Stephen, Goddard Space Flight Center
Space-based lidars have made many key Earth science observations. They provide unique advantages of spatial, spectral and temporal resolution because they carry their own laser illumination source. Despite many highly successful missions, however, lidar instruments are not being flown regularly in Earth orbit due to their cost, size, power requirements, and risk. In this Instrument Concept Demonstration (ICD), our team proposes to develop an innovative combination of lidar technologies to help overcome these critical challenges. Our team will demonstrate key instrument capabilities to enable lower cost, more regular missions.
This work targets three new technologies that address the most critical drivers of space lidar size, weight and power (SWaP). When successful these will enable SmallSat implementation of traditionally bulky, power-hungry lidar instruments.
These technologies are: (1) miniaturized and efficient wavelength-tunable seed lasers using photonic integrated circuits (PICs) and hollow-core photonic crystal fiber (HC-PCF) gas cells; (2) compact, efficient, high peak power optical amplifiers using highly-doped, large-mode-area fiber laser technology; and (3) a lightweight deployable, membrane receiver telescope coupled with custom free-form optics aberration correction.
These cutting-edge technologies address the major drivers for SWaP on a lidar mission, so combined they can enable a space lidar on a much smaller satellite that reduces cost but still meets stringent performance requirements.
Although the technologies that our team will address are broadly applicable to many lidar concepts, our team will target those for GSFC's CO2 Sounder, a carbon dioxide (CO2) integrated-path differential-absorption (IPDA) lidar. The lidar measurement of CO2 serves as an important testbed for the technology. The Earth science community and NASA have long recognized the importance of laser-based spectroscopic measurements for greenhouse gases from space because it allows greater coverage and avoids several known bias errors inherent in passive measurements. Our team is uniquely positioned to do this work with years of experience developing the airborne CO2 Sounder as well as space-based, and other airborne lidars. Our team has partnerships with the University of California Santa Barbara (UCSB) for photonic integrated circuits and with NeXolve for membrane telescope component development. Our team has the critical expertise in understanding the science measurements, developing the component technologies, and in verifying the component performance. The proposed 18-month program will increase the technology readiness from level 2 to 3.
Compact Hyperspectral Air Pollution Sensor-Demonstrator (CHAPS-D)
William Swartz, Johns Hopkins University Applied Physics Laboratory
Air pollution is responsible for ~7 million premature deaths every year. Past and current satellite missions in low Earth orbit have characterized air pollution distributions and established trends at fixed local solar times but in most cases cannot resolve individual emission sources without statistical post-analysis. Current and planned geostationary satellites will add diurnal information but lack global coverage. The Decadal Survey calls for a robust, comprehensive observing strategy for the spatial distribution of air pollution at high spatial, high temporal resolution. This will not be possible in a sustainable way without technological advancements.
The Compact Hyperspectral Air Pollution Sensor (CHAPS) is a hyperspectral imager (HSI) using free-form optics in a form factor suitable for accommodation on a small satellite or hosted payload. CHAPS will make measurements of air pollution at unprecedented spatial resolution from low Earth orbit (1 x 1 km2) and will characterize, quantify, and monitor emissions from urban areas, power plants, and other anthropogenic activities. The compact size and relatively lower cost of CHAPS makes a constellation feasible for the first time, with unprecedented spatiotemporal sampling of global point pollution sources. A CHAPS constellation represents a new observing system making science-quality measurements of air pollution, meeting new Decadal Survey requirements.
The objective of the CHAPS–Demonstrator (CHAPS-D) IIP project is the airborne demonstration of a CHAPS prototype instrument. CHAPS derives heritage from the TROPOspheric Monitoring Instrument (TROPOMI) on the Sentinel-5 Precursor, which uses a free-form mirror telescope. Free-form optics is an emerging technology with potentially huge advantages over traditional optical designs, including fewer optical surfaces, less mass and volume, and improved image quality. The free-form optics design demonstrated by the CHAPS D IIP will be generalizable to other wavelengths between 270 and 2400 nm, making it applicable to a wide variety of Earth science problems, including public health, atmospheric composition, surface biology and geology, land use/agriculture, marine and terrestrial ecosystems, the cryosphere, volcanic eruptions, and natural disaster response.
As a case study, we will focus this IIP project on the measurement of nitrogen dioxide (NO2). NO2 is a primary ingredient of air pollution, as it is a toxic gas at high concentrations, a marker for combustion-related pollutants and co-emitted air toxins, and the main precursor of tropospheric ozone and nitrate aerosols. CHAPS-D will combine a radiometrically calibrated HSI (300–500 nm @ 0.5-nm resolution) with associated detector and payload electronics. It will be as close to the ultimate space design as feasible within the scope of the IIP. For example, we will impose the design constraints for the payload of a 6U CubeSat. With these constraints in mind, we will introduce new technologies for on-board instrument calibration. With new, innovative passive metrology, we will be able to constantly monitor the instrument for continuous on-board correction of the measurement data.
The project total period of performance is from January 2020 through December 2022. The first project year focuses on the instrument design and the fabrication of the free-form optics, detector, and electronics. The second year will see the integration of the instrument, laboratory calibration, and ground-based (zenith-sky) measurements. The third year features a series of aircraft flights, where we will validate the performance of CHAPS-D, retrieve NO2 vertical column densities from measured radiance spectra, and compare these retrievals with extant ground-based, airborne, and operational space-based NO2 products. This will raise the CHAPS-D TRL from 2 to 5, preparing the compact hyperspectral imaging technology to tackle numerous Earth science objectives.
Concurrent Artificially-intelligent Spectrometry and Adaptive Lidar System (CASALS)
Guangning Yang, Goddard Space Flight Center
We propose to develop a brassboard version of a polar-orbiting SmallSat observing system which integrates adaptive lidar, hyperspectral imaging and on-board artificial intelligence (AI) technologies. The brassboard will demonstrate instrument performance required for space for key sub-systems. The technology, the Concurrent Artificially-intelligent Spectrometry and Adaptive Lidar System (CASALS), will provide high-priority measurements which support scientific studies and societal applications related to the carbon cycle and ecosystems, cryosphere response to climate change, natural hazards and atmospheric clouds and aerosols. The lidar, with altimeter and atmosphere profiling channels, will adaptively distribute the laser beam to specified locations across a swath using a photonic integrated circuit seed laser, wavelength tuning circuitry, a high-power fiber amplifier and a wavelength-to-angle mapping dispersive grating. This capability will enable measurement continuity with the ICESat-2 and GEDI lidar missions and, for the first time from space, achieve 3-D lidar imaging of a swath. The receiver telescope will employ free-form optics to substantially reduce its volume compared to traditional designs. A novel broadband filtering approach will reject solar background noise using a second grating. The signal photons will be detected using a linear-mode, photon-sensitive detector array with time-domain multiplexing electronics to differentiate from which location the photons are returned. The receiver telescope will be shared by the lidar and MiniSpec, a visible-NIR-SWIR hyperspectral imaging sensor which will provide information on target properties. MiniSpec also uses free-form optics for volume reduction. AI-assisted machine learning will be used for real-time hyperspectral image classification to support autonomous decision making, including optimized lidar beam targeting and data volume reduction by means of spectral band subsetting, on-orbit generation of products and product compression. Together, the concurrent information on vertical structure from the lidar and target properties from the spectral data will enable new scientific and application capabilities not achieved separately. The results will address five Earth Science Decadal Survey observable recommendations: ecosystem structure, ice elevation, snow depth and water equivalent, topography and 3-D vegetation and the atmosphere boundary layer. Our work will advance several space system technologies, including combined active/passive sensing, photonic integrated circuits, emerging sensor technologies, free-form optics and compact electronics. We will demonstrate smart sensing methods coupled to emerging machine learning information processing technologies. On-platform computational capacity will be used to coordinate among instruments and models of physical phenomenon, and react to changing environmental conditions. The period of performance is from January 1, 2020 to December 31, 2022. The technical readiness level at the start will be 2 and achieve 4 upon completion.
Multi-Spectral, Low-Mass, High-Resolution, Planar Integrated Photonic Imagers
Ben Yoo, University of California, Davis
We propose to demonstrate a new telescope concept that provides a low-mass, low-volume, integrated, and highly manufacturable alternative to the traditional bulky optical telescope.
The proposed new instrument consists of millions of optical interferometers densely packed onto photonic integrated circuits (PICs) to measure the amplitude and phase of the visibility function at spatial frequencies that span the full synthetic aperture. This Segmented Planar Imaging Detector for Electro-Optical Reconnaissance (SPIDER) utilizes many photonic interferometric circuits each employing sub-micron scale optical waveguides and nano-photonic structures fabricated on a silicon PIC with micron scale packing density to form the necessary interferometers. The newly proposed method utilizes standard processes at a silicon photonic and silicon CMOS foundries for wafer-scale SPIDER PIC fabrication, CMOS readout circuit fabrication, and assembly into a functional and robust integrated SPIDER. Benefits to NASA missions are multi-fold: (a) reduction of weight by ~100 x and volume by ~1000x, (b) significant simplification of assembly and integration, (c) order of magnitude reduction in cost and manufacturing time utilizing commercial silicon photonic and CMOS foundries, (d) robust operation in challenging environments with large temperature variations, vibrations, and shocks, (e) modular scalability to larger apertures, and (f) simultaneously offering high-resolution and low-resolution images from groups of long and short baseline interferograms. NASA IIP provides a unique opportunity to add the new innovations to facilitate commercial transition opportunities with Lockheed Martin and commercial foundries.
Signals of Opportunity Synthetic Aperture Radar for High Resolution Remote Sensing of Land Surfaces
Simon Yueh, Jet Propulsion Laboratory
The goal of our proposal is to develop the Synthetic Aperture Radar (SAR) Technology based on a unique combination of P-band Signals of Opportunity (SoOp) technique and sparse array technology for high resolution satellite remote sensing of Snow Water Equivalent (SWE) and Root Zone Soil Moisture (RZSM). The SoOpSAR concept will potentially lead to a significant reduction of cost and risk by an order of magnitude in comparison with the current available SAR technologies, which require dedicated high power transmit source, large deployable antenna aperture, complex deployment and hence large satellites.
Specifically, we target the second element of the IIP call on Instrument Concept Demonstration (ICD) to advance the TRL of SoOpSAR technology concept from 2 to 3.
The objectives of the proposed research are:
1. Complete proof-of-concept demonstration of the SoOpSAR technology by ground-based experiments;
2. Advance system concept by performing trade studies for resolution, swath, sparse array optimization, and uncertainty analysis of receiver timing and positioning errors.
The proposed SoOpSAR based on P-band Signals of Opportunity will provide an order of magnitude improvement in spatial resolution than the conventional SoOp technologies to enable applications, such as flood monitoring/forecasts and precision farming. Furthermore, the conventional spaceborne monostatic P-band SAR is currently not allowed to operate over North America and Western Europe due to frequency allocation by the International Telecommunication Union, which designates the US Space Objects Tracking Radar (SOTR) as the primary user of the 435 MHz band. The proposed SoOpSAR technology, operating at 260 and 360 MHz bands, could fill the gap for high-resolution radar imaging of land surfaces at P-band.
High resolution (~100m) remote sensing of soil moisture/snow water content is critical for modeling of land surface hydrological processes and applications. Despite their importance, SWE and RZSM, which are critical water storage elements, are arguably two of the least measured hydrologic states in the Earth System, in part due to the challenges and high cost of current spaceborne SAR technologies, which require large antenna apertures and hence large satellites. The proposed SoOpSAR concept is highly relevant to NASA Earth Science, specifically motivated by the stated science goal in the 2014 NASA Science Plan to: “Enable better assessment and management of water quality and quantity to accurately predict how the global water cycle evolves in response to climate change.” The ability of SoOpSAR will also address the needs of terrestrial snow water storage designated as one of the critical variables for the Earth Explorer Missions in the 2017 NASA Decadal Survey report.
We have completed a preliminary system performance analysis. The expected signal to noise ratio is exceptional and will enable accurate soil moisture and snow water content retrieval. For the IIP-ICD SoOpSAR proof-of-concept testing, we will develop five receivers for testing using a ground-based moving vehicle. The receivers will be mounted with various horizontal spacings to acquire data to simulate and test the use of sparse array concept for high across-track resolution processing. We will also conduct detailed system error analyses to determine the requirements on sparse array position control and knowledge accuracy requirements.
Our team members have demonstrated expertise in science algorithms, SoOp techniques, and SAR technologies and will complete the proposed tasks on cost and schedule.