Project Selections for ACT-22

13 Projects Awarded Under the Advanced Component Technology (ACT) Program

12/05/2022 – NASA’s Science Mission Directorate, NASA Headquarters, Washington, DC has selected 13 proposals for the Advanced Component Technology Program (ACT-22), a technology development program managed by the Earth Science Technology Office (ESTO). With these selections, ESTO is pioneering the next generation of highly innovative technologies for Earth science remote sensing. The ACT-22 solicitation called for disruptive technology with particular focus on photonic integrated circuits (PICs), quantum remote sensing, and metamaterials.

Stephanie Sandor-Leahy and William (Bill) Deal, both from Northrop Grumman, will lead teams that use PICs for hyperspectral infrared sensing (Sandor-Leahy) and hyperspectral microwave sounding of the planetary boundary layer (Deal). The field of quantum remote sensing is an exciting new frontier for Earth science remote sensing. ESTO is thrilled to partner with the following selected principal investigators from small businesses and universities pioneering this new paradigm-shifting technology: Kurt Vogel (Vescent Photonics), Shane Verploegh (Coldquanta), Matthew Cashen (Vector Atomic), and Peter Rakich (Yale University).

Metamaterials also offer new, highly innovative technologies to answer pressing Earth science questions. Brian Drouin (JPL) aims to develop ultra-violet spectropolarimetry enabled by meta-grating technologies that will allow for detection of ozone near the surface, which has implications for air quality and human health. Mark Stephen (NASA GSFC) and team will develop a segmented, deployable telescope prototype based on metalens technology. The foldable, origami-inspired mechanical packaging could enable SmallSat implementation of large aperture optical instruments (e.g., lidars), thereby replacing the need for traditional, bulky telescopes. Daniel Wasserman, from the University of Texas, will use metamaterials to create an ultra-compact machine-learning driven platform for room temperature mid-wave infrared remote sensing. Aaron Diebold (Metacept, Inc.) aims to develop a W-band metasurface cloud sensor that is envisioned to eventually be incorporated into a cloud targeting radar.

As ESTO is open to any truly disruptive technology, two of the selected projects do not fit into the three previously-mentioned focus areas. Ramy Tantawy, from SenseICs Corporation, will develop a Detection and Ranging System on a Chip (DARSoC). With its dramatic – even revolutionary – reduction in cost and SWaP, DARSoC could help to enable low cost SmallSat missions for both active and passive remote sensing in the future. Jonathan Sauder, from JPL, aims to develop a solid, under constrained multi-frequency deployable antenna, which is envisioned to compactly launch into space and open to a full 2-meter diameter solid antenna for radiometers and/or radars.

Fifty-seven ACT-22 proposals were evaluated. Abstracts for the 13 awards, which have a total dollar value of approximately $15.5M over three years, are as follows:

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Earth-observing PIC (EPIC) – Component Development
Mate Adamkovics, Lockheed Martin Inc.

Imaging spectrometers based on photonic integrated circuits (PICs) are poised to take advantage of rapid advances in nanofabrication to revolutionize the capabilities of remote sensing instruments in Earth Science. Interferometric imagers based on PIC devices have long been envisioned as a revolutionary sensor technology that can dramatically reduce the size, weight, and power (SWaP) of optical instruments (sensors) by eliminating the need for a traditional telescope and active optics. Eliminating components and reducing the requirements for alignment, together with the production efficiencies associated with wafer fabrication, can dramatically reduce costs for constellations of sensors. Lockheed Martin (LM) has unique resources and the institutional heritage to develop an Earth-observing PIC (EPIC) Multispectral Aerosol Polarimeter (MAP) for Earth Science. In this proposal we describe the definition, design, fabrication, and optimization plan for the fundamental PIC component of an imaging spectropolarimeter.

Low-SWaP and low-cost instrumentation that can be manufactured at scale will increase the number of sensors available to future Earth Science missions. Increasing the number of sensors will enable measurements that require multiple (simultaneous) vantage points. Additional sensors on orbiting platforms will improve revisit times and the frequency of sampling. Redundancy and reliability also both improve with the number of sensors. The proposed component development addresses Earth Science mission objectives that dramatically benefit from multiple, low-cost sensors.

This work will be performed from Jan 1, 2023 to Dec 31, 2024, and our objective is to fabricate the optimized component that will demonstrate the viability of future PIC instrumentation. We will demonstrate the polarization sensitivity and selectivity that is required for the remote characterization of aerosol. We will optimize end-to-end instrument throughput with a goal of achieving model-predicted insertion losses (IL) for the structures designed on the PIC. We will develop a sub-structure level insertion loss budget for the PIC during development and characterization that will guide instrument design as the PIC component is scaled to the performance requirements of an EPIC MAP mission. The Entry TRL the PIC technology is 2 and the Exit TRL is 4.

The four proposed tasks are to: (1) optimize waveguide grating coupler performance, (2) microfabricate — 3D print — lenslets for free-space coupler onto gratings, (3) optimize and test coherent combiner performance, and (4) assemble and characterize the optimized fundamental PIC component. The methodology for each task differs in technical detail, but in general follows the cycles of learning, which a series of iterative steps to design, fabricate, and test a particular sub-component of the PIC for optimization.

The proposed work is relevant to NASA ESTO Advanced Component Technology (ACT) program priorities, specifically the “particular focus on instrument subsystems and components based on integrated photonic circuits” noted in the ACT solicitation. This effort advances a rapidly emerging technology that is both broadly applicable to future imaging instruments as well as being specifically related to the Earth system observing objective of aerosol characterization

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Design for Atomic Gravity Gradiometer for Earth Research (DAGGER)
Matthew Cashen, Vector Atomic, Inc.

The Advanced Component Technology (ACT) program seeks technology development leading to subsystem-level spaceborne measurement techniques in support of the Science Mission Directorate’s Earth Science Division. Under ACT, Vector Atomic proposes the Design for Atomic Gravity Gradiometer for Earth Research (DAGGER). Our goal is to demonstrate the enabling hardware for a high-performance, space-based atomic gradiometer. DAGGER can provide a rapid and low-cost route to deploying an atomic sensor in space, serving as a pathfinder mission for future ultrahigh performance devices.

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Ultra RF
William Deal, Northrop Grumman Inc

Recently, techniques for ultra-wideband spectrometry have been proposed which would enable significant new science and could substantially simplify the complexity of atmospheric sensing instruments. Specifically, the “Ultra-Wideband Photonic Spectrometer for PBL Sensing” ACT-20 project is developing an RF photonic spectrometer for a millimeter wave radiometer back-end. Significantly, this RF photonic spectrometers should offer an order of magnitude increase in instantaneous RF bandwidths compared to today’s spectrometers and could provide as much as 100-200 GHz of instantaneous RF bandwidth.

We propose to build an RF front-end that could leverage the capabilities of the Ultra-Wideband Photonic Spectrometer by developing a single-channel RF front-end covering the Ultra-Wide RF bandwidth of 20-200 GHz. For this reason, we refer to this system as “Ultra RF”. This front-end will be comprised of broadband antenna integrated with broadband low noise amplifiers (LNAs) which will be fabricated in Northrop Grumman’s ultra-high frequency IACC25 MMIC technology. This technology features fT and fMAX of 750 and 1500 GHz, respectively. To demonstrate viability, we propose to test the final RF front-end with the RF photonic spectrometer being developed on the ACT-20 project.

The Ultra RF front-end will be integrated into a single assembly to maintain effective bandwidth. This is essential for covering the 20-200 GHz bandwidth. The antenna will be a double ridged waveguide horn antenna with a transition to microstrip. This allows the LNAs to be directly integrated to the transition using a wirebond. Our simulations show that low noise amplifiers with good sensitivity can feasibly operate across the 20-200 GHz bandwidth. We will also design 20-200 GHz traveling wave amplifiers (TWAs). These amplifiers have higher output power compared to low noise amplifiers and will be needed to handle the amplified noise power in the 20-200 GHz bandwidth and to drive the modulator with adequate power to insure high dynamic range. Initial simulations for the horn, LNA and TWA are included in the proposal.

Experimental validation of the Ultra RF front-end will be essential for validating the success of the project. Validation is complicated by the large bandwidths, which are not accommodated by any form of coaxial interface or waveguide interface. The Ultra RF front-end will be validated by banded RF measurements (RF and radiometric), as well as final integration with the Ultra-wideband RF Photonic Spectrometer for demonstration of viability.

If successful, the Ultra RF front-end system paired with the Ultra-Wideband RF Photonic Spectrometer will enable significant reduction in system complexity, which will reduce the Size, Weight, and Power of deployed systems and will enable decade bandwidth atmospheric sensing needed for planetary boundary measurements.

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Metasurface Antenna for Cloud-Targeting Radar (MACTRad): W-Band Metasurface Cloud Sensor
Aaron Diebold, MetaCept, Inc.

The Metasurface Antenna for Cloud Targeting Radar (MACTRad) component plans to enable the elusive study of time-resolved radar observations of clouds and precipitation. Most W-band (94GHz) spaceflight solutions do not provide the needed swath due to lower integration times resulting in reduced sensitivity. We plan to develop an electronically steered metasurface antenna targeting cloud radar applications that can dynamically track cloud features during a satellite overpass. In addition, V- and W-band radar antennas targeting high resolution suffer from deployment challenges related to array sizes and stringent surface tolerances at short wavelengths. The proposed component will leverage a dual-metasurface reflector architecture harnessing scalable metasurface design methodology to reduce control electronics complexity. Further, its stowable design will be complemented by adaptive beamforming and self-correction of structural irregularities related to deployment.

Currently, innovative compactable and steerable antennas are not available at frequencies above Ka band. This limits global coverage and ultimately the statistical relevance of the long-term measured data. Mechanical scanning is discouraged by the high scanning speeds required to achieve sufficient integration time. Moreover, there is mounting interest in platforms that are increasingly of the unmanned vehicle (UAV), smallSat and microSat variety where size, weight, power, and cost (cSWAP) considerations are paramount.

High-efficiency W-band antennas can be realized using free space feeds to avoid detrimental feed line losses. Conventional W-band approaches have employed reflectors fed with static feed antennas in a fixed orientation at the focal point, resulting in a geometry unsuitable for stowing. Planar metasurfaces can be designed to be deployable, but flexible steering requires high precision and a large number of control lines, complicating deployment. An electronically steerable metasurface in a reflective antenna architecture can limit the control complexity, avoid feed line losses, and enable adaptive strategies for deployment error correction, all while drastically decreasing cost and development time. In addition to the adaptive W-band system envisioned, this technology would provide valuable swath for V-band pressure radar systems and could even emulate the conical scan.

The final deliverable will consist of the combined dual-metasurface reflector antenna, including an electronically steered metasurface feed as well as the metasurface reflector antenna and preliminary design of housing selected based on deployment considerations. Adaptive feed procedures will be developed to optimize steering performance while simultaneously correcting for structural irregularities. All FPGA control components, PWB materials, metals and other ecosystem items would be chosen to have space heritage while also trying to be low-cost and manufacturable.

The teams at Duke and Metacept undertaking this effort collectively embody extensive metamaterial expertise, including formative theoretical research, innovative metasurface antenna technologies, and advanced radar systems for applications including science, communications, radar, and security screening. Electronically steered metasurface devices like the proposed structure have been successfully developed within this team from initial concept to functioning prototype. Co-investigators and collaborators at NASA Goddard Space Flight Center will provide the required scientific justification guiding the metasurface design. The electronically steerable dual-metasurface reflector antenna and its associated control architecture is TRL 1-2, although the metasurface feed itself may take advantage of existing high-TRL technologies developed by one of the team members for a 77 GHz radar in production for autonomous vehicle applications. We expect the exit TRL of the delivered component to be TRL 4.

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Compact ultra-violet spectropolarimetry enabled by meta-grating technologies
Brian Drouin, Jet Propulsion Laboratory

Significant differential absorption in the ultraviolet (UV) Huggins bands of ozone presents a variable, ozone specific polarimetric signature that can be discerned with sufficient sensitivity spectro-polarimetric measurements to separate the signature of harmful near surface ozone from the stronger signals of stratospheric ozone. As outlined as a ‘most important’ objective in the 2017 Earth Science Decadal survey, the earth science air quality community stands to benefit from tracking ozone in the planetary boundary layer to enable scientific and societal benefit efforts surrounding human and eco-system health. Existing methods for ozone detection are mostly effective in the stratosphere (UV and microwave) and upper troposphere (IR), and/or for measurement of total column ozone (UV). However, separation of the critical near surface signals requires the development of new methods. We propose an ambitious effort to realize the promise of polarization specific meta-surface gratings to enable a compact UV imaging spectropolarimeter. Such an instrument could take advantage of the natural differences in Rayleigh scattering at the variable penetration depths across the ozone Huggins bands, measuring the more strongly polarized light that is specific to near surface ozone absorptions. This technical team has demonstrated viable near-infrared polarization specific meta-gratings and is poised to iterate the design four times in the three year period of performance to determine best fabrication processes associated with development of viable ultraviolet polarization specific meta-gratings. Recognizing the challenging issues with both material selection and precision lithographic methods associated with UV applications, we will also explore another point solution involving a lower risk curved grating in a Dyson system, combined with a pupil-slicing optical element and wire-grid polarizers. This risk-reducing approach will improve the chances of providing viable, compact, architectures for rapid infusion into Earth Science missions. These UV systems are currently TRL1, so our Key Milestones involve TRL development including (1) producing designs that meet science metrics [TRL2]; (2) fabricating candidate components, and (3) ultimately characterizing the components at UV wavelengths to determine performance [TRL3]. A successful effort will result in viable components ready for use in follow-on system development that could be readied for Earth System Explorer mission opportunities

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Low-power Integrated Acousto-Optics for Atomic Quantum Sensors
Peter Rakich, Yale University

Quantum measurement techniques based on matter-wave interferometry have matured from early laboratory experiments into field-useable systems capable of precision remote sensing of Earth’s gravitational field. The unprecedented sensitivity of atom-based gravimeters and gradiometers is further enhanced when operating in microgravity environments, opening the possibility for high-resolution gravity cartography from orbit. The strong potential for atom interferometry in space is exemplified by NASA’s Cold Atom Laboratory which has been operated onboard ISS since 2018 and provides multi-purpose capabilities as a technology demonstration.

A common requirement for atom interferometers, and other atom-based quantum sensors such as Rydberg-atom-based RF-electric sensors and atomic clocks, is the need for complex laser and optical systems (LOS) used for atomic state preparation, control, and interrogation. Typically, these occupy bulky optical breadboards and require operating powers in the hundreds of Watts. While there has been much progress toward micro-integration of high-performance lasers, amplifiers, and detectors, there is currently no compact integrated alternative to free-space acousto-optic frequency shifters, which are used to precisely control laser spectra for atom manipulation. As a result, component-level advances are required for reduction in size weight and power and complexity of future space-deployable atomic quantum sensors.

To overcome the limitations of existing acousto-optic components, we propose a new integrated photonic architecture based on a GaN-on-Sapphire piezo-optic platform to realize energy-efficient and compact acousto-optic devices. This material system allows simultaneous excitation and guidance of acoustic waves, as well as low-loss optical waveguiding suitable to produce extremely efficient acousto-optic interactions, with high optical power handling capabilities at the wavelengths of 780-852 nm used for Rb and Cs-based atomic sensors. This work will result in flexible acousto-optic frequency shifters and modulators with mW-drive powers (>100x improvement over state of the art) that can be readily implemented in existing quantum sensor systems.

Existing state-of-the-art atomic quantum sensors utilize bulk acousto-optic modulators (AOMs) to precisely tune the frequency and amplitude of optical beams. Commercial AOMs are mature components that harness optical scattering from piezoelectrically-driven hypersound waves inside of a crystal. Due to their bulk-optical nature, they are relatively large (inch-scale) and require high RF drive powers >0.1-1 W—corresponding to wall-plug power consumption of several Watts per individual component. For future space-capable quantum sensors, that rely on numerous AOMs to operate, this represents a substantial barrier to size and power reduction.

Under the ACT program, we will design and fabricate integrated acousto-optic devices in GaN-on-Sapphire, with the target goal of achieving high-performance single-sideband modulators/frequency shifters with mW-level drive powers. This superb efficiency is enabled through confinement of optical and elastic waves on wavelength-scales, radically enhancing acousto-optic coupling as compared to bulk devices. Preliminary studies show the potential for near-unity conversion efficiency of optical signals to different frequencies with >40 dB single-sideband rejection. Through this first-generation effort, these devices will be fiber-coupled to be compatible with existing breadboard-based quantum sensor systems with immediate benefit to power consumption. Future work to implement switching, routing, and attenuation based on the same piezo-optic interactions will allow fully chip-based synthesis of the numerous beams needed to perform atomic quantum sensor experiments, significantly reducing the footprint and complexity of future space-deployable systems.

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Heterogeneous Integration of High Operating Temperature Barrier IR Detectors and Waveguides: Integrated Photonics for IR Hyperspectral Sensing
Stephanie Sandor-Leahy, Northrop Grumman Inc

Northrop Grumman (NG) and the Jet Propulsion Laboratory (JPL) propose to heterogeneously integrate JPL’s High Operating Temperature Barrier Infrared Detectors (HOT-BIRD) with NG’s infrared (IR) photonic waveguide chips forming the core component of a compact IR photonic spectrometer. Under the NASA ESTO SLI-T program, NG is developing a short wave IR photonic sensor, where an entire spectrometer (including optics, detectors, and readout electronics) can fit in a volume comparable to that occupied by an FPA assembly alone in current-day systems. The effort proposed under this ACT will extend the operational range of the photonic spectrometer instrument into the mid wave infrared (MWIR), enabling a miniaturized hyperspectral instrument capable of meeting NASA/NOAA’s GEO IR imaging mission requirements. This architecture also aligns with NASA’s desire for flexible low SWAP instruments that can be inserted on any platform from ground to air to space. We have carried out fundamental device modeling and developed approaches for fabricating MWIR-LWIR waveguides and waveguide components, and defined requirements for infrared detectors. The recently invented JPL HOT-BIRD technology offers a breakthrough solution for the realization of low-cost, high-performance photonic FPAs with excellent uniformity, operability, robust manufacturability, and lower development cost. HOT-BIRD detectors exhibit very low 1/f noise and high temporal stability, thus enabling long integration times and eliminating frequent calibrations. Under the proposed effort, our team will optimize detector and waveguide geometries, heterogeneously integrate the devices, and demonstrate functionality of the integrated components.

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Solid Underconstrained Multi-Frequency Deployable Antenna
Jonathan Sauder, Jet Propulsion Laboratory

A solution for a high frequency (up to 240 GHz), wide bandwidth, deployable reflector is needed to enable a low-cost and platform-versatile approach for the integration of three key instruments in upcoming Earth Science space missions. Cloud and precipitation radar payloads require a ~2-meter antenna aperture to capture the evolution of atmospheric processes at high spatial resolution. Microwave radiometers require an antenna operating from 6 to 200 GHz with a ≥ 2-meter diameter conically scanning (spinning) antenna for adequate footprint. The Differential Absorption Radar (DAR) instrument, pioneered by JPL, requires a large ~2-meter diameter antenna to focus and detect radar signals from hydrometeors at frequencies spanning from 155 to 175 GHz. Currently, all approaches for deployable reflectors operating above 90 GHz are in the TRL2-TRL3 range, and none appear to be conducive to spinning applications. Therefore, current mission baselines require a solid reflector, increasing cost and spacecraft size. A deployable reflector that supports frequencies from 6-240 GHz would decrease the cost of future missions, enabling missions that are performance-constrained by the size of antennas to fit on a smaller spacecraft, thereby enabling constellations.

To provide a solution to this antenna need, we are proposing the Solid Underconstrained Multi-Frequency (SUM) deployable antenna, a multi-segment, offset-fed parabolic solid deployable antenna system, which would enable large, high-frequency apertures to deploy from a compact volume of stacked segments. The proposed antenna is 2 meters in diameter, operating at frequencies between 2 GHz and 240 GHz, and can stow in a volume of 0.5 x 0.56 x 0.7 m^3. The core elements of the SUM deployable antenna consist of the aperture segments (semi-hexagons), rough deployment guides (high strain composite (HSC) rods), and systems for retrieval, preloading (cable), and kinematic location. When stowed, the segments stack neatly on top of each other into a compact volume. After launch, launch locks are activated, releasing the segments, and the HSC rods deploy the system into an initial configuration. Two HSC rods arrange each element in its proper orientation, so the system can be pulled together. After the deployable antenna opens, the cables are then retracted, slowly reeling in each of the segments into the final deployed shape. Kinematic joints precisely locate each segment relative to each other within 20 microns, preloaded in place by the cable, for an overall surface root mean squared (RMS) error of ~60 microns. The final system has only rigid segments in the design, meaning it is not subject to errors from creep. Because of its under-constrained deployment configuration, unlike hinged antennas, the segments can be stored anywhere on the spacecraft where there is spare volume, maximizing stowed efficiency.

Under this ACT, we will first build a prototype of the kinematic joint, and a small-scale prototype of the system. Then, a full-scale set of 3 segments will be constructed, deployment tested multiple times, and then the RF performance will be measured, demonstrating component validation in a laboratory. This work will occur over three years, and raise the TRL of the concept from an entry TRL of 2, to an exit TRL of 4.

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Metalens Origami Deployable Lidar (MODeL) Telescope
Mark Stephen, NASA Goddard Space Flight Center

Our team, responding to the ACT request for “deployable telescope technologies that specifically use flat lens technologies for lidars,” [A.46] will develop a segmented, deployable telescope prototype based on metalens technology, foldable, origami-inspired mechanical packaging and active optical aberration correction to enable small-sat implementation of large aperture optical instruments. Our flat lens technology is based on another ACT-requested technology – metasurfaces, enabling unprecedented optical performance in a small, lightweight package. This telescope will increase performance and reduce size, weight and power (SWaP), to “enable or dramatically enhance Earth observation remote sensing measurements in new, innovative ways.” [A.46] We propose to demonstrate the technology for a lidar application because the overall telescope requirements are somewhat relaxed compared to many imaging applications. Deployable lidar telescopes can benefit seven of the 2017 Earth Science Decadal Survey Explorer and Incubation Targeted Observables that can be addressed with Lidar – Greenhouse gases, Ice elevation, Snow Depth and Snow Water Equivalent, Terrestrial Ecosystem Structure, Atmospheric Winds, Planetary Boundary Layer, Surface Topography and Vegetation. Our team will mature deployable telescope technology in time to be considered for mission concepts in the late 2020s and beyond.

A key goal of the ACT call is to “reduce the size, weight, power requirements, … and cost of Earth science remote sensing observation systems.” [A.46] A fundamental limitation in the trend toward smaller optical instrumentation and spacecraft is volume availability for collection apertures. A certain power-aperture product is required to obtain adequate signal for lidar (and many other) measurements. The amount of light that can be collected is a function of collection area, so a 2× increase in telescope diameter yields a 4× increase in light collection. Unfortunately, the volume required for traditional telescopes roughly scales as the cube of the collection diameter, so a 2× increase in diameter yields an 8× increase in volume. Our team’s disruptive deployable telescope technology is therefore mission-enabling because it yields large-satellite performance with small-satellite cost by increasing aperture while shrinking the launch volume and decreasing the required laser power.

Our team proposes Meta-optic lens elements grown on silica wafers, mounted in thin frames that fold up in origami-inspired collapsible structures and deploy in a large flat aperture, enabling Evolved Expendable Launch Vehicle (EELV) Secondary Payload Adapter (ESPA)-class science Lidar instruments from low-Earth orbit (LEO). Meta-optics allow thin, flat, very lightweight optics to perform the same function as much larger and more expensive shaped counterparts like lenses and mirrors. Flat, transmissive lens-type optics are also more tolerant to mechanical distortions because the light deflection is not based on surface shape.

Our team is uniquely qualified to successfully complete the work proposed. GSFC is a world leader in space-based lidar systems with expertise in the design, analysis, manufacture, integration, test, delivery and operation of satellite-born lidars and optics. Penn State University is a pioneer in meta-optics development and recently set a record for aperture-size in optical metalenses. Brigham Young University is a leader in the design and analysis of space-based compliant mechanisms and origami-inspired structures. MMA Design brings innovative concepts and proven devices in space-based deployed structures and control systems. Together this team has the capabilities, facilities and expertise to successfully complete the proposed research effort. We propose a three-year effort to take the deployable telescope from a TRL-2 concept to a TRL-4 prototype demonstrating the critical performance requirements and the deployment function.

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Low Cost, Size, Weight, and Power, Radiation Hard, Time-of-Flight LiDAR or Infrared Radiometry System on a Chip for Earth Orbit and Planetary Missions
Ramy Tantawy, SenseICs Corporation

The goal of the ACT program is to develop and demonstrate component and subsystem level technology that enhances earth observation remote sensing in new innovative ways while simultaneously reducing the cost, size, weight, and power (C-SWAP) requirements of the technology. NASA uses light detection and ranging (LiDAR) technology and infrared (IR) radiometry for atmospheric measurements, geographical data retrievals, ocean profiling, satellite validation, and algorithm development. LiDAR and radiometry technology for Earth observations in the future are primarily focused on studying factors that impact weather, air quality, and climate. The objective of this proposal is to develop a low C-SWAP System on a Chip (SoC) robust enough for space-based Time-of-Flight (ToF) LiDAR and IR Radiometry. Our Detection and Ranging System on a Chip (DARSoC) will have a reconfigurable front end to allow adaption, accommodating a range of detector specifications and will be robust enough for space-based missions. The ACT program solicits new technologies to support future developments within six focus areas: carbon cycle and ecosystems, water and energy cycle, climate variability and change, atmospheric composition, weather and atmospheric dynamics, and earth surface and interior. A strength of our proposed technology is that our DARSoC is reconfigurable and versatile, meaning it is compatible for missions within each of these focus areas. Missions that have been conducted in the past pertaining to these focus areas include the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO), Global Ecosystem Dynamics Investigation lidar (GEDI), and the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER). For future missions, capabilities that are desired are higher accuracy, higher information content, and optimized readout electronics. Utilizing components that are low cost, size, weight, and power provide the flexibility of focusing on these vital functions. In addition, our DARSoC will be radiation tolerant, making it suitable for in-space missions. A final requirement of the ACT program is to reduce development risks and time. Our DARSoC leverages IP from a radiation tolerant TRL 5 prototype designed for another project giving us a strong starting point for some circuits and knowledge on the radiation tolerance of the technology. Our DARSoC will be equipped with a 14-bit analog readout path for radiometry applications and can provide under 50 ps timing resolution for ToF. The SoC will include a highly re-configurable fast analog front end and timing discriminator (FEaD) that will be designed for compatibility with a wide range of photomultiplier and solid-state LiDAR detectors and infrared radiometers on the market and currently in development. The SoC back-end will include a low noise phase locked loop (PLL) for receipt of an input from an external ultra-stable oscillator. The PLL will provide multiplication of the oscillator time reference to higher frequencies and subsequently used to capture the laser ToF. Additionally, the radiometry path will include a low-noise PGA followed by high resolution, reconfigurable, asynchronous SAR ADC to amplify and digitize the sensitive radiometric signals. The proposed radiation hardened by design SoC will process the ToF or ADC data and provide a low-latency range measurement to the mission’s control and data handling. Incorporating our proposed technology into future Earth science LiDAR or radiometry missions can not only allow for ground-breaking scientific discoveries but provide scientists with measurements intended to study human health and improve lives.

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Quantum Atomic Rydberg Radiometer for Earth Measurements (QuARREM)
Shane Verploegh, ColdQuanta, Inc.

Decades of operational and scientific mission experience have proven that microwave radiometers (MR) are invaluable for collecting accurate, frequent data resulting in atmospheric sounding and surface imaging measurements of a wide range of geophysical phenomena. Retrievals of atmospheric temperature and humidity profiles are obtained routinely from several MR (e.g. ATMS, AMSU, SSMI/S) using channels near the 60 GHz (V-band) oxygen and 183 GHz (G-band) water absorption features. These data, and the derived profiles, support scientific research and are key inputs to weather forecasts and climate models. The European Center for Medium-range Weather Forecasts has determined that sounding from MRs provides the single greatest benefit to weather forecasting of any measurement type.

Budget pressures are driving a re-evaluation of the entire weather observation architecture with opportunities seen in alternative platforms, particularly in relatively inexpensive options that can be deployed as constellations. As these constellation architectures become more competitive with the traditional, large systems they drive innovation in Earth observing technologies. Sensors must evolve to lower Size, Weight and Power (SWaP), without impact to performance to achieve these cost reductions.

The proposed Quantum Atomic Rydberg Radiometer for Earth Measurement (QuARREM) MR quantum system replaces RF electronics in conventional MR (i.e., bandpass filters, low noise amplifiers (LNA), mixers and intermediate frequency (IF) channelization electronics) with a single compact atomic vapor cell sensor integrated into a directive antenna. Lasers excite atoms in the vapor to Rydberg states that are highly sensitive to electric fields and frequency selective. QuARREM allows the definition of multiple frequency channels spanning 20 to 200 GHz in the same atomic sensor by tuning one laser. Our atomic system improves radiometric resolution enabled by a sensitivity to bandwidth enhancement of 4 – 40x over conventional MR. Measurement uncertainty is reduced by eliminating the need for external calibration and associated errors through in-measurement SI-traceable self-calibration. QuARREM does not generate 1/f (flicker) noise which is problematic at high frequencies in conventional MR. Finally, our approach provides a low SWaP alternative to conventional MR, via a robust measurement chamber volume less than 5 cm3. The resulting RF/quantum atomic integrated platform is directly applicable to retrievals such as atmospheric moisture and temperature profiles and surface parameters.

This QuARREM project includes the following tasks:

1. Fundamental modeling: System modeling and theory extension to supplement previously funded work, will include noise contributions and verify absolute calibration points. The initial emphasis will be on operation within the 50/60 GHz V-band. We will compare this quantum approach to conventional MR.
2. Testbench development: Develop a testbench with capability to explore this phenomenon in direct relation to temperature sounding in the V-band. This development contributes to optimization of the detection architecture, miniaturization of optics, and integration into antennas.
3. Vapor cell fabrication: Concurrent with test bench development, an iterative prototyping of the atomic vapor cell will be performed. This effort is to move from traditional glass “vials” to integrated structures that perform an optimized dual function of RF waveguiding and laser-induced fluorescence.
4. Absolute calibration development: We plan to experimentally demonstrate this concept using a reference cell of the same type prototyped in task 3. Direct comparison to a SI-traceable calibrated blackbody source will be used to gauge performance.

The key sub-system in QuARREM is the measurement chamber in task 3. We will focus on making a compact, shock-and-vibration hardened package and will advance the TRL for this component from 2 to 4.

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Low SWaP-C Modular Laser Architecture for Laser-Cooled Quantum Sensors and Atomic Clocks
Kurt Vogel, Vescent Photonics LLC

Vescent Photonics, LLC (Vescent) proposes to develop a compact, low-power, environmentally robust, frequency agile laser system for use with space-based light-pulse atom interferometry (LPAI) and other cold-atom-based sensing and timing systems. This proposal specifically addresses the development of high-performance laser systems with low size, weight, power, and cost (SWaP-C) for spaceborne quantum gravity gradiometry (QGG) based on LPAI. Spaceborne QGG has been proposed and evaluated to offer higher temporal and spatial resolution in global gravity monitoring measurements for Earth sciences. At this time, however, successful deployment of spaceborne QGG is limited by the lack of suitable frequency-stabilized lasers that can withstand the rigors of space flight while meeting the high-performance requirements for LPAI. The proposed laser system will meet the challenging performance and environmental requirements for space-borne LPAI while still providing a manufacturable and highly configurable architecture to meet the future needs of other types of space-based quantum sensors and atomic clocks.

In the proposed effort, we will build a low SWaP-C, modular laser system that will be compatible with a cesium-based quantum gravity gradiometer being developed by the Jet Propulsion Laboratory (JPL). Vescent will design and build the laser system based on a hybrid approach that combines micro-optical components, fiber-optics, and photonic integrated circuits to reduce the volume of the electro-optics packages while substantially improving their environmental robustness and manufacturability. These electro-optical packages will be tightly integrated with ultralow-SWaP, low-noise electronics for performing active feedback control of the laser optical frequencies and intensities. Our proposed modular architecture can be easily configured for a variety of measurement strategies and will allow much faster development of future space-based LPAI systems. JPL will provide requirements for the laser system and perform integration testing of the Vescent laser system with their LPAI-based gravity gradiometer. The successful development of this new laser system will provide the frequency-stabilized light required for LPAI in QGG, enabling practical implementation and infusion of QGG to future earth gravity measurement and monitoring missions beyond today’s capabilities.

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Ultra-compact Machine-Learning-driven platform for room temperature mid-wave infrared remote sensing
Daniel Wasserman, University Of Texas, Austin

This program aims to develop new classes of mid wave infrared (MWIR, 3-5 microns) sensors for Earth Science applications. The proposed effort consists of two thrusts: (i) MWIR detector development, (ii) room temperature MWIR focal plane arrays (FPAs) and development of a novel sensing paradigm, the metasensor, where the FPA is deterministically coupled to the outside world with diffractive metasurface structures.

The proposed program aims to advance our ability to detect and image in the MWIR, benefiting Earth Science monitoring of surface temperatures, atmospheric scattering, and vegetation cover. Since modern high-performance MWIR sensors typically require significant cooling for efficient operation, our proposed effort will have immediate impact on the field of remote sensing. The demonstration of a highly efficient, low-noise room-temperature MWIR detector will significantly decrease the size, weight, power, and cost of airborne/space-based remote-sensing. The proposed program will benefit data collection for weather forecasting models and the understanding (and mitigation) of climate change. In the longer-term, the metasensor offers a potentially transformational advance to MWIR imaging. Metasensing will enable multi-modal information collection, drastically reduce the size and complexity of the imager by integrating detectors and front optics within the same static chip, and simultaneously move the tasks related to focusing, aberration correction, etc. from imaging time to software (ML-based) post-processing, thereby enabling future mining of existing data with extra sensing modalities or improved algorithms.

The proposed effort will leverage the team’s combined expertise in theory, numerical techniques, machine-learning, optical and electronic design, epitaxial growth, nano-fabrication, and optical and electronic characterization. We will demonstrate high external quantum efficiency (EQE) MWIR detectors, operating at room temperature, with significantly decreased dark current and thus high specific detectivity. The detectors’ architecture is designed to decouple EQE from detector volume and thus avoid the typical trade-offs that limit infrared (IR) detector design. Further, we propose to quantum engineer IR-absorbing semiconductor superlattices, improving dark current not only by reduced detector volume, but by careful engineering of the absorbing material to minimize high temperature parasitic processes. These high-performance detectors will be integrated with coupling structures, optimized to control the detectors’ spectral and polarimetric response. Novel, machine learning-based algorithms will be designed to develop such diffractive coupling structures.

We will design, grow, fabricate and characterize proof-of-principle focal plane arrays (FPAs) leveraging our room temperature MWIR detectors, demonstrating our detector architecture’s immediate suitability for existing MWIR imaging applications. At the same time, we will explore the novel metasensor architecture. Far from the simple metalenses that mimic refractive optics, albeit in a compact space, the metasensor couples incident light to multiple detector elements (with different wavelength/polarization response) within the MWIR FPA, thereby allowing the platform to simultaneously analyze multiple aspects (frequency, direction, polarization) of incident light with proper software post-processing. We will develop such post-processing techniques based on semi-analytical solutions of Maxwell equations and on machine-learning, aiming to demonstrate multi-modal information processing (scene reconstruction, polarimetric imaging, edge detection, etc) within MWIR metasensors.

 

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