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Land-reflected signals from a geosynchronous communication satellite broadcasting in P-band (367.5 MHz) were captured in low Earth orbit using a simple dipole antenna. A delay-Doppler map (DDM) was generated through autocorrelation. Estimates of the specular point delay were obtained from the lag of the second peak in the DDM with a bias of 239.4 m and a standard deviation of 44 m (12 m over a frozen lake) with respect to a predicted orbit model. Relative magnitudes of the first and second DDM peaks fell within the range of values predicted using dielectric models for the frozen ground and lake. Lastly, retrievals of surface reflectivity were generated using a range of realistic values for the transmitter link budget G/T, these also fell within the range of possible values for the antenna gain pattern. Given the lack of calibration and the large uncertainties in the receiver orbit and attitude, this agreement is sufficient to conclude a successful demonstration of the fundamental principle of single-antenna reflectometry in P-band. P-band reflectometry may offer a new approach to remote sensing of sub-canopy and root-zone soil moisture.

High-performance graphene-HgCdTe detector technology has been developed combining the best properties of both materials for mid-wave infrared (MWIR) detection and imaging. The graphene functions as a high mobility channel that whisks away carriers before they can recombine, further contributing to detection performance. Comprehensive modeling on the HgCdTe, graphene, and the HgCdTe-graphene interface has aided the design and development of this MWIR detector technology. Chemical doping of the bilayer graphene lattice has enabled p-type doping levels in graphene for high mobility implementation in high-performance MWIR HgCdTe detectors. Characterization techniques, including SIMS and XPS, confirm high boron doping concentrations. A spin-on doping (SOD) procedure is outlined that has provided a means of doping layers of graphene on native substrates, while subsequently allowing integration of the doped graphene layers with HgCdTe for final implementation in the MWIR photodetection devices. Successful integration of graphene into HgCdTe photodetectors can thus provide higher MWIR detector efficiency and performance compared to HgCdTe-only detectors. New earth observation measurement capabilities are further enabled by the room temperature operational capability of the graphene-enhanced HgCdTe detectors and arrays to benefit and advance space and terrestrial applications.

Broadband antireflection (AR) optical coatings covering the ultraviolet (UV) to infrared (IR) spectral bands have many potential applications for various NASA systems. The performance of these systems is significantly limited by signal loss due to reflection off substrates and optical components. Tunable nanoengineered optical layers offer omnidirectional suppression of light reflection/scattering with increased optical transmission to enhance detector and system performance particularly over IR band wavelengths. Nanostructured AR coatings enable the realization of optimal AR coatings with high laser damage thresholds and reliability in extreme low temperature environments and under launch conditions for various NASA applications. We are developing and advancing high-performance AR coatings on GaSb and various other substrate types for spectral bands ranging from UV to LWIR. The nanostructured AR coatings enhance transmission of light through optical components and detector devices by greatly minimizing reflection losses over range of incidence angles, providing substantial improvements over more conventional thin film AR coating technologies. In this paper, we review our latest developments in high performance nanostructurebased AR coatings, focusing primarily on recent efforts in designing and fabricating AR coatings for the LWIR spectral band for performance improvements in airborne and space detector applications.

In this paper, we will report our recent efforts in achieving high performance in Antimonides type-II superlattice (T2SL) based infrared photodetectors using the barrier infrared detector (BIRD) architecture. The high operating temperature (HOT) BIRD focal plane arrays (FPAs) offer the same high performance, uniformity, operability, manufacturability, and affordability advantages as InSb. However, mid-wavelength infrared (MWIR) HOT-BIRD FPAs can operate at significantly higher temperatures (

High performance detector technology is being developed for sensing over the mid-wave infrared (MWIR) band for NASA Earth Science, defense, and commercial applications. The graphene-based HgCdTe detector technology involves integration of graphene with HgCdTe photodetectors allowing higher performance detection over 2-5 μm compared with photodetectors using only HgCdTe material. The graphene layer functioning as a high mobility channel reduces recombination of photogenerated carriers in the detector to further enhance performance. Graphene bilayers on Si/SiO2 substrates have been doped with boron using a spin-on dopant (SOD) process. The p-doped graphene is then transferred onto HgCdTe substrates for high mobility layers in MWIR photodetectors. Various characterization techniques including Raman spectroscopy and secondary-ion mass spectroscopy (SIMS) have analyzed dopant levels and properties of the graphene throughout various stages of development to qualify and quantify the graphene doping and transfer. The objective of this work is demonstration of graphene-based HgCdTe room temperature MWIR detectors and arrays through modeling, material development, and device optimization. The primary driver for this technology development is enablement of a scalable, low cost, low power, and small footprint uncooled MWIR sensing technology capable of measuring thermal dynamics with better spatial resolution for applications such as remote sensing and earth observation.

In this presentation, we will report our recent efforts in achieving high performance in Antimonides type-II superlattice (T2SL) based infrared photodetectors using the barrier infrared detector (BIRD) architecture. The high operating temperature (HOT) BIRD focal plane arrays (FPAs) offer the same high performance, uniformity, operability, manufacturability, and affordability advantages as InSb. However, mid-wavelength infrared (MWIR) HOT-BIRD FPAs can operate at significantly higher temperatures (

Recent experimental investigations in Bi-Layer Graphene (BLG) have shown interesting and useful electrical behavior that can be leveraged in building novel device applications. One such behavior being carrier multiplication effects within the BLG. We propose to use a heterostructure of BLG-CdTe-HgCdTe as a detector structure that marries this effect along with the unique bandalignment of the heterostructure which suggest an Ohmic contact for the electrons but a Schottky barrier for the holes. Using a dissipative quantum transport model, namely the Non-Equilibrium Green’s Functions with self-consistent Born approximation accounting for electron-electron and electron-phonon interactions, we calculate energy and position resolved electron and hole currents through these heterostructure and discover a 20X ratio of electron-to-hole ratio in an illustrative simulation which demonstrates the potential for reducing the hole contribution to dark current and modulating the recombination mechanisms and therefore the lifetime of the carriers in the heterostructure.

In this presentation, we will report our recent efforts in achieving high performance in Antimonides type-II superlattice (T2SL) based infrared photodetectors using the barrier infrared detector (BIRD) architecture. The high operating temperature (HOT) BIRD focal plane arrays (FPAs) offer the same high performance, uniformity, operability, manufacturability, and affordability advantages as InSb. However, mid-wavelength infrared (MWIR) HOT-BIRD FPAs can operate at significantly higher temperatures (

Front-illuminated p-i-n GaN-based ultraviolet (UV) avalanche photodiodes (APDs) were grown by metalorganic chemical vapor deposition (MOCVD) on 25 mm dia. bulk Ammono® n-GaN substrate having a low etch pit density (EPD) less than 5 × 104 [cm-2] and processed into 6×6 APD arrays. The devices employed N-ion implantation to achieve sidewall passivation. Evaluation of these 6×6 arrays will help to confirm the uniformity of the epitaxial materials and device processing. The maximum avalanche gain reached ~ 3×105 at the breakdown (current limited). The dark current density was 10-9 A/cm2 at reverse bias up to -20 V and the APDs exhibited a reverse breakdown voltage of 81 ± 1 V for all 36 devices without any leaky devices, confirming a high uniformity of the growth and fabrication processes.

Broadband antireflection (AR) optical coatings covering the ultraviolet (UV) to infrared (IR) spectral bands have many potential applications for various NASA systems. The performance of these systems is substantially limited by signal loss due to reflection off substrates and optical components. Tunable nanoengineered optical layers offer omnidirectional suppression of light reflection/scattering with increased optical transmission to enhance detector and system performance. Nanostructured AR coatings enable realization of optimal AR coatings with high laser damage thresholds and reliability in extreme low temperature environments and under launch conditions for various NASA applications. We are developing and advancing high-performance AR coatings on various substrates for spectral bands ranging from the UV to IR. The nanostructured AR coatings enhance the transmission of light through optical components and devices by significantly minimizing reflection losses, providing substantial improvements over conventional thin film AR coating technologies. The optical properties of the AR coatings have been measured and fine-tuned to achieve high levels of performance. In this paper, we review our latest work on high performance nanostructure-based AR coatings, including recent efforts in the development of the nanostructured AR coatings for UV band applications.

Detection of ultraviolet (UV) bands offers increased spatial resolution, small pixel sizes, and large format arrays, thus benefitting a variety of NASA, defense, and commercial applications. AlxGa1-xN semiconductor alloys, which have attracted much interest for detection in the UV spectral region, have been shown to enable high optical gains, high sensitivities with the potential for single-photon detection, and low dark current performance in ultraviolet avalanche photodiodes (UV-APDs). We are developing GaN/AlGaN UV-APDs with large pixel sizes that demonstrate consistent and uniform device performance and operation. These UV-APDs are fabricated through high quality metal organic chemical vapor deposition (MOCVD) growth on lattice-matched, low dislocation density GaN substrates with optimized material growth and doping parameters. The use of these low defect density substrates is a critical element to realizing highly sensitive UV-APDs and arrays with suppressed dark current and jitter under high electric fields. Optical gains of 5×106 and greater with enhanced quantum efficiencies over the 320-400 nm spectral range have been demonstrated, enabled by a strong avalanche multiplication process. We are additionally using device technology developed for high voltage GaN p-i-n rectifier devices to enable advanced Geiger-mode UVAPDs with single-photon counting capability. This technology provides extremely low leakage currents in the reverse bias range near avalanche breakdown, a necessary requirement for stable Geiger-mode operation. The variable-area GaN/AlGaN UV-APD detectors and arrays being developed enable advanced sensing performance over UV bands of interest with high resolution detection for NASA Earth Science applications.

Broadband antireflection (AR) optical coatings covering the ultraviolet (UV) to infrared (IR) spectral bands have many potential applications for various NASA systems. The performance of these systems is substantially limited by signal loss due to reflection off substrates and optical components. Tunable nanoengineered optical layers offer omnidirectional suppression of light reflection/scattering with increased optical transmission to enhance detector and system performance. Nanostructured AR coatings enable realization of optimal AR coatings with high laser damage thresholds and reliability in extreme low temperature environments and under launch conditions for various NASA applications. We are developing and advancing high-performance AR coatings on various substrates for spectral bands ranging from the UV to IR. The nanostructured AR coatings enhance the transmission of light through optical components and devices by significantly minimizing reflection losses, providing substantial improvements over conventional thin film AR coating technologies. The optical properties of the AR coatings have been measured and fine-tuned to achieve high levels of performance. In this paper, we review our latest work on high performance nanostructure-based AR coatings, including recent efforts in the development of the nanostructured AR coatings for UV band applications.

Graphene-HgCdTe heterostructure based mid wave IR (MWIR) detectors are being designed for NASA Earth Science applications. Combining Density Functional Theory (DFT) based calculations of the bandstructure with carrier generation and transport model of this detector, we study the essential physics of this novel detector design and project its performance. Combining the best of both these materials can yield high performance and superior detection capabilities.

Over the past decade, the NASA Earth Science Technology Office (ESTO) has strategically invested funds in programs that have yielded substantial benefits to the Sustainable Land Imaging (SLI) program.Some of these investments, such as the SLI-Technology (SLI-T) program were funded using SLI funds set aside to reduce the risks and costs for future SLI needs. Other programs, such as Advanced Component Technologies (ACT), Instrument Incubator Program (IIP), Advanced Information Systems Technology (AIST), and In-Space Validation of Earth Science Technologies (InVEST), address the broader Earth Science Land Imaging needs with direct benefit to SLI. This paper will highlight the relevant programs and indicate the ways that they have enabled and will enable the short and long-term SLI program needs and budgetary constraints. Driving requirements and the ways these are satisfied with each components or system will be presented. Example data that demonstrates the performance of these new concept demonstrations will be shown.

In this presentation, we will report our recent efforts in achieving high performance in Antimonides type-II superlattice (T2SL) based infrared photodetectors using the barrier infrared detector (BIRD) architecture. The initial BIRD devices (such as the nBn and the XBn) used either InAs absorber grown on InAs substrate, or lattice-matched InAsSb alloy grown on GaSb substrate, with cutoff wavelengths of ~3.2μm and ~4μm, respectively. While these detectors could operate at much higher temperatures than existing MWIR detectors based on InSb, their spectral responses do not cover the full (3 – 5.5μm) MWIR atmospheric transmission window. The T2SL BIRD devices not only covers the full MWIR atmospheric transmission window, but the full LWIR atmospheric transmission window and beyond. The LWIR detectors based on the BIRD architecture has also demonstrated significant operating temperature advantages over those based on traditional p-n junction designs. Two 6U SmalSat missions CIRAS (Cubesat Infrared Atmospheric Sounder) and HyTI (Hyperspectral Thermal Imager) are based on JPL’s T2SL BIRD focal plane arrays (FPAs). Based on III-V compound semiconductors, the BIRD FPAs offer a breakthrough solution for the realization of low cost (high yield), high-performance FPAs with excellent uniformity and pixel-to-pixel operability.

In this presentation, we will discuss the advantages of using an in-pixel digital read out integrated circuit and type-II strained layer superlattice detector array technology to elevate the operating temperature of the focal plane array for Earth remote sensing instruments.

Long-wavelength infrared (LWIR) focal plane arrays (FPAs) needed for Earth Science imaging, spectral imaging, and sounding applications have always been among the most challenging in infrared photodetector technology due to the rigorous material growth, device design and fabrication demands. Future small satellite missions will present even more challenges for infrared FPAs, as operating temperature must be increased so that cooler (and radiator) volume, mass, and power can be reduced. To address this critical need, we are working on following three technologies. 1) Type-II superlattice (T2SL) nBn type barrier infrared detector, which combines the high operability, spatial uniformity, temporal stability, scalability, producibility, and affordability advantages of III-V detectors. 2) The resonator pixel technology, which uses metasurface light trapping techniques to achieve strong absorption in a small detector absorber volume, thereby enabling enhanced QE and/or reduced dark current. 3) High dynamic range 3D Readout IC (3D-ROIC), which integrates a digital reset counter with a conventional analog ROIC to provide a much higher effective well capacity than previously achievable. The resulting longer integration times are especially beneficial for high flux/dark current LWIR applications as they can improve signal-to-noise ratio and/or increase the operating temperature. By combining these three technologies, this project seeks to demonstrate a cost-effective, high performance LWIR FPA technology with significantly higher operating temperature and sensitivity than previously attainable, and with the flexibility to meet a variety of Earth Science TIR measurement needs, particularly the special requirements of small satellite missions.

The compact thermal imager (CTI) is a dual-band, strained-layer-superlattice (SLS) detector–based instrument that was installed on the exterior of the International Space Station (ISS) in conjunction with the third Robotic Refueling Mission 3 (RRM3) in 2018. The CTI serves as a pathfinder for future thermal infrared capability on Landsat. The CTI incorporates an SLS hybrid, a dual-band 3–5 and 8–10 μm, electrically switchable, 320×256 array with 30 μm2 pixels, bonded to an Indigo ISC0903 Readout Integrated Circuit (ROIC). The telescope was built around an integrated detector cryocooler assembly developed under a NASA Small Business Innovative Research award with QmagiQ, LLC. The cooler is a Ricor K508 and the front-end optics is a custom-designed, doublet lens telescope with a 150 mm focal length. The ground resolution is 80 meters/pixel from the ISS altitude of 400 km. A filter creates two spectral channels from the dual bands, 3.3–5.4 and 7.8–10.2 μm. The detector hybrid control electronics is a custom-developed system based on the Teledyne Imaging Systems SIDECAR Application-Specific Integrated Circuit. This module provides the electronic interface from the RRM3 SpaceCube on-board processor to the detector/ROIC assembly. The primary goal of this mission was to perform a technology demonstration of the SLS technology and the commercial cooler technology elevating the Technology Readiness Level (TRL) to TRL 9 on a bare-bones budget and relatively fast development cycle. Some science objectives include locating fires, approximating land surface temperatures, and monitoring evapotranspiration, sea ice, and glacier dynamics. In this paper, we will present the design of the focal plane, optics, electronics, and mechanical structure of the CTI. We will also describe the operation and qualification tests that were performed to bring the CTI to the NASA TRL 6 in preparation for the launch on a SpaceX Dragon from the Kennedy Space Center.

Long-wavelength infrared (LWIR) focal plane arrays (FPAs) needed for Earth Science imaging, spectral imaging, and sounding applications have always been among the most challenging in infrared photodetector technology due to the rigorous material growth, device design and fabrication demands. Future small satellite missions will present even more challenges for LWIR FPAs, as operating temperature must be increased so that cooler (and radiator) volume, mass, and power can be reduced. To address this critical need, we are working on following three technologies. 1) Type-II superlattice (T2SL) barrier infrared detector (BIRD), which combines the high operability, spatial uniformity, temporal stability, scalability, producibility, and affordability advantages of the quantum well infrared photodetector (QWIP) FPA with the better quantum efficiency and dark current characteristics. A mid-wavelength infrared (MWIR) T2SL BIRD FPA is a key demonstration technology in the (6U) CubeSat Infrared Atmospheric Sounder (CIRAS) funded under the ESTO InVEST Program. A LWIR T2SL BIRD FPA is also being developed under the ESTO SLI-T Program for future thermal infrared (TIR) land imaging needs. 2) The resonator pixel technology, which uses nanophotonics light trapping techniques to achieve strong absorption in a small detector absorber volume, thereby enabling enhanced QE and/or reduced dark current. 3) High dynamic range 3D Readout IC (3DROIC), which integrates a digital reset counter with a conventional analog ROIC to provide a much higher effective well capacity than previously achievable. The resulting longer integration times are especially beneficial for high flux/dark current LWIR applications as they can improve signal-to-noise ratio and/or increase the operating temperature. By combining the aforementioned technologies, this project seeks to demonstrate a cost-effective, high-performance LWIR FPA technology with significantly higher operating temperature and sensitivity than previously attainable, and with the flexibility to meet a variety of Earth Science TIR measurement needs, particularly the special requirements of small satellite missions.

The shorter wavelengths of the ultraviolet (UV) band enable detectors to operate with increased spatial resolution, variable pixel sizes, and large format arrays, benefitting a variety of NASA, defense, and commercial applications. AlxGa1-xN semiconductor alloys, which have attracted much interest for detection in the UV spectral region, have been shown to enable high optical gains, high sensitivities with the potential for single photon detection, and low dark current performance in ultraviolet avalanche photodiodes (UV-APDs). We are developing GaN/AlGaN UV-APDs with large pixel sizes that demonstrate consistent and uniform device performance and operation. These UV-APDs are fabricated through high quality metal organic chemical vapor deposition (MOCVD) growth on lattice-matched, low dislocation density GaN substrates with optimized material growth and doping parameters. The use of these low defect density substrates is a critical element to realizing highly sensitive UV-APDs and arrays with suppressed dark current under high electric fields.Optical gains greater than 5X10 (exp 6) with enhanced quantum efficiencies over the 350-400 nm spectral range have been demonstrated, enabled by a strong avalanche multiplication process. Furthermore, we are developing 6X6 arrays of devices to test high gain UV-APD array performance at ~355 nm. These variable-area GaN/AlGaN UV-APD detectors and arrays enable advanced sensing performance over UV bands of interest with high resolution detection for NASA Earth Science applications.

A high-performance graphene-based HgCdTe detector technology is being developed for sensing over the mid-wave infrared (MWIR) band for NASA Earth Science, defense, and commercial applications. This technology involves the integration of graphene into HgCdTe photodetectors that combines the best of both materials and allows for higher MWIR(2-5 m) detection performance compared to photodetectors using only HgCdTe material. The interfacial barrier between the HgCdTe-based absorber and the graphene layer reduces recombination of photogenerated carriers in the detector. The graphene layer also acts as high mobility channel that whisks away carriers before they recombine, further enhancing the detector performance. Likewise, HgCdTe has shown promise for the development of MWIR detectors with improvements in carrier mobility and lifetime. The room temperature operational capability of HgCdTe-based detectors and arrays can help minimize size, weight, power and cost for MWIR sensing applications such as remote sensing and earth observation, e.g., in smaller satellite platforms. The objective of this work is to demonstrate graphene-based HgCdTe room temperature MWIR detectors and arrays through modeling, material development, and device optimization. The primary driver for this technology development is the enablement of a scalable, low cost, low power, and small footprint infrared technology component that offers high performance, while opening doors for new earth observation measurement capabilities.

In this presentation, we will discuss the advantages of using an in-pixel digital read out integrated circuit and resonator pixel technology with the type-II strained layer superlattice detector array to elevate the operating temperature of the focal plane array for Earth remote sensing applications.

In this paper, we report our recent efforts in achieving high performance in Antimonides type-II superlattice (T2SL) based infrared photodetectors using the barrier infrared detector (BIRD) architecture, resonator pixel light coupling mechanism, and digital read out integrated circuits (DROICs).

In this presentation, we will report our recent efforts in achieving high performance in Antimonides type-II strained-layer superlattice (T2SLS) based infrared photodetectors using the barrier infrared detector (BIRD) device architecture. The recent emergence of barrier infrared detectors such as the nBn [1] and the XBn [2] have resulted in mid-wave infrared (MWIR) and long-wave infrared (LWIR) detectors with substantially higher operating temperatures than previously available in III-V semiconductor based MWIR and LWIR detectors. The initial nBn devices used either InAs absorber grown on InAs substrate, or lattice-matched InAsSb alloy grown on GaSb substrate, with cutoff wavelengths of ~3.2 µm and ~4 µm, respectively. While these detectors could operate at much higher temperatures than existing MWIR detectors based on InSb, their spectral responses do not cover the full (3 – 5.5 µm) MWIR atmospheric transmission window. There also have been nBn detectors based on the InAs/GaSb type-II superlattice absorber [3] .

Long-wavelength infrared (LWIR) focal plane arrays (FPAs) needed for Earth Science imaging, spectral imaging, and sounding applications have always been among the most challenging in infrared photodetector technology due to the rigorous material growth, device design and fabrication demands. Future small satellite missions will present even more challenges for LWIR FPAs, as operating temperature must be increased so that cooler (and radiator) volume, mass, and power can be reduced. To address this critical need, we are working on following three technologies. 1) Type-II superlattice (T2SL) barrier infrared detector (BIRD), which combines the high operability, spatial uniformity, temporal stability, scalability, producibility, and affordability advantages of the quantum well infrared photodetector (QWIP) FPA with the better quantum efficiency and dark current characteristics. A mid-wavelength infrared (MWIR) T2SL BIRD FPA is a key demonstration technology in the (6U) CubeSat Infrared Atmospheric Sounder (CIRAS) funded under the ESTO InVEST Program. A LWIR T2SL BIRD FPA is also being developed under the ESTO SLI-T Program for future thermal infrared (TIR) land imaging needs. 2) The resonator pixel technology, which uses nanophotonics light trapping techniques to achieve strong absorption in a small detector absorber volume, thereby enabling enhanced QE and/or reduced dark current. 3) High dynamic range 3D Readout IC (3DROIC), which integrates a digital reset counter with a conventional analog ROIC to provide a much higher effective well capacity than previously achievable. The resulting longer integration times are especially beneficial for high flux/dark current LWIR applications as they can improve signal-to-noise ratio and/or increase the operating temperature. By combining the aforementioned technologies, this project seeks to demonstrate a cost-effective, high-performance LWIR FPA technology with significantly higher operating temperature and sensitivity than previously attainable, and with the flexibility to meet a variety of Earth Science TIR measurement needs, particularly the special requirements of small satellite missions.

Front-illuminated GaN p-i-p-i-n separate-absorption and multiplication avalanche photodiode (SAM-APD) epitaxial structures were grown by metalorganic chemical vapor deposition (MOCVD) on n-type bulk GaN substrates and fabricated into 4×4 arrays with a large detection area of 100×100 μm2. The SAM-APD array showed a uniform distribution of dark current density of JDark

The intense development in imaging spectrometers and related technology has yielded systems that are highly performing. Current grating-based designs utilize focal plane arrays with aberrations controlled to a fraction of a detector element and low F-numbers for high etendue to maximize the signal to noise performance. Tailored grating facets using two or more blaze angles optimize the optical efficiency across the full 400-2500 nm solar reflective spectral range. Two commonly used forms, the Offner-Chrisp and Dyson designs, are adaptations of microlithographic projectors with a concave or convex mirror replaced by a shaped grating; maintain a high degree of spatial-spectral uniformity. These gratings are relatively difficult to manufacture using either e-beam lithography or diamond machining. The challenge for optical designers is to create optical forms with reduced size, weight, and power (SWaP) requirements while maintaining high performance. We have focused our work in this area and are developing a breadboard prototype imaging spectrometer that covers the full VNIR/SWIR spectral range at 10 nm spectral sampling, has a large swath of 1500 spatial samples, and is compact. The current prototype is for an F/3.3 system that is 7 cm long with an 8 cm diameter with aberration control better than 0.1 pixel assuming an 18 μm pixel pitch. The form utilizes a catadioptric lens and a flat dual-blaze immersion grating. The flat grating simplifies manufacturing and we are currently exploring the manufacture of the grating through grayscale optical lithography where the entire pattern can be exposed at once without stitching errors.

Electro-optical detection in ultraviolet (UV) and near-infrared (NIR) bands has distinct advantages for various applications. UV/NIR wavelengths are desired for a variety of NASA, defense and commercial applications. While UV and NIR detection technologies are governed by similar physical principles, a major differentiating factor lies in the choice of detector materials. Using the GaN/AlGaN material system, we are developing avalanche photodiodes (APDs) as discrete devices with high gains and responsivities. These devices, based on high crystalline quality metal organic chemical vapor deposition (MOCVD) growth on lattice-matched GaN substrates, demonstrate uniform and reliable distribution of breakdown voltage and leakage currents with gains of above 106. For NIR detection we have employed epitaxial layer deposition of germanium on silicon for room temperature operation. This development is focused on demonstrating very low noise performance as a result of low dislocation densities and dark currents. Both these material/device technologies can be adapted to create arrays of detectors for a variety of applications. The primary objective in developing these sensing and imaging technologies is to advance the state-of-the-art to benefit diverse UV/NIR applications for NASA, defense, and commercial applications.

The development of remote sensing using an imaging spectrometer is traced from its origins to the current highly performing spectral sensors. The advancement of the technology has primarily been driven by novel optical designs and focal plane array development. Current state-of-the-art dispersive sensors, employing innovative grating or prism arrangements, operate at low F-numbers while maintaining a high degree of aberration control. These challenging designs have been implemented in hardware with alignment tolerances on the order of microns. The application of imaging spectrometers to science problems that require highly accurate radiometry necessitates new characterization approaches that combine state-of-the-art radiometric sources and detailed sensor models. Future challenges are to reduce the size, weight, and power requirements while maintaining the performance of current systems.

For 46 years, the Landsat program has been providing continuous, consistent and high-quality data used routinely by decision makers both inside and outside the government, for a wide range of natural resource issues. In 2015, NASA Earth Science Technology Office (ESTO) has established the Sustainable Land Imaging Technology (SLI-T) Program to research, develop, and demonstrate new measurement technologies and reduced costs for future land imaging measurements. This paper provides information regard current SLI-T tasks to reach the program goals.

For 18 years NASA Earth Science Technology Office(ESTO) has been investing in remote sensing related technologies. During this period ESTO has invested in more then 900 tasks. These tasks are managed under multiple programs, which cover the whole spectrum of technologies from component to full up satellite in space and software. Many of these technologies have been successfully infused into space missions like Aquarius, SMAP, CYGNSS, SWOT, TEMPO and others. Researchers are demonstrating remote sensing instruments with various improved capabilities such as incorporating innovative spectrometers, or a single chip with spectral imaging capabilities. Recent technological developments in novel sensor materials, including those for hyperspectral imaging such as strained superlattice and barrier architectures, promise significant improvements in performance. Various read-out circuit architectures are improving functionality for higher-performance focal plane arrays, including incorporating intelligence into focal planes. Adding intelligence into sensors will lead to efficient utilization of limited onboard resources like power, and data rate. ESTO is actively investing in sensor technologies, instrument concepts, information technology and data processing algorithms for both active and passive remote sensing space applications. Recent investments have been for Sustainable Land Imaging(SLI-T), Inspace validation of technology (InVEST) and Instrument Incubator Program (IIP). This presentation will focus on remote sensing techniques and related technology investments by NASA/ESTO.

For more then 18 years NASA Earth Science Technology Office has been investing in remote sensing technologies. During this period ESTO has invested in more then 900 tasks. These tasks are managed under multiple programs like Instrument Incubator Program (IIP), Advanced Component Technology (ACT), Advanced Information Systems Technology (AIST), In-Space Validation of Earth Science Technologies (InVEST), Sustainable Land Imaging – Technology (SLI-T) and others. This covers the whole spectrum of technologies from component to full up satellite in space and software. Over the years many of these technologies have been infused into space missions like Aquarius, SMAP, CYGNSS, SWOT, TEMPO and others. Over the years ESTO is actively investing in Infrared sensor technologies for space applications. Recent investments have been for SLI-T and InVEST program. On these tasks technology development is from simple Bolometers to Advanced Photonic waveguide based spectrometers. Some of the details on these missions and technologies will be presented.

Two approaches to achieving reduced-defect active regions in III-N devices are discussed - confined epitaxy and heteroepitaxy on step-free SiC surfaces. In confined epitaxy, sapphire substrates (either GaN coated or not) are patterned with a dielectric mask and then III-N device structures are selectively and vertically grown in the openings using metalorganic chemical vapor deposition (MOCVD). In heteroepitaxy on step-free SiC surfaces, SiC mesas are created that have surfaces completely free of atomic steps and then used as substrates for conventional MOCVD III-N growth. In both approaches significant reductions in extended defect densities (10-100x) are observed and manifest in improved electroluminescence efficiency of UV emitters and leakage currents in UV detectors. Extensions of these efforts and other structural characterization results will be presented. Modeling results suggesting directions for future efforts will also be discussed.

200 keV Si implantations were performed in the dose range of 5 × 1012 − 1 × 1014 cm−2 in GaAs grown on Si. For comparison implants were also performed in GaAs layers grown on GaAs substrates. Implanted layers were annealed by both furnace and halogen lamp rapid thermal anneals. Significantly lower donor activations were observed in GaAs layers grown on Si substrates than in the layers grown on GaAs substrates. Extremely low dopant activations were obtained for Be implants in GaAs grown on Si. Photoluminescence and photoreflectance measurements were also performed on the implanted material.

We have developed microshutter array systems at NASA Goddard Space Flight Center for use as multi-object aperture arrays for a Near-Infrared Spectrometer (NIRSpec) instrument. The instrument will be carried on the James Webb Space Telescope (JWST), the next generation of space telescope, after the Hubble Space Telescope retires. The microshutter arrays (MSAs) are designed for the selective transmission of light from objected galaxies in space with high efficiency and high contrast. Arrays are close-packed silicon nitride membranes with a pixel size close to 100x200 μm. Individual shutters are patterned with a torsion flexure permitting shutters to open 90 degrees with minimized stress concentration. In order to enhance optical contrast, light shields are made on each shutter to prevent light leak. Shutters are actuated magnetically, latched and addressed electrostatically. The shutter arrays are fabricated using MEMS bulk-micromachining and packaged utilizing a novel single-sided indium flip-chip bonding technology. The MSA flight system consists of a mosaic of 2 x 2 format of four fully addressable 365 x 171 arrays. The system will be placed in the JWST optical path at the focal plane of NIRSpec detectors. MSAs that we fabricated passed a series of qualification tests for flight capabilities. We are in the process of making final flight-qualified MSA systems for the JWST mission.