TOPIC: S6 Earth Science Instrument and Sensor Technology

• Technology leading to significant improvements in capability, availability, or cost of large format (> 2.5 cm diameter), very narrow band (<5 cm^-1 full-width at half-maximum [FWHM]), polarization insensitive, high throughput infrared (6 - 15 µm) optical filters. These filters must be able to operate in vacuum at cryogenic temperatures.
  
• High performance four-band two-dimensional (2D) arrays (128x128 elements or more) in the 0.4 - 2.5 µm wavelength range with high quantum efficiencies (60%-80% or higher) in all spectral bands, low noise, and ambient temperature operation.
  
• Detector arrays with unusual 3-dimensional geometries. Of particular interest is the development of a photon counting system with multiple cylindrical detecting elements (detecting surface on the outside edge) formed into a stack connected through one end to the cable leading to the readout electronics. The stack should be 2 to 5 cm in length with at least 12, and up to 48, individual elements. The diameter of the stack/elements should be minimized and on the order of 0.5 cm or less. Each detector element should have a clear field of view for most of the 360 degrees perpendicular to the stack. Exact details for the sensitivity are negotiable at this early stage, but applications are for fluorescence type measurements.
  
• High performance 2-color array detectors (128x128 or higher) covering the 3 - 15 micron spectral range with high efficiencies, low noise and operating at relatively high temperatures (>150K desired, 80K minimum).
  
• Improved cryogenic stepping motors with high running torques at 80K. The motors must operate in vacuum and at temperatures at or below 80K. It is desired that these motors have minimal size and power requirements, and especially important that they use minimal current. Typical torque values desired are in the range of 10 - 20 oz-inches. Proposed motors should have at least 200 steps per revolution of the axis.
  

• Cloud and aerosols with emphasis on aerosol optical properties;
  
• Wind profiles using direct-detection (noncoherent) lidar, or coherent-detection (heterodyne) lidar, or both;
  
• Land topography (vegetation, ice, land use); and
  
• Molecular species (carbon dioxide, ozone, and water vapor).
  

1. Pulsed, single frequency, diode laser or fiber laser based seeded MOPA systems are desired due to inherent robustness, efficiency, thermal and alignment stability. If the cost per unit is reasonable, and the size is small, then many of these can be installed on a spacecraft for either parallel operation or as backup units to lengthen the life of the mission. Systems with the following specifications are solicited:
   
   
   • Stable single frequency operation at 1047nm, 1064 nm, or 1570 nm;
     
   • Small, integrated assemblies that can generate CW powers in the 100's of mW to several Watts range and higher peak power pulsed operation yielding at least 10 to 500 nJ pulse energies;
     
   • Fiber laser and amplifier designs with high SBS suppression;
     
   • Gaussian pulsewidths between 100 ps and 50 ns;
     
   • MOPA design configuration is desired where the pulse production cavity is short and more readily impedance matched for the fast rise times, gain switching, etc.;
     
   • A semiconductor amplifier, or possibly a small cm-scale rare Earth doped fiber amplifier, can be coupled to the oscillator chip's output, itself contained in a hermetic butterfly or similar package;
     
   • Repetition rates as low as 100 Hz and as high as 10 kHz are needed, with pulsed lifetimes in the trillion shot regime (10¹²);
     
   • Single mode, polarization maintaining (PM) fiber output is needed;
     
   • Short term drift less than 1 MHz;
     
   • Second and third harmonic generation techniques that can be packaged with the CW and pulsed diode or fiber laser sources to produce additional wavelengths in the visible or ultraviolet.
     
   
   
2. High speed fiber multiplexers for single and multimode fiber. A 1-to-10, or greater, multiplexer that is capable of switching on the order of 10 to 100 kHz with low insertion losses is required. Unit must be small, lightweight, and use little power. Single mode fiber version must be capable of handling high power (>100 microJoules at 10 kHz at 1064 nm). Multimode version will be used in low power applications and must be compatible with 0.22 NA fiber with 100 to 600 micron core size. Switching speeds faster than 10 microseconds are required.
   
   
3. Efficient and compact single frequency solid state or fiber lasers operating at 1.5 and 2.0 micron wavelength regimes suitable for coherent lidar applications. These lasers must meet the following general requirements: pulse energy 2 mJ to 100 mJ, repetition rate 10 Hz to 200 Hz, and pulse duration of approximately 200 nsec.
   
   
4. Single element, low noise, high quantum efficiency, HgCdTe avalanche photodiode detector (APD) capable of photon counting at rates >10 MHz for use in the 1570 nm range. Should be suitable for operation with a thermal electric cooler.
   
   
5. Lightweight compact lidar telescopes operating at one or more of the primary laser wavelengths in 1.0 to 2.0 micron wavelength region. The general requirements are: optical quality better than 1/6 wave at 632 nm, mass density less than 12 kg/m², and aperture diameter from 10 cm to 30 cm. Proof of scalability to 50 to 75 cm diameter for deployment in space is required.
   
   
6. Interferometric lidar aft-optics receiver subsystems/components to separately derive aerosol and molecular backscatter via High Spectral Resolution Lidar (HSRL) technique. The subsystem/component is to be implemented into a HSRL system with the goal of independently derive aerosol backscatter and extinction. Subsystems/components are needed at 355 and 532 nm wavelengths. Architectures could be based on Fabry Perot, Mach Zehnder, or other interferometric implementations. Resolving power of the order of 1 GHz and high frequency stability of pass/stop bands are required. Concepts must address issues associated with etendeau of large-aperture (1 - 1.5 m) lidar receivers with field of view of the order of 200 micro-radians.
   
   
7. CCD detectors with high quantum efficiency at 355 and 532 nm for spaceborne lidar instruments measuring cloud and aerosol backscatter and extinction. CCD detectors are needed to replace single element PMT detectors for imaging fringes from interferometric elements of a HSRL instrument. Clocking schemes to move charge on the CCD to achieve on-chip profile averaging and reduce dark current and readout noise should be considered.
   

• Measurements of atmospheric properties including temperature, humidity, solar radiation, clouds, liquid water, ice, precipitation, carbon dioxide, methane, and sulfur dioxide;
  
• Measurements of three-dimensional atmospheric winds near the Earth's surface, and within the troposphere and lower stratosphere, with high spatial resolution and accuracy. Of particular interest are systems intended for measurements of atmospheric fluxes as well as those for convection;
  
• Measurements of oceanic properties including inherent and apparent optical properties, ocean temperature and salinity, and sea surface height.
  

• Imaging radiometers, receivers, or receiver arrays on a chip;
  
• Microwave and millimeter-wave frequency sources as an alternative to Gunn diode oscillators. Compact (<10 cm³) self-contained oscillators with output frequency between 40 GHz and 120 GHz, low phase noise <125 dBc/Hz at 10 kHz, high output power (>100 mW), and low power consumption (<10 W);
  
• Wideband and ultra-wideband sensors with >15dB cross-pole isolation across the bandwidth;
  
• Low noise (<1000 K) with low conversion loss (< 6 dB), compactly designed (< 8 cm³), heterodyne mixers requiring low local oscillator drive power (<2 mW) with RF input frequency range between 100 GHz and 1 THz;
  
• Undersampling, multibit, analog-to-digital converters with Multigigahertz RF input bandwidth, low power consumption, and associated digital signal processing logic circuit;
  
• Low power, lightweight microwave with DC power consumption of less than 2 W;
  
• Electronic design approaches and subsystems that can be incorporated into microwave radiometers to detect and suppress RFI within or near the reception band of the radiometer, thus insuring higher data quality;
  
• Innovative new designs for highly stable noise-diode or other electronic devices as additional reference sources for onboard calibration. Of particular interest are variable correlated noise sources for calibrating correlation-type receivers used in interferometric and polarimetric radiometers;
  
• Monolithic microwave integrated circuit (MMIC), low-noise amplifiers (LNA). Of particular interest are LNAs covering the frequency range of 165 to 193 GHz with low 1/f noise, and having a noise figure of 6.0 dB or better; and
  
• GPS receiver systems for application as bi-static altimeters and scatterometers.
  

• Sensor elements with low mutual coupling allowing close spacing within large arrays;
  
• Large format, millimeter wave, focal plane array modules for large-aperture passive imaging applications; and
  
• Large aperture, deployable antenna concepts. Such large apertures can be real or synthetic. Of particular interest are highly compact launch configurations.
  

• New technology calibration reference sources for microwave radiometers that provide greatly improved reference measurement accuracy. Of particular interest are high emissivity (near-black-body) surfaces for use as onboard calibration targets for microwave radiometers-which will significantly reduce the weight of aluminum core target designs, while reliably improving the uniformity and knowledge of the calibration target temperature; and
  
• New approaches, concepts, and techniques for microwave radiometer system calibration over or within the 1-300 GHz frequency band-which provide end-to-end calibration to better than 0.1K, including corrections for temperature changes and other potential sources of instrumental measurement drift and error.
  

• L-band SAR for surface deformation, topography, soil moisture measurements:
  
  • Lightweight, electronically steerable, dual-polarized, L-band phased-array antennas;
    
  • Lightweight deployable antenna structures and deployment mechanisms suitable for very large aperture systems (e.g., 2x100m antennas);
    
  • Rad-hard, high-efficiency, low-cost, lightweight L-band T/R modules;
    
  • L-band MMIC single-chip T/R modules;
    
  • High-power L-band transmitters (2KW to 10KW);
    
  • Integrated (e.g., ASIC) arbitrary waveform generators;
    
  • High performance, low power, rad-hard, real-time SAR processors and SAR data processing algorithms and data reduction techniques;
    
  • Thin-film membrane compatible electronics. This includes: Reliable integration of electronics with the membrane, high performance (>1.2GHz) transistor fabrication on flex material including identifying new materials, process development and techniques that have potential to produce large area passive and active flexible antenna arrays.
    
• Ku-band and Ka-band interferometers for snow cover measurement over land (Ku-band) and wetland and river monitoring (Ka-band):
  
  • Large, stable, lightweight, deployable structures (10-50 meter interferometric baseline);
    
  • Phase-stable Ku-band and Ka-band electronically steered phased arrays and multi-beam antennas;
    
  • Lightweight deployable reflectors (Ku-band and Ka-band);
    
  • Phase stable Ku-band and Ka-band receive electronics and T/R modules;
    
  • High-power Ka-band transmitters (2KW to 10KW);
    
  • High performance, low power, rad-hard, real-time radar processors and SAR data processing algorithms and data reduction techniques.
    
• X-band to W-band doppler radars for precipitation and cloud measurements:
  
  • High efficiency RF power amplifier (Ku-, Ka-, and W-band);
    
  • Compact, low loss phase shifters (Ka- and W-band);
    
  • High power and low insertion loss transmit-receive switches (Ka-,W-band);
    
  • Wide dynamic range low noise amplifiers (Ka- and W-band);
    
  • Low sidelobe (-90 dB) pulse compression technology (W-band);
    
  • Compact frequency synthesizer (Ku- and Ka-band);
    
  • High power, low sidelobe, compact antennas for high altitudes (X-Ka-band).
    
• Low Frequency (HF, VHF and UHF) airborne sounders:
  
  • Technology for creating large Ground Penetrating Radar (GPR) baselines with wireless phase lock loops;
    
  • High Power (800W), linear amplifiers;
    
  • Innovations in system design or hardware improvements to minimize the effect of the transmit signal leakage into receiver.
    

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