CLARREO UW & Harvard Team Proposed IIP Activities (with description of underlying research) Fred Best CLARREO Meeting at NIST 12 June, 2008 University of Wisconsin

Slide 2 CLARREO Meeting at NIST 12 June 2008 Proposed IIP Activities & Required NIST Capabilities for CLARREO Topics CLARREO IIP Scope Proposed IIP Technologies with Background Development Summary  On-orbit Absolute Radiance Standard (OARS)  On-orbit Cavity Emissivity Module (OCEM)  On-orbit Spectral Response Module (OSRM)  Dual Absolute Radiance Interferometers (DARI) TRL Progressions and Program Milestones

Slide 3 CLARREO Meeting at NIST 12 June 2008 Proposed IIP Activities & Required NIST Capabilities for CLARREO A New Class of Advanced Accuracy Satellite Instrumentation (AASI) for the CLARREO Mission The objective of the proposed IIP work is to develop and demonstrate the technologies necessary to measure IR spectrally resolved radiances with ultra high accuracy (< 0.1 K 3- sigma brightness temperature at scene temperature) for the CLARREO benchmark climate mission.

Slide 4 CLARREO Meeting at NIST 12 June 2008 Proposed IIP Activities & Required NIST Capabilities for CLARREO CLARREO Radiometric Performance The uncertainty of the blackbody radiating temperature (45 mK, 3-sigma) dominates, except for large wavenumbers at cold temperatures where the assumed telescope temperature change of 20 mK between earth and calibration views becomes important. We assumed an emissivity of with uncertainty and a blackbody temperature of 300 K, while the instrument is at 285 K. Estimated 3-sigma calibrated brightness temperature uncertainty shown as a function of scene brightness temperature, based on use of the AASI.

Slide 5 CLARREO Meeting at NIST 12 June 2008 Proposed IIP Activities & Required NIST Capabilities for CLARREO CLARREO Viewing Configuration Viewing configuration providing immunity to polarization effects. CLARREO FTS Scene Mirror Provides Earth and Space Views as well as Views to Targets Involving Technologies Developed Under this IIP, That Give Unprecedented Absolute Calibration Accuracy on-orbit. Developed under this IIP

Slide 6 CLARREO Meeting at NIST 12 June 2008 Proposed IIP Activities & Required NIST Capabilities for CLARREO Proposed Technologies (OARS) On-orbit Absolute Radiance Standard (OARS) that uses multiple phase change material signatures to establish absolute temperature knowledge to 10 mK throughout the lifetime of the satellite. The OARS is a source that will be used to maintain SI traceability of the radiance spectra measured by separately calibrated dual interferometer sensors.

Slide 7 CLARREO Meeting at NIST 12 June 2008 Proposed IIP Activities & Required NIST Capabilities for CLARREO UW-SSEC Developed GIFTS EDU Blackbody Performance Significantly Exceeds Specifications Blackbody Controller Card Measurement Range233 to 313 K Temperature Uncertainty < 0.1 K (3  ) < K Blackbody Emissivity> 0.996> Emissivity Uncertainty < (3  ) < Entrance Aperture1.0 inch Mass (2 BBs + controller)< 2.4 kg 2.1 kg Power (average/max)< 2.2/5.2 W 2.2/5.2 W Specification As Delivered GIFTS Engineering Development Unit Key Parameter Blackbody (2) 1” Cavity Aperture Aluminum Cavity Support Tube/ Thermal Isolator Aluminum Enclosure Thermistor Temperature Sensors Thermofoil Heater

Slide 8 CLARREO Meeting at NIST 12 June 2008 Proposed IIP Activities & Required NIST Capabilities for CLARREO GIFTS Blackbody Thermofoil Heater Aluminum Cavity Thermistor Assemblies (5) Glass-filled Noryl Cavity Support Tube / Thermal Isolator Aluminum Enclosure Cavity Surface Aeroglaze Z306 Glass-filled Noryl Base Mechanical Support for Enclosure 1” Cavity Aperture Base Thermistor

Slide 9 CLARREO Meeting at NIST 12 June 2008 Proposed IIP Activities & Required NIST Capabilities for CLARREO A new approach compared to the traditional laboratory approach Traditional Laboratory Calibration Scheme (based on long-term thermal stability at melt temperatuere) Melt Signature Configuration (based on temperature signature while transitioning through melt temperature) Blackbody Cavity Temperature Sensors (3) -View AA - (expanded) Melt Materials (3 different) Blackbody Cavity A A Temperature Controlled Bath Melt Material Temperature Probe Heater Outer insulation not shown Fixed Point Reference Material

Slide 10 CLARREO Meeting at NIST 12 June 2008 Proposed IIP Activities & Required NIST Capabilities for CLARREO Question Can a melt material mass of < 1/1000 th of the cavity mass give the accuracy needed for CLARREO? YES!

Slide 11 CLARREO Meeting at NIST 12 June 2008 Proposed IIP Activities & Required NIST Capabilities for CLARREO Anatomy of a Melt Signature Time Temperature Ga Melt Cavity held at constant temperature Constant ∆Power Applied Cavity response if no melt material present With melt complete, cavity temperature rises When Ga melt material is present, the added power goes into changing the phase to liquid - no cavity temperature rise. melt plateau

Slide 12 CLARREO Meeting at NIST 12 June 2008 Proposed IIP Activities & Required NIST Capabilities for CLARREO SSEC Engineering Test Cavity (configured for melt tests) Blackbody Cavity 1 cm Thermistor potted into custom housing then threaded into aluminum cavity. Thermistor 0.38 g of Ga melt material placed into thermistor housing modified with stainless steel sleeve and nylon plug. Melt Material

Slide 13 CLARREO Meeting at NIST 12 June 2008 Proposed IIP Activities & Required NIST Capabilities for CLARREO Gallium Melt Repeatability Ramps with similar melt times match very closely Ramp 66 was 8 months after other ramps Ramps 38 and 41 were done inside the chamber; the rest outside 20 mK Zoom view

Slide 14 CLARREO Meeting at NIST 12 June 2008 Proposed IIP Activities & Required NIST Capabilities for CLARREO Melt Time Comparisons

Slide 15 CLARREO Meeting at NIST 12 June 2008 Proposed IIP Activities & Required NIST Capabilities for CLARREO Longer Melt Time = Better Accuracy Ga Melt 20 mK * Asymptote of Model Fit is within 1mK of Ga Melt Point *

Slide 16 CLARREO Meeting at NIST 12 June 2008 Proposed IIP Activities & Required NIST Capabilities for CLARREO Cavity Gradient Very Low During Melt Circumferential Heater Thermistor HBB-A Thermistor HBB-B Ga Melt Material Aluminum Blackbody Cavity Temperature gradient between spatially separated temperature sensors only ~1.2mK, even during “fast” 4800 sec. melt. ∆ Temp. ( C) (HBB-BHBB-A) mK

Slide 17 CLARREO Meeting at NIST 12 June 2008 Proposed IIP Activities & Required NIST Capabilities for CLARREO Thermal Modeling Axisymmetric Thermal Model  Explore relationships between important system parameters and melt behavior. Heat leak effects due to cabling. Mass and aspect ratio of melt material. Ramp Power. Thermal Resistance between melt material and cavity. Thermal Resistance between thermistor and melt material.  Explore and predict the impact of variations in the external temperature environment on Melt Signatures.  Predict and optimize melt signature behavior of different materials. A thermal model was developed and tuned to agree with test data, and then used to:

Slide 18 CLARREO Meeting at NIST 12 June 2008 Proposed IIP Activities & Required NIST Capabilities for CLARREO Measured Melt Signatures (using GIFTS BB Configuration) -40 °C-20 °C0 °C20 °C40 °C °C Mercury 0.00 °C Water °C Gallium Melt Signatures Provide Absolute Temperature Calibration Accuracies Better Than 10 mK Time [s] Temperature [°C] Water Melt = 0 °C Approach Exponential Fit Thermistor Temperature Mercury Melt = °C Thermistor Temperature Mercury Melt (test data)Water Melt (test data)Gallium Melt (test data) Gallium Melt = °C Thermistor Temperature

Slide 19 CLARREO Meeting at NIST 12 June 2008 Proposed IIP Activities & Required NIST Capabilities for CLARREO Implementation for CLARREO (GIFTS Blackbody Embodiment) Small quantities of Water, Gallium, Mercury, and possibly more materials are imbedded in the blackbody cavity, providing three or more known temperature reference points. The thermistors will be interleaved in the cavity between these reference materials. During the melt plateaus, the thermistor resistances corresponding to the phase change points are measured. The thermistors are fully characterized over the entire range of temperatures represented by the three (or more) reference materials, by using the traditionally obtained Steinhart & Hart Coefficients. Temperature calibration points are established by sequentially passing through the melt plateaus of the reference materials.

Slide 20 CLARREO Meeting at NIST 12 June 2008 Proposed IIP Activities & Required NIST Capabilities for CLARREO Benefits of This Novel Approach Absolute temperature calibration is provided on-orbit on-demand. Concept is simple and requires very little mass. Very high accuracy is obtained – each temperature calibration point associated with a melt material can be established to well within 10 mK, and more accuracy is obtainable with longer melt times. Implementation requires straight-forward modification of an existing flight hardware design (GIFTS). Scheme provides temperature calibration of all the blackbody cavity thermistor sensors, over a significant temperature range – allowing normal blackbody operation at any temperature within this range.

Slide 21 CLARREO Meeting at NIST 12 June 2008 Proposed IIP Activities & Required NIST Capabilities for CLARREO IIP Focus for OARS Optimize Containment System used for the Miniature Phase Change Cells. –Surface Tension dominating Gravitational effects. –Melt signature enhancement. –Containment and Melt Material Compatibility. »Melt contamination from Dissolution »Liquid Metal Embrittlement of containment system Demonstrate performance after accelerated life testing to simulating full mission lifetime. Optimize melt algorithm refinements. Refine thermal modeling.

Slide 22 CLARREO Meeting at NIST 12 June 2008 Proposed IIP Activities & Required NIST Capabilities for CLARREO Proposed Technologies (OCEM) On-orbit Cavity Emissivity Module (OCEM) that directly determines the on-axis emissivity of the OARS throughout the instrument lifetime on-orbit. Two versions will be developed: –one using a quantum cascade laser source (Harvard), and –one based on a heated halo source (Wisconsin). Harvard QCL ApproachUW Heated Halo Approach

Slide 23 CLARREO Meeting at NIST 12 June 2008 Proposed IIP Activities & Required NIST Capabilities for CLARREO IIP Focus for OCEM Quantum Cascade Laser Source OCEM (Harvard) –Optimize power coupling of the QCL to the infrared optical fiber. –Embed detectors directly into the blackbody cavity wall allowing a direct measurement of surface emissivity. –Conduct end-to-end Interferometer tests to determine cavity emissivity. Heated Halo Source OCEM (Wisconsin) –Configure system to be integrated into the 1” OARS Blackbody. –Conduct end-to-end interferometer tests with OCEM to verify required noise performance and stability.

Slide 24 CLARREO Meeting at NIST 12 June 2008 Proposed IIP Activities & Required NIST Capabilities for CLARREO Proposed Technologies (OSRM) On-orbit Spectral Response Module (OSRM) that uniquely determines the spectral instrument line shape of the interferometers over the lifetime of the instrument on-orbit. Signature of the instrument lineshape superimposed on a blackbody spectrum. The baseline spectrum is that of a room temperature blackbody. The monochromatic radiation from a QCL at 1263 cm -1 is directed into the cavity and the resulting spectrum resolved at 0.5 cm -1 reveals the spectrometer lineshape.

Slide 25 CLARREO Meeting at NIST 12 June 2008 Proposed IIP Activities & Required NIST Capabilities for CLARREO IIP Focus for OSRM Develop OSRM Cavity with optimized diffuse reflectivity. Develop appropriate stable QCL power driver allowing the long integration times needed to determine the ILS to the desired level of precision. Conduct end-to-end interferometer testing to verify performance and stability.

Slide 26 CLARREO Meeting at NIST 12 June 2008 Proposed IIP Activities & Required NIST Capabilities for CLARREO Proposed Technologies (DARI) Dual Absolute Radiance Interferometers (DARI) for measuring spectrally-resolved radiances over a major part of the thermal infrared spectral domain. Fourier Transform Spectrometer (FTS) systems with strong flight heritage will be configured for detailed performance testing and design trades as part of this IIP. –UW Focus - High Performance FTS –Harvard Focus - Far IR

Slide 27 CLARREO Meeting at NIST 12 June 2008 Proposed IIP Activities & Required NIST Capabilities for CLARREO DARI IIP Configurations & Focus HPFTS University of Wisconsin LWFTS Harvard University Interferometer core GOSAT FTS / ACE-FTS Hybrid (Based on “TOKYO” Bench Unit) Existing Harvard University Commercial ABB/Bomem Interferometer Beamsplitter options Zinc Selenide Si baseline configuration is the unique ABB/Bomem design that uses a single plane parallel beamsplitter with no compensator to improve efficiency, especially in the far IR Cesium Iodide baseline configuration is the unique ABB/Bomem design that uses a single plane parallel beamsplitter with no compensator to improve efficiency, especially in the far IR Detector(s)PV MCT / InSB / TBDDGTS Pyro, TBD CoolerNGST Pulse Tube MicrocoolerN/A ElectronicsCommercial ABB control electronicsExisting control electronics Tasks / GoalsDemonstrate required radiometric performance coupled with the spectral properties needed to realize this level of performance for atmospheric spectra (with a focus on traditional FTIR wavelength regions) Address the effects of vibrations (cooler and external sources) on spectral properties (ghosts), Address the immunity to mean operating temperature differences and short term variations, Details of the beamsplitter design related to its fundamental configuration, materials choices, and thickness will be explored. Demonstrate required radiometric performance coupled with the spectral properties needed to realize this level of performance for atmospheric spectra (with a focus on the FIR) Provide a testbed for advanced FIR photoconductor development. Investigate the impact of detector linearity and sensitivity on the calibration accuracy in the FIR

Slide 28 CLARREO Meeting at NIST 12 June 2008 Proposed IIP Activities & Required NIST Capabilities for CLARREO CLARREO IIP High Performance FTS Absolute Radiance Interferometer

Slide 29 CLARREO Meeting at NIST 12 June 2008 Proposed IIP Activities & Required NIST Capabilities for CLARREO CLARREO IIP Far IR FTS Absolute Radiance Interferometer

Slide 30 CLARREO Meeting at NIST 12 June 2008 Proposed IIP Activities & Required NIST Capabilities for CLARREO FTS: GOSAT/TANSO ACE-FTS Hybrid adapted for Far IR representative of flight model interferometer requirements commercial ABB electronics. Cooler: NGST Pulse Tube Microcooler To minimize cost and schedule NGST will provide, on a temporary basis, a micro-compressor and tactical electronics while fabricating a coaxial cold head, reservoir tank and inertance line as part of the program. These subassemblies will be assembled and performance testing conducted to validate the cooler system operation. Low power, low mass, low vibration, long life The High Performance FTS subsystem to be developed by UW-SSEC will include an interferometer with diode laser-based metrology and multiple beamsplitter options (at least ZnSe and Si), a detector/dewar subassembly, and a small pulse-tube mechanical cooler, all chosen for their strong spaceflight heritage such that detailed performance testing can be conducted on a subsystem with a clear path to space. Detector/Dewar Assembly Single dewar Cold-finger/bellows interface to cooler Similar to existing UW-SSEC S-HIS detector/dewar subassembly single cold field stop, refractive elements to focus the aperture stop onto the detectors at least two semi-conductor detectors chosen for high linearity. IIP High Performance FTS Subsystem - Key Elements

Slide 31 CLARREO Meeting at NIST 12 June 2008 Proposed IIP Activities & Required NIST Capabilities for CLARREO IIP Technology Advancement

Slide 32 CLARREO Meeting at NIST 12 June 2008 Proposed IIP Activities & Required NIST Capabilities for CLARREO TRL Progression and Program Milestones