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

CLARREOUW & Harvard Team

Proposed IIP Activities(with description of underlying research)

Fred Best

CLARREO Meeting at NIST12 June, 2008

University of Wisconsin

CLARREO Meeting at NIST 12 June 2008Proposed IIP Activities & Required NIST Capabilities for CLARREOSlide 2

Topics

• CLARREO IIP Scope

• Proposed IIP Technologies with Background Development SummaryOn-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


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.


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 0.999 with 0.0006 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.

0.00

0.02

0.04

0.06

0.08

0.10

0.12

200 220 240 260 280 300 320

Scene Temperature [K]

Bri

ghtn

ess T

Err

or

[K]

200 cm-1 500 cm-1 1000 cm-1 1500 2000 cm-1

CLARREO Requirement

0.00

0.02

0.04

0.06

0.08

0.10

0.12

200 220 240 260 280 300 320

Scene Temperature [K]

Bri

ghtn

ess T

Err

or

[K]

200 cm-1 500 cm-1 1000 cm-1 1500 2000 cm-1

CLARREO Requirement


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 underthis IIP


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.


UW-SSEC Developed GIFTS EDU Blackbody Performance Significantly Exceeds Specifications

BlackbodyController

Card

Measurement Range 233 to 313 K 233 to 313 K

Temperature Uncertainty < 0.1 K (3 ) < 0.056 K

Blackbody Emissivity > 0.996 > 0.999

Emissivity Uncertainty < 0.002 (3 ) < 0.00072

Entrance Aperture 1.0 inch 1.0 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” CavityAperture

AluminumCavity

SupportTube/ThermalIsolator

AluminumEnclosure

ThermistorTemperatureSensors

ThermofoilHeater


GIFTS Blackbody

ThermofoilHeater

AluminumCavity

ThermistorAssemblies (5)Glass-filled Noryl

Cavity Support Tube / Thermal

Isolator

AluminumEnclosure

CavitySurfaceAeroglazeZ306

Glass-filledNoryl Base

MechanicalSupport forEnclosure

1” CavityAperture

BaseThermistor


A new approachcompared 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)

BlackbodyCavity

TemperatureSensors (3)

-View AA -(expanded)

Melt Materials(3 different)

BlackbodyCavity

A

A

Temperature Controlled Bath

Melt Material

TemperatureProbe

Heater

Ou

ter

ins

ula

tio

n n

ot

sh

ow

n

Fixed Point Reference Material


Question

• Can a melt material mass of < 1/1000th of the cavity mass give the accuracy needed for CLARREO?

• YES!


Anatomy of a Melt Signature Gallium - Ramp38 Match

29.700

29.720

29.740

29.760

29.780

29.800

29.820

29.840

29.860

0 5000 10000 15000 20000

Time (seconds)

Te

mp

era

ture

(d

eg

C)

Model Prediction

No Melt Model

29.7646

Time

Tem

per

atu

re

Ga Melt

Cavity held at constant

temperatureConstant ∆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


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


Gallium Melt Repeatability

Melt Comparison

29.700

29.720

29.740

29.760

29.780

29.800

29.820

29.840

0 2000 4000 6000 8000 10000 12000 14000 16000

Time (Seconds)

Tem

per

atu

re (

C)

Ramp66

Ramp36

Ramp37

Ramp38

Ramp41

29.7646

• 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

Melt Comparison Zoom

29.760

29.762

29.764

29.766

29.768

29.770

29.772

29.774

29.776

29.778

29.780

2000 4000 6000 8000 10000 12000

Time (Seconds)

Tem

per

atu

re (

C)

Ramp66

Ramp36

Ramp37

Ramp38

Ramp41

29.7646

20 mK

Zoom view


Melt Time Comparisons

Melt Time Comparison

29.760

29.770

29.780

29.790

29.800

29.810

29.820

5000 10000 15000 20000 25000 30000 35000 40000 45000

Time (sec)

Te

mp

era

ture

(C

)

Ramp43, 5k

Ramp38, 8k

Ramp40, 32k

29.7646


Longer Melt Time = Better Accuracy

Ga Melt29.764

29.766

29.768

29.770

29.772

29.774

29.776

29.778

29.780

0 5,000 10,000 15,000 20,000 25,000 30,000

Melt Duration [s]

Mid

-melt

Tem

pera

ture

[C

]

Group-1

Group-2

Group-3

Ga Melt Temp

Data Fit

Melt Comparison Zoom

29.760

29.762

29.764

29.766

29.768

29.770

29.772

29.774

29.776

29.778

29.780

2000 4000 6000 8000 10000 12000

Time (Seconds)

Tem

per

atu

re (

C)

Ramp66

Ramp36

Ramp37

Ramp38

Ramp41

29.7646

20 mK

*

Asymptote of Model Fit is within 1mK of Ga Melt Point*


Cavity Gradient Very Low During MeltCircumferential

Heater

ThermistorHBB-A

ThermistorHBB-B

Ga MeltMaterial

AluminumBlackbody

Cavity

Temperature gradient between spatially separated temperature sensors only ~1.2mK, even during “fast” 4800 sec. melt.

HBBB-HBBA

-0.0015

-0.0010

-0.0005

0.0000

0.0005

0.0010

0.0015

0.0020

0 2000 4000 6000 8000 10000 12000 14000 16000

Seconds

Tem

p (

C)

HBBB-HBBA 10 per. Mov. Avg. (HBBB-HBBA)

Ramp43 (4.8k melt)

29.550

29.600

29.650

29.700

29.750

29.800

29.850

29.900

29.950

0 2000 4000 6000 8000 10000 12000 14000 16000

Seconds

Tem

p (

C)

HBB A HBB B 29.7646

∆ T

emp

. (

C)

(HBB-B HBB-A)-

1.2

mK


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:


29.66

29.68

29.70

29.72

29.74

29.76

29.78

29.80

29.82

29.84

29.86

0 5,000 10,000 15,000 20,000 25,000

-39.00

-38.98

-38.96

-38.94

-38.92

-38.90

-38.88

-38.86

-38.84

-38.82

-38.80

25,000 30,000 35,000 40,000 45,000 50,000

-0.10

-0.08

-0.06

-0.04

-0.02

0.00

0.02

0.04

0.06

0.08

0.10

20,000 25,000 30,000 35,000 40,000 45,000

Measured Melt Signatures(using GIFTS BB Configuration)

-40 °C -20 °C 0 °C 20 °C 40 °C

-38.87 °CMercury

0.00 °CWater

29.77 °CGallium

Melt Signatures Provide Absolute Temperature Calibration Accuracies Better Than 10 mK

Time [s]

Te

mp

era

ture

[°C

]

Water Melt = 0 °C

Approach Exponential Fit

ThermistorTemperature

Mercury Melt = -38.87 °C


Mercury Melt (test data) Water Melt (test data) Gallium Melt (test data)

Gallium Melt = 29.765 °C



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.


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.


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.


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 Approach UW Heated Halo Approach


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.


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.


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.


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


DARI IIP Configurations & FocusHPFTS

University of WisconsinLWFTS

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 / TBD DGTS Pyro, TBD

Cooler NGST Pulse Tube Microcooler N/A

Electronics Commercial ABB control electronics Existing control electronics

Tasks / Goals •Demonstrate 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


CLARREO IIP High Performance FTS Absolute Radiance Interferometer


CLARREO IIP Far IR FTS Absolute Radiance Interferometer


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


IIP Technology Advancement

TRL 3 (Entry) TRL 4 TRL 5 TRL 6 (Exit)

OARS with Miniature Phase Change Cells (MPCC)

IR&D analytical studies/laboratory results with mock-up blackbody gave proof-of-concept that small quantities of phase change materials provide distinct melt signatures (within 10mK).

Integration of flight compatible containment system, sealing technology, and supercooling dopants into MPCC for component testing (material compatibility, super-cooling, accelerated-life).

Integration of the MPCC into a breadboard blackbody for testing to establish melt plateaus in a relevant thermal environment that simulates on-orbit temperature fluctuations.

System integration of MPCC with the OARS. End-to-end testing with FTS sensor in a thermal environment simulating on-orbit temperature fluctuations, using autonomous melt algorithms.

OCEM On-orbit Cavity Emissivity Module - Heated Halo Source

IR&D analytical studies/ lab-oratory results with SSEC AERI blackbody, the NIST TXR, and Heated Halo component gave proof-of-concept for accurate absolute cavity emissivity measurement.

Integration of breadboard Heated Halo and AERI blackbody with FTS sensor in place of NIST TXR. Testing will demonstrate performance and provide a full characterization in a laboratory setting.

Integration of the developed Heated Halo OCEM & AERI blackbody with FTS sensor. Testing will demonstrate performance and provide a full characterization in a thermal-vacuum environment.

Integration of the Heated Halo OCEM & OARS blackbody with FTS Sensor. Testing will demonstrate performance and provide a full characterization in a thermal-vacuum environment.

OCEM On-orbit Cavity Emissivity Module - QC Laser Source

Analytical studies supported by laboratory experimental results using a mock-up blackbody and a QCL have provided a proof-of-concept that cavity emissivity can be obtained.

Development of blackbody cavity with integrated MCT detectors and fiber coupled QCL. Demonstrate performance in a laboratory and optimize the system for maximal SNR.

Integration of the QCL-OCEM elements into an OARS blackbody. Test performance in the vacuum environment.

Integration of the QCL-OCEM & OARS BB with High Per-formance and Longwave FTS. Testing will demonstrate per-formance and provide character-ization in thermal vacuum.

OSRM On-orbit Spectral Response Module - QCL

Analytical studies supported by lab results using a mock-up BB and a QCL provided a proof-of-concept that FTS ILS can be obtained with high accuracy.

Integration of cavity with coupled QCL. Demonstrate performance in a lab. Optimize system for appropriate signal levels and integration time.

Test OSRM with a range of ILS in the vacuum environment.

Integration of the OSRM with High Performance and LW FTS. Demonstrate performance and provide full characterization in thermal vacuumt environment.

DARI -High Performance FTS

All components (FTS, cooler, and detector) are at high TRL, but have not been combined to test end-to-end performance.

Integration of components into a breadboard to demonstrate performance in a laboratory environment.

Integration of components into prototype & performance testing in a simulated on-orbit thermal and vibration environment.

Testing of prototype system (with silicon beamsplitter) in a thermal vacuum environment.

DARI -Far IR FTS

FTS and baseline detector are at high TRL, but have not been combined to test end-to-end performance in CLARREO context (with OSRM, OCEM).

Integration of components into breadboard to demonstrate laboratory performance with OSRM, OCEM.

Integration of components into prototype & performance testing in vacuum environment.

Testing prototype system in thermal vacuum environment.


TRL Progression and Program Milestones

Documents

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