Presenter: Kurt Thome

CLARREO Science Team Meeting 8July 2010: N - 1Use or disclosure of the data contained on this sheet is subject to the restrictions on the IMR cover page

Presenter: Kurt Thome

Reflected Solar SuiteKurt Thome, Jason Hair & RS Team

Deputy Project Scientist


Requirements includes inter-calibration

RSS RequirementsSocietal Benefit

ScienceObjective

Level 1 Science Requirements

Level 2 Measurement Requirements

Level 2 Mission Requirements

Enable knowledgeable policy decisions based on internationally acknowledged climate measurements and models through:

- Observation of high accuracy long-term climate change trends

- Use the long term climate change observations to test and improve climate forecasts.

Highly accurate and SI-traceable decadal change observations sensitive to climate radiative forcings, responses, and feedbacks:

CL.PRJ.1.REQ.3000•Verif iable on-orbit accuracy•Traceable to SI standards•Decadal climate change relevant time and space scales

CL.SYS.1.REQ.1005 Accuracy demonstrated to be SI traceable to the relevant NIST standard and maintained throughout the sensors lifecycle.

CL.SYS.1.REQ.4002 Observations from 2 Earth orbiting observatories

CL.SYS.1.REQ.4011Observatories designed for a 3-year minimum lifetime. Inf rared spectra

temperature and water vapor feedbackscloud feedbacksdecadal change of :•Temperature prof iles •Water vapor prof iles•Clouds, radiative f luxes•GHG radiative ef fects

CL.PRJ.1.REQ.3001Inf rared radiance spectra of the Earth and its atmosphere with:•Systematic error that corresponds to ≤ 0.1 K radiance calibration uncertainty (3s)•Sampling to provide global coverage and degrade climate trend accuracy by less than 15%

CL.SYS.1.REQ.1001Measurements in the Inf rared Spectra:•Spectral range 200 – 2000 cm -1

•Spectral resolution 1 cm -1 apodized (0.5 unapodized)

•NeDT < 10K (1s), 250-2000 cm -1

•Earth nadir direction, 0.2 deg•GIFOV ≥25 km across•Ground sampling interval ≤ 200 km•Systematic error ≤ 0.100 Kelvin (3s)

CL.SYS.1.REQ.6001 Both observatories in polar orbits:•Orbit Period: 5820.6

0.25 seconds (609 km 200m)

•Inclination: 90 0.1•Eccentricity: ≤0.001•Ground Track Repeat Cycle: 60.83 days (903 distinct paths)

•Ground Track Error: 12.5 km cross track at AN f rom target ground track established by the 60.83 day ground track repeat cycle.

•Plane Separation: 90 in the Right Ascension of the Ascending Nodes (RAAN)

•Time separation: No less than 10 minutes in polar crossing times

Solar ref lected spectra cloud feedbacks snow/ice albedo feedbacksdecadal change of :•Clouds•Radiative f luxes•Snow cover, sea ice, land use

CL.PRJ.1.REQ.3002Solar spectral nadir ref lectance of the Earth and its atmosphere relative to the solar irradiance spectrum with:•Absolute uncertainty ≤ 0.3% relative to global mean ref lected solar energy (2s) •Sampling to provide global coverage and degrade climate trend accuracy by less than 15%

CL.SYS.1.REQ.1002Measurements in the Solar Ref lected Spectra:•Spectral range 320 – 2300 nm•Spectral sampling 4 nm, resolution 8 nm•GIFOV ≤0.5 km by 0.5 km•SNR > 33 for 380 to 900 nm, >20 elsewhere, for 0.3 reflectance, solar zenith angle 75

•Swath width ≥ 100 km•Polarization sensitivity <0.25% (2s) <1000 nm, <0.75% elsewhere

•Radiometric calibration uncertainty ≤0.3% of reflectance

GNSS-ROdecadal change of temperature prof iles

CL.PRJ.1.REQ.3003Atmospheric refractivity with:•Uncertainty of 0.03% for 5-20 km altitude

•Annual means in 10º latitude zones over all longitudes

CL.SYS.1.REQ.1003Measure the phase delay rate of GNSS transmitted signal occulted by the atmosphere:•Altitudes 5-20 km, 200 m vertical resolution•Uncertainty ≤0.5 mm/sec

CL.SYS.1.REQ.1004 Measure averaged microwave ref ractivity:•Over 1 year 10 latitudinal zones, over all longitudes,

•Altitudes 5–20 km, 200 m vertical resolution •Uncertainty ≤0.03 %

NOTEOrbit Def inition considered science sampling requirements and reference intercalibration requirement

Reference inter-calibration•Broadband CERES•Operational sounders (CrIS, IASI) •Operational imagers (VIIRS, AVHRR, Landsat)

CL.PRJ.1.REQ.3010 CLARREO shall enable inter-calibration with climate relevant operational sensors.


• Spectral range: 320 – 2300 nm

• Spectral sampling: ≤4 nm

• Spectral resolution: 8 nm

• Sampling interval at nadir from 600 km orbit: 0.5 km

• Spatial resolution per sample:– 70% of energy from within a 0.5 km x 0.5 km area– ≥ 95% within a 1.0 km x 1.0 km area

• Swath width at nadir from 600 km orbit: >100 km

• SNR values for a single sample (defined for a typical radiance, Ltyp, based on a reflectance of 0.3 and incident solar zenith angle of 75 degrees):

– SNR> 20 for wavelengths 320 – 380 nm– SNR> 33 for wavelengths 380 – 900 nm– SNR> 20 for wavelengths 900 – 2300 nm

• Polarization sensitivity for 100% polarized input:– <0.25% (TBD) below 1000 nm and – <0.75% (TBD) at other wavelengths

• Radiometric calibration accuracy: 0.3% of albedo (integration of reflectance across all wavelengths) and within individual bands

Requirements

RSS Level 2 Requirements


Sensor Design

Original RSS Instrument Concept3x Optical Packages• Blue Channel 320-640nm• Red Channel 600-1200nm• NIR (Near Infra-Red) 1150-2300nm

Detector PlaneThermal Radiators

Main Electronics Box(On S/C)

Attenuator wheel Control Electronics

(On S/C)

Instrument Support Platform

Heat Pipes


• Commonality of design of three boxes aids in calibration

• All-aluminum materials including telescope optics

• Offner design• Cooled focal planes tailored

for each spectral region• Depolarizers reduce impact

of scene polarization• Attenuator wheel for

reducing solar irradiance for reflectance retrieval

Single box layout

RSS Instrument Concept Design

InstrumentOptical Bench

SunshieldDetectorAssembly

Detector Electronics

Telescope Optics

Depolarizer Assembly

AttenuatorWheel


CLARREO-1 RSIS Goals• Develop modified instrument concept to coincide with a “single”

instrument spacecraft– Reduce the instrument mass – Fit within funding caps and profiles provided by the project

• Meet all of the RS science requirements including intercalibration

• Proposed solution – reduce three boxes to two boxes– Assume a development plan for CLARREO-1 consisting of

1 Breadboard 1 Prototype/EDU 1 Flight Unit

– The development plan for RSIS on CLARREO-2 depends on what is developed for CLARREO -1


• The RSIS instrument concept for an RSIS dedicated spacecraft revolves around a two spectrometer approach

• Blue spectrometer remains the same– Silicon-based detector– 320 to 640 nm– Single order grating

• Red and NIR spectrometers combined– 600 to 2300 nm– Dual order grating; multi-blazed– HgCdTe detector– Dual attenuator wheel

• Combining the Red and NIR channels into one spectrometer leverages the capability of the MCT detector

2-box design


• Three-box approach was chosen for several reasons– Lowest overall risk– Simpler design, fabrication, build, and test/calibration– Higher component TRL– Detectors had flight history– Depolarizers and attenuators could be tailored spectrally– Characterization/calibration more straightforward

• 2-box approach satisfies many of these– Increased risk to the calibrate the Red/NIR spectrometer due to

the increased stray light from the dual order grating– Mitigate attenuator spectral sensitivity through multiple attenuator

wheels• The specific impacts of the dual order system will have to be

evaluated though the breadboard program

Why not 2-box from the start?


Two-box concept

2x Optical Packages• Blue Channel 320-640nm• Red/NIR Channel 600-

2300nm

Detector PlaneThermal Radiators

Main Electronics Box(Inside S/C)

Attenuator wheel Control Electronics(Inside S/C)

Instrument Support Platform


Two-box approach


GNSS-RO POD Antenna

Star Trackers

GPS Antennas


Instrument• Mass: 67 kg CBE, 86kg with 28% confidence factor• Power: 96 W Avg, 118 W Peak CBE, 125 W Avg, 153 W Peak with 30%

confidence factor• Data Rate: Still being reviewed, but it looks like an allocation of 100

Gbits/day and 150 Mbps Data Rate to the SSR would provide good margin with a 30% confidence factor

• Thermal Radiator: 0.1m^2 mounted on the side of the S/C• Spacecraft pointing control: 360 arcsec control, 72 arcsec knowledge• Spacecraft roll slew rate: up to 2 deg/s• Planned Orbit: 609km• Mechanical Interface: 2 spectrometers mounted to the top of the S/C, 2

Electronics boxes (Main EB, and Attenuator Wheel EB) mounted inside S/C, thermal radiator mounted to S/C cold side

• Electrical Interface: LVDS connection to SSR, 1553 or 422 communication bus


• Baseline approach to reflectance retrieval is ratio of earth-view data to solar-view data

• Single detector scans entire solar disk

• Response of ith detector is

• Bidirectional reflectance distribution function (BRDF) is

Level 1 Science requirement is stated in terms of a reflectance retrieval

Reflectance Retrieval

RS x y

T A Eisenso r x

iso lar

so lar so lary

attenu ato r a ttenu a to r so lar

so lar so la r

,

, ( , )

( )

B R D FL

ES

R AT A R

S x yi

ea rth iearth

sun so lar

iear th

isensor

sensor sensor

a ttenua tor a ttenua tor isensor

so larx

iso la r

so lar so laryso la r so la r

,, ,

,

,

,

co s( )

co s ( , )


• Reflectance retrieval, calibration and inter-calibration requirements lead to three basic operating modes

– Solar Calibration– Nadir Data Collection – Inter-calibration of LEO/GEO

assets (avg. 2x per orbit)• Verification of calibration

drives the need for Lunar Views

Three basic operating modes for RSS instrument

Operating Modes


• Solar calibration allows for– Correction of degradation of sensor response

Temporal degradation of detectors and optics Detector-to-detector changes

– Evaluation of stray light• Solar view is non-trivial

– Irradiance source rather than radiance source

– 50,000 times higher energy level

– Requires attenuating approaches

Reflectance retrieval uses direct solar view

On-Orbit, Solar Calibration

Each detector images full solar disk

RS x y

T A Eisen sor x

iso lar

so la r so lary

a tten ua tor a ttenu a tor so lar

so lar so lar

,

, ( , )

( )

RS r

T A Esensor i

i jso lar

ifla t fie ld

j

a tten ua tor a ttenua tor so lar

, , ,

( )

Solar disk imaged by multiple detectors


• Attenuators provide the 50,000x reduction in solar energy

• All approaches are spectrally dependent• Pinhole Aperture

– Diffraction effects lead to spread of solar “image”– Small-sized aperture affects diffraction grating

dispersion• Perforated Plate

– Avoids materials degradation problems– Trade on size and number of holes relative to

attenuation and beam uniformity• Neutral Density Filters

– Attenuate using either absorption or interference effects– Temporal degradation needs evaluation

Direct solar view requires an attenuating mechanism

Attenuators for Solar Calibration Mode


• CLARREO reflectance retrieval relies on the ratio of the benchmark data to the solar data

– Account for temporal variability in sensor– Can be converted to absolute radiance using a known solar irradiance

• Need to include uncertainties in sensor characterization– Straylight changing

Sensor solid angle (footprint) Sensor aperture Attenuator area

– Detector response uncertainties Nonlinearity Polarization Flat field correction

Calibration overview

B R D FS

R AT A R

S r

a ar r ri

ea rth iea rth

isenso r

senso r sensor

a tten ua tor a tten ua torsenso r

so lark

k lso lar

kfla t fie ld

l

sensorstra yligh t

sen sorstray ligh t

a ttenu a torstray lig h t

ifla t fie ld

ino n linea rity

ipo la riza tion,

,

,, ,

, , ,

( )

co s


Full Calibration


• Each attenuator must be used for solar views

• Lunar verification follows similar scanning

Single-Multiple Image Calibration


Flat-Fielding Calibration


• Characterize the sensor to SI-traceable, absolute radiometric quantities during prelaunch calibration

Watt Irradiance mode Radiance mode

• Determine geometric factors for conversion to reflectance

– On-orbit calibration “validates” the prelaunch calibration

– Solar and lunar views used to determine temporal changes

• Key is to ensure prelaunch calibration simulates on-orbit sources

– Absolute irradiance calibration for solar view

– Simulated geometry of solar and lunar views for stray light

• Successful transfer to orbit achieved when sensor behavior can be accurately predicted

Simulating and predicting on-orbit sources is basis of calibration

Calibration Approach

Prelaunch LaboratoryMeasurements

No

CalibratedYes

Sensor Model

Model/Measurment

Agree?

On-Orbit SensorMeasurements

On-Orbit SensorMeasurementsPredicted On-Orbit

Sensor Output

UpdateModel


Meeting L1 Measurement Requirements

• The effort is determining the measurements needed to satisfy/understand the development of the sensor model

• Preliminary independent study indicated CLARREO Reflected Solar requires nearly order of magnitude improvement in radiometric accuracy

• Dominant error sources identified as stray light and attenuator characterization

• Efforts to reduce these errorsources rely on

– Minimizing sensor complexity– Choosing appropriate approaches for SI traceability– Emphasizing calibration throughout sensor development lifecycle

RS Calibration

No

Model/Measurment

Agree?

On-Orbit SensorMeasurementsPredicted On-Orbit

Sensor Output

UpdateModel


Calibration Overview

* Measurements to achieve SI traceability for transfer to orbit

AttenuatorcharacterizationA Ta ttenua tor a ttenua tor,

R i jsensor,

r Ri jfla t fie ld sen sor, ,

Absoluteresponse

Relativeresponse

Sensor Artifactsa a

r rsenso rstra ylig h t

sen so rstra yligh t

a ttenu atorstra ylig h t

i jnon lin ea rity

i jpo la riza tion

, ,

Attenuatorverification A Tattenua to r a ttenua tor,

R i jsensor,

r Ri jfla t fie ld sen so r, ,

Absoluteresponse eval.

Relativeresponse

Sensor Artifactsa a

r rsensorstra ylig h t

sensorstra ylig h t

a tten ua to rstra ylig h t

i jno nlin earity

i jpo lariza tion

, ,

Time

Attenuatorverification A Ta ttenua tor a ttenua tor,

r Ri jfla t fie ld sensor, ,

Relativeresponse

Green box showsdominantparametersdetermined fortransfer to orbit

*

*

Prelaunch OperationsPost-launch


• Attenuator verification relies on trending of lunar views without attenuator

– Compare to trend of sensor output while viewing sun with attenuator in place

– Different trend behavior indicates attenuator issue• Comparison of solar irradiance reported by CLARREO to other on-

orbit sensors indicates whether absolute calibration is maintained in going to orbit

– Indicates whether geometric factors are well understood (attenuator area)

– Stability of absolute detector response• Relative response measured in laboratory compared to that derived

on orbit for consistency• Artifact determination

– Sun and moon provide sharp boundaries for stray light, ghosting– Stellar and planetary sources provide point sources for evaluation of

spatial response– Polarization sensitivity assessed using earth-view scenes (e.g., ocean

views at large angles)– Non-linearity evaluated by varying attenuators– Size of source effect is most difficult to issue to understand

Calibration overview

Attenuatorverification A Tattenu a tor a ttenu a tor,

R i jsensor,

r Ri jfla t fie ld sensor, ,

Absoluteresponse eval.

Relativeresponse

Sensor Artifactsa a

r rsenso rstrayligh t

senso rstrayligh t

a ttenu ato rstray ligh t

i jno nlin ea rity

i jpo la riza tion

, ,

*

*

Post-launch


SIRCUS Traceability


• SIRCUS provides a feasible option for simulating on-orbit sources

• Absolute response• Stray light

• SIRCUS relies on a set of well-understood tunable lasers

– Variety of techniques used to condition laser output

– Output characterized by CLARREO Transfer Radiometer and monitors on sphere

• Provides a monochromatic source that can achieve 0.1% absolute uncertainty

* POWR – Primary Optical Watt Radiometer


SIRCUS and CLARREO


• Ultimate goal is to have a portable SIRCUS-like facility for calibration of RS instrument

• Portability needed to ensure its use at a vendor facility• Necessary to achieve needed accuracy

• SIRCUS-like facility includes• Monochromatic source

• Irradiance• Radiance• Cover full spectral range of CLARREO

• Broadband transfer radiometers• Monitor output of source

• Transfer radiometer #1 – VNIR• Transfer radiometer #1 - SWIR

• Maintain traceability to NIST laboratories• Transfer radiometer #2 – VNIR• Transfer radiometer #2 - SWIR


Inclusion of SIRCUS for CLARREO• Including a SIRCUS-like source in the preflight calibration chain permits preflight,

absolute radiometric calibration of solar view to better than 0.2%• Diagram below gives top-level error sources and expected error budget


ElectronicsOffset

EarthView k=2

0.08% 0.05%Sensor

Characteristics

Jitter

BackgroundOffset

0.1%0.05%

DetectorsROIC

Analaog

Inclusion ofSIRCUS

reduces strayand scattered

lightuncertainties by

>1 order ofmagnitude

ROIC ReadNoise

Quantization Noise

Electronics Noise

Near-FieldBackground

Noise

Dark Current Noise

Signal PhotonNoise

IntegrationTime

Optical Efficiency

WavelengthCalibration

Point SpreadFunction

PolarizationSensitivity

Line SpreadFunction

Responsivity and Rel. Gain

Detector Linearity

SceneThermal

ScatteredLight

Stray Light and Flare

Sensor Thermal

RadiometricRandom

Boresight

Random

Non-random

0.3% on singlemeasurement

0.1%

Sensor thermal is afterdark subtraction

Thermal backgroundimportant at λ>1.8 μm


Broadband Approaches• Sources calibrated in SIRCUS-like measurements are limited in bandpass

– Small regions of wavelength can be tested– Cannot calibrate all CLARREO spectral and spatial detectors simultaneously

• Hyperspectral Image Projector (HIP) currently under development at NIST would provide a broadband source

– Can match desired spectral source– Traceablity can be achieved through a SIRCUS-like calibration– Also provides opportunity to develop a solar simulated source

• SIRCUS and HIP can be replicated at a CLARREO facility


HIP schematic


• Clearly the key technology developments are– SIRCUS facility– RS Transfer Radiometer

• A SIRCUS-based absolute calibration in radiance is currently demonstrated by NIST at the 0.2% accuracy

– Stray light is readily characterized by a SIRCUS-based calibration– Polarization sensitivity measurements are also feasible with SIRCUS

• Focus on developing broadband calibration techniques– HIP can be used to bridge the broadband gap

More development to understand the accuracy Prototype development scheduled to be complete in 18 months

– Characterization of filtered transfer radiometers by SIRCUS also permits extension to broadband sources

• Significant technology development is not required but rather advancements in current approaches are needed

– Robust, portable SIRCUS facility– Transfer Radiometers with sufficient spectral coverage– Broadband stray light and polarization systems of sufficient fidelity

Requirements Compliance

Technology Development/Path to 0.3%


Error Budget• Radiometric calibration

requirements of RSS instrument can be met with currently-available approaches

• Requires inclusion of NIST-based methods

– Detector-based transfer radiometers

– Narrow-band SIRCUS aproaches

– HIP-based scene projections

B R D FR S

R S r

T AA

a ar r ri j

earthsenso r

i jearth

i jsen sor

ii jso lar

i jfla t field

j

a ttenua to r a ttenua to r

sensor sen sor

sensorstray ligh t

senso rstray ligh t

a ttenua torstrayligh t

i jfla t field

i jno n linearity

i jp o lariza tion,

,

, , ,, , ,


Line SpreadFunction Artifacts

EarthView

Reflectanceuncertainty

0.1% 0.03%

0.3%

0.2%

0.1%

0.2%

Earth:SolarRatio

SolarView

Spectral

Solar AttenuatorFactor

WavelengthCalibration Artifacts

Percentuncertainties inreflectance; k=2


Calibration Flow

RS Calibration

Assemble FLT Optics Package(Blue Band)

Assemble FLT Instrument(3 Boxes)

Ground Operations

Post-Launch Operations

Thermal/Vac Test- Survival -

BalanceDeep Calibration

Thermal/Vacuum Test

Calibration Stability Check

Requirements Verification

Environmental Test

Subsystem/Component

Measurements

Assemble FLT Optics Package(Red Band)


BalanceDeep Calibration


Environmental Test

Subsystem/Component

Measurements

Assemble FLT Optics Package(NIR Band)


Balance

Deep Calibration


Environmental Test

Subsystem/Component

Measurements


Environmental Test

Acceptance Review

Delivery to Payload I&T

Payload I&T

Thermal/Vacuum Test


Payload Delivery to Spacecraft I&T


Environmental TestSpacecraft I&T

Thermal/Vacuum Test


LaunchRequirements Verification

Environmental Test

Post-Launch Checkout

In-Orbit Calibration Validation


• Aperture and Grating Quantity Trade Study– Proceed with 3 Aperture, 3 Grating Design

Lowest overall Risk Simpler design, fabrication, build, and test Lower cost Higher component TRL

• Detector Material Trade Study– Blue Band Material Selected – Silicon; Red and NIR Band Material Selected – MCT (substrate

removed) Only consider main-stream detector technology Only consider materials with flight history Meets Spectral Requirement

• Wavelength Range Trade Study– Spectral range to cover from 320 to 2300 nm

Upper limit chosen due to loss of signal from reduced solar irradiance and strong water vapor and carbon dioxide absorption

Short-wavelength limit chosen to provide sufficient spectral range for accurate retrieval of total shortwave flux

• Polarization Requirements Trade Study– Polarization sensitivity <0.50% below 1000 nm and <0.75% at other wavelengths for a 100% polarized

input Value required to limit uncertainty in benchmark data set to contribute <0.1% of total radiometric calibration

budget

Trade Studies

Trade Studies Completed


Inst #2250K

Inst #1270K

Inst #3230K

Per pixel SNR requirement

7 11 7

Worse case detector temps


Radiometric Performance Margin: Ltyp; Sun View; Lmax

2.8E6 pe’sWell Capacity

Wavelength - um

Inst #129.7ms integration



2.8E6 pe’sWell Capacity

Wavelength - um



Inst #37.1ms integrationInst #2

250K

Inst #1270K

Inst #3230K

Per detector SNR requirement

67 67110

Worse case detector temps


Dual-Double Wedge Depolarizer with OA at 90, Wedge angles clocked at 45

Polarization Sensitivity Compliance


Add text description; label requirements lines; define DOLP


• Phase A breadboard and EDU development requires a parallel development of calibration GSE• Calibration development plan also includes development of calibration methods and protocols

applicable for flight instruments• Calibration development plan follows Phase A plans to reduce instrument risks and close trades

– Solar/earth view ratio for reflectance Laboratory capability to provide irradiance (point) source and radiance (extended ) source Solar- and lunar-based measurement capability Geometric characterization of sensor field of view

– Attenuator characterization Spectral transmittance Aperture-area measurements

– Path to SI traceability (source and detector standards) Narrow-band source (SIRCUS) Broad-band source (HIP) Transfer radiometers

– Stray light modeling capability– Polarization sensitivity measurement

Component-level depolarization characterization System-level polarization sensitivity

– Focal plane and grating characterization Uniformity Stability Noise

Phase A plans


Long Lead Procurements

Component Fabrication, Procurement

Breadboard Plan

Component Characterization

Optical Package Assembly

Performance Test and Calibration

Earth, Sun, Moon Measurements

May 2011

Layout &Analysis

Aug 2011

ComponentFab, Procure

Dec 2011

Optics PackageAssembly

Comp.Charact.

Oct 2011

Perf. Test,Cal.

March 2012

Earth, Sun,Moon Meas.

April 2012

Calibration(incl. NIST)

July 2012Aug 2010

Long Lead Procurement Start(Detector, Grating, Depolarizer)

Layout and Analysis

Characterization and Calibration

Description• Detectors• Depolarizers• Gratings

Risk Reduction• Items available when other

parts ready

Description• Measure Performance

• Detectors• Depolarizers• ND Filters• Gratings/Optics

Risk Reduction• Validate analytical

performance models with measured performance

• Measure Detector noise levels, Validate noise reduction by averaging

• Evaluate stray light

Description• Develop a breadboard

based on the blue band spectrometer

Risk Reduction• Allows lower cost breadboard

development using Si detectors• Focuses effort on component

and calibration risk mitigation

Description• Calibrate with a NIST

traceable FEL Lamp• Flat Panel, Spherical

Integrator Cal.

Risk Reduction• Begin NIST traceable

calibration• Begin developing cal.

processes

Description• Measure Sun and Earth to

generate Reflectance• View Moon and Sun

Risk Reduction• Begin to validate operations

approaches• First time that Sun and Earth

will be viewed to generate Reflectance

Description• Continue cal. evaluation

with GSFC facilities• Calibrate with SIRCUS

at NIST

Risk Reduction• Continue NIST traceable calibration to

higher accuracies• Begin developing cal. processes• Evaluate the ability to calibrate the

design


Breadboard Plan• Breadboard plan was modified slightly in March

– Build an optical package starting with the Blue band (320-1150 nm) design Blue band selection will allow achievement of more objectives than any other band (items 1,2,4,5, and 6)

quicker, with possibly lower cost options for detectors– Build optical package for the Red/NIR band (600-2300 nm) designs– Evaluate detector options based on cost, with the possibility of a stepped approach of cheaper vs.

more functional detectors to begin a stepwise learning and testing approach based on available budget– The optical package would have a feature for using attenuators– Validate reflectance retrievals in laboratory and field– NIST-based measurements to evaluate calibration techniques and error budgets

• Breadboard objectives– Demonstrate the ability to view the sun and the scene and output reflectance by taking the ratio of the

Solar irradiance and the measured value Feasibility of attenuation methods: perforated plate, pinhole plate, neutral density filters

– Develop and check calibration protocols and methods Path to SI traceability (source and detector standards)

– Demonstrate the ability to design and produce optics, with the optics in the Blue band (320-1150 nm) being the most challenging

– Demonstrate ability to minimize polarization sensitivities– Demonstrate the ability to control and characterize stray light including multiple-order gratings– Demonstrate the ability to measure shortwave IR (600-1200nm) (Red)

Demonstrate the use of detector technology Validate ability to control thermal stability Make measurements past 900nm


Calibration Development Plan• Phase A breadboard and Prototype development requires a parallel development of calibration GSE• Calibration development plan also includes development of calibration methods and protocols applicable for flight

instruments• Calibration development plan follows Phase A plans to reduce instrument risks and close trades

– Solar/earth view ratio for reflectance Laboratory capability to provide irradiance (point) source and radiance (extended ) source Solar- and lunar-based measurement capability Geometric characterization of sensor field of view

– Attenuator characterization Spectral transmittance Aperture-area measurements

– Path to SI traceability (source and detector standards) Narrow-band source (SIRCUS) Broad-band source (HIP) Transfer radiometers

– Stray light modeling capability– Polarization sensitivity measurement

Component-level depolarization characterization System-level polarization sensitivity

– Focal plane and grating characterization Uniformity Stability Noise


NIST Standards Development

• NASA/NIST personnel work collaboratively to develop portable SIRCUS• Obtain NIST SIRCUS schematics and parts list

•Finalize development plan based on tests conducted in NIST’s prototype facility

•Design transfer radiometers•Procure parts•Breadboard development

•Procure additional parts (e.g., integrating sphere, speckle removal system)•Begin assembly at GSFC

•Procure parts •Begin assembly

•Conduct testing to establish standard uncertainties in irradiance and radiance responsivity calibrations to less than 0.1%

•Conduct testing to establish instrument radiometric scale•Deliver DMD to GSFC

•Deliver CXRs to GSFC•Integrate with portable SIRCUS

Design a portable version of the NIST SIRCUS facility

Procure tunable lasers to cover desired wavelength range

(320nm – 2300nm)

Assemble SIRCUS facility

Outcome: Provides monochromatic source that can achieve 0.1% absolute accuracy of irradiance sources

FY 2011 FY 2012 FY 2013 FY 2014

Design CXRsConstruct/Test CXRs

(coverage from 320 nm to 2300 nm)

Complete testing of CXRs

Outcome: Enables SI-traceable radiance

comparisons in the UV, visible, and near-infrared

Design DMD-based spectrally tunable calibration source

Outcome: Provides a broadband source that can

reproduce expected reflected solar brightness

levels and spatial distributions

Assemble DMD Complete TestingDMD

Complete TestingSIRCUS


• Activities of breadboard relevant to SIRCUS– Develop and check calibration protocols and methods

Path to SI traceability Detector-based methods

– Demonstrate the ability to control stray light– Demonstrate the ability to measure shortwave IR (600-1200nm)

(Red)• Development of SIRCUS-like facility takes place during

breadboard work– Not necessary to complete SIRCUS for breadboard– Necessary to understand how it would be used

• Higher fidelity error budget

Breadboard and SIRCUS

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