Revision of ACRIMSAT/ACRIM3 TSI results based on LASP/TRF diagnostic testing for the effects of...

$: Revision of ACRIMSAT/ACRIM3 TSI results based on LASP/TRF diagnostic testing for the effects of scattering, diffraction and basic SI scale traceability$
Revision of ACRIMSAT/ACRIM3 TSI resultsbased on LASP/TRF diagnostic testingfor the effects of scattering, diffraction

and basic SI scale traceability

ACRIMSAT/ACRIM3

ACRIM3 TEAM

Dr. Richard C. WillsonPrincipal Investigator

ACRIM

Sandy KwanACRIMSAT Project Manager

JPL

Roger HelizonInstrumentation Consultant

Dr. Nicola ScafettaCo-Investigtor

Duke University

AGU Session G21C Tuesday Dec 6 2011

Richard C. Willson 1

ACRIM3 Guidance from the NASA 2009 Senior Review



ACRIM Gap(Composite TSI trends) ‘Annual’ signal differences

Scale difference(Calibration)

ACRIM3 2009 Senior Review directed tasks:

Investigation of ACRIM3 - TIM TSI Scale Difference

Approach: Characterize ACRIM3 flight backup instrument at the LASP/TRF 1

• The LASP/TRF team, led by Greg Kopp, conducted the TRF testing procedure

ACRIM3 self-calibration compared with TRF/NIST 2 cryo-radiometric scaleDiagnostic testing to evaluate ACRIM3 scattering and diffraction effects

• The ACRIM3 Team, led by Dick Willson, prepared and operated the ACRIM Instrument

Analyzed test data and shared results with LASP and NRL3

Derived scale/scattering/diffraction corrections for ACRIM3 observationsApplied corrections to the ACRIM3 database and ACRIM Composite TSI time series

• The NRL team, led by Jeff Morrill, provided independent oversight of TRF testing

Observed TRF testing and convened review of the preliminary results (Dec. 2010)Conducted scattering, diffraction and cavity reflectance modeling/testing

1 Laboratory for Atmospheric and Space Physics (LASP) Total Solar Irradiance Radiometer Facility (TRF)2 National Institute of Standards and Technology3 Naval Research Laboratory



ACRIM3 Sensor



• Most ACRIM3 flight backup components fabricated during flight instrument build

• ACRIM3 flight backup represents ACRIM3 flight instrument properties and performance

Laboratory for Atmospheric And Space Physics (LASP)

Total Solar Irradiance Radiometer Facility (TRF)

532nm transfer laser

TRF Cryogenic Radiometer(Traceable to NIST)

Test Chamber

Moveable Transfer Stage

Rastering Mirror

Collimator

ACRIM3 Flight BackupInstrument



ACRIM3 Sensor Module and Irradiance Testing Modes

BASIC POWER COMPARISON (SI UNITS) 5mm Circular BeamUnder-fill Primary aperture

CALIBRATE SCATTERING IN LOWER VIEW LIMITING ASSEMBLY10mm Circular BeamOver-fill primary aperture, Under-fill View Limiting aperture and Baffle

CALIBRATE TOTAL SCATTERING & DIFFRACTION15mm Circular BeamOver-fill View Limiting aperture

Front View of Sensor Module



ACRIM3 LASP/TRF Characterization Results

Preliminary ACRIM TRF Test (Oct 2010)

• Basic optical power: ACRIM and TRF scales agree within ~ 500 ppm

• Scattered light and Diffraction: ACRIM view-limiting assembly signal ~ 6000 ppm

• ACRIM flight backup apertures of lower quality than ACRIM3 flight apertures

Mirror surface finish inferior to ACRIM3 flight specificationsPossible cause of excess scattered light

• ACRIM TRF re-test required to evaluate scattering effect of primary aperture surface

ACRIM Sensor B aperture replaced with ACRIM3 flight spareACRIM Sensor A left unchanged as control for second test

ACRIM TRF Re-test (Jan – Feb 2011)



ACRIM3 LASP/TRF Characterization Summary

Basic optical power scale observations 1

• Sensor A: ~ 200 ppm (+/- ~ 600 ppm)• Sensor B: ~ 450 ppm (+/- < 100 ppm)

Scattered light and diffraction results 1,2

• Oct 2010 test:

Sensor A: ~ 7000 ppmSensor B: ~ 6000 ppm

• Jan – Feb 2011 re-test:

Sensor A: ~ 6500 ppmSensor B: ~ 5000 ppm

• Diffraction component ~ 1000 ppm 3



1 Ratio to the TRF cryo-radiometric scale

2 Uncertainty of scattering & diffraction results ~ 500 ppm

3 Based on LASP interpretation of annular beam test results

ACRIM3 LASP/TRF Characterization

Conclusions

• Basic optical power scales: ACRIM3, TRF & NIST agree within 500 ppm

• ACRIM scattering and diffraction effects: 5000 ppm (+/- ~ 500 ppm)

• Correction of ACRIM3 results for scattering and diffraction is required

• ACRIM3 basic scale agrees with TRF and NIST within the uncertainty the TRF test

Comments

• The LASP/TRF is a valuable diagnostic tool for TSI radiometry

• Independent ACRIM and LASP analyses of TRF data agreed within their uncertainties

• Substitution of flight quality aperture in Sensor B reduced scattering by ~ 1000 ppm

• Additional testing could reduce TRF test uncertainties



ACRIM3 flight data algorithm updated per TRF test findings

• A temperature dependent reference voltage correction was re-implemented with the following effects:

An ‘annual’ component in the ACRIM3 results was reduced (by ~ 300 ppm)The average noise level of results increased (~ 50 ppm)The ACRIM3 self-calibration (native) scale increased (~ 1000 ppm)

• A TRF-derived Scattering, Diffraction and TRF/NIST Scale correction (SDS) was applied

ACRIM3 data were reprocessed to level 1 with the reference voltage correctionThe SDS correction was applied – lowering the ACRIM3 scale by 5000 ppmSDS-corrected results were processed to level 2 (sun-satellite distance correction)Final results corrected for sensor degradation using ACRIM self-calibration process

Application of TRF Test Results to ACRIM3 Results





ACRIM3_EM

Graphical Summary of ACRIM3 TRF Test Resuts



TRF-derived correctionreduces calibration scale,does not affect TSI trending



ESA MissionsNASA Missions

AGU Session G21C Tuesday Dec 6 2011 16Richard C. Willson



Resolution of ‘ACRIM Gap’ Issue

Experimental

• Continue data processing, analysis and dissemination of ACRIMSAT/ACRIM3 results

• TRF re-test ACRIM3_EM to reduce scattering, diffraction and basic scale result uncertainties

• Investigate apparent absence of an annual scattering & diffraction signal (~ 170 ppm)

• Investigate the signal noise level increase (~ 50 ppm) with updated algorithm

ACRIM3 Science Team Continuation: FY 2012-2013



Science Investigations

• TSI trending and ‘ACRIM Gap’ implications of new solar magnetic activity data

• Possible solar/Planetary barycentric motion effects on Solar Activity, TSI and climate (w/Scafetta)

• TSI signature of the 2012 transit of Venus (w/Pasachoff)

• Publish ACRIM/TRF findings and their TSI monitoring significance

ACRIM3 Science Team Continuation: FY 2012-2013



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