ACRIM Satellite TSI Observations, Scales and Traceability Active in the context of the NASA-NIST TSI Workshop Day2 Presentations and Discussion ACRIM Active Cavity Radiometer Irradiance Monitor Experiments ACRIM3 SCIENCE TEAM Dr. Richard C. Willson Principal Investigator Columbia University acrim@acrim.com ACRIM3 INSTRUMENT TEAM Roger S. Helizon Instrument Scientist ACRIMSAT Project Mgr. Jet Propulsion Laboratory roger@simdac.jpl.nasa.gov ACRIMSAT/ACRIM3 AGU Fall Mtg 2005: SH33C R C Willson - Columbia University

Constructing composite TSI time series: bridging the ACRIM ‘gap’ 0.35 % AGU Fall Mtg 2005: SH33C R C Willson - Columbia University

Satellite TSI Observations, Scales and Traceability TSI database sustained since 1980 by redundant, overlapping experiments Precise traceability (relative precision) is the most important quality of the database Sensor degradation calibration is the primary contributor to precise traceability TSI monitoring experiments self-calibrate degradation using redundant sensors TSI database traceability 1980 – 2005: ~ 100 ppm Current state of the art: ~ 5 ppm/yr TSI database cannot be sustained by measurement accuracy TSI experiments self-calibrate in the International System of Units (SI) Calibration is based on pre-flight sensor metrology Scale differences result from systematic metrology errors SI uncertainty varies among experiments but none are significantly less than ~ 0.1 % R C Willson - Columbia University AGU Fall Mtg 2005: SH33C

Rationale for ‘bridging’ the ACRIM Gap and constructing a composite TSI time series AGU Fall Mtg 2005: SH33C R C Willson - Columbia University

AGU Fall Mtg 2005: SH33C R C Willson - Columbia University

R C Willson - Columbia University AGU Fall Mtg 2005: SH33C

Relative effects of ERB & ERBE ACRIM ‘gap’ ratios on TSI composites AGU Fall Mtg 2005: SH33C R C Willson - Columbia University

Paradigm Test of ERB and ERBE ACRIM ‘gap’ ratios TSI variability paradigm: TSI is proportional to solar magnetic activity on solar cycle time scales During the ACRIM ‘gap’ the average solar magnetic activity level increased steadily The Nimbus7/ERB upward trend during the ‘gap’ is compatible with the paradigm The ERBS/ERBE downward trend during the ‘gap’ is incompatible with the paradigm ERBE degradation during ACRIM ‘gap’ equals the ACRIM - PMOD trend difference R C Willson - Columbia University AGU Fall Mtg 2005: SH33C

NASA/NIST TSI Workshop Day2 A NASA/NIST TSI Workshop was convened in July 2005 with the following purposes: Investigate the 0.35 % ACRIM3_VIRGO - TIM scale difference Provide a state of the art assessment of TSI satellite monitoring The Day2 discussions focused on the traceability of satellite TSI experiments’ launch calibrations throughout both their missions and the duration of the 27 year TSI database R C Willson - Columbia University AGU Fall Mtg 2005: SH33C

NASA/NIST TSI Workshop Day2: ACRIM Calibration Traceability Instrument Predicted SI Uncertainty (ppm) Sensor agreement at launch (ppm) Realizable SI Uncertainty (ppm) Total mission Degradation (ppm) Degradation Uncertainty (ppm/yr) ACRIM1 1000 1021 600 < 5 ACRIM2 4090 1500 ACRIM3 2068 360 < 3 AGU Fall Mtg 2005: SH33C R C Willson - Columbia University

NASA/NIST TSI Workshop Day2: SOHO/VIRGO Calibration Traceability Instrument Predicted SI Uncertainty (ppm) Sensor agreement at launch (ppm) Realizable SI Uncertainty (ppm) Total mission Degradation (ppm) Degradation Uncertainty (ppm/yr) SOHO hiatus sensor change (ppm) DIARAD 500 4100 366 tbd 200 PMO6V 1200 633 3000 300 SOHO gap SOHO Hiatus Attribution: C. Frohlich NASA/NIST TSI Workshop AGU Fall Mtg 2005: SH33C R C Willson - Columbia University

NASA/NIST TSI Workshop Day2: SORCE/TIM Calibration Traceability Instrument Predicted SI Uncertainty (ppm) Sensor agreement at launch (ppm) Realizable SI Uncertainty (ppm) Total mission Degradation (ppm) Degradation Uncertainty (ppm/yr) TIM 100 660 ~ 100 10 SOHO gap AGU Fall Mtg 2005: SH33C R C Willson - Columbia University

NASA/NIST TSI Workshop Day2 Conclusions The 0.35 % ACRIM3_VIRGO - TIM scale difference cannot be explained Additional experimental work is required: Comparisons of ACRIM3, VIRGO and TIM sensor technology with NIST laboratory laser-based scale transfer standards Real time comparisons of ACRIM3, VIRGO and TIM sensor technology using the sun as the source at the JPL Table Mtn. Solar Test Site R C Willson - Columbia University AGU Fall Mtg 2005: SH33C