Active Cavity Radiometer Irradiance Monitor

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 Publications by or with Richard C. Willson, ACRIM Principal Investigator

  Hyperlinks provided where possible. Number of citations in { } brackets.

Willson, R.C., (1967) Radiometer comparison tests, JPL Tech.  Memorandum 33‑371,  Jet Propulsion Laboratory, Pasadena, CA

Willson, R.C., (1969), Experimental and theoretical comparison of the JPL active cavity radiometric scale and the international pyrheliometric scale, Tech. Report 32‑1365, Jet Propulsion Laboratory, Pasadena, CA

Willson, R.C., (1971), The active cavity radiometric scale, the international pyrheliometric scale and the solar constant, J. Geoph. Res., 76, p.4325 {8}

Willson, R.C., (1971), Radiometer Comparison Tests, Report 900‑446, Jet Propulsion Laboratory, Pasadena, CA

Willson, R.C., (1972), Results of the 1972 Table Mountain radiometer and radiation scale comparisons, Informal report, Jet Propulsion Laboratory, Pasadena, CA

Willson, R.C., (1972), Experimental comparisons of the International Pyrheliometric Scale with the Absolute Radiation Scale, Nature, 239, p. 208; DOI:10.1038/239208a0 {15}

Willson, R.C., (1973), Active Cavity Radiometer, J. Appl. Optics, 12, P. 810 {35}

Willson, R.C., (1973), New radiometric techniques and solar constant measurements, J. Solar Energy, 14, P. 203 {4}

Willson, R.C., (1973), Advances in Pyrheliometric Instrumentation, Proc. Solar Energy Data Workshop, National Science Foundation, Silver Spring, MD, Nov., 1973, p. 50

Willson, R.C., (1974), Absolute Radiometry and the Solar Constant, Proc. of the Symposium on Solar Radiation ‑ Measurements and Instrumentation, Smithsonian Institution, Rockville, MD, Nov., 1973. {4}

Willson, R.C., (1974), Absolute Radiometry and the Solar Constant, Space Optics, National Academy of Sciences, Washington, DC, p.502 {4}

Willson, R.C., (1975), Instrumentation for measurements of solar irradiance and atmospheric optical properties, Proc. Soc, Photo‑Optical Instrumentation Engineers,  p.  31,  San Diego, CA, USA {42}

Willson, R.C., (1975), JPL Absolute Radiometry and Solar Constant Measurements, Proc. Workshop on the Solar Constant and the Earth's Atmosphere, Ed. H. Zirin, J. Walter, Big Bear Solar Observatory, Big Bear City, CA, May 19‑21, 1975, p. 301

Willson, R.C., J.R. Hickey, (1977), 1976 rocket measurements of  the constant and their implications for variation in the solar output in cycle 20, in The Solar Output and  Its Variation, Ed. by O.R. White, Colorado Associated University Press, Boulder, CO, USA, 1977

Duncan, CH.,  R.G. Harrison, J.R. Hickey, J.M. Kendall Sr., M.P. Thekaekara, R.C. Willson, (1977), Rocket calibration of the Nimbus‑6 solar constant measurements, Appl. Opt.,  16, p. 2690 {42}

Willson, R. C. (1978), Accurate Solar ‘Constant’ Determinations by Cavity Pyrheliometers, J. Geophys. Res., 83(C8), 4003–4007.

Willson, R.C., (1979), Active cavity radiometer type IV, Applied Optics, Vol. 18, Issue 2, pp. 179-188 DOI:10.1364/AO.18.000179 {35}

Willson, R.C., (1980), Active cavity radiometer type V, Applied Optics, Vol. 19, Issue 19, pp. 3256-3257 DOI:10.1364/AO.19.003256

Willson, R.C., C.H.  Duncan, J. Geist, (1980), Direct Measurement of Solar Luminosity Variation, Science,  207, p. 177 {52}

Willson, R.C., (1981), Solar Total Irradiance Observations by Active Cavity Radiometers, Solar Physics,  74, p.218

Willson, R.C., Hudson, H.S., (1981), Astroph. J. Lett., 24, p. 185

Willson, R.C., Gulkis, S., Janssen, M., Hudson, H.S., Chapman, G.A., (1981),  Observations of solar irradiance variability, Science, 211, p. 700  {107}

Willson, R.C., (1981d), Observation of solar irradiance variations in balloon, rocket and satellite experiments, Proc. of IAMAP 3rd Scientific Assembly, Hamburg, FRG, August, 1981

Willson, R.C., (1981e), Satellite Observations of Solar Irradiance Variability, Working Report # 94, Swiss Meteorological Institute, Zurich, 1981

Willson, R.C., (1982), Solar Irradiance Variations and Solar Activity, J. Geoph. Res., 86, P. 4319

Hudson, H.S., Silva, S., Woodard, M., Willson, R.C., (1982), Effects of Sunspots on Solar Irradiance, Solar Physics, 76, p.211 {52}

Hudson, H.S., Willson, R.C., (1982), Sunspots and Solar Variability, in The Physics of Sunspots, Proc. of Conference on Sunspots, Ed. by L. Cram and J. Thomas, Sacramento Peak Observatory, Sunspot, AZ

Willson, R.C., (1983d), Solar Radiation, Understanding Climate: A Strategy for Solar and Earth Radiation Research 1984‑94, Ed. R. Schiffer, Office of Space Science and Applications, NASA, Washington, DC, 1983, pp. 6‑13.

Willson, R.C., (1984), Measurements of Solar Total Irradiance and its Variability,  Space Science Reviews,  38, pp. 203‑242 {42}

Willson. R.C., (1984), Solar Total Irradiance Observations by the SMM/ACRIM I experiment, Solar Irradiance Variations on Active Region Timescales, NASA Conference Publication 2310, Ed. by B.J. LaBonte, G. Chapman, H.S. Hudson & R.C. Willson, pp. 1‑42

Willson, R.C., (1985), Solar Total Irradiance and Its spectral Distribution, The Encyclopedia of Physics, 3rd Ed., Ed. by Robert M. Besancon, Van Nostrand & Co., New York, 1985, pp. 1135‑1143

Willson, R.C., (1985), Solar Irradiance Variability Monitoring by Active Cavity Radiometers, Proc. Conf. on Advances in Absolute Radiometry, Ed. P. Foukal, Cambridge, MA, June 24‑25, 1985, p. 6.

Willson, R.C., Hudson, H.S., Frohlich, C., Brusa, R.W.; (1986), Long Term Downward Trend in Total Solar Irradiance,  Science,  234, pp 1114 (53}

Willson, R.C., (1987), Results of Space‑Based Total Solar Irradiance Experiments, Proc. of Workshop on Solar Radiative Output Variation, Ed. P. Foukal, National Center for Atmospheric Research, Boulder, CO, Nov. 9‑11, 1987, p. 143

Willson, R.C., Hudson, H.S., (1988), Solar Luminosity Variations in Solar Cycle 21, Nature,  332, pp. 810‑12. {155}

Willson, R.C., (1988), Space‑Based Solar Irradiance Measurements, Proc. New Developments and Applications in Optical Radiometry, Ed. N. Fox, National Physical Laboratory, Teddington, Middlesex, UK, April 12‑13, 1988

Willson, R.C., (1990), Solar Irradiance Variations during Solar Cycles 21 and 22, NASA Conf. Report 3086, Ed. by K. Schatten, A. Arking, p. 279 {133}

Willson, R.C., Hudson, H.S., (1991), The Sun's Luminosity Over a Complete Solar Cycle, Nature, 351, pp. 42‑44 {163}

Frohlich, C., Foukal, P.V., Hickey, J.R., Hudson, H.S., Willson, R.C., (1991) Solar Irradiance Variability from Modern Measurements, The Sun in Time, Univ. of Arizona Press, Tucson, AZ, 1991, pp. 11‑29

Livingston, W., Donnely, R., Grigoryev, V., Demidov, M., Lean, J., Steffen, M., White, O., Willson. R., (1991), Total Irradiance Variability 1980‑88, The Sun as a Star, Ed. by W. Livingston, Univ. of Arizona Press, Tucson, AZ , 1991, pp. 1109 ‑ 1160

Willson, R.C., (1992), Solar Total Irradiance Monitoring, Past, Present and Future, EOS Transactions ‑ AGU, V. 73, No. 14, p. 242, 1992 

Willson, R.C., (1992), Solar Total Irradiance Variations detected by Flight Experiments: 1978‑1992, EOS Transactions ‑ AGU, V. 73, No. 43, p. 435, 1992

Willson, R.C., (1993), Solar Irradiance, Chapter 1, Global Change Atlas, Ed. R. Gurney, J. Foster, C. Parkinson, Cambridge University Press,  1993, pp. 5 ‑ 18

Willson, R.C., (1994), Solar Monitoring has a Past and Present, Does it have a Future?, in The Sun as a Variable Star, Proceedings of IAU Colloquium 143, Cambridge University Press, pp. 4-10

Willson, R.C., (1994), Irradiance Observations of SMM, Spacelab 1, UARS and ATLAS Experiments, in The Sun as a Variable Star, Proceedings of IAU Colloquium 143, Cambridge University Press, pp. 54-62

Willson, R.C., (1994), Solar Total Irradiance Variability and its Climate Implications`, EOS Transactions ‑ AGU, V. 75, No. 16, p. 288, 1994

Willson, R.C., (1994d), The Power of the Sun, Chapter 2 of 'The Many Faces of the Sun', Ed. K. Strong, J. Saba and B. Haisch, Springer‑Verlag, 1995

Lean, J., J. Mariska, K. Strong, H. Hudson, L. Acton, G. Rottman, T. Woods, and R. Willson (1995), Correlated Brightness Variations in Solar Radiative Output from the Photosphere to the Corona, Geophys. Res. Lett., 22(5), 655-658.

Hansen, J.,  Willson, R., et al. (1997), Forcings and chaos in interannual to decadal climate change, J. Geophys. Res., 102(D22), 25,679–25,720.

Willson, R.C., (1997) Total Solar Irradiance Trend During Solar Cycles 21 and 22, Science, 277, 1963-1965, 1997.DOI: 10.1126/science.277.5334.1963 {133}

Willson, R. C., and A. V. Mordvinov (1999), Time-Frequency Analysis of Total Solar Irradiance Variations, Geophys. Res. Lett., 26(24), 3613–3616

Mordvinov, A.V., and R.C. Willson,  (2001) Effects of Activity Complexes and Active Longitudes on Variations in Total Solar Irradiance, Astronomy Letters, Vol. 27, No. 7, pp. 451–454, 2001

Willson, R.C., (2001) The ACRIMSAT/ACRIM3 Experiment – Extending the Precision, Long-Term Total Solar Irradiance Climate Database, The Earth Observer, May/June 2001, V. 13, No. 3, pp. 14-17, 2001.

Hansen, J.,  (2001) Willson, R., et al. (2002), Climate forcings in Goddard Institute for Space Studies SI2000 simulations, J. Geophys. Res., 107(D18), 4347, DOI:10.1029/2001JD001143.

Willson, R.C., Precision of the long-term total solar irradiance database, Proc. Of the 2002 Characterization and Radiometric Calibration for Remote Sensing (CALCON 2002) mtg., Viewgraph 16, Available on CD-ROM from Space Dynamics Laboratory, Utah State University, Logan, UT, 2002.

Willson, R. C., and A. V. Mordvinov (2003), Secular total solar irradiance trend during solar cycles 21–23, Geophys. Res. Lett., 30(5), 1199, DOI:10.1029/2002GL016038.   [PDF version, PDF version of Supporting Material] {65}

Scafetta, N., and R. C. Willson (2009), ACRIM-gap and TSI trend issue resolved using a surface magnetic flux TSI proxy model, Geophys. Res. Lett., 36, L05701, DOI:10.1029/2008GL036307

Joseph D'Aleo, Olavi Kärner, Richard C. Willson, and Ian Clark, (2009) 'Solar Changes and the Climate' in Critical Topics in Global Warming: Supplementary Analysis of the Independent Summary for Policymakers, Fraser Institute, April 21, 2009

Scafetta,N. & Willson,R.C., (2013) ,Planetary harmonics in the historical Hungarian aurora record (1523–1960), Planetary andSpaceScience(2013),

Scafetta,N.,Willson,R.C., (2013), Empirical evidences for a planetary modulation of total solar irradiance and the TSI signature of the 1.09-year Earth-Jupiter conjunction cycle, Astrophys Space Sci, DOI 10.1007/s10509-013-1558-3

Scafetta,N. & Willson, R.C.,  (2013) - Multiscale comparative spectral analysis of satellite total solar irradiance measurements from 2003 to 2013 reveals a planetary modulation of solar activity, Pattern Recogn. Phys., 1, 123–133, 2013,, DOI:10.5194/prp-1-123-2013

Scafetta,N. & Willson, R.C.,  (2014) - ACRIM total solar irradiance satellite composite validation versus TSI proxy models, Astrophysics & Space Science, DOI 10.1007/s10509-013-1775-9

Willson, R.C.,  (2014), ACRIM3 and the Total Solar Irradiance database, Astrophys Space Sci, DOI 10.1007/s10509-014-1961-4



ACRIM Presentations:


American Institute of Aeronautics and Astronautics (AIAA):


Richard C. Willson, Past Variation of Total Solar Irradiance and Future Monitoring Needs (2004)


American Geophysical Union (AGU):


Willson, R. C., Trend in Total Solar Irradiance Detected Between Solar Cycle Minima, (A51A-01), 1997 AGU Fall Meeting,  (URL to A51A-01)

Willson, R. C., The Climate Total Solar Irradiance Variability Database, (U52A-01), 1997 AGU Spring Meeting,  (URL to U52A-01)

Willson, R. C., and A. V. Mordvinov, Total Solar Irradiance variability derived from extended satellite missions, (A51G-03 INVITED), 2000 AGU Spring Meeting, (URL to A51G-03)

Willson, R. C., and A. V. Mordvinov, ACRIM2 Observations and the Long Term Total Solar Irradiance Database, 2001 AGU Fall Meeting, Session A41D (Oral), 2001. (URL to A41D)

Willson, R. C., H S Hudson, J M Pap, Total Solar Irradiance Variability: Do Observations or Models Imply a Secular Change?, Co-conveners of special sessions SH21B (Oral), 2002 AGU Fall Meeting, 2002. (URL to SH21B)

Willson, R.C., H.S. Hudson, Total Solar Irradiance Monitoring: Results and Strategies, Co-conveners of special sessions SH31C (Oral) and SH32A (Poster), 2003 AGU Fall Meeting, 2003. (URL to SH31C)  (URL to SH32A)

Willson, R.C., S. Sofia, Secular Variation of Total Solar Irradiance and Climate, Co-conveners of special sessions SH51E (Oral) and SH53A (poster), 2004 AGU Fall Meeting, 2004. (URL to SH51E)  (URL to SH53A)

Willson, R.C., R.S. Helizon, Satellite TSI Observations, Scales and Traceability in the context of the NASA-NIST TSI Workshop Day2 Presentations and Discussion, SH33C-06, Co-convener of special sessions SH33C (Oral) and SH53A (poster), 2005 AGU Fall Meeting, 2005. URL to SH33C)

Willson, R.C., A Critical Review of Measurements and Models of Composite Total Solar Irradiance, Co-convener of special sessions SH22B (Oral) and SH23B (Poster), 2005 AGU Spring Meeting, 2005. (URL to SH22B)  (URL to SH23B)

Willson, R.C., Total Solar Irradiance Variations and Their Impact on Climate, Co-convener of special session SH41A (Oral), 2006 AGU Fall Meeting, 2006. (URL to SH41A)

Willson, R.C., Total Solar Irradiance Trends During Solar Cycles 21-24, Co-convener of special session SH43A (Poster), 2006 AGU Fall Meeting, 2006.  (URL to SH43A)

Willson, R.C., The Total Solar Irradiance Record and Its Continuity, (Poster GC42A-03), Co-convener of special session GC42A, (Oral), 2007 AGU Fall Meeting, 2007.  (URL to GC42A)

Willson, R.C., Three Decades of Total Solar Irradiance Monitoring, (Poster GC23A), Co-convener of special session GC23A, (Poster), 2008 AGU Fall Meeting, 2008.  (URL to GC23A)

Willson, R.C., The satellite total solar irradiance database (Poster GC11A-0678), Co-convener of special session GC11A, (Poster), 2009 AGU Fall Meeting, 2009.  (URL to GC42A)

R. C. Willson; R. Helizon; S. Kwan, Traceability of Satellite TSI observations and their significance for the TSI database , (Poster GC21B-0867), 2010 AGU Fall Meeting, 2010.  (URL to GC21B)

R. C. Willson; R. Helizon; S. Kwan, Comparisons of ACRIM3 and the LASP/TRF, (Invited - oral presentation GC33C-03), 2010 AGU Fall Meeting, 2010.  (URL to GC33C-03)

R. C. Willson, Revision of ACRIMSAT/ACRIM3 TSI results based on LASP/TRF diagnostic test results for the effects of scattering, diffraction and basic SI scale traceability, (Poster GC21C-04), 2011 AGU Fall Meeting, 2011.  (URL to GC21C-04)

R. C. Willson; Nicola Scafetta, Validation of the ACRIM composite TSI by solar surface magnetic field proxies, (GC22E-05), 2010 AGU Fall Meeting, 2012.  (URL to GC22E-05)


Calibration Conference (CALCON):


Richard C. Willson, Precision of the Long-term Total Solar Irradiance Database (2002)

Richard C. Willson. ACRIM TSI Results and Composite TSI Time Series (2003)


Committee on Space Research (COSPAR):



R C Willson, Judit Pap & A V Mordvinov, Variations in Total Solar Irradiance include a + 0.04 percent per decade trend in the satellite monitoring record during 1978 - 2004 (2004)


International Symposium on Remote Sensing of Environment (ISRSE):


Richard C. Willson; A. Mordvinov, J. Hansen, H. Hudson, ACRIM Observations and Variations of Total Solar Irradiance During the Past 25 Years (2003)


SORCE Science Team Meetings:


Richard C. Willson, ACRIM3 Observations and Variations of Total Solar Irradiance during solar cycles 21-23 (2003)

Richard C. Willson, ACRIM Composite Total Solar Irradiance Time Series, Dec 2003

Richard C. Willson, The Total Solar Irradiance (TSI) Database, September 2010



Universities Space Research Association (USRA):


Richard C. Willson, Total Irradiance: Calibration Issues & Recent Results (2004)




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