NCEI has acquired legacy solar irradiance datasets from multiple sources over many decades. These data are provided, ‘as is,’ and in most cases the linked documentation is the entirety of available information at NCEI. Newer versions of some of these datasets and models may be available elsewhere. In some cases, older data may also be found in the Space Weather Legacy Print Publications. The directories are ftp folders that you must paste into a file explorer to access. Other locations for TSI data include LASP Interactive Solar Irradiance Data Center and Data.gov.
Questions and comments may be directed to ncei.info@noaa.gov
Data Access
Current web pages related to ultraviolet (UV) solar spectral irradiance data:
Some datasets and model information that were formerly hosted at NCEI are now available at the following URLs:
Solar Ultraviolet Spectral Irradiance Datasets
The following products contain older solar ultraviolet spectral irradiance data. All links are ftp links that can be accessed by pasting the ftp address into a file explorer. See the dropdowns below for more information on each.
The main folder for this older data is Solar Ultraviolet Descriptive Text. Mg II Core-to-wing ratio data (1978-2007)
This is the R. Viereck NOAA Space Environment Center) dataset. The Mg II core-to-wing ratio is derived from the ratio of the h and k lines of the solar Mg II feature at 280 nm to the background or wings at approximately 278 nm and 282 nm. The h and k lines are variable chromospheric emissions while the background emissions are more stable. The result is a robust measure of chromospheric activity. The ratio is a good measure of solar UV and EUV emissions.
This is the John C. Arveson dataset.
200 - 2495 nm. Results are presented of an experiment to determine extraterrestrial solar spectral irradiance at the Earth's mean solar distance within the 300-2500 nm wavelength region. Spectroradiometric measurements were performed during eleven research flights on board a NASA CV-990 aircraft at altitudes between 11.6 km and 12.5 km. Precision of the measurements was better than +/- 1 percent. Absolute accuracy of the resultant extraterrestrial solar spectral irradiance is about +/-3 percent over most of the measurement range. A listing of results is presented at intervals varying from 0.1 nm throughout most of the uv-visible Fraunhofer region to 5 nm in the continuum region of the infrared. Additionally, a listing of solar spectral irradiance, smoothed over the detailed Fraunhofer structure, is presented for engineering use.
This is the H.E. Hinteregger dataset.
- A status of SERF1 (WORD document) is available. Several problems with the data are discussed.
- EUV flux data sc21obsc.dat from the Extreme UltraViolet Spectrometer (EUVS) on Atmosphere Explorer E (AE-E) (descriptive text) cover15 wavelength groups for the time period from the 182nd day of 1977 to the 160th day of 1981. A program was written by Dean Pesnell to read the EUV data file.
- The data are normalized to the reference spectrum SC21REFW.DAT. The EUV reference spectra and related EUV model parameters are based on the measurements and work of H.E. Hinteregger and his colleagues. The model and reference spectra (R74113, F74113, F76REF, SC21REFW) are described by Hinteregger et al. (GRL 8, 1147, 1981). The spectra and model are based on rocket measurements and simultaneously obtained EUV fluxes by the AE-C and AE-E spectrometers.
- The EUVS instrument is described in an article by Hinteregger in Radio Science, Vol. 8, No. 4, 349-360, 1973. Other references are available. Hans Hinteregger's Explanation of the EUV reference spectrum and notes of EUV flux observations are also available.
This is the R. Donnelly dataset.
Data Description describes Heath and Schlesinger's work on the Solar Backscatter Ultraviolet (SBUV) experiment on the NIMBUS7 satellite. They showed that the core-to-wing ratio of Mg II h and k lines was a good measure of the temporal variations of the solar UV flux, including long-term variations, because the ratio is relatively insensitive to drifts in instrument sensitivity. These NIMBUS data are not normalized to solar cycle minimum.
- Six year NIMBUS data set Nov 7,1978- Oct 27,1984.
- NIMBUS 6 year data set plus NOAA9 data May 27, 1986 - Dec 31,1988
This is the G. Anderson and L. Hall (AFGL) dataset.
The solar spectra files contain the wavelength in Angstroms and the solar irradiance in photons cm-2 s-1 A-1. The instrument had two detectors in the focal plane, one giving the spectrum in 0.1 A resolution and the other in 1.0 A resolution, both with a wavelength step increment of .02 A.
- File d78tnth83 data are 0.1A resolution, block averaged over 5 samples in the raw data. For wavelengths 2000 to 2077.4A, the spectrum from the 1983 measurement was used. For 2077.5 to 3100 A, the 1978 flight data were used.
- File afgl83 data are from the 1983 flight, in 1.0 A resolution, in steps of 0.5A. The measurements were made from a balloon near 40 km and extrapolated to zero optical depth by correcting for ozone, O2 Herzberg continuum absorption, and Rayleigh scattering. No correction is made for Schumann-Runge absorption, so there is some slight signature from the 0-0 and 1-0 bands of that system near 2000 A and 2025 A.
This is the R. Donnelly dataset.
Data Description Mg II core-to-wing ratio developed by Heath and Schlesinger for solar UV measurements on SBUV NIMBUS7 experiment are extended to the SBUV2 NOAA9 satellite data. A modified ratio is used to reduce noise. Values are converted to equivalent Nimbus 7 values using a linear regression relation.
- NOAA9 data May 27, 1986-Dec 31, 1988
- NIMBUS 6 year data set plus NOAA9 data May 27,1986-Dec 31, 1988
This is the D. Pesnell and W. Hoegy dataset. (Jan. 3, 1979-Jan 29, 1992)
Data Description explains how the flux is monitored. The Ipe Solar EUV Flux Index comes from a rhenium-coated Langmuir probe on Pioneer Venus Orbiter. There are 4096 data values, with gaps up to 37 days in length. The solar rotation period is roughly 29 days when viewed from Venus, not 27 days as seen from Earth.
- Pioneer-Venus Orbiter Langmuir Probe database -- date is YYYY/MM/DD and the Ipe current is in nanoamps.
This is the G. P. Anderson dataset.
Data Description The three files contain polynomial coefficients for generating oxygen Schumann-Runge cross sections. The coefficients span the spectral range 49,000 to 57,000 cm-1, recorded at 0.5 cm-1 intervals. Calculated cross sections will represent Schumann-Runge band and continuum cross sections only. The Herzberg continuum cross section, if desired, must be added separately. See the appendix in the readme file for a typical Fortran program for an isothermal path.
- The readme file suggests using file 130-190.cf4 for temperatures between the range 130K to 190K, use file 190-280.cf4 for temperatures between 190K to 280K, and use file 280-500.cf4 for temperatures between 280K to 500K. Please note that the polynomial-generated cross sections will be significantly in error if calculated outside of these bounds.
- Each of the three files contains six columns -- Column 1 = Wavenumber (cm-1); Column 2 = Coefficient A; Column 3 = Coefficient B; Column 4 = Coefficient C; Column 5 = Maximum percent error in fit over the relevant temperature range; and Column 6 = Temperature at which maximum error occurs.
- For additional information, please refer to Minschwaner, K., G.P. Anderson, L.A. Hall, and K. Yoshino, Polynomial Coefficients for Calculating O2 Schumann-Runge Cross Sections at 0.5 cm-1 Resolution, J. Geophys. Res., Vol 97, pp. 10.103-10.108, 1992.
Data Access
TSI Composite Database
Total Solar Irradiance (TSI) Composite Database is compiled from many satellite TSI data collected from 1978 to present day by Claus Frohlich and Judith Lean
Radiometrically, the composite is based on the Active Cavity Radiometer Irradiance Monitor (ACRIM-I and II) records collected before the start of the ACRIM-I measurements in1980, during the spin mode of Solar Maximum Mission (SMM), and bridging the gap between ACRIM-I and II. Corrected data are inserted by shifting the level to fit the corresponding ACRIM data over an overlapping period of 250 days on each side of the ACRIM sets. In early 1996, the Variability of Solar Irradiance and Gravity Oscillations (VIRGO) data collection satellite took over and shifted to agree with ACRIM-II. Finally the composite records are adjusted via ACRIM-II to SARR (Space Absolute Radiometer Reference) which was introduced by Commelynck et al. (1995) and allows for the comparison of different space experiments. The data from the Earth Radiation Budget Experiment (ERBE) and ACRIM-III, as well as an empirical model, are used for comparisons and for internal consistency checks.
For more information, please visit the web site of the World Radiation Center.
Active Cavity Radiometer Irradiance Monitor (ACRIM)
The Active Cavity Radiometer Irradiance Monitor (ACRIM) measured the total variability of solar irradiance with active cavity radiometer solar monitoring sensors on several satellites. The ACRIM Composite Total Solar Irradiance (TSI) Time Series Database was compiled from many satellite TSI data from 1978-2001 by Richard Wilson. The dataset and related information including plot are in the ACRIM3 composite. ACRIM 3 was successfully launched on board the NASA ACRIMSAT spacecraft on December 20, 1999. The ACRIM composite time series is constructed from combinations of satellite TSI data sets.
- NNAA3 uses Nimbus7 ERB and ACRIM1, 2, and 3 results (plot)
- NNAVA3 replaces the 1996-1998 ACRIM2 results with the two year VIRGO results (plot)
TSI Data from Individual Satellites
Data Description (October 1984-August 2003)
From 1984 to present, total solar irradiance (TSI) values were obtained from the solar monitor on the Earth Radiation Budget Satellite (ERBS) non-scanner instrument. The ERBS solar monitor is an active cavity radiometer, similar in design to the Active Cavity Radiometer Irradiance Monitors (ACRIM) which have flown on the NASA Solar Maximum Mission (SMM), Upper Atmosphere Research Satellite (UARS), and Atmospheric Laboratory for Applications and Science (ATLAS) spacecraft missions. The ERBS satellite was placed into orbit on October 5, 1984, and the solar monitor is still operating properly, after almost 18 years. The measurement precision is about 0.01 percent, while the accuracy is 0.2 percent. At least once every 14 days, the Sun is observed by the monitor. The averaged irradiance values represent an almost instantaneous level, and not a daily average.
- ERBS satellite Biweekly Database
Data Description (November 16,1978 to December 13,1993 )
From 1978 to 1993, Total Solar Irradiance (TSI) values were obtained from the solar monitor on the NASA NIMBUS (named for the latin word for raincloud) non-scanner instrument. The NIMBUS solar monitor is an active cavity radiometer, similar in design to the Active Cavity Radiometer Irradiance Monitors (ACRIM) which have flown on the NASA Solar Maximum Mission (SMM), Upper Atmosphere Research Satellite (UARS), and Atmospheric Laboratory for Applications and Science (ATLAS) spacecraft missions. The paper "The Nimbus-7 Solar Total Irradiance: A new Algorithm for its Deviation" by D.V. Hoyt, H.L. Kyle, J.R. Hickey, and R.H. Maschoff (JGR, vol 97, pp 51-63) describes the methodology used to reduce the data.
NIMBUS satellite Biweekly database in x-y plottable format.
Data Description (January 23, 1985 - December 20, 1989)
From 1985 to 1989, total solar irradiance (TSI) values were obtained from the solar monitor on the NOAA9 and NOAA 10 nonscanner instruments. The NOAA solar monitor is an active cavity radiometer, similar in design to the Active Cavity Radiometer Irradiance Monitors (ACRIM) which have flown on the NASA Solar Maximum Mission (SMM), Upper Atmosphere Research Satellite (UARS), and Atmospheric Laboratory for Applications and Science (ATLAS) spacecraft missions.
Data Description (February 16, 1980 - June 1, 1989)
From 1980 to 1989, TSI values were obtained from the solar monitor on the SMM non-scanner instruments. The SMM solar monitor is an active cavity radiometer, similar in design to the Active Cavity Radiometer Irradiance Monitors (ACRIM) which have flown on the NASA Solar Maximum Mission (SMM), Upper Atmosphere Research Satellite (UARS), and Atmospheric Laboratory for Applications and Science (ATLAS) spacecraft missions.
Data Description (February 16, 1980 - June 1,1989)
From 1980 to 1989, TSI values were obtained from the solar monitor on the SMM non-scanner instruments. The SMM solar monitor is an active cavity radiometer, similar in design to the Active Cavity Radiometer Irradiance Monitors (ACRIM) which have flown on the NASA Solar Maximum Mission (SMM), Upper Atmosphere Research Satellite (UARS), and Atmospheric Laboratory for Applications and Science (ATLAS) spacecraft missions.
Data Description (October 4, 1991 - December 31,1997)
The second Active Cavity Radiometer Irradiance Monitor experiment (ACRIM II) was launched in September 1991 as part of the science payload of the Upper Atmosphere Research Satellite (UARS). The variations on solar rotational and active region time scales are clearly seen. The large, short-term decreases are caused by the TSI blocking effect of sunspots in magnetically active regions as they rotate through our view from Earth. The peaks of TSI preceding and following these sunspot "dips" are caused by the faculae of solar active regions whose larger areal extent causes them to be seen first as the region rotates on our side of the sun and last as they rotate over the opposite solar limb. The downward trend through the 1991-1997 period is similar in slope and amplitude to that observed by ACRIM I during the declining phase of solar cycle 21. From the peak of solar cycle 21 to its minimum, the TSI decreased by about 0.08 percent. It appears likely from the ACRIM II results thus far that the cycle 22-23 minimum in TSI will occur during 1997, near the average solar cycle period of about 11 years after the cycle 21-22 minimum, and with a similar decrease relative to the maximum of cycle 22 in the 1990-1991 period.
Older Databases
This is a Dr. John C. Arvesen dataset.
NASA research aircraft database
Results are presented of an experiment to determine extraterrestrial solar spectral irradiance at Earth's mean solar distance within the 300-2500 nm wavelength region. Spectroradiometric measurements were performed during eleven research flights on board a NASA CV-990 aircraft at altitudes between 11.6 km and 12.5 km. Precision of the measurements was better than +/- 1 percent. Absolute accuracy of the resultant extraterrestrial solar spectral irradiance is about +/-3 percent over most of the measurement range. A listing of results is presented at intervals varying from 0.1 nm throughout most of the uv-visible Fraunhofer region to 5 nm in the continuum region of the infrared. Additionally, a listing of solar spectral irradiance, smoothed over the detailed Fraunhofer structure, is presented for engineering use.
Data Description (1902-1954)
The Smithsonian Astrophysical Observatory (APO) gathered solar constant data during at least 49 years of solar monitoring. The solar constant is the total amount of energy received from the sun per unit time per unit area exposed normally to the Sun's rays at the average Sun-Earth distance and outside of Earth's atmosphere. The purpose of this APO project was to determine an accurate value for this energy flux and to determine whether or not the Sun's total energy output is indeed constant in time.
Notwithstanding all of the shortcomings and controversy inherent in the data, this program is the longest and most carefully conducted solar radiation program in the 20th century. Dr. Vernon Derr estimated that to fully understand and correct the database, the research efforts of two qualified scientists studying the data for approximately two years would be needed. The 47 data files are available via the ftp site.