Solar Data at NSSDC

Volume 12, Number 3, September 1996
By David Batchelor

[Ed. Note--David Batchelor has been NSSDC's solar data acquisition scientist for almost ten years. David is moving on to other challenges at Goddard. NSSDC appreciates his significant contributions. His article below reflects the major benefit to NSSDC and its customers of his years here.--Joseph King]

NSSDC has acquired and distributed a rapidly increasing volume and variety of solar data in the past decade. This article presents a brief summary of what is available.

An easy way to get a list of NSSDC's solar holdings is to consult the NASA Master Directory and click the "Data Set Information" link. A query form will appear, and the user may enter "Solar Physics" in the blank marked "Discipline:" and "NSSDC" in the blank for "Data Center:." Then, clicking the "Submit Query" button will bring up the list of NSSDC solar holdings. Highlights are described below.

Solar Activity Data Sets

The millions of hard and soft X-ray images and spectra collected by the on-going YOHKOH mission are regularly archived at NSSDC as they become public. The state of the Sun's X-ray corona and flares are observable with unprecedented precision in the YOHKOH data, and Interactive Data Language (IDL) data analysis software from the principal investigator teams is included. The Hard X-Ray Telescope obtains 7-arcsec resolution images in the 20 - 80 keV band; the Soft X-Ray Telescope obtains 4-arcsec images in the 0.1 - 4 keV band. The Wide-Band Spectrometer collects spectra in the 3 keV - 20 MeV band and is also sensitive to neutrons. The Bragg Crystal Spectrometer records flux in the Fe XXV, Fe XXVI, Ca XIX, and S XV lines. The data are distributed on 8-mm tapes corresponding to one week of data per tape, with about 1 GB of data on each tape. NSSDC shares responsibility for distributing the YOHKOH data with the Solar Data Analysis Center (SDAC) at Goddard Space Flight Center (see http://umbra.nascom.nasa.gov/); the SDAC provides tape replications in small numbers and analysis guidance, and NSSDC provides replications of large numbers of tapes. NSSDC can also provide YOHKOH data files via the near-line NASA Data Archive and Distribution System (NDADS).

The Sun as seen with the YOHKOH Soft X-Ray Telescope 3-45A. October 25, 1991

The SDAC and NSSDC also share responsibility to distribute Solar Maximum Mission (SMM) archive data. (See http://umbra.nascom.nasa.gov/smm/.) SMM was in orbit 1980-1989 for the study of solar activity. NSSDC holds the Coronagraph/Polarimeter image data set in photographic form and on tapes.

The C/P images were made with several broad-band filters in visible light and reach as low as 1.5 solar radii and as high as 5 solar radii, with 250 images taken per day on some days. The Ultraviolet Spectrometer/Polarimeter recorded spectra and raster images in the 1170 - 3600 A band. The Soft X-Ray Polychromator did the same in the 1.4 - 22.5 A band. The Hard X-Ray Imaging Spectrometer recorded images with 8 arcsec resolution in the 3.5 - 30 KeV band. The Hard X-Ray Burst Spectrometer obtained full-Sun spectra in the 30 - 500 keV range, with sub-second time resolution. The Gamma-Ray Spectrometer performed similarly in the 10 keV - 140 MeV range. All of these data are of continuing value to solar activity investigations.

Solar Gamma-Ray Burst Resources

Several gamma-ray spectrometers have monitored high-energy solar flares besides the ones on SMM. Solar gamma-ray bursts were monitored with the International Sun-Earth Explorer (ISEE) 3 spacecraft contemporaneously with SMM, from 1978 to 1987. NSSDC holds the data and analysis software for the gamma-ray spectrometer on ISEE 3.

The Pioneer Venus Orbiter spacecraft also contained a gamma-ray spectrometer, and NSSDC hold those data from the 1978-1983 era. NSSDC also holds Compton Gamma-Ray Observatory data from the Burst and Transient Source Experiment (BATSE), which has collected gamma-ray spectra of solar bursts (.05 - 30 GeV) since launch in 1990. (See also http://umbra.nascom.nasa.gov/batse/batse_years.html.) Ulysses hard X-ray burst data are also available since 1990 in the 25-150 keV range.

Older Solar Activity Data of Interest

The Skylab missions in 1973-1974 collected thousands of images and spectra. The S-054 images in various bands of the 3 - 20 A range are available on NDADS for near-line access and network file delivery. The Skylab white-light coronagraph images are especially useful for correlative investigations with the other Skylab images. NSSDC also holds spectra from the other Skylab instruments, in the EUV band.

The Sun as seen with the Skylab Soft X-Ray Telescope 2-60A. May 31, 1973

The Orbiting Solar Observatory missions recorded solar X-ray and UV images and spectra from 1962-1978. From the Orbiting Solar Observatory (OSO) 7 the EUV spectroheliograph recorded raster images with 5 arcmin resolution in the 17 - 40 nm band, and the Hard X-Ray Spectrometer provided simultaneous spectroheliograms in the .5 - .8 nm and .8 - .95 nm bandpasses. The OSOs also recorded coronagrams and other measurements.

In the 1960-1973 era a series of Solar Radiation (SOLRAD) spacecraft recorded UV and X-ray fluxes, providing an especially long time span of well-calibrated full-Sun data.

Solar Irradiance and Spectroscopy

The Spacelab-1 mission measured the solar UV spectrum in the 200-358 nm band, which is available from NSSDC. There are also irradiance data sets from the Solar Mesospheric Explorer UV spectrometer and from the Nimbus 7 Earth Radiation Budget instrument.

Solar Radio Observations

ISEE 3 also recorded solar radio bursts in the 41 KHz - 1980 KHz band, 1978-1987. The HELIOS spacecraft recorded solar radio flux in the 50 KHz 2 MHz band, and NSSDC holds data for 1974-1977. The Interplanetary Monitoring Platform (IMP) 6 also recorded solar flux in the 50 kHz - 3.5 MHz range. Voyager 1 and 2 carried Planetary Radio Astronomy receivers, which also recorded solar bursts and are in NSSDC holdings.

The Request Coordination Office can provide contacts to answer questions about these archive data.

David Batchelor has been NSSDC's solar data acquisition scientist for almost ten years.

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Author:Miranda Beall
Curators: Erin Gardner and Miranda Beall
Responsible Official: Dr. Joseph H. King, Code 633
Last Revised: 21 Nov 1996 [EDG]