NOAA / Space Weather Prediction Center

Information About and Access to SOONSPOT Data


1) Characteristics of the data:
2) Identifications of the SOON sites:
3) How to determine if SOONSPOT archives have the desired data:
4) How to get SOONSPOT data:
5) How to view data using SolarSoft software (SSW) under IDL 6):
6) Data sources and contacts:

H-alpha and white light solar data from the U.S. Air Force SOON observatories are available for use by the scientific community. The SOON system is a global network which often provides nearly continuous coverage in full disk and large scale H-alpha images. The name SOONSPOT stands for SOON Solar Patrol on Tape, where SOON refers to the Solar Observing Optical Network of four solar observatories maintained and operated by the U.S. Air Force 50th Weather Squadron. The refracting telescopes have apertures of 25.3 cm (10-inches) and have vacuum optics.


1) Characteristics of the data:

The digitally recorded data are written onto 8-mm Exabyte tapes. The images are written in extended FITS format with header information on timing, pointing coordinates, image scale and sky transparency. The FITS files are written by the Unix archive utility called "cpio". (Here is a sample FITS header.) All images are 512 x 512 pixels and are either full disk or large scale images of features with ~0.8 arc-sec pixels covering ~6.4 arc-min field of view. The full disk H-alpha images are normally obtained every 30 minutes. Large scale images are recorded every 5 minutes in the absence of activity, but the cadence increases to 30 seconds during the pre-flare and rising flux periods of solar flares In addition, the large scale H-alpha images are interleaved with similarly scaled continuum images (called B2 images) every 30 minutes. The system began partial operation in May 1994 and is now collecting many hundreds of images each day from four sites located around the world. (All images have celestial north at top and east to the left as read by IDL. Images are not corrected for P angle, but B and P angles are included in the header for each image.)


2) Identifications of the SOON sites:

Observatory               Lat.   Lon.   Observing   Date of First

                                        Hours (UT)  SOONSPOT Data

Learmonth, Australia      S21    E115   0030-0930   Nov. 12, 1994   

San Vito, Italy           N41    E18    0630-1630   Nov. 19, 1994  

Ramey, Puerto Rico        N18    W67    1130-2030   Sep. 09, 1994  

Holloman, New Mexico      N33    W106   1330-0100   May  17, 1994  

Palehua, Hawaii*          N21    W158   1730-0230   May      1996

* The site at Palehua was dismantled and shipped to Sacramento Peak in New Mexico in April of 1997 to facilitate a major upgrade to the SOON system. Here is a world map showing the SOON Observatory locations.

3) How to determine if SOONSPOT archives have the desired data:

The four sites always collect full disk H-alpha images when the sun is visible. A link to a listing of all full disk images is available. In addition to full disk imaging, the NOAA/Space Weather Prediction Center directs the sites to collect SOONSPOT large scale images on up to five target regions on a daily basis. This is accomplished through daily transmissions of the Data Acquisition Report (DAR) message issued at 21:30 UT to all sites. (Note that any solar location can be targeted this way which facilitates coordinated or campaign observations. Contact Alan Kiplinger for more information.) Note that any given site has the freedom to collect data on regions beyond those listed in the DAR message, thus the only sure way to know if the desired data are in any given large scale image is to use the SOONSPOT on-line catalog.

To use the catalog, one uses wigits to set the time limits of the search interval (such as the duration of an active region crossing), then one sets valid heliocentric or Carrington coordinates for the target at a given time. After pressing the wigit to start the search, the results are listed in terms of tape names and file numbers of image files containing the target as it rotates across the sun. This file can be downloaded and used by the investigator for data dumps at one of three locations.

About tape labeling: Note that SOONSPOT tape labels and filenames on the tapes are returned by the on-line catalog. The tape labels are designed to identify when, where, and with what version of the software that the data was written. A typical tape label returned by the catalog looks like: h961205b03. A breakdown of the label is:



The filenames returned by the search engine reveal: 1) the observing site with the first letter, 2) the target with the next four numbers (9999 means full disk), and the day of year in the last three digits of the prefix. The files contain extended FITS image files containing up to 120 512x512 byte images of the Sun in H-alpha in a single file.  There is a letter designation following the 4-digit target number identifying which 120 image file was taken on a given day.  For example, if  300 images were taken of region 8210 at Holloman on day 215. There would be files labelled H8210A215, H8210B215 and H8210C210 with the
last file containing only 60 images.

4) How to get SOONSPOT data:

It should be recognized that there are three sets of SOONSPOT data. There are two "original" data sets recorded at the sites. One of these resides at the Lockheed Palo Alto Research Laboratory. The other resides at NOAA/SWPC. Copies of the LPARL tapes since the fall of 1997 are maintained at NASA Goddard's Solar Data Analysis Center (SDAC). Contact persons for all data sets are listed in part 6. Persons involved in Yohkoh research may wish to work with the LPARL data set. Persons involved in other NASA related research, such as SOHO, may want to use the SDAC copy at Goddard. Others should request the data from the SWPC data set.

Note that due to limited resources, there are reasonable as well as unreasonable requests. For example, to ask for all full disk images would require mounting and reading the entire data set of a few hundreds of tapes. Conversely to ask for a few days of large scale images of an active region's transit should be more reasonable and involve mounting fewer that 10 tapes. Note that small data sets can be placed on the WWW, while larger data sets may require Exabyte tapes or CD-Rom as storage media.  A single SOONSPOT extended FITS file can contain up to 120 images and is approximately 32 Mbytes.


5) How to view data using SolarSoft software (SSW) under IDL

The data is readable by SOLARSOFT (SSW) software. To read a single data file and display a movie under ther Interactive Data Language (IDL) and SSW, one should read the file into IDL structures in memory with a command like:


At this point, one may display the data as a movie with:


An important concept to remember is that most datasets that are handled by SSW are represented by one image per file. The "read_soon" command allows one to read up to multiple images per file in each extended FITS file. Moreover, read_soon can read multiple extended files and filter the output according to the second parameter (details are beyond the scope of this message).  Note that the 30s cadence is envoked 5 minutes BEFORE the flare trigger and reverts back to 5 minute cadence at flare maximum. p.s. To upgrade your Solarsoft SoftWare to read SOONSPOT data type (under IDL and SSW):


and include the line:   ssw_path,'$SSW_SOON'      in your "" file.

It is important to know that SOONSPOT images have celestial North at top, not solar. Thus the images are rotated by the P angle which is also given in the FITS headers. Thus it is possible to map SOONSPOT data onto other datasets using the absolute coordinates in the SOONSPOT headers. This is accomplished by using the rot_map procedure developed by Dominic Zarro (NASA/GSFC) and the read_soon on procedure from Sam Freeland (LMSAL). An example of the recommended IDL/SSW syntax is:


This should plot the image rotated onto a 10x10 arc-min field of view with a heliographic grid of 10 degree resolution.

6) Data Sources and Contacts:

For Yohkoh Related Research (LPARL):

 Nariaki Nitta (LPARL) ph: 650-354-5458

 or Greg Slater ph: 650-354-5208

 For other NASA related research (NASA/GSFC SDAC):

 Amy Skowronek ph: 301-286-4713

 Other solar research from the world community:


 Alan Kiplinger ph: 303-492-2011 (CU)

A final comment is that SOONSPOT data is a gift to the scientific community from an operational U.S. Air Force mission. It is not always perfect in the sense that occasional images may differ from the header information due to the need for observers to tune and adjust the instruments for their needs. -- such differences generally obvious. The SOONSPOT archive program records blindly to these infrequent interruptions, but for the vast majority of the time, the data is of high or good quality. It is my hope that we can return this gift by using the data to help understand the nature of solar activity and to aid in the predictabilty of the activity and its effects.