Until November 2001, SUSIM data products were produced by the UARS Central Data Handling Facility at the Goddard Space Flight Center (NASA) using algorithms and software developed by the SUSIM UARS team at the E. O. Hulburt Center for Space Research at the Naval Research Laboratory (NRL). The processing of the SUSIM data comprises several steps which produce different levels of data products. For example, level 0 data is the reformatted raw telemetry data from the UARS spacecraft. Currently, the level 3 irradiance data is available at the SUSIM UARS ftp* site. In addition, the very latest version (V21r2) of the Mg II 279.9 Index can be found there (and only there).
The complete level 3 data set contains 1 nm integrated solar UV spectral irradiances and their associated errors gridded to 1 nm for wavelengths 115.5 to 410.5 nm. It also contains selected solar indices derived from the SUSIM data.
Proper calibration of instrument optical path responsivity degradation is an important problem of extended solar UV measurements. The two subtypes of level 3 data, 3AS and 3BS, differ in how this degradation is estimated in the processing of the data.
Level 3AS data is typically produced the day after the UV solar spectrum is measured. This is what is used to generate the daily plot of the UV irradiance spectrum. These irradiances are calculated using an extrapolated values of responsivity determined from earlier calibrations for the elements in the optical path. Because these irradiance results are much more uncertain than the 3BS data (described below), the quantitative versions of these data are not released.
Level 3BS data is typically produced months after the solar data is originally measured. The irradiances and indices are corrected for optical responsivity degradation based on interpolation from surrounding (i.e. both before and after) calibration measurements. Data originally processed to level 3AS are reprocessed to 3BS after the later biannual calibrations are completed and analyzed. Currently, SUSIM UARS version 21 L3BS irradiance data is available from UARS day 31 (12-Oct-91) through UARS day 3881 (27-Apr-02) at our FTP site. The version 21 L3BS irradiances plus the solar indices are expected to be soon available at the DAAC*.
The Mg II Index has been shown to be a useful proxy for solar UV irradiance. Although one version of the Mg II index is available from the GSFC DAAC, it is recommended that the latest improved version (V21r2) be used. It is available via the SUSIM ftp site.
SUSIM reference solar minimum irradiance spectra (115-410 nm) at two wavelength resolutions are now available:
The SUSIM UARS data may be retrieved from either:
Note that the format and content of what is available from these sources differ.
GSFC DAAC archives data from all of the UARS instruments. Currently, SUSIM version 20 (V20) L3BS data is available at the DAAC. The L3BS data consists of the solar irradiances between 115.5 and 410.5 nm at 1 nm intervals, the 6 solar indices, and an SFDU* header, in individual files for each available experiment day. These binary files consist of a stream of bytes whose floating point data is in IEEE format. Warning: VAX users will require software to convert this floating point data to VAX format. Follow these instructions to obtain SUSIM UARS data:
1. Go to the GSFC DAAC home page at http://daac.gsfc.nasa.gov/ 2. Click the Search and Order icon link. 3. Choose Data Sets and then UARS.
Follow the on-line instructions to navigate through the menus to select and order SUSIM UARS data. For assistance call the DAAC's Help Desk at 301-614-5224 or 1-800-257-6151 or send mail to the DAAC's Helpdesk
Within the SUSIM UARS ftp archive, the file name are as descriptive of the contained data as possible. The file name extension indicates the type of file. The text below shows these types.
The following is a list of the SUSIM data files available on the SUSIM UARS ftp site. The file name is descriptive of the file's contents, e.g. the first file in the list is a file which describes the version 21 level 3BS XDR format data file. Note that identifiers of the type Vxx refer to the data version number and Dxxxx-xxxx refer to the data file's UARS day range. The "C03" refers to a cycle number and reflects the fact that errors were found in the original V21 data which was soon corrected. This designation serves to differentiate between the two versions.
The SUSIM UARS project provides an FTP directory for public access to SUSIM data. Data products and related materials produced by SUSIM UARS personnel at NRL are kept at ANON$DISK:[ANONYMOUS.PUB.UARS] directory. These can be accessed using a browser (e.g. Netscape) or through a command-line driven ftp client program. To retrieve the SUSIM data using the latter, please follow the following instructions:
1. FTP to SUSIM UARS site: {ftp susim.nrl.navy.mil}
2. Anonymous login onto the ftp site: {anonymous}
3. Enter password: {yourname@yourhost.yourdomain}
4. Change to pub.uars directory: {cd pub.uars}
5. For .XDR type files, change transfer mode to binary: {binary}
6. Download the desired file {get file.name}.
Note that in some cases, due to problems caused by the NRL firewall, one may need to do the ftp data transfer in "active" rather than "passive" mode. If one gets an error response referring to a bad domain name after step 5, this is probably the case. Use the "help" command in your ftp client program to learn how to change to active mode.
CDHF Central Data Handling Facility DAAC Distributed Active Archive Center ftp File Transfer Protocol (Program) GSFC Goddard Space Flight Center HDF Hierarchical Data Format IDL Interactive Data Language (A commercial product) NASA National Aeronautics and Space Administration NCSA National Center for Supercomputing Applications nm NanoMeters NRL Naval Research Laboratory SFDU Standard Formatted Data Unit SUSIM Solar Ultraviolet Spectral Irradiance Monitor UARS Upper Atmosphere Research Satellite UV UltraViolet XDR eXternal Data Representation
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