SORCE Data Product Use of HDF 5 James

SORCE Data Product Use of HDF 5 James Johnson and Suraiya Ahmad NASA Goddard Space Flight Center, Code 902 Goddard Earth Sciences Distributed Active Archive Center Greenbelt, MD 20771 jjohnson@daac. gsfc. nasa. gov Overview SORCE Level 3 Data Products The Solar Radiation and Climate Experiment (SORCE) launched successfully on January 25, 2003 aboard a Pegasus XL rocket into a 645 km altitude and 40° inclined orbit. SORCE is a key element in NASA’s Earth Observing System (EOS) with the aim of measuring the solar radiation incident on the Earth’s upper atmosphere. Management of the SORCE mission is provided by the Laboratory for Atmospheric and Space Physics (LASP), at the University of Colorado in Boulder. The SORCE principle investigator is Dr. Gary Rottman. The LASP facility is responsible for spacecraft mission operations support, and the processing, analysis and validation of all science data products. The standard data products are then delivered to the NASA Goddard Earth Sciences Distributed Active Archive Center (GES DAAC), located at the Goddard Space Flight Center, for permanent archiving and distribution to the public. The primary science goals of SORCE are to provide precise daily measurements of the total solar irradiance (TSI), and solar spectral irradiance (SSI) across the ultraviolet, visible and near-infrared regions. Long-term observations of solar radiation are crucial in understanding solar activity and solar events, and the role of solar variability on the upper atmospheric chemistry, dynamics, and climate change. Variations of TSI over the 11 year solar cycle are on the order of 0. 1%, but show greater variations due to short-term solar activities (flares, solar storms, sunspots). Changes in solar irradiance by as little as 0. 25% per century can have profound effects on the planet’s climate. As an example, the late 17 th century cooling referred to as the ‘little ice age’ is believed to have occurred in Europe due to minimum sunspot activity (no sunspots recorded from 1650 -1715, known as the ‘Maunder Minimum’) and minimum total solar radiance. SORCE will provide the data to improve our understanding of long-term climate change, natural variability and climate prediction. For more information on the SORCE mission, please see the LASP SORCE web site at http: //lasp. colorado. edu/sorce. The SORCE spacecraft includes four instruments: the Total Irradiance Monitor (TIM), Solar Stellar Irradiance Comparison Experiment (SOLSTICE), Spectral Irradiance Monitor (SIM), and the soft X-ray Ultraviolet Photometer System (XPS). These instruments use state-of-the -art technology to provide more accurate spectral and total solar irradiance measurements compared to precursor sensors. SOLSTICE &B A TIM Spectral Range all 200 – 2000 nm 115 -320 nm 1 -34 nm Spectral Resolution N/A 0. 2 – 33 nm 0. 1 nm 5 – 10 nm Sensor Type absolute radiometer (electrical substitution radiometer ) Fèry Prism Spectrometer Modified Monk -Gilleison spectrometers Filter Photometer with 12 photodiodes Accuracy Absolute: 0. 1% Relative: 0. 01% Absolute: 0. 3% Relative: 0. 1% Absolute: 5% Relative: <1% Absolute: 20% Relative: 4% Sensor Heritage ACRIM series, most recently ACRIM III on ACRIMSAT. UARS SOLSTICE SEE on TIMED, SNOE, and rocket XPS New. XPS All of the SORCE level 3 data products are available in the new HDF 5 file format. The data are stored in HDF 5 datasets using the compound datatype, i. e. they represent a table. The solar spectral irradiance products contain four tables, while the total solar irradiance files contain just a single table. Each file contains a set of file level attributes, and each table dataset also includes a set of attributes. And because the SORCE data are in tabular format, one may also use the H 5 lite library to read the data. Users need easy access to the data without worrying about details of file formats (ASCII is often preferred). SORCE Standard Data Products Long Name SORCE Level 3 Solar Spectral Irradiance 6 Hourly Mean SORCE Level 3 Solar SORCE Level 3 Total Spectral Irradiance Daily Solar Irradiance 6 Mean Hourly Mean SORCE Level 3 Total Solar Irradiance Daily Mean Short Name SOR 3 SSI 6 SOR 3 SSID SOR 3 TSID Spectral Characteristics SIM: 300 -2000 nm on a fixed wavelength scale at 1 TIM: all wavelengths -34 nm intervals SOLSTICE: 115 to 300 nm range at 1 nm intervals XPS: 1 -34 nm at 5 -10 nm intervals and 121. 6 nm at 1 nm resolution File Sizes 0. 75 MB Description Contents include: files per day) (4 0. 08 MB (one file per day) SOR 3 TSI 6 0. 2 – 1. 0 MB (cumulative 0. 1 – 0. 3 MB file, delivered once per month) (cumulative file, delivered once per month) Contain the total solar irradiances accumulated • SOLSTICE and SIM spectra on a fixed wavelength scale over the entire mission. • • (see above) SOLSTICE and SIM spectra as a basis-spline leastsquares model fit to the spectra Six channels from the XPS instrument Selected spectral absorption and emission lines (Mg-II, etc. ) Other parameters (Carrington latitude and longitude, Sun -Earth distance, etc. ) Example using NCSA HDFView to see contents of SORCE solar spectral irradiance file. Tool is free and allows users to see contents of data files and save to ASCII. Useful non-graphical tools include NCSA h 5 dump and h 5 ls. An IDL session using its H 5_BROWSER showing a plot of the daily averaged total solar irradiance corrected for all known instrument and operational effects and reported at a standard distance of 1 A. U. By importing the data into IDL, one can then manipulate the data and produce plots specific to ones needs, or save the data to any number of output formats for later use. HDF 5 wrapper calls are also available for more experienced users. IDL is a very powerful tool and used widely throughout the science community. Data Access and Services DAAC Search and Order: http: //daac. gsfc. nasa. gov/data Data Pool: ftp: //g 0 dps 01 u. ecs. nasa. gov/ EOS Data Gateway: http: //eos. nasa. gov/imswelcome All of the SORCE level 3 and eventually any level 4 data products will be made available through the GES DAAC Search and Order interface. The GES DAAC interface utilizes a simple point-and-click approach for searching and ordering both on-line and near-line data products that are archived locally. The data are organized using a hierarchical design into tables according to different “Views” (e. g. by data set, data product, parameter). For certain products one may use spatial, temporal, orbital, or other attribute search features to narrow your search to exactly what you want. The ECS data pool maintained at the GES DAAC is a new large (50 TB capacity) online anonymous ftp server that allows users quick access to specific data holdings. Due to its relatively small size, the entire set of SORCE level 3 data products will always be available from the data pool to download. The EOS Data Gateway (EDG) is the interface for all Earth science data available in NASA’s Earth Observing System Data Information System and related data centers. Through the EDG one can search for and acquire various Earth science data products from the EOS instruments, such as MODIS, MISR and SORCE, as well as from other instruments, such as TRMM, Landsat, etc. Tools and Services: The GES DAAC will provide C, Fortran and IDL tools for reading and displaying the SORCE HDF 5 data files. Online documentation, guides and FAQs, describing these data will also be available. For information describing the new HDF 5 file format and access to the libraries, please see the web site http: //hdf. ncsa. uiuc. edu/hdf 5. HDF 5 is maintained by the National Center for Supercomputing Applications (NCSA), located at the University of Illinois, at Champaign. Users with questions concerning data orders or questions about DAAC holdings should contact the user help desk. Users should also contact the help desk when requesting hardcopy documentation or posters. Contact information for the GES DAAC help desk is listed below: • e-mail: help@daac. gsfc. nasa. gov • telephone: 1 -301 -614 -5121 (local), 1 -877 -422 -1222 (toll free) • fax: 1 -301 -614 -5121 http: //daac. gsfc. nasa. gov