Data Access and Services

EOS Data Gateway: http://eos.nasa.gov/imswelcome

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.

DAAC Search and Order: http://daac.gsfc.nasa.gov/data

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.

Data Pool: ftp://g0dps01u.ecs.nasa.gov/

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.

Tools and Services:

The GES DAAC will provide C, Fortran and IDL tools for reading and displaying the SORCE HDF5 data files. Online documentation, guides and FAQs, describing these data will also be available. For information describing the new HDF5 file format and access to the libraries, please see the web site http://hdf.ncsa.uiuc.edu/hdf5. HDF5 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

SORCE Data Product Use of HDF5SORCE Data Product Use of HDF5

SORCE Level 3 Data ProductsAll of the SORCE level 3 data products are available in the new HDF5 file format. The data are stored in HDF5 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 H5lite library to read the data. Users need easy access to the data without worrying about details of file formats (ASCII is often preferred).

An IDL session using its H5_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. HDF5 wrapper calls are also available for more experienced users. IDL is a very powerful tool and used widely throughout the science community.

http://daac.gsfc.nasa.gov

James Johnson and Suraiya Ahmad

NASA Goddard Space Flight Center, Code 902Goddard Earth Sciences Distributed Active Archive CenterGreenbelt, MD 20771

jjohnson@daac.gsfc.nasa.gov

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 17th 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.

SORCE Standard Data Products

Long Name SORCE Level 3 Solar Spectral Irradiance 6-Hourly Mean

SORCE Level 3 Solar Spectral Irradiance Daily Mean

SORCE Level 3 Total Solar Irradiance 6-Hourly Mean

SORCE Level 3 Total Solar Irradiance Daily Mean

Short Name SOR3SSI6 SOR3SSID SOR3TSI6 SOR3TSID

Spectral Character-istics

SIM: 300-2000 nm on a fixed wavelength scale at 1-34 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

TIM: all wavelengths

File Sizes 0.75 MB (4 files per day)

0.08 MB (one file per day)

0.2 –1.0 MB (cumulative file, delivered once per month)

0.1 – 0.3 MB (cumulative file, delivered once per month)

Description Contents include:• SOLSTICE and SIM spectra on a fixed wavelength scale

(see above)

• SOLSTICE and SIM spectra as a basis-spline least-squares 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.)

Contain the total solar irradiances accumulated over the entire mission.

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 h5dump and h5ls.

TIM SIMSOLSTICE

A & BXPS

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

AccuracyAbsolute: 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.

New.UARS SOLSTICE

SEE on TIMED, SNOE, and rocket XPS

Overview