Chris Pankratz
SORCE Data Processing and Availability
Laboratory for Atmospheric and Space Physics
1234 Innovation Dr
Boulder, CO 80303
chris.pankratz@lasp.colorado.edu
Abstract
The SORCE Science Data System produces Total Solar Irradiance (TSI) and Solar Spectral
Irradiance (SSI) data products on a daily basis, which are formulated using measurements from the
four primary instruments on board the SORCE spacecraft. The TIM instrument provides
measurements of the TSI, whereas the SIM, SOLSTICE, and XPS instruments collectively provide
measurements of the solar irradiance spectrum from 1 nm to 3000 nm (excluding 31-115 nm,
which is covered by the TIMED SEE experiment). The Science Data System utilizes raw
spacecraft and instrument telemetry, calibration data, and other ancillary information to produce a
variety of data products that have been corrected for all known instrumental and operational
factors.
Since the beginning of routine operations in late February 2003, instrument
characterization and processing algorithms have matured sufficiently to permit scientific use of
SORCE data. “Level 3” science data products are now routinely being produced, and are being
delivered to the Goddard Earth Sciences (GES) Distributed Active Archive Center (DAAC) for
public release.
Overview
• All data processing is performed by the SORCE Science Data System (SDS), located at the
SORCE Science Operations Center (SOC) at the Laboratory for Atmospheric and Space Physics
in Boulder, Colorado, USA
• Algorithms are implemented as described in the SORCE Algorithm Theoretical Basis Document
(ATBD) to produce science data products. See http://lasp.colorado.edu/sorce/science_algorithm.html
Level 0
Level 1B
Level 1A
Irradiance Data at
Instrument Resolution
Telemetry, Status
Science Processing
Level 2
Telemetry Processing
Level 3 Irradiance Data
Instrument
Total Solar Irradiance (TSI)
Solar Spectral Irradiance
300-2000 nm 1-34 nm intervals
115-300 nm 1 nm intervals
0.1-34 nm
5-10 nm intervals
LASP, Boulder, Colorado
Conversion and
Calibration Parameters
Unprocessed Filtered
Telemetry
Raw Telemetry
Commands
Mission Operations
Real-time
Operations
Mission
Analysis
Science
Plans
Ground Stations
Planning and
Scheduling
Level 3
SIM
SOLSTICE
XPS
Irradiance Data
Daily and 6-Hour averages
Spacecraft
Ephemerides
NORAD
Science Data
Processing
Level 4
- Released to DAAC
WWW
GSFC
DAAC
Long Name
Modeled Results
- Available from LASP
Geophysical
Parameter
Public
(possible future product)
DAAC Short Name
Spectral
Characteristics
Nominal Operations Timeline
Processing to Level 3
Preliminary Inspection
File Sizes
Preview Data Released to DAAC
In-flight Calibration Measurements
Detailed Inspection
Continued Validation
Description
3 Months
2 Days
1 Day
Reception from Spacecraft
Flare Observed 28 October 2003
Compute Time-dep Params
Quality Inspection
Release to DAAC
Total Solar Irradiance (W/m²)
Normalized to 1 AU
Provided at true-Earth distance as well as 1 AU
SORCE Level 3 Solar Spectral Irradiance
Daily Mean
SOR3SSI6
SOR3SSID
SIM:
300-2000 nm on a fixed wavelength scale
(1-34 nm, variable)
SOLSTICE: 115 to 300 nm at 1 nm intervals
XPS:
0.1-34 nm at 5-10 nm intervals and 121.6 nm
0.32 MB
(one file per day)
SORCE Level 3
Total Solar Irradiance
6-Hourly Mean
SORCE Level 3
Total Solar Irradiance
Daily Mean
SOR3TSI6
SOR3TSID
TIM: all wavelengths
0.2 –1.0 MB
0.1 – 0.3 MB
(cumulative file, delivered
(cumulative file, delivered
monthly)
monthly)
Files are written using HDF5 format.
Files are written using HDF5 format
Contents include:
Contents Include
• SOLSTICE and SIM spectra on a fixed wavelength scale • The total solar irradiances accumulated over the entire
(see above)
mission.
• Six channels from the XPS instrument
• Selected spectral absorption and emission lines (Mg-II,
Note:
etc.) - Forthcoming
Files will be delivered as ASCII in the future
• Other parameters (Carrington latitude and longitude, SunEarth distance, etc.)
Data Availability
♦ SORCE standard data products are available via the SORCE web site and from the Goddard Earth Sciences DAAC free of charge
− SORCE Web Site serves as a good gateway to SORCE data and permits direct download of ASCII TSI Products. Also includes links to
products at the DAAC. http://lasp.colorado.edu/sorce/data_access.html
− GES DAAC – via the DAAC SORCE Gateway - http://daac.gsfc.nasa.gov/upperatm/sorce/
• GES DAAC Search and Order
• NASA Earth Observing System (EOS) Data Gateway (EDG)
• GES DAAC FTP Data Pool
DAAC Data Pool: ftp://g0dps01u.ecs.nasa.gov/
The ECS data pool maintained at the GES DAAC is a 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 provides 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 HDF5 file format, 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 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
• SIM is a Fèry Prism Spectrometer which provides irradiance measurements from 200
nm to 3000 nm with a spectral resolution varying from 1 to 33 nm
• The SIM ESR detector provides the primary absolute calibration for the SIM
instrument, and operates on the same principal and uses the same detector
methodology as the active cavity radiometer in the SORCE TIM instrument.
• SIM contains four focal plane photodiodes, which are used to acquire the solar
spectrum in a "fast-scan" mode, which provides the requisite time cadence and the
spectral resolution that is not possible with the much “slower” ESR detector.
• Data Quality / Status
• On-orbit instrument characterization is still in progress, and all data are still considered
provisional. Certain instrumental artifacts are present within the data and a few onorbit instrument calibrations have not yet been applied.
• Released spectra are formulated from only two of the four SIM detectors (VIS1 &
VIS2), restricting spectral coverage to 309 – 1000 nm. The full spectrum out to 3000
nm will be available following completion of prism transmission calibration.
• Present data are suitable for detecting relative irradiance changes not requiring
precision better than 0.2 % per year. The data exhibit discrete “jumps” or
discontinuities at the ~0.1% level from day to day, which are being investigated.
• Absolute accuracy is presently not better than approximately 2%, pending forthcoming
calibrations
• Reprocessing of version 2 data is nearing completion, and data through the present will
be delivered to the GES DAAC in early-to-mid December 2003.
• SOLSTICE
Solar Spectral Irradiance (W/m²/nm)
SORCE Level 3 Solar Spectral
Irradiance
6-Hourly Mean
Solar Spectral Irradiance (SSI)
• The SORCE SOLSTICE, SIM, and XPS instruments together provide measurements of the full-disk Solar Spectral Irradiance (SSI)
from 1 nm to 2000 nm, excluding 34-115 nm, which is not covered by the SORCE instruments.
• The standard “Level 3” science data products consist of daily and 6-hourly average irradiances, reported at a mean solar distance of
1 astronomical unit (AU).
• Two data products are produced - one containing daily means and the other containing four 6-hourly means. Each SSI product
contains science results for one UT calendar day. Updates will occur daily.
SIM Irradiance Time Series
• SIM
SORCE Product Summary
Science
Analysis
Science Operations
SORCE TSI Data Record
• The TIM instrument measures the Total Solar Irradiance (TSI), monitoring
changes in incident sunlight to the Earth's atmosphere using an ambient
temperature active cavity radiometer
• The standard “Level 3” TSI science data products consist of daily and 6-hourly
average irradiances, reported at zero relative line-of-sight velocity with respect
to the Sun at both a mean solar distance of 1 astronomical unit (AU) and at the
true Sun-Earth distance.
• Two TSI data products are produced - one containing daily means and the other
containing four 6-hourly means. Each TSI product contains science results for
the entire SORCE mission. Updates to Level 3 TSI data occur monthly.
• To construct these products, high time cadence measurements (every 50
seconds) from the TIM instrument are combined to produce representative daily
and 6-hourly values of the TSI.
• Shuttered operation of the instrument corrects for thermal background, and
state-of-the-art phase sensitive detection algorithms applied to the data at the
shutter fundamental reduce noise and sensitivity to drifts. The TIM shutter
period is 100 seconds; four such cycles are weighted to give a single irradiance
measurement at a 50 second cadence. These so-called “Level 2” data are
averaged over an entire day as well as over each 6-hour interval to formulate the
two primary TSI data products.
• Data Quality / Status
• On-orbit instrument characterization is still in-progress, and a few minor
corrections are still under development.
• Present data are suitable for detecting relative changes of TSI not requiring
precision less than 0.2 W/m² (150 ppm) per year
• Present absolute accuracy is estimated to be 0.4 W/m² (300 ppm), although
there remains an unresolved difference between TIM and other radiometers.
• Data are now available through late November 2003
Data Management
System
Exp. Histories
Uplink Parameters
TIM
Total Solar Irradiance (TSI)
• Product Overview
This poster provides an overview of the SORCE data processing system, summarizes the present
state of the processing algorithms and the quality of the current SORCE data products, and
provides details on how to access SORCE science data products.
• Product Overview
0.08 MB
(one file per day)
• SOLSTICE provides precise daily measurements of solar spectral irradiance at
ultraviolet wavelengths from 115 nm to 300 nm with a spectral resolution of
approximately 0.1 nm, an absolute accuracy of better than 5%, and a relative
accuracy of 0.5% per year
• SORCE SOLSTICE is a follow-on to the very successful SOLSTICE launched
aboard the Upper Atmospheric Research Satellite (UARS) in 1991. The new
SOLSTICE makes daily solar irradiance measurements and compares them to
the irradiance from an ensemble of 18 stable early-type stars. This approach
provides an accurate monitor of instrument in-flight performance and provides
a basis for solar-stellar irradiance comparison for future generations.
• Data Quality / Status
• On-orbit instrument characterization is still in-progress, and all data are still
considered provisional, owing to several important on-orbit calibrations that
are still being prepared, most notably instrument degradation.
• Present data are suitable for detecting relative irradiance changes over
relatively short periods of time (~1-2 solar rotations) but not for long-term
studies.
• A recent reprocessing of SOLSTICE version 3 data is nearing completion,
after which all data through the present will be delivered to the GES DAAC.
These data should be available in early-to-mid December 2003.
XPS Irradiance 0-7 nm Band
• XPS
• The XPS measures the solar soft x-ray (XUV) irradiance from 1 to 34 nm (in 5 discrete
bandpasses) and the bright hydrogen emission at 121.6 (H I Lyman-alpha).
• Of all the SORCE instruments, the XPS is most sensitive to flare events on the Sun as
the solar XUV radiation often changes by a factor of 2 to 10, or more, during flares.
• Data Quality / Status
• The current data available at the DAAC include version 3 XPS data. These data are
known to be of good quality and are appropriate for research and/or publication.
Data Access and Services
DAAC Search and Order: http://daac.gsfc.nasa.gov/data
• 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).
• Provides the most streamlined WWW interface to the SORCE
Data
• Fastest response time of WWW-based interfaces
EOS Data Gateway: http://eos.nasa.gov/imswelcome
• The EOS Data Gateway (EDG) is the
standard 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.
• Response time can be slower due to the
overhead of delivering all EOS data
products