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Summary:
The Solar-Stellar Irradiance Comparison Experiment (SOLSTICE) is one of
10 instruments aboard the Upper Atmosphere Research Satellite (UARS). Its
primary objective is the daily measurement of solar UV spectral irradiance.
Data collection began 03 October 1991 and has continued, with a few
interruptions, to the present. SOLSTICE data have been processed to levels
1, 2, 3AS and 3BS. Currently, SOLSTICE level 3BS version 9 data products
are available from the Goddard Space Flight Center
(GSFC) Distributed Active Archive Center (DAAC).
Table of Contents:
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- UARS SOLSTICE LEVEL 3BS DAILY SOLAR DATA
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- The SOLSTICE level 3BS data represent a subset of the UARS
dataset. SOLSTICE measures solar ultraviolet spectral irradiance at
wavelengths between 119 nm and 420 nm to produce 1 nm resolved
gridded irradiances. SOLSTICE also reports the intensities of 7 solar
lines.
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The objective of the UARS SOLSTICE is to measure the full-disk
Solar UV irradiance and determine solar variability on three basic
time scales:
- short-term variations spanning time periods of minutes to
hours (exemplified by solar flares),
- intermediate-term variations lasting days to weeks
(characterized by the solar rotation and the development of
active regions),
- long-term variations (associated with the 11-year sunspot
cycle or the 22-year magnetic field cycle).
The instrument was designed to have a high relative accuracy and
precision and to follow the short and intermediate-term variations
at and below the one-percent level.
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- Solar UV Spectral Irradiance
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- The SOLSTICE Level 3BS data include gridded irradiances
representing 1 nm integrations over the whole spectral range and
their formal errors derived from the data along with the values of 7
solar lines for each mission day. Each file consists of three records
called SFDU, LABEL, and DATA. SFDU and LABEL records contain
descriptive information about the instrument and the data. The DATA
record contains the gridded irradiances and their errors followed by
parameter names (seven solar line intensities and errors) and
parameter values.
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- The UARS SUSIM
level 3BS gridded irradiance data has the same format and units
except that the wavelength regions are slightly different. While
there may be some similarity in the parameters and solar indices, the
SUSIM versions of these, in general, have different definitions and
units.
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- Name:
- Dr. Gary J. Rottman
- Address:
- Laboratory for Atmospheric and Space Physics
- University of Colorado
- 1234 Innovation Dr.
- Boulder, CO 80303-7814
- Telephone Numbers:
- Voice: (303) 492-8324
- Fax: (303) 492-6444
- Electronic Mail Address:
- Gary.Rottman@lasp.colorado.edu
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- Solar-Stellar Irradiance Comparison Experiment
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- Name:
- Barry Knapp
- Address:
- Laboratory for Atmospheric and Space Physics
- University of Colorado
- 1234 Innovation Dr.
- Boulder, CO 80303-7814
- Telephone Numbers:
- Voice: (303) 492-8970
- Fax: (303) 492-6444
- Electronic Mail Address:
- Barry.Knapp@lasp.colorado.edu
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- The general data gathering technique performed by the SOLSTICE
Instrument is described in detail in the "Solar-Stellar Irradiance
Comparison Experiment" article listed in the referece
section 17.1 below.
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The UARS SOLSTICE instument is a three-channel ultraviolet
spectrometer that measures the magnitude of the solar spectral
irradiance in the wavelength range 118 to 425 nm. The
instrument design permits observations of both the sun and of
bright blue stars using the same optical path. Entrance and
exit slit sizes along with different integration periods are
used to accomodate the several orders of magnitude difference
between the brightness of the sun and the stars.
The UARS SOLSTICE is mounted on a two-axis pointing platform
which can track the sun and stars with an accuracy of 1.5 arc
minutes. SOLSTICE is pointed toward the Sun during the daylight
portion of each orbit, and toward stars during most of the
nighttime portion of the orbit. One or more full spectral scans
of the sun at the instrument resolution is completed each
orbit. Stellar observations, requiring much longer integration
times, are made at a few selected wavelengths throughout the
SOLSTICE spectral range, with typically one or two stars at one
or two wavelengths being observed each orbit.
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- Satellite data are collected from a near-circular Earth orbit
of about 585 km altitude and 57 degree inclination.
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- Upper Atmosphere Research Satellite (UARS).
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- UARS was launched in September 1991 with the mission of
investigating the chemistry, dynamics, and energy inputs of the
Earth's upper atmosphere. See the UARS Project
and UARS
Platform documents for more information.
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- Data are telemetered from UARS through the Tracking and Data Relay
Satellite System (TDRSS) to the Data Capture Facility (DCF) at NASA GSFC.
There the data are given an initial quality check, and are then forwarded
to the UARS
Central Data Handling Facility (CDHF). The instrument PI teams are
connected to the CDHF through remote analysis computers (RACs), where
they have developed software to convert the raw data to higher level
processed data. The CDHF uses the production software to convert the
level 0 data to level 1, 2, 3AS, and 3BS data. The Goddard DAAC acquires
the UARS data from the CDHF.
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- The user is referred to the SOLSTICE SFDU
metadata documents for any problems with the data. Further
questions may answered by contacting the SOLSTICE team at the
addresses listed above.
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- 119 nm to 420 nm.
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- The resolution is that of a 1 nm "boxcar" convolved with the
completely resolved full-disk solar spectrum.
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- All SOLSTICE Level 3BS data are gridded every nm on the half
nm.
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Temporal coverage is from 3 October 1991 to the present. The
GSFC DAAC currently has the first 5 years of SOLSTICE level 3BS
data (up to 31 December 1996). Listed below are the dates
within the above period for which SOLSTICE data is missing or
unavailable:
13-OCT-1991
03-NOV-1991
04-DEC-1991
03-JUN-1992 to 10-JUL-1992
14-JUL-1992 to 17-JUL-1992
21-SEP-1992
05-AUG-1993 to 08-AUG-1993
18-SEP-1993 to 21-SEP-1993
16-MAR-1994
30-MAR-1995 to 05-APR-1995
18-APR-1995 to 20-APR-1995
16-MAY-1995 to 23-MAY-1995
30-JUN-1995 to 02-JUL-1995
30-JUL-1995 to 31-JUL-1995
08-SEP-1995
15-OCT-1995 to 18-OCT-1995
03-FEB-1996 to 11-FEB-1996
08-MAY-1996 to 09-MAY-1996
14-MAY-1996
22-JUL-1996 to 28-JUL-1996
03-SEP-1996
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- Daily.
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The main parameter is the gridded solar irradiances at 1 nm
resolution from 119.5 to 420.5 nm. There are also parameters
related to the data and seven solar indices. These include:
- Mean Solar Distance (MSD).
- H I Lyman alpha (hydrogen @ 121.6 nm) line intensity and
error
- O I (oxygen @ 130.4 nm) line intensity and error
- C IV (carbon @ 154.8 nm) line intensity and error
- C I (carbon @ 156.1 nm) line intensity and error
- C I (carbon @ 165.6 nm) line intensity and error
- Mg II (magnesium @ 280.0 nm) core-wing ratio intensity
and error
- Ca II (calcium @ 393.3 nm) core-wing ratio intensity and
error
- Carrington longitude
- Carrington latitude
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The level 3BS solar spectral irradiances are an array of solar
fluxes, corrected for instrument degradation. The additional
solar parameters are described below:
The emission lines, H I Lyman alpha, O I, C IV, C I (156.1
nm) and C I (165.6 nm), are integrated intenities above the
continuum. The Mg II and Ca II, are core to wing ratios of the
integrated intensities of the line doublet divided by the mean
(instantaneous) intensity of the continuum outside the
self-absorbing regions. The MSD is the distance from the
satellite to the sun at 1200 GMT on the day of the measurement.
The Carrington latitude and longitude corresond to the
heliographic latitude and longitude of the sub-earth point on
the sun at 1200 GMT.
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The solar spectral irradiance is expressed in units of
watt/m3. The units of measurement for the solar
parameters and lines are:
- UARS Mean Solar Distance (MSD) in Astronomical Units
(AU).
- The H I, O I, C IV, and C I emission line intensity and
error in [W/m3]nm
- Mg II, and Ca II core-to-wing ratio and error in nm.
- Carington latitude and longitude in degrees.
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- All values are postive real numbers.
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SOLSTICE Level 3BS granules are produced daily. Each granule is a
multi-file granule consisting of two files:
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The binary data file (files ending with PROD, or *PROD
extension) which contains the gridded irradiance data, and
quality, as well as observation time, the mean solar distance,
7 solar lines and errors and Carrington latitude and longitude.
- An ASCII metadata file (files ending with META, or *META
extension) associated with the data file containing items such as
the PI assigned quality flag and record length size of the data
file.
The format for granule file names is
SOLSTICE_L3BS_Ddddd.Vvvvv
_Ccc_xxxx, where dddd is the UARS day (0001 = 12 September
1991), vvvv is the data version number, and cc is the data version
cycle number. The file extension xxxx is either PROD for the binary
data files, or META for the ASCII metadata files.
The average size for a SOLSTICE Level 3BS granule is about 13
kB. The *META files are small, only about 700 bytes each.
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- The data are in a native UARS format. The files were originally
created on a VAX/VMS system at the UARS CDHF, and now exist as UNIX
stream files at the Goddard DAAC. SOLSTICE data file structures are
presented in the Standard Formatted Data Units (SFDU) documents
listed in the References section.
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- Segemented, wavelength-dependent exponential detector
degradation functions are computed (using coefficients from a
calibration file) for the given day at each wavelength and
applied to the irradiance and integrated irradiance data. No
degradation correction is made to reported core/wing ratios.
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- UARS/SOLSTICE Level 3B Processing for a given day uses as
input the corresponding SOLSTICE Level 3A file, and a table
(calibration file) of instrument degradation function
coefficients which have been determined by analysis of SOLSTICE'S
observations of selected bright blue stars whose irradiances in
the 115-425 nm spectral range are assumed to be constant with
time. The time-degradation function (which varies with
wavelength) is applied to the Level 3A irradiance spectrum and
the integrated irradiance of the selected spectral emission
features (but not to the core/wing ratios), to produce the Level
3B product.
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- Version 9 data differ from version 8 in the use of improved
(longer time coverage) degradation coefficients, and additional
(Level 2) second-order calibrations (e.g., voltage, temperature,
and PMT "turn-on" effects. Reprocessing of the data occur about
once or twice a year.
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- None.
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- The data record of SOLSTICE level 3BS product contains the 1
nm resolution irradiances and associated qualities for
wavelengths between 119.5 nm to 420.5 nm, starting wavelength,
and solar parameters. There are five solar line intensities and
their errors, two core-to-wing ratios and their errors, the mean
solar distance at noon GMT, and the Carrington latitude and
longitude at noon GMT.
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Sample SOLSTICE level 3BS spectrum:
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The standard error is calculated for each irradiance using the
counting statistics and the calibration errors. The typical
uncertainty of the relative irradiance is less than 1 percent
for solar measurements. Not reported is the 2-4 percent
uncertainty in the absolute knowledge of the irradiances
related to the pre-flight photometric calibrations.
Also, the SOLSTICE Level 3 products are carefully filtered
to remove data which may be questionable due to larger than
normal pointing uncertainty, contamination by the South
Atlantic Anomaly or atmospheric absorption, or which are
significantly outside the range of values expected over a solar
cycle or observed over the last several orbits.
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- Precision information is placed in the form of a measurement
standard deviation into the "data quality" field corresponding to
each 1nm gridded irradiance. The solar line intensities and
core-to-wing ratios also include standard deviations.
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- None.
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- Data files are checked to ensure that they are properly
transferred and translated from their original VAX/VMS format at
the UARS CDHF to the DAAC's UNIX format. No additional data
checks are performed by the DAAC.
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- The data files exist as UNIX stream files at the DAAC. Binary
data are big-endian IEEE formatted. The binary data files should be
read on 32 bit machines running UNIX operating systems. This is
especially important for fields which are IEEE floating point values,
such as the profile data and quality values. If you are going to use
a non 32-bit and/or non-UNIX machine, then you will need to write
your own conversion routines to read the data files. File record
length information is only listed in the ASCII metadata files (*META
extension) which accompany the data and parameter files.
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- None at this time.
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- SOLSTICE Level 3 solar data may be used for any investigation
that does not need a spectral resolution finer than 1 nm, or time
resolution less than one day. SOLSTICE Level 3BS data may be used for
studies of either short-term (e.g. 27-day) or long-term (e.g.
11-year) solar variability at the level of a few percent.
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- None.
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- The SOLSTICE instrument continues to acquire data. Future
reprocessing of the data are anticipated.
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Simple read/dump programs are available for reading the SOLSTICE
level 3AS and 3BS data files. The read programs are available in
both Fortran and C languages. These programs simply print the file
contents to the screen.
The *META and *PROD files (see section 8 Data
Granularity) must be kept in the same directory, because the
programs require the *META file as the input parameter in order to
read the *PROD file. The *META file is necessary because it
contains file record length information, which is not in the *PROD
files.
If you are using the Fortran READ programs you may need to
change the OPEN statement. Some machines read 4 byte words, while
other machines read 1 byte. If the program isn't working correctly,
you should try chang RECL=RECSIZ/4 to RECL=RECSIZ.
Contact science@eosdata.gsfc.nasa.gov for
problems with the read/dump software.
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To compile the programs, just type:
f77 FILE_NAME.F -o FILE_NAME (Fortran programs)
or cc file_name.c -o file_name (C programs)
Below are examples showing how to run the programs:
$ READUMP_L3BS_DATA (Fortran program)
PLEASE ENTER META DATA FILE NAME BELOW:
SOLSTICE_L3BS_D0001.V0003_C01_META
or $ readump_l3at_data SOLSTICE_L3BS_D0001.V0003_C01_META (C program)
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- Name:
- Help Desk
- Address:
- NASA Goddard Space Flight Center
- Distributed Active Archive Center
- Code 610.2
- Greenbelt, MD 20771
- Telephone Numbers:
- Phone: 1-301-614-5224
- FAX: 1-301-614-5268
- Electronic Mail
Address:
- daacuso@daac.gsfc.nasa.gov
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The UARS SOLSTICE data are archived at the GSFC DAAC, and can be
identified by the attributes listed below.
Data Set = UARS
Data Product = SOLSTICE L3BS DAILY SOLAR DATA
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The SOLSTICE level 3BS data files can be obtained from the Goddard
DAAC by several mechanisms. These include the following:
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Anonymous
FTP. The entire SOLSTICE Level 3BS data set can be
downloaded from the DAAC anonymous FTP server located at
daac.gsfc.nasa.gov, in directory
http://disc.sci.gsfc.nasa.gov/data/uars/solstice. This area can
also be accessed through the World Wide Web at
ftp://daac.gsfc.nasa.gov/data/uars/solstice. For convenience,
the data files are arranged in directories by instrument,
level, year, and month (e.g. data/uars/solstice/3bs/1993/10).
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The DAAC Web-Based Archive
Interface provides a means for searching and
ordering data. To search the data holdings and place an order,
go to the DAAC Home Page located at "/index.shtml", and click
on the "Search and Order" icon. Next, pick the "Data Set" link,
and from there choose "UARS".
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Earth
Observing System Data Gateway (EDG). You can place
orders for the UARS data through the Earth Observing System
(EOS) Data Gateway. From here you can also order data products
from other data centers. The web address for the EDG is
"http://eos.gsfc.nasa.gov/imswelcome/".
- DAAC Help
Desk. Data can also be obtained by contacting the
GSFC DAAC Help Desk listed above.
Data can be ordered electronically (FTP).
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- The DAAC currently supports only level 3BS data products from
SOLSTICE.
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- The SOLSTICE level 3BS data are available. See the section above on
Procedures for Obtaining Data for specific
information.
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- Satellite/Instrument/Data Processing
Documentation:
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- Reber, C. A., C. E. Trevathan, R. J. McNeal, and M. R.
Luther, The Upper Atmosphere Research Satellite (UARS) Mission,
J. Geophys. Res. 98, D6, 10643-10647, 1993.
- Rottman, G. J. and Woods, T. N., "In-Flight Calibration of
Solar Irradiance Measurements by Direct Comparison with Stellar
Observations", SPIE Proceedings, 924, 136-143, 1988.
- Rottman, G. J., Woods, T. N., and Sparn, T. P.,
"Solar-Stellar Irradiance Comparison Experiment 1. 1. Instrument
Design and Operation", J. Geophys. Res. 98 (1993),
10667-10677,
- Woods, T. N., Rottman, G. J., and Ucker, G. J.,
"Solar-Stellar Irradiance Comparison Experiment 1. 2. Instrument
Calibrations", J. Geophys. Res. 98 (1993), 10679-10694.
- Rottman, G. J. and T. N. Woods, "UARS Solar Stellar
Irradiance Comparison Experiment (SOLSTICE)", SPIE Proceedings,
2266, 317-329, 1994.
- Journal Articles and Study
Reports:
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- Woods, T. N., D. K. Prinz, J. London, G. J. Rottman, P. C.
Crane, R. P. Cebula, E. Hilsenrath, G. E. Brueckner, M. D.
Andrews, O. R. White, M. E. VanHoosier, L. E. Floyd, L. C.
Herring, B. G. Knapp, C. K. Pankratz, and P. A. Reiser,
"Validation of the UARS Solar Ultraviolet Irradiances: Comparison
with the ATLAS1 and 2 Measurements", J. Geophys. Res., 101,
9541-9569, 1996.
- Goddard DAAC IMS online
documentation:
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- DATA PRODUCT
- A collection of parameters packaged with associated ancillary and
labeling data. Uniformly processed and formatted. Typically uniform
temporal and spatial resolution.
- DATA SET
- A logically meaningful grouping or collection of similar or
related data. Data having mostly similar characteristics (source or
class of source, processing level and algorithms, etc.).
- GRANULE
- A Granule is the smallest aggregation of data which is
independently managed.
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| CDHF |
Central Data Handling Facility |
| DAAC |
Distributed Active Archive Center |
| DCF |
Data Capture Facility |
| EOS |
Earth Observing System |
| FOV |
Field of View |
| GSFC |
Goddard Space Flight Center |
| IMS |
Information Management System |
| km |
kilometer |
| m |
meter |
| MSD |
mean solar distance |
| mW |
milliwatts |
| NASA |
National Aeronautics and Space Administration |
| nm |
nanometer |
| PI |
Principal Investigator |
| RAC |
Remote Analysis Computer |
| SFDU |
Standard Formatted Data Units |
| SOLSTICE |
Solar-Stellar Irradiance Comparison Experiment |
| SSPP |
Solar Stellar Pointing Platform |
| SUSIM |
Solar Ultraviolet Spectral Irradiance Monitor |
| TDRSS |
Tracking and Data Relay Satellite System |
| UARS |
Upper Atmosphere Research Satellite |
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- 17 Jul 1997
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- 17 Jul 1997
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- -- web-contact-disc@listserv.gsfc.nasa.gov
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http://disc.sci.gsfc.nasa.gov/guides/GSFC/guide/uars_solstice_l3bs_dataset.gd.shtml
 UARS
Project
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