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Data acquired from very high spectral resolution
monitoring of the Earth's atmosphere provides an overwhelming
amount of information. This information is gathered when thermal
infrared radiation passes through the Earth's atmosphere and
reaches a sensor. The infrared radiation forms a highly convolved
signal, containing both emission and absorption, from the entire
length of the ray path. To harness this data, NASA's Jet Propulsion
Laboratory (JPL), Pasadena, California, Earth Observing System
(EOS) programs, the Deep Space Network (DSN), and various Department
of Defense (DOD) technology demonstration programs, combined
their technical expertise to develop the software, SEASCRAPE.
SEASCRAPE, licensed
by the California Institute of Technology (Caltech), automatically
inverts complex infrared data and makes it possible to obtain
estimates of the state of the atmosphere along the ray path.
Former JPL staff members created a small entrepreneurial firm,
Remote Sensing Analysis Systems, Inc., of Altadena, California,
to commercialize the product. The founders believed that a commercial
version of the software was needed for future U.S. government
missions and the commercial monitoring of pollution.
With the inversion
capability of this software and remote sensing instrumentation,
it is possible to monitor pollution sources from safe and secure
distances on a noninterfering, noncooperative basis. The software
allows the user to determine the presence of pollution products,
their location and their abundance along the ray path.
The inversion
process utilizes first principle physical modeling, rather than
the usual differencing of observations. The capabilities of this
technique allow for maximum sensitivity of the instrument. In
addition, the inversion can be done on individual pixels if desired,
meaning there is no inter-pixel dependence forced upon the analysis.
The observer is free to make use of whatever data is available,
without having to obtain data sets that are composed of pollution
and pollution-free pixels for comparison.
| SEASCRAPE
software allows the user to determine the presence of pollution
products, their location, and their abundance. |
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Given that the inversion is a quantitative
statistical product, not only are estimates of the pollution
obtained, but also the uncertainties in those estimates. Knowing
the uncertainty associated with each estimate is a very useful
by-product of this technique. In short, one knows how much of
a particular substance would have to be present under the observed
scenario for the instrument to detect its presence. For pollution
control conformance monitoring, that is as important a measurement
as the detection of the pollution class itself.
This software, now known as SEASCRAPE_Plus,
is currently available for Macintosh, HP, Sun, Dec, and Alpha
machines in executable form. Porting it to PCs and to other UNIX/LINUX
machines is straight-forward since the source code, while large
(over one million lines), is written in ANSI Standard C. Currently,
the graphical user interface (GUI) used to interact with the
code, is written in Interactive Data Language, (IDL). The software
has been cleared by the Department of Commerce for export, and
is currently used by numerous research and engineering organizations
around the world. Hopefully, SEASCRAPE will assist researchers
in combating pollution.
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