README

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RT Retrieval Framework
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Jet Propulsion Laboratory, California Institute of Technology. 
Copyright 2017 California Institute of Technology. 
U.S. Government sponsorship acknowledged.

This software (NASA NTR-49044) retrieves a set of atmospheric/surface/instrument
parameters from a simultaneous fit to spectra from multiple absorption bands.
The software uses an iterative, non-linear retrieval technique (optimal
estimation). After the retrieval process has converged, the software performs an
error analysis. The products of the software include all quantities needed to
understand the information content of the measurement, its uncertainty, and its
dependence on interfering atmospheric properties.

The software provides a flexible, efficient, and accurate tool to retrieve the
atmospheric composition from near-infrared spectra. Its unique features are:

* Spectra from ground-based or space-based measurement with arbitrary
observation geometry can be analyzed.
* The retrieved parameters can be chosen from a large set of atmospheric (e.g.,
volume mixing ratio of gases or aerosol optical depth), surface (e.g.,
Lambertian reflection), and instrument (e.g., spectral shift or instrument line
shape parameters) parameters.
* The software uses an accurate, state-of-the-art, multiple-scattering radiative
transfer code combined with an efficient polarization approximation to simulate
measured spectra.
* The software enables fast and highly accurate simulations of broad spectral
ranges by an optional parallelization of the frequency processing in the
radiative transfer model.

The software was originally created for JPL's OCO, ACOS and OCO-2 projects for
Level-2 processing.

Documentation
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Documentation on setup and compiling of the software can be found in the
doc/users_guide.pdf PDF file, or online in HTML form at:
http://nasa.github.io/RtRetrievalFrameworkDoc/ 

For information on the algorithms used by the software the OCO2 L2 Algorithm
Theoretical Basis Document can be found at the Goddard DAAC: 
http://disc.sci.gsfc.nasa.gov/OCO-2/documentation/oco-2-v6/OCO2_L2_ATBD.V6.pdf

For further information on the methods used by OCO, see the OCO-2 project
publications page: 
http://oco.jpl.nasa.gov/science/publications/