Government Resource for Algorithm Verification, Independent Test, and Evaluation (GRAVITE) system is a National Oceanic and Atmospheric Administration (NOAA) system, developed and deployed by Joint Polar Satellite System (JPSS) Ground Project to support Calibration and Validation (Cal/Val), Data Quality Monitoring, and Algorithm Investigation, Tuning and Integration. GRAVITE enables novice and expert users to discover and obtain data easily by using standard protocols. The Pull Server is a component of the GRAVITE version 3.0 (GV3.0) system. It provides a mechanism to download remote data file(s) using easy-to-understand download rules. When there are few rules pertaining to the same remote location, it can be grouped using a product paradigm. A download rule can be defined with only three pieces of information: remote server, source, and target location. The source and target location can be specified using calculated fields as well as regular expressions. The rules are then converted into a “wget” statement, which is a popular utility for downloading remote files. This solves most of the compatibility issues with connecting to a remote server.

The software relies on a simple configuration file, which defines the download rules. The download rules are then fed to a rule engine, which calculates all the date variables, and converts environment variables with their values for source file location. The engine then downloads the file and applies renaming rules to a saved file.

There are times when an FTP server does not support globbing characters like ?, *, [], etc. In such cases, the rule engine does a directory listing and applies pattern matching to the list of files. The file is downloaded when the name matches to a specified pattern.

This work was done by Peyush Jain, Richard Ullman, and Gyanesh Chander of NASA Goddard Space Flight Center; and Chintu Mistry of GVT, LLC. GSC-16927-1

NASA Tech Briefs Magazine

This article first appeared in the November, 2015 issue of NASA Tech Briefs Magazine.

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