Online access to weather satellite imagery through the World Wide Web

Both global area coverage (GAC) and high-resolution picture transmission (HRPT) data from the Advanced Very High Resolution Radiometer (AVHRR) are made available to Internet users through an online data access system. Older GOES-7 data are also available. Created as a "testbed" data system for NASA's future Earth Observing System Data and Information System (EOSDIS), this testbed provides an opportunity to test both the technical requirements of an online data system and the different ways in which the general user community would employ such a system. Initiated in December 1991, the basic data system experienced five major evolutionary changes in response to user requests and requirements. Features added with these changes were the addition of online browse, user subsetting, dynamic image processing/navigation, a stand-alone data storage system, and movement from an X-windows graphical user interface (GUI) to a World Wide Web (WWW) interface. Over its lifetime, the system has had as many as 2500 registered users. The system on the WWW has had over 2500 hits since October 1995. Many of these hits are by casual users that only take the GIF images directly from the interface screens and do not specifically order digital data. Still, there is a consistent stream of users ordering the navigated image data and related products (maps and so forth). The authors have recently added a real-time, seven-day, northwestern United States normalized difference vegetation index (NDVI) composite that has generated considerable interest.