Communications, information, documents and modules are being distributed by the Internet. The development, scheduling, management, as well as educational information, are being created in HTML (HyperText Markup Language) for viewing by WWW browsers. In most instances, general interest information will be distributed via web browsers and not by E-mail. Some graphics files, such as the very detailed maps of the rocks and soil activity around the Viking Landers are too large for direct viewing on many machines ( >30 MegaBytes). Such files will be available by anonymous "FTP" file transfer protocol. If we can obtain support, we will make available many of the >20 man-years of meteorological data and descriptive information developed during the Viking mission.

The Unidata Internet Data Distribution system and software enable us to provide reliable, essentially real time, nationwide access to the Mars educational modules and data, without the problems such as those associated with severe system loading during the Shoemaker-Levy Comet's impact with Jupiter. This is vital during Pathfinder Mission Operations, as the demand will be very high and easily would swamp single servers and local Internet nodes, ( and most likely regional nodes).

A simplified Unidata flow chart illustrates the core components of the Unidata system important for this application. Each level fans out to as many as eight lower level "relay" or "leaf" sites, the fan out having been determined by operational experience. All operations are automated and routinely deliver products which are automatically incorporated into web pages. Mars data and information will be distributed to collaborating Unidata sites, and then on to collaborating non Unidata mirroring sites, as illustrated below. The data load for Pathfinder is so small (compared to the first tier stations' normal weather data load, routing of 1 -- 2 Giga Bytes/day) that it will be essentially imperceptible.

In the diagram below, the DEC 3000-900 will mainly serve the Mars components of this program in the North West and throughout the nation, while the "UW Unidata site" machine currently contains web pages for "Live from Earth and Mars" and serves the Unidata weather products from Hawaii to Alaska to Arizona. The UW Unidata machine, served by a 100 Mega Bit/Sec link, and a backup system, provide distribution with a manual switchover in case of its failure or its feeds. Updates to the Unidata software will provide for automated selection of another server during 1996 at which time we may decide to use the DEC 3000-900 as the alternate server for both these functions. The workstations indicated in red have been generously provided by Digital Equipment Corporation for this and other "Live from Mars" components.

Unidata is a national program that is governed by universities and funded by the Division of Atmospheric Sciences of the National Science Foundation, NSF. The program's mission is to provide innovative computing and networking technologies that empower universities to acquire and use atmospheric and related data, much of it in real time. The Unidata Program Center is managed by the University Corporation for Atmospheric Research (UCAR) in Boulder, Colorado. The Unidata Local Data Management (LDM) software and infrastructure developed for data management and distribution are very easy to use, powerful, and well tested.

The development of the LDM software, as well as various support and monitoring functions that facilitate its use for distributing data to more than 120 universities nationwide, is one activity of the Unidata Program Center in Boulder, Colorado. Among the data recipients are eight first tier sites such as ours at UW, each of which automatically distributes 1-2 gigabytes of data daily, unattended, to approximately 120 other Unidata sites. The Program Center, which operates on modest NSF funding (about $15 million over the 12 years of Unidata's existence), also developed the widely used netCDF software library and is responsible for supporting and enhancing several other systems that are popular in university departments of meteorology and related sciences. An old list of the first tier UW and its relay sites may be viewed here.

Partial flow chart

• "the "UW Unidata" machine" fans out to six more second tier sites in the region covering from Alaska to Hawaii to Arizona
• Each site can serve multiple "Unidata to Public Interface"s
• Each Unidata site can also directly serve the public.