Table of Contents:                                                                                                                                   Page

             1.  Purpose ....................................................................................................................................... 1

             2.  Description .................................................................................................................................. 1

             3.  Data Products .............................................................................................................................. 3

             4.  Organizational Responsibility ......................................................................................................... 4

1.                  Purpose.  This Chapter provides an overview of the operation and management of telecommunications associated with operational Doppler weather surveillance radar (WSR-88D) systems.  The WSR-88D is sometimes referred to as the Next Generation Weather Radar (NEXRAD) radar system.

2.                  Description.  The tri-agency WSR-88D network consists of approximately 117 National Weather Service (NWS) and 23 Department of Defense (DOD) operational WSR-88Ds within the 48 conterminous states and a large number of user workstations interconnected via a combination of dial-up and dedicated 9.6- Kbps telecommunications circuits.  There will also be 14 addi- tional Federal Aviation Administration (FAA) WSR-88Ds in Alaska, Puerto Rico, Hawaii, and the Bahamas.  A WSR-88D has three major system components:  the radar data acquisition (RDA) unit, the radar product generator (RPG), and the principal user processor (PUP).

The RDA consists of an antenna, transmitter, receiver, signal processor, and related components.  The major function of the RDA is to transmit a radar signal; receive, detect, and process the radar radio frequency returns; and generate base radar data for transmission to the RPG.

The RPG equipment supports the processing, generation, local storage, distribution, and archiving of WSR88D products; the control of the RDA operating modes; and the monitoring of the operational status of the overall WSR-88D unit.  A wide-band data link is used to exchange base radar data, radar status, and control data between an RDA and its associated RPG.  The wide- band T-1 (i.e., 1.544 megabits per second) data link at a particular site might be either a microwave link, a dedicated cable, a fiber optic communications link, or a commercial T-1 circuit depending, usually, on the distance involved.  The unit control position (UCP) is an integral part of the RPG and is the equipment from which overall system functions are defined, initiated, monitored, and controlled.

The PUP comprises the user workstation hardware and software that support the products requested from the RPG, and the communications interfacing capability to and from the RPG.

The typical configuration of an NWS WSR-88D site has the RPG located within a Weather Forecast Office (WFO), although there are a few NWS sites that have the RPG located within the RDA shelter.  Nevertheless, all 117 conterminous NWS PUPs are hard- wired to their associated RPG via a 56-Kbps dedicated data link.  In all configurations, each RPG provides data in a form that any PUP can retrieve upon request via a dedicated or dial-up telecommunications link.

An NWS RPG typically has 8 to 10 dedicated dial-up ports assigned exclusively for NWS users which include National Centers, River Forecast Centers, WFOs, and regional headquarters sites.  Included within these 8 to 10 assigned ports are ports to allow PUP users at non-collocated NWS sites to access data from that site.  There is also a dial-up port on all NWS RPGs to allow for the exchange of rain gauge data between RPG sites and the Gauge Data Support System sites.  A Principal User External System (PUES) port is assigned at most NWS RPGs to provide data to the Automation of Field Operations and Services (AFOS) system via a dedicated 4.8- or 9.6-Kbps commercial communications link.  The typical NWS RPG also has two dedicated and five dial-up ports assigned exclusively for DOD users and two dedicated and two dial-up ports assigned exclusively for FAA users.

The typical configuration of a DOD WSR-88D site has both the RDA and RPG collocated within the shelter.  This configuration typically has the DOD-controlled UCP connected remotely via a dedicated 9.6-Kbps commercial link and at least one DOD PUP user connected as a dedicated 9.6-Kbps commercial link.

At DOD RPGs, there are typically five to six dial-up ports assigned for NWS users to retrieve data.  At a few DOD sites, the NWS has a dedicated 9.6-Kbps telecommunications circuit connected to the DOD RPG in order to provide continuous data to a  "supplemental" PUP located at an NWS WFO.  The NWS also has a PUES-dedicated communications link to selected DOD RPGs to support data transmission at a rate of 4.8- or 9.6-Kbps.  The typical DOD RPG also has two dedicated and five dial-up ports assigned exclusively for DOD users and two dedicated and two dial-up ports assigned exclusively for FAA users.

The typical configuration of a FAA WSR-88D site has both the RDA and RPG collocated within the shelter.  This configuration typically has two UCPs.  One UCP is located at the NWS WFO for operational purposes and connected to the RPG remotely via a dedicated 9.6-Kbps commercial link.  The other FAA-controlled UCP is typically located in the Air Route Traffic Control Center, for maintenance purposes, and is connected to the RPG remotely via a dedicated 9.6-Kbps commercial link.  At least one FAA PUP user is typically connected via a dedicated 9.6-Kbps commercial link to the RPG.

At FAA RPGs that are all located outside of the 48 conterminous states, there are typically five to seven dial-up ports assigned exclusively for NWS users.  The NWS also typically has two ports assigned for dedicated commercial links, one as an AFOS PUES port and the other as a PUP user connected via a 9.6-Kbps commercial link.  The typical FAA RPG also has two dedicated and five dial- up ports assigned exclusively for DOD users and two dedicated and two dial-up ports assigned exclusively for FAA users.
 
The NEXRAD Communications Service (NCS) is an integrated data communications network which interconnects all NWS and DOD sites.  It provides commercial dial-up and dedicated narrow-band circuits, operating at 9.6-Kbps, needed to provide access to all NWS and DOD RPGs from any NWS or DOD site.

3.                  Data Products.  The UCP controls the selected data product set that any "associated" or "non-associated" PUP can retrieve.  An associated PUP is one that is connected to the RPG via a dedicated link while a non-associated PUP is one that is connected via a dial-up telecommunications circuit.  An associated PUP user has access to the set of all products generated at the RPG.  A non-associated PUP user has limited access to the product set as determined by the UCP.

External users have access to WSR-88D products via the NEXRAD Information Distribution Service (NIDS).  The NIDS is provided by commercial companies that have entered into formal agreements with the NWS to connect, for a fee, to all NWS, FAA, and DOD
WSR-88D sites in the 48 conterminous states, Alaska, Hawaii, and the Caribbean.  In addition to the WSR-88D products generated by the RPG, NIDS providers may also produce enhanced products of interest to their customers.

4.                  Organizational Responsibility.  The Observing Systems Branch of the Systems Integration Division, Office of Systems Operations, is responsible for all NIDS operations and agreements.

The Configuration Management Section of the WSR-88D Operational Support Facility (OSF) in Norman, Oklahoma, is responsible for maintaining a master WSR-88D system data base that includes the dial-up and dedicated circuit identifiers, telephone numbers, passwords, and adaptation data for each site.  The Hotline Section of the OSF is responsible for providing troubleshooting analysis and support for telecommunications failures.

Regional WSR-88D meteorologists coordinate password changes to the dial-up ports for the regional WSR-88Ds.

Regional Communications Managers and field office Electronics Systems Analysts are initially responsible for trouble-reporting to the telephone companies for failed circuits.  Unresponsiveness on the part of telephone companies, or any chronic circuit problems should be immediately reported to the Telecommunications and Dissemination Branch of the Systems Integration Division.

Area Electronics Supervisors and Electronics Systems Analysts are responsible for maintaining any microwave links, dedicated cable, or fiber-optic communications links, other than commercial T-1, within their area of responsibility.

The Telecommunications and Dissemination Branch is responsible for the following:

                  a.  acquiring and managing all commercial T-1 facilities required to provide wide-band communications between NWS RDAs and RPGs;

                  b.  acquiring and managing all commercial dedicated and dial-up circuits needed to provide communications between NWS PUPs and RPGs;

                  c.  providing coordination with the Defense Commercial Communications Office and DOD on the NCS contract, monitoring the performance of the contractor-provided service for the NWS, and issuing contract orders to acquire or change narrow-band telecommunications service required by NWS field offices; and
 
                  d.  providing financial management of the entire NWS WSR-88D telecommunications network.