Table of Contents:                                                                                                                               Page

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

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

                 3.  Data Flow ............................................................................................................................ 2

                 4.  Organizational Responsibility ................................................................................................ 3

1.                  Purpose.  This Chapter provides an overview of the operation and management of the telecommunications associated with operational Automated Surface Observing System (ASOS) sites.

2.                  Description.  The ASOS program is a fully integrated and automated surface weather information system that consists of approximately 250 National Weather Service (NWS) and
600 Federal Aviation Administration (FAA) systems.  In addition, a relatively small number of Department of Defense (DOD) sites may also be provided with ASOS.  The ASOS system reduces, and in some cases eliminates, the necessity for manual surface observing and monitoring operations.  Each ASOS system automatically collects, processes, formats, displays, archives, and reports the weather elements included in an automated surface weather observation.  There are four major units that comprise an ASOS system:  the acquisition control unit (ACU), data collection package (DCP), peripherals, and sensors.  The ACU and DCP are the heart of the system and are connected by either radio frequency communications, a hard-wired dedicated link, or a 2.4-Kbps dedicated commercial telecommunications circuit.

The ACU is the central controlling element of the ASOS.  It receives weather information from the sensors via the DCP.  The  ACU processes the weather data and makes the data available to users through the peripheral devices attached to the system.

The DCP processes the weather data being received from the sensors and transfers the data to the ACU.  The typical configuration of an ASOS system has one DCP located remotely on the sensor pad.  However, there are many ASOS systems that are configured with more than one remote DCP installed at strategic locations at the airport.  Communications between the ACUs and the DCPs are controlled by the ACU.

The complement of peripheral devices consists of up to three operator interface devices (OID), up to four video display units (VDU), up to nine controller video displays (CVD), an FAA
handset, and a printer.  The OID is the primary input/output device for the system and is used by the observer to monitor or edit the weather data being reported and/or add additional information to the ASOS observation.  The VDU and CVD are display devices that provide weather data to users.

A typically configured ACU distributes weather observation messages and special weather reports to a variety of NWS and FAA users, via nine ports.  There are two ports, one "dial-up" and one "dedicated," on all NWS ASOS ACUs; they support interfaces to the Automation of Field Operations and Services (AFOS) system.  Port 1 is the dial-up port and provides 1.2-Kbps backup connection to AFOS via a direct dial circuit.  Port 2 of the ACU is the dedicated port and provides a 2.4-Kbps connection to AFOS via either a dedicated hard-wired link or a dedicated commercial telecommunications circuit.

Ports 3B, 3C, 4A, and 9 are connected to OIDs, CVDs, and VDUs via either dedicated hard-wired links or dedicated commercial 1.2/2.4-Kbps telecommunications circuits.  The CVDs are used to display the surface data to the FAA Air Traffic Controllers in airport control towers.  The VDUs display the surface data to the airport personnel.

Port 5B provides a computer-generated voice message that is accessed by the aviation public through a dial-in port.  Depending on the size of the airport, this dial-in port supports two to four dial-in lines, in rotary.  Port 6 serves as the interface to the FAA's communications systems (e.g., the GS200/Automated Weather Observing System Data Acquisition System).  Port 8 is a dial-in/out port with two lines for both remote operational and maintenance functions that are performed by the ASOS Operations and Monitoring Center (AOMC) of the NWS.  In addition, the National Climatic Data Center (NCDC) downloads ASOS data from designated sites via port 8.

3.                  Data Flow.  Hourly and special weather observations are available to users on both the FAA and NWS networks.  The NWS Telecommunication Gateway (NWSTG) provides the interface point for transferring data between the FAA and NWS communications networks.  ASOS messages will also be available to other users through the NWSTG.  ASOS data will be available to system users in Standard Hydrometeorological Exchange Format.

4.                  Organizational Responsibility.  The Telecommunications and Dissemination Branch of the Systems Integration Division, Office of Systems Operations, is responsible for the following:

                      a.  providing overall management of all commercial dedicated and dial-up circuits between the NWS and FAA field sites;

                      b.  providing financial management over all commercial dedicated and dial-up circuits that are a part of the ASOS network;

                      c.  processing all NOAA Telecommunications Service Authorization actions to acquire, change, or remove ASOS telecommunications services at NWS and FAA sites; and

                      d.  providing overall management of Radio Frequency Authorizations (RFA) for ASOS radio frequency data acquisition links.

The Systems Operations Center of the Office of Systems Operations is responsible for the AOMC operations, including:

                      a.  providing around-the-clock monitoring, maintenance, and software support for ASOS sites;

                      b.  maintaining the site-specific configuration and parameter files;

                      c.  providing a precision time source; and

                      d.  maintaining a record of changes made to ASOS site-specific files using a software configuration management program and providing timely information on the changes to NCDC.

The NWS Regional Communications Managers and electronic technicians are responsible for the maintenance of commercial ASOS circuits in their Regions and for reporting service problems to the commercial telephone companies.  Unresponsiveness on the part of telephone companies or any chronic circuit problems should be reported immediately to the Telecommunications and Dissemination Branch of the Systems Integration Division, Office of Systems Operations.

The FAA is responsible for the acquisition of data from FAA ASOS sites and for RFAs issued for ground-to-air radios.