ISCS Major System Components

The ISCS is composed of three major components.

1. the data provider
2. the data delivery and acquisition system for data broadcast and collection
3. the end processor (site work station).

NWSTG TECH CONTROL CENTER

FIRST COMPONENT - The Washington WAFC communications facility and the GTS/Regional Telecommunications Hub (RTH) on the GTS/Main Telecommunications Network (MTN) are located together in Silver Spring MD. They jointly comprise the first component of the overall system. This component distributes grid products, generated observational collectives, and worded forecast messages. These products are received from other communication centers or built at the Gateway. They are distributed on multiple data streams of the ISCS. The data is transmitted using the X.25 protocol from the Washington RTH/WAFC to the communications service provider and up-linked via a satellite facility.

VSAT ANTENNA

SECOND COMPONENT - The delivery and acquisition system is a communications provider which uses satellite technology for this component. This component provider is currently MCI Corporation under a openly competed contract with the U.S. National Weather Service (NWS). The MCI satellite system uses Hughes Corp. up-link facilities located at Andover, Maine for utilization of a contracted space segment of an Intel satellite at 325.3 E over the Atlantic Ocean and also an up-link at Yacolt, Washington for utilization of the an Intel satellite at 177 E over the Pacific Ocean. The satellite broadcast uses a C-band (5-6 Ghz) system. The Hughes VSAT (2.4 meter antenna, RF electronics), and a Memotec FR 970 PAD is the downlink equipment. These components comprise the communications system and will be placed where users establish their service. The global area of potential reception of the two satellites will cover two thirds of the globe.

WORK STATION

THIRD COMPONENT - A computer processing system must be connected to the communications port of the Memotec FR 970 device. This system is selectable by the user, but the interface of the selected system must be prepared to utilize from 3 to 6 virtual X.25 Permanent Virtual Channels to receive the various data streams. The system can be a stand alone work station as the third part of the ISCS system. This system will receive the data stream and stores the data for retreival and use. Countries (or agencies within authorized countries) desiring connection to the ISCS satellite broadcast system may select any work station. There are several commercial companies around the world who have built computer systems to perform this work station functional capability.

Companies currently known to us are:

• Global Science & Technology, Inc. - Greenbelt, Maryland, USA
• Info-Electronics Systems Inc. - Montreal, Canada
• COROBOR Systemes - Vitry, France, and
• Almos Systems BV - Culemborg, Netherlands

(This list does not imply NWS endorsement of these products.)

A few meteorological services in other countries have interfaced the MCI VSAT system with their own computer systems, as the interface and data formats are a WMO International standard.

The NWS, with WMO, and ICAO cooperated in a competitive contract for an initial first work station for delivery to some countries needing access to the MCI contracted ISCS communications system. The Alden Electronics Corporation was the initial supplier. This work station is the STAR4 system and is a complete package of hardware and software. The operations and maintenance or O & M was included upon purchase. The software used UNIX as the base operating system. The applications software is capable of message receipt, storage, display. The system included an FTP applications software package. The STAR4 has an optional applications software package that was designed to permit construction and transmission of standard WMO meteorological messages to the Washington RTH when the MCI/VSAT is configured as a two-way site. The work station has three communication connectivity options for data movement within the receiving center. This capability is for distribution beyond the initially VSAT connected work station. These options are LAN connectivity within the local work site, Dial-in alphanumeric data acquisition, and a duo-connection X.25 device for two STAR4 work stations located at two separated sites using one VSAT.

A discussion of the local multiple work station STAR4 LAN connectivity option is provided, for informational purposes. A good knowledge of the UNIX operating system is needed to implement the LAN option, and possibly knowledge of the DOS or Windows 95/NT operating system is needed if the additionally connected work station is other than a STAR4.