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Thursday, 01 September 2005 00:00 |
| International News Services sources: |
BY MARK ROWE
THE METEROLOGICAL Office, the UK's national weather service, the Met Office, has launched a new version of its satellite-distribution weather advice service. The new upgraded SADIS2G (second generation) is being rolled out to air traffic control units (ATCs) and will gradually supersede the existing SADIS system. It is expected that all users of the original SADIS will moved onto the new version by the end of December 2008. The intention of the World Meteorological Organisation (WMO) and ICAO is that there will be no additional new users of the original SADIS.
SADIS, or SAtellite DIStribution, provides 24-hour information from an Intelsat 904 satellite based above the Indian Ocean. It offers customers - ATCs and airlines - data on a range of factors, including winds in the upper atmosphere, temperatures and significant weather events and allows airlines to make safety-critical and operational decisions as well as enabling them to improve route planning and streamline costs. The system has coverage for 60% of the earth's surface, ranging from eastern Atlantic, Cape Verde (20° W) to central Australia (140° E). Two similar satellites located over the Atlantic and the Pacific Oceans provide the complementary ISCS service, which covers the rest of the world.
SADIS2G comprises alphanumeric OPMET (OPerational METeorological) data, such as aerodrome meteorological reports and forecasts and SIGMET warning messages. It is a dedicated ICAO system, regulated and controlled under ICAO Standards and Recommended Practices.
The new SADIS2G system is engineered around 'open source' protocols and formats, including the use of Internet protocol (IP). This avoids locking users into proprietary systems and resolves the problem of obsolescence in SADIS hardware. It is designed to distribute essential World Area Forecast System (WAFS) products and global OPMET data to ATC desktops, and enables the Met Office-based WAFC (World Area Forecast Centre) London to distribute data to more than 90 ICAO states in Africa, Europe and western Asia - the rest of the world is covered by WAFC Washington, supported by the US National Weather Service. These systems are broadcast only, which means that two-way communication between the client end system and the host does not occur. As a result data is presented as 'spoofed' IP, or 'spoofed' X.25. The OPMET data goes through a real-time quality controller via NATS, which sends the data on to the Met Office. SADIS 2G is non-prescriptive and can easily be integrated into other systems. Data output can be configured to a number of common protocols, including UDP multicast, WMO TCP/IP or X.25 PVCs. SADIS 2G uses existing available bandwidth on the same satellite lease, which is used to provide the 1G service. No additional purchase of bandwidth was required.
"SADIS 1G hardware is largely obsolete in the sense that it is very costly to maintain, and there are few options for supplying new systems," said Richard Orrell, senior international aviation analyst at the Met Office. "It was becoming very difficult to source new hardware. SADIS 2G is a 'future proof' system, and the modulation and protocols differ from SADIS 1G. The new hardware uses modern up-to-date technology and economies of scale ensure that the compatible receivers are of high quality."
The Met Office charges nothing to individual users. Instead, its costs involved in the provision of the operational broadcast are recovered through an international cost recovery scheme managed through ICAO. Ultimately these costs are recovered on route charges. The whole SADIS service is provided to the civil aviation community at a cost of approximately GBPounds 500,000. SADIS 2G hardware typically costs GBPounds 3,000 - 5,000, at least 50% cheaper than the cost of comparable 1G hardware.
One of the cost benefits for ATCs is the ability to make real-time benefits by enabling them to improve route planning and streamline costs. It also allows airlines to make safety-critical and operational decisions by providing data on winds in the upper atmosphere and temperatures, and significant weather events. "It's managed by ICAO's international steering group, so the mechanism exists for SADIS2G users and ICAO members to feed the requirements into it," said Mr Orrell. "It's very open, transparent and democratic. The data is constantly evolving. In the past we would use the T-4 pre-determined areas but now users can get the raw data and they can visualise it over user-defined areas."
The roll-out of SADIS 2G is in its early stages and is being obtained by users through third parties. So far, there are only two installations to date in Western Europe: Météo Suisse, the Swiss National Meteorological Centre, and Belgocontrol, the ATC for Belgium up to 8,000 metres.
Belgocontrol is facing initial problems with data reception but expects these to be swiftly resolved. "SADIS is a vital system for us as it provides us with all meteorological data needed to prepare briefing and flight documentation for pre-flight planning and in-flight replanning for international aviation," said Wim Demol, of Belgocontrol's Meteorological Department. "The upper level winds and temperature forecasts are directly used by Belgocontrol and Eurocontrol ATC units for the calculation of Estimated Times Overhead route points. Incorrect winds and temperatures would mean that all time related events and information is wrong. This can have negative effects. It could we mean get in touch with the next ATC unit at the wrong time and would mean we give them an incorrect time for when the aircraft is expected to enter their airspace. We decided to upgrade to SADIS 2nd generation because this system uses more state-to-the-art technology offering higher speeds - and thus more timely data reception - and higher reliability."
Two of the other initial users are the ATCs for Romania and Syria. "The Syrians didn't have SADIS at all, so they were keen to take the latest technology immediately," said Erick Nuwendam, pre-sale adviser for Corobor, the Paris-based company responsible for installing SADIS 2G for ATCs. "The Romanians are upgrading from SADIS 1G and they feel it is really helping their network. They want to be compatible with ICAO as soon as possible.
"The main benefits they cite are that it is just easier to set up and use, more transparent and more efficient to use. It's an off-the-shelf unit and it's less expensive. In a sense the ATC users won't notice any difference from before, except that there won't be any disruption. It's more reliable. With the original SADIS there was the risk of outages from the X.25 protocol. The fact that this is not a risk simplifies the jobs for the engineers and the staff at ATCs as they are in control of their environment."
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