Backup of GMS-5 with GOES-9

Background

Prior to 22 May 2003, the Geostationary Meteorological Satellite (GMS-5) operated by the Japan Meteorological Agency (JMA) provided meteorological data over the Asia-Pacific Region. GMS-5 was the main source of satellite data over the Australian region for the forecast and warning system of the Commonwealth Bureau of Meteorology. However, due to technical problems with the main imaging instrument on GMS-5, an American instrument called the Geostationary Operational Environmental Satellite (GOES)-9 took over as a backup in May 2003.

GMS-5 was due to be replaced by a satellite called MTSAT in November 1999, however the launch vehicle for MTSAT failed and the satellite was destroyed. Significant efforts to extend the usable life of GMS-5 were implemented by JMA in July 2001, so that it operated for more than 3 years beyond its design life.

JMA negotiated with USA's National Oceanic & Atmospheric Administration (NOAA) for GOES-9 to be moved over the Western Pacific to provide images in place of the ailing GMS-5 until its replacement is launched. The replacement is a new Japanese satellite called the Multi-Functional Transport Satellite (MTSAT-1R), which is expected to become operational in 2004. GOES-9 is located at longitude 155 degrees east and is now the primary source of geostationary satellite data for the Asia-Pacific Region including Australia.

Figure 1: Timeline showing reception of geostationary satellite data at the Commonwealth Bureau of Meteorology

Implications

The implications of the Bureau using GOES-9 as its main source of weather satellite data are as follows:

• the GOES-9 images are qualitatively very similar to GMS-5 images;
• geostationary coverage area is altered due to a different satellite position (GOES-9 is 15^o further East than GMS-5 - see figure 2);
• hourly imagery is generally available;
• full-disc coverage is available (this was not available for some GMS-5 scans in early 2003);
• an additional infrared channel at 3.9 microns is available;
• the GOES-9 visible channel is affected by coherent noise and this data is of slightly lower quality than might otherwise be expected;
• the satellite operator, USA's National Oceanic & Atmospheric Administration (NOAA), needs to undertake regular maintenance of the GOES-9 satellite and there are also eclipse periods, so that during the year there are occasions when some images are not available due to these protective actions by the operator;
• Data collection Platform (DCP) operations (e.g. remote Automatic Weather Stations relaying weather data via satellite) continue unchanged with GMS-5 as the operational satellite for DCP purposes.

Figure 2: GOES-9 coverage from longitude 155^oE
(colours are computer-generated: this is not an actual satellite image)

Impact on Services

The Bureau's Space Based Observations Section ensured that the transition between GMS-5 and GOES-9 in May 2003 was streamlined, the aim being to maintain continuity of service levels. However users should be aware that GOES-9 will provide satellite images in place of GMS-5 only until MTSAT-1R, the replacement for GMS-5, is operational in 2004.

Also, given uncertainties with GOES-9 including possible outages for maintenance and eclipse operations, the Bureau's contingency plan will be in place so any possible adverse impact on services, although difficult to quantify, should be minimal. In the unlikely event of failure of both GOES-9 and GMS-5, other weather satellite data will be made available to fill the gap in coverage as far as possible.

Further information can be obtained from:

Japan Meteorological Agency's GMS-5 backup procedures

NOAA GOES-9 Status

GOES-9 observations schedule (NOAA site)

GOES technical details (NASA site)

GOES planned outages

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