Introduction

The aim of the EUMETSAT Advanced Retransmission Service (EARS) is to provide polar satellite data from the EUMETSAT Metop and National Oceanic and Atmospheric Administration (NOAA) satellites with a timeliness suited to the needs of European operational short range regional numerical weather prediction models. The geographical coverage of EARS is primarily over data-sparse sea areas around Europe.

EARS comprises three separate polar satellite instrument data services; these are the existing EARS-ATOVS and the EARS-AVHRR and pilot EARS-ASCAT. Each of the EARS services retransmits observations from an instrument or an instrument group and aims at providing a homogeneous service across the NOAA and Metop polar orbiting satellite platforms.

Traditionally polar satellite data from the NOAA satellites has been received via two methods:

• via the once per orbit data download from the spacecraft to the central NOAA ground station
• via the direct transmission from the satellite to a High Resolution Picture Transmission (HRPT) station on ground

The first mechanism provides global coverage data to end-users, but with delays of three to six hours after the time of measurement. The second mechanism provides the data virtually at the time of measurement, but the geographical coverage is limited to the region around the HRPT reception station. EARS provides improvements on both of these methods by offering a large geographical coverage combined with timely retransmission. This is achieved by establishing a network of existing HRPT stations around the Atlantic and Arctic Oceans and rapid distribution of the collected instrument data to end-users.

The figure below illustrates this using the example of the current EARS-ATOVS service.

System Overview

The satellites and instruments supported by the EARS are as follows:

Network of HRPT/AHRPT stations 

The aim of the EARS has been achieved through the close cooperation of organisations willing to operate the network of HRPT stations. A major consideration has been to optimise the area of data coverage and to reduce system costs by making use of existing stations.

The network of HRPT/AHRPT stations acquires and processes the Metop and NOAA satellite HRPT/AHRPT telemetry data and forwards the generated meteorological products to EUMETSAT. These products are then disseminated to the users via EUMETCast and the RMDCN/GTS.

The relationship between the system elements making up EARS is shown in Figure 1.

The following organisations provide the HRPT network:

- Centre de Meteorologie Spatiale - Meteo-France (CMS)
- Danish Meteorological Institute (DMI)
- Hellenic National Meteorological Service (HNMS)
- Kongsberg Satellite Services (KSAT)
- Environment Canada/Environnement Canada (EC)
- National Oceanic and Atmospheric Administration (NOAA)
- National Institute for Aerospace Technologies (INTA)
- ROSHYDROMET - SRC Planeta

All these organisations currently receive HRPT data. The station locations contributing to EARS are given in the table below.

	Station Name		Country		Operated by		Location (lat, long)		Pictures
	Gander		Canada		EC		48.94°N, 54.57°W
	Edmonton						53.33°N, 113.5°W
	Gilmore Creek (Alaska)		USA		NOAA		64.97°N, 147.40°W		1 | 2 | 3
	Monterey						36.35°N, 121.55°W
	Wallops Island						37.8°N, 75.3°W
	Ewa Beach						21.33°N, 158.07°W
	Miami						25.74°N, 80.16°W
	Lannion		France		CMS		48.7°N, 3.5°W
	Saint-Denis (La Réunion)						20.91°S, 55.50°E
	Maspalomas		Spain		INTA/INSA		27.78°N, 15.63°W		1
	Kangerlussuaq		Greenland		DMI		66.98°N, 50.67°W		1
	Svalbard		Norway		KSAT		78.13°N, 15.23°E		1 | 2
	Athens		Greece		HNMS		37.815°N, 23.769°E		1
	Moscow		Russian Federation		ROSHYDROMET		55.759°N, 37.569°E

Note: Investigations into the failure of the Metop-A AHRPT side A concluded that the root cause was heavy ion radiation causing the failure of a component of the AHRPT Solid State Power Amplifier (SSPA). To minimise the risk of failure of the Metop-A AHRPT-B unit whilst still offering the User community a service, EUMETSAT has implemented a "partial" AHRPT service in those areas where the risk of damage from heavy ion radiation is reduced. For southbound passes, AHRPT side B is activated for all orbits over the North Atlantic and European area starting at around 60°N. The AHRPT is then switched-off before the spacecraft reaches the Southern Atlantic Anomaly region, at around 10°N. The switch-on of the AHRPT service for the descending passes over Europe and North Atlantic region, will allow ASCAT, ATOVS and AVHRR data to be available in due course from the EARS network of stations.

To complement the partial Metop-A AHRPT-B service, a Fast Dump Extract service is being implemented. This service utilises the most recent part of the X-band global dump received at Svalbard from the northbound passes. The ASCAT, ATOVS and AVHRR data streams can thus be provided with high timeliness for regional data. This data will be made available via the EUMETCast-Europe service.

Development Milestones

February 2010
Addition of Moscow to the EARS-ATOVS service.

September 2009 
Addition of Kangerlussuaq to the EARS-AVHRR service.
Addition of EARS-ASCAT level 2 wind products to the GTS.
Addition of Saint Denis (La Réunion) to EARS-ATOVS.

July 2009
NOAA-19 becomes operational, replacing NOAA-18 in EARS-AVHRR.

February 2009
Maspalomas Metop ATOVS products available from the Metop partial AHRPT service.

December 2008
Start of EARS-ASCAT pilot service, using data from the fast dump extract system at Svalbard.

November 2008
Athens and Lannion Metop ATOVS products available from the Metop partial AHRPT service.

August 2008
Addition of Athens to the EARS-AVHRR service.

July 2008
The EUMETSAT Council decides to continue EARS services for the duration of the EPS program and to extend it with a pilot IASI service.
End of pilot AVHRR service. EARS-AVHRR service declared operational. EARS-ASCAT trial service for beta users. 

December 2007
Addition of Gander to the EARS-AVHRR pilot service.

April 2007
Start of EARS-ATOVS products dissemination from Gander HRPT station.

October 2006
Start of EARS-ATOVS products dissemination from Svalbard HRPT station.

August 2006
Start of EARS-ATOVS products dissemination from Lannion HRPT station.

Jul/Aug 2006 - Extension of EARS-AVHRR trial services to include Lannion, Svalbard and Maspalomas stations.

May 2006
Start of trial ERS-SCAT demonstration service as part of the preparations for the EARS-ASCAT Pilot service.

March 2006
Start of trial EARS-AVHRR service on EUMETCast Europe (Ku-band).
Start of pilot service based on a single station, Maspalomas, sending AVHRR segment files via EUMETCast.

December 2005
The EUMETSAT Council decide to continue and extend the existing EARS service for a period of four years. In addition to continuation of the ATOVS Retransmission Service, the EARS service is extended with the pilot ASCAT Retransmission Service and the pilot AVHRR Retransmission Service.

September 2005
Test data available via ftp, trial dissemination with test data. 

January - October 2005
Preparation of Operational Service Specification for EARS-AVHRR & EARS-ASCAT.

January 2005
Start of operational EARS-ATOVS Service.

December 2004
End of Pilot EARS-ATOVS Service.

November 2002
Start of Pilot EARS-ATOVS Service. Early operations of the service include a sub-set of the planned HRPT stations. The remaining HRPT stations and service support are added during the first months of operation. Experience from the Pilot Operational Service was gathered and used to assess the service, define improvements and consider possible extensions to the service.

February - July 2002
EUMETCast broadcast trials.

December 2001 - October 2002
Development of the Service. This includes establishing agreements with the HRPT stations, establishing the necessary communications network, establishing the broadcast service, development of the necessary hardware and software systems and deploying these at the HRPT station sites.