• Introduction
• Historical background
• Instruments on board
• The satellite
• Conclusions
• References

FIGURE

• Figure 1

The European Space Agency’s mandate include to undertake research, development and demonstration of Earth Observation related space technologies. The MetOp satellites, which prototype is planned for 2003, will be the European contribution to the world meteorological polar satellite system, replacing the "morning" satellites, provided by the U.S. at present. MetOp will embark a NOAA payload, plus European advanced instruments. The satellites are being developed by ESA in co-operation with EUMETSAT, which has the overall responsibility of the European Polar System EPS, which main objectives are to furnish data for operational meteorology and climate monitoring. Some instruments on MetOP will provide detailed information on the atmospheric temperature/humidity profiles, essential for weather forecasting. Other parameters will be available from the scatterometer and the global ozone instrument, continuation of the ERS series. The use of MetOp data is expected to contribute to the improvement of meteorological and other applications, plus to Earth Sciences research. Industrial activities for the manufacturing of the satellites started in February 1998, under the leadership of MMS (F).

Keywords: meteorology, climatology, remote sensing, satellites

1. Introduction

The Directorate of Applications of the European Space Agency (ESA) has, among others, the objective of making a contribution from the space to the monitoring and study of the environment (i.e. pollution, climate), Earth resources (renewable and non-renewable) management and monitoring, operational meteorology and solid earth/geophysics. ESA achieved experience in geostationary meteorological satellites (Meteosat), after a first launch in 1977. Similarly, ESA was successful in the development and operations of polar remote sensing satellites ERS (1991, 1995) embarking mainly active radar instruments. The current programs have as main elements: ERS, Envisat, MSG, MetOp and Earth Watch/Explorers. Envisat-1, MSG-1 and MetOp-1 are currently under implementation phase (C/D).

2. Historical background

During the eighties, ESA had been planning to build an Earth Observation multi-disciplinary Polar Platform for flying by the end of the century. At some stage, it was decided that the instruments of meteorological operational nature would be better put together in a separate satellite, based on the polar platform design. Such satellite/s, called MetOp, would be the European contribution to the World’s Meteorological Organization (WMO) satellite system, as replacement of the morning meteorological polar satellites provided now by the USA (NOAA/TIROS series). In order to provide continuity and complementarity, the NOAA payload would also be flown in such satellite.

The remaining instruments, geared mainly to non-meteorological applications, were then put together in the multi-mission Envisat satellite, to be launched in the mid of year 2001.

The European Organization for the exploitation of Meteorological operational Satellites, EUMETSAT, co-operates with ESA in the MetOp venture. This was also the case for Meteosat since 1986, and for Meteosat Second Generation MSG to be launched in 2002. EUMETSAT has the overall responsibility of the European Polar System EPS. This includes the three MetOp satellite’s launches, operations of the ground segment during 14 years, development of some instruments, and procurement of the two recurrent satellites, while contributing to the development of the prototype (MetOp-1), which is under ESA’s technical responsibility.

3. Instruments on board

The MetOp satellites, have been designed to embark instruments provided by NOAA, EUMETSAT, ESA and other European partners. MetOp will have different performances than the actual NOAA system due to a platform designed with high pointing accuracy, full on board recording capacity, digital high rate and low rate communication system, encryption capability and an increased payload.

The instruments embarked on MetOp 1 & 2 are:

• Advanced Scatterometer ASCAT, based on the ERS -1/2 heritage
• Global Ozone Monitoring Experiment GOME-2, based on the ERS-2 heritage
• Global positioning system Receiver for Atmospheric Sounding GRAS,
• High Resolution Infrared Sounder IASI,
• Microwave Humidity Sounder MHS,
• Advanced Microwave Temperature Sounder AMSU,
• Advanced Very High Resolution Radiometer AVHRR,
• Advanced ARGOS Data Collection System,
• Search & Rescue receiver and a Space Environment Monitor SEM.

MetOp’s main objectives are to furnish data for operational meteorology and climate monitoring. Many of the above instruments (IASI, MHS, AMSU, GRAS) will give detailed information on the atmospheric temperature/humidity profiles, essential for weather forecasting.

ESA is developing three of the instruments to be embarked on MetOp:

• The ASCAT will provide continuously the information collected by three radar antennae working in C-band and illuminating two swaths of 550 km each, separated 660 km. The inferred vector winds over the oceans and the back-scatter over land and ice areas will provide key information for marine weather and climate applications.
• GOME-2 is a nadir-viewing spectrometer to measure radiation in the ultraviolet and visible range of the spectrum: four channels covering the 240 to 790 nm spectral range. The design of the instrument is such that the swath width may be decided to vary up to 1920 km, with a spatial resolution of 40 x 40 km (960 km swath and 0.1875 s integration time) and 40 x 5 km (for polarisation monitoring). The calibrated solar irradiances and Earth radiance spectra with auxiliary geophysical information (e.g. polarisation and cloud fraction) will be disseminated by Eumetsat after 2h 15 min of sensing. Column amounts of the trace gases and vertical profiles of Ozone will be derived after 3 hours of the measurement being made. Ozone profiles and information about other atmospheric components will be useful for Numerical Weather Prediction (NWP) models and for environmental and climate monitoring.
• The radio-occultation technique well established for characterizing planetary atmospheres will be used for the first time in an operational mission such as MetOp. GRAS will be a receiver suited for the GPS system which will provide information about the Earth’s atmosphere refractivity. A total of 500 to 1000 occultations per day, covering the entire globe, are expected.

The instruments on MetOp-3 will be essentially the same, but some may be updated at a latter stage.

4. The satellite

MetOp will fly nominally at 820 km in a 5-day repeat orbit with an Equator descending crossing time at 9.30 am. It has been designed to be compatible for launch by Soyuz ST (in the process of being confirmed) or Ariane 5, with the possibility of sharing launch opportunities in the later. The three satellites of the series should span for an operational period of at least 14 years, with an expected life time of 5 years each.

Data will be continuously recorded on board and dumped to the acquisition station/s once per orbit for further processing and dissemination to users by Eumetsat within 2h 15 min. This will allow a global coverage, which will be completed every one to three days, depending on each instrument's swath. A direct broadcasting of data will also be possible via a high rate HRPT and a low rate LRPT link, thus allowing their exploitation mainly for now-casting purposes.

There are twelve ESA member states contributing to the development of the prototype satellite and some of the instruments on-board. The main contractor for the industrial consortium building the satellite is Matra Marconi Space (France). The industrial activities started in February 1998 and the prototype is expected to be ready for storage in 2003. The launch date is being

5. Conclusions

The envisaged mission is expected to fulfil the European requirements for operational meteorology and climate monitoring, while allowing European scientists to continue and enlarge their research in a diversity of Earth Sciences fields, continuing the ERS and complementing the Envisat missions. It will also contribute to the global surveillance of air, land, sea and ice environment, by setting up the basis for a number of new operational applications.

6. References

ESA Bulletin number 102- May 2000