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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.

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