The 0 degree image service is the main mission of Meteosat Second Generation (MSG).
The SEVIRI instrument allows for a complete image scan (Full Earth Scan) once every 15-minute period. Each 15-minute period, or repeat cycle, consists of eight segments of image data, with the exception of the HRV channel, which has 24 segments. Each segment has 464 lines of image data.
The 0 degree service comprises High Rate SEVIRI image data, in 12 spectral bands from the satellite's field of view, processed in near real-time to Level 1.5.
The data are accompanied by the appropriate ancillary information that allows the user to calculate the geographical position and radiance of any pixel. Before distribution to the user, the data are compressed using lossless compression in the form of Wavelet License Registration.
As well as the High Rate SEVIRI product, meteorological products are also generated and disseminated to the user community in near real-time. For a comprehensive list, consult the Product Navigator.
A secondary Low Rate SEVIRI service is also provided comprising of a subset of five SEVIRI spectral channels. Data are compressed using lossy JPEG compression prior to onward distribution to the user.
The nominal coverage of the prime MSG service — the geostationary service from the MSG satellite located at 0 degrees longitude — includes the whole of Europe, the Atlantic Ocean, all of Africa and at locations where the elevation to the satellite is greater than or equal to 10°.
A repeat cycle prologue file precedes the delivery of the image segments and a repeat cycle epilogue file follows after the delivery of the segments and contains final quality information for the image. The image segments are numbered and a fixed relationship between the image segment number and the line offset is established. The image segment numbering direction follows the radiometer scan direction.
High Rate SEVIRI image data consist of geographical arrays of various sizes of image pixels, each pixel containing 10 data bits, representing the received radiation from the earth and its atmosphere in the 12 spectral channels. Of these 12 spectral channels, 11 provide measurements with a resolution of 3 km at the sub-satellite point with the 12th, the High Resolution Visible (HRV) channel, providing measurements with a resolution of 1 km:
The Low Rate SEVIRI services comprises the following five spectral channels:
- Channel 1 (VIS 0.6)
- Channel 3 (IR 1.6)
- Channel 4 (IR 3.9)
- Channel 5 (WV 6.2)
- Channel 9 (IR 10.8)
Illustration of the fine detail visible with the HRV channel (AVI, 10.4MB). The low-level clouds over the Po Valley in the morning are visible, as well as convection along the Appennines in the afternoon, producing cirrus anvils.
The HRV channel supports a mode of operation known as Alternative HRV Scanning Mode Operations. In this mode it is possible to introduce a horizontal split into the HRV image, and separately specify the E-W offset of the HRV image window above and below the split.
From the start of MSG routine operations until 31 August 2005, the HRV scanning mode was fixed as follows:
- Split position: Line 914
- E-W offset for lower window: Chosen to east-justify the image
- E-W position for upper window: Chosen to optimise the coverage of the European region
From 31 August 2005 onwards, the lower window shifted to follow the daily illumination. The configuration is as follows:
- Between 00:00 and 14:00 UT the lower HRV window is east-justified so as to optimise the coverage of the Indian Ocean region.
- Between 14:00 and 17:00 UTC the lower HRV window moves every hour, on the hour incrementally westwards, until in becomes west-justified.
- Between 17:00 and 00:00 UTC the lower HRV window is west-justified to optimise the coverage of the Atlantic Ocean.
From 17 August 2018 onwards, for the FES prime mission, the upper window is shifted to the west position at 10:00 UTC every day (instead of 17:00 UTC previously) to allow for a better coverage of the Azores Islands. The current configuration is as follows:
- Between 00:00 UTC and 10:00 UTC, the upper HRV window is at its nominal position centred on Europe (covers from 40-deg E longitude to 20-deg W longitude).
- At 10:00 UTC the upper HRV window is shifted about 10-deg longitude in the westward direction.
- Between 10:00 UTC and 00:00 UTC the upper HRV window is kept in the westward shifted position.
- At 00:00 UTC the upper HRV window is shifted back to the normal position.
High Rate SEVIRI Image Product contains numerous image quality indicators. These indicators provide information on the completeness, geometric quality, radiometric quality, and timeliness of the Level 1.5 product, as well as information on the quality and completeness of the Level 1.0 Image from which the Level 1.5 Image Product was derived. See MSG Level 1.5 Image Product - Quality Indicators (PDF, 365 KB).
Mission swaps (transferring operations from one Meteosat satellite to another Meteosat satellite) are performed to ensure continuity of the 0 degree service in the event of a longer service outage. Such service outages may be caused by anomalies or be due to routine spacecraft maintenance requiring sensor switch-off.