From the end of 2022 onwards, the first MTG satellites will gradually launch into space where, in a geostationary orbit, they will supply more precise weather forecasts for Europe - with a major contribution from OHB technology. © OHB

Taking a precise look at the atmosphere

MTG Meteosat Third Generation - One of the most complex development programs of satellites in Europe

If extreme weather events are not identified early enough, there is the potential for populations to be exposed to huge natural phenomena with very little warning. The ability to forecast heavy rains, storms and the like with precision is therefore of great importance if possible safety measures are to be taken early on. But more precise weather forecasts are also a basic requirement for agriculture and air traffic. The MTG (Meteosat Third Generation) weather satellite program holds out the prospect of improving forecasting ability. From the end of 2022 onwards, the first MTG satellites will gradually launch into space where, in a geostationary orbit, they will supply more precise weather forecasts for Europe - with a major contribution from OHB technology. MTG, among the most complex development programs of satellites in Europe, is the third generation of European weather satellites developed and realized for EUMETSAT (Exploitation of Meteorological Satellites).
OHB’s involvement covers responsibility for all six satellite platforms, two IRS (infrared sounding) instruments for both sounder satellites and the four telescope assembly units for the Flexible Combined Imager of the imager satellites. In addition, OHB is also the prime contractor for the MTG-S Mission. In short, FCI and IRS instruments make weather phenomena visible. Rupert Feckl, project manager for MTG instruments at OHB, talks about the technology that makes the climate measurable in this interview.

Ten years have gone by since the contract for MTG weather satellite program was signed - what specific technological challenges did the development of the IRS instrument present?

Rupert Feckl: The challenges from a technological aspect were many. This much was clear to us right from the start. For this reason, the ESA in various competition studies launched key technologies in advance in collaboration with the European aerospace industry. They involved, for example, designing a new generation of infrared detectors with previously unseen sensitivity. Especially low-interference, active coolers were built in order to achieve an operating temperature of around 52 Kelvin, about minus 220°C, on the retina of the detectors. In orbit, the satellite is directly exposed to the sun for most of the time. It is quite a design challenge to ensure that the sun does not shine directly into the instrument. On the other hand, it is extremely cold on the side facing away from the sun. The two effects result in very changeable thermal strain. Materials expand and then contract, which would be deadly for finely adjusted optical devices. And so the satellite’s thermal budget needs to ensure that temperatures are absolutely constant all the time. This requires a number of design measures so that the optical instrument can consistently supply a constant data quality. A SCAN mechanism, which directs the primary mirror of telescopes to observation points on Earth with absolute precision, ensures that the instrument always faces the Earth in the right position. We have ensured that this precision can be guaranteed 24/7 and for an operating period of ten years without any need for maintenance. The OHB team has always responded with a high degree of flexibility and feats of creative engineering, and the collaboration with partners and principals has, on the whole, been outstandingly successful.

Will OHB go into series production with the IRS instrument going forward?

We really hope so. This is something we are currently pursuing with determination. For many decades, meteorologists the world over have wished they had access to so-called infrared interferograms, which allow the distribution of temperatures and the movement of gases in the atmosphere to be measured. The data calculated help to predict extreme weather events with much greater precision. Our IRS instrument makes this possible. But at the time development of the IRS began in 2010, people were not sure whether it could actually be realized. Seasoned aerospace nations such as the U.S. had in the past tried and failed to produce comparable instruments, never managing to bring anything of the kind to market maturity. If I look at the current status of development of the IRS at OHB, it is highly likely that we will be able to deliver on our performance commitments. As a result, the interest among meteorological agencies worldwide in the data such an instrument produces has seen a further significant increase. We hope to be able to secure export orders for IRS models in the near future. To this end, we have already entered into intensive talks with weather agencies and possible partners in various regions around the world.

How does OHB contribute to the Flexible Combined Imager tool?

Imager technology delivers pictures in the visible light spectrum. These data have been actively used by weather agencies for decades. Over the years the technology used in imager instruments has developed considerably. We were able to improve the number of spectral channels, that is, the color of images, the precision of resolution and the coverage and repeatability of image data. In addition, the IRS supplies further data in the infrared light spectrum, including information on the composition of the atmosphere and the movement of air layers in relation to each other.
From a technological perspective, we need to specify that the two primary instruments, FCI and IRS, share a large number of technological features, such as the scanner, the detector cooling and the thermal and mechanical design. For this reason, IRS is in many places a “freeloader” on the development progress made by the imager instrument. Every technical obstacle we overcame with the FCI helped us at the same time with the development of the IRS. These technological synergies were the main reasons that the ESA and EUMETSAT chose our bid. This represents an outstanding performance we managed to achieve here at OHB.

What stages will the MTG instruments pass in the coming months?

As far as the FCI instrument is concerned, OHB has essentially already fulfilled its role successfully: We delivered our parts for the first flight model to our partner, Thales Alenia Space, in summer 2020. At the moment, this first FCI flight model is in the final assembly stage at TAS before being integrated into the first MTG-I imager satellite. At its Bremen site OHB has manufactured and tested the first satellite platforms for the MTG-I satellites with great success and delivered it on time. The next step following the “mating” between instrument and platform to form the complete satellite is the preparations for transportation and the actual start of the launchers. The first MTG-I launch is scheduled for the end of 2022.
Two of the IRS flight models are at a substantially advanced integration status at OHG in the ISO-5 cleanrooms. We expect two material TAS-F subsystems in the first quarter of 2021, which will be integrated into the complete instrument in the course of the year. This first flight model will undergo its final environmental and performance checks at the end of 2021/beginning of 2022. In mid-2022 it will be moved to Bremen for integration into the MTG-S satellite, then further tests and preparations for the launch will be made. The first MTG-S satellite is scheduled to go into orbit at the end of 2023. We are thus extremely well-prepared in Bremen and Oberpfaffenhofen to secure and realize additional follow-up orders for MTG instruments or satellites.