The polar ice caps are melting, the sea level is rising. A new satellite will take a very close look at the oceans. But its start is delayed.Sea level rise is one of the greatest threats posed by climate change. The European Space Agency (ESA) said in a press release that this rate of increase has increased over the past 25 years. In order to keep an eye on what is happening, the world's oceans must be constantly monitored. For this purpose, a new earth observation satellite is now to be launched. It bears the name "Sentinel 6 Michael Freilich" and is supposed to map 95 percent of the ice-free oceans every ten days and provide essential information for ongoing oceanographic and climate studies.
The mission is a cooperation between Esa, the US space agency NASA, the European meteorological satellite agency Eumetsat, and the US weather and oceanography agency NOAA. The satellite is the first of two identical satellites to be launched into space. It is named after Michael H. Freilich, the recently deceased former director of the NASA earth observation department. Sentinel means guardian.
Unprecedented accuracy
We now get a global measurement every ten days, that is, a picture of the situation, says the director for earth observation programs at Esa, Josef Aschbacher. The satellite provides data that has not been available so precisely before.It scans the oceans from a height of more than 1,300 kilo-meters with an accuracy of less than a millimetre, as they say. It is equipped with a radar altimeter for this purpose. The condition of the sea surface is recorded using so-called altimeter radar pulses. A microwave radiometer also measures the amount of water vapor in the atmosphere that affects the radar pulses.
As a high-precision component, the new satellite is intended to supplement the monitoring of the planet from space. There are sure to be a few hundred satellites that are currently in orbit and monitoring the earth, says Josef Aschbacher. The Europeans are leading here because the system covers everything - from science to weather forecasting to civil protection.
According to the plan, the satellite should launch from Brandenburg Air Force Base in California on November 10th with a SpaceX Falcon 9 launcher. Now the launch is delayed somewhat, as Esa and Metatarsus reported this week. A new date is not yet known. The background to this is that the engines of the launch vehicle have to be checked again. The second, identical satellite is to follow in five and a half years. According to Josef Aschbacher, the entire project cost those involved in the USA and Europe around 400 million euros each. As part of the Copernicus earth observation program, the satellite is to be controlled from a new Metatarsus control center in Farmstead, as program manager Manfred Luger said.
Conclusions about the thickness of the ice are possible
The radar pulses from the satellite are transmitted, reflected by the sea surface and received again. Nobody can do anything with the data at first. That has to be implemented in a high-precision distance measurement, explains Manfred Luger. The exact determination of the location in the orbit is the great challenge of the mission. Wave heights would have to be resolved and atmospheric influences had to be factored out in distance measurements.
There are two independent navigation systems on board for determining the location, and the satellite orbit is regularly measured with a laser. According to Aschbacher, in conjunction with other satellites, conclusions can be drawn about the density and thickness of ice. This is important. For example, the melting of the Greenland ice has tripled since the 1990s.
There are also other parameters that have to be measured more precisely, said Esa director Josef Aschbacher. One of the greatest challenges is the more precise measurement of the greenhouse gas carbon dioxide. This is still not precise and comprehensive enough. For the future, Aschbacher would like a satellite system that measures all of these parameters. The data could then be linked and coupled with artificial intelligence. This makes it possible to make real predictions and simulations about the Earth system, for example how high the sea level would rise in different temperature scenarios.
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