The headquarters of European Agency for Meteorological Satellites in Darmstadt ("City of Science"!) Was easy to spot: It's shaped like one of their early weather satellites, with a central cylinder and protruding wings.
In the gardens outside, large-scale models of their space-based fleet line up like cocktail tables at a wedding in the bushes. They look indecent. Unlike airplanes, whose graceful lines and smooth skin help them to slip through the atmosphere, they have fine protuberances and a packed appearance. One looks like a gold-immersed engine, the other looks like a washing machine with a blown-off case.
Still, it was nice to see her there. The thing about weather satellites is that they work out of sight. We see them before the start, half under construction, blown out under fluorescent lights and thundered by technicians in hare suits. Or we see them in the renderings of artists, the sci-fi images of spacecraft zooming in orbit.
But I went to Darmstadt to see them in a new way, the moment they come closest to Earth.
Yves Bühler, Director of Technical and Scientific Assistance at EUMETSAT, said when I met him in his sunny corner office. He was dressed as a French rocket scientist: a crisp white shirt, a broad collar and a breast pocket full of fine pens. "But it has become much more accurate worldwide. And it has also become much more accurate in the middle area – so one week, two weeks. Why this? Because the satellite observations cover the earth evenly. There is no black hole in an area. "
Today's weather forecasts are better than ever, since the observation of the atmosphere and the use of these observations for fine-grained computer simulations -" weather models "- which allow a safe prediction of the future sky, 5, 6, 7, even 8 days in the future Ahead.
For today's weather forecasts, the global view is everything. The perspectives seen on your smartphone apps, in on-air meteorologists' television screens, or in airline shipping centers, all stem from supercomputer weather models, which are insatiable data consumers. The best and most global data come from satellites. But not all weather satellites are the same.
Two categories of weather satellites fly around the Earth today: geostationary orbiters and polar orbiters. The geostationary or GEOs revolve in the same direction as the earth's rotation, leaving them motionless in the sky. They provide constantly updated information about a single area of the atmosphere and provide the pretty pictures we associate with weather satellites.
The polar or near-Earth orbiters known as LEOs fly deep and fast. They circle the planet from north to south and from south to north, flying over each geography with a different geography and cutting a pattern around the globe like a knife peeled with a knife. They specialize in quantitative data, collect numerical measurements of temperature and humidity, and pass them millions of times to supercomputer weather models. When it comes to having significant predictive effects, especially for more than a few days in the future, they are the champions.
However, numbers are hard to spot, so it's the geostationary satellites, the GEOs, and the dramatic images they produce that suck in all the air.
Similarly, not all weather satellites in a nation are the same. In this decade, the US geostationary satellite program – GOES – is in the midst of a $ 11 billion renovation by Lockheed Martin. This money pays off for the life of four satellites, of which the first two were launched in 2016 and 2018, but the figure is still shocking, especially when adding up the annual total budget of the National Meteorological Service at around $ 1 billion per year ,
Strictly speaking, American weather satellites cost more for the flight than the entire forecasting system they support. This effort can be seen as evidence of the importance of satellites for today's weather forecasts, but also indicates the bureaucratic complexity of the system.
New American weather satellites were prone to delays, breakdowns and cuts in congressional funding. This leads to frequent hand wrestling over a "satellite gap" where old satellites fail before new ones can take their place. In 2018, the latest GOES (GOES-17) had problems cooling one of its main instruments in the sun, making it unusable at certain times of the day and year. The problem was resolved 97 percent by software and operational changes, and the cooling system is redesigned, but the problems are hard to ignore.
Complex systems have complex problems, but they do not have to be. While the US system is bureaucratic in its development and operation, the European Meteorological Satellite Agency EUMETSAT keeps its structure simple. It is an independent organization funded and overseen by the weather services of 30 nations. The 450 employees are accommodated on the uniform campus in Darmstadt and are led under a uniform line. They have ten functioning weather satellites in orbit and plan to launch a dozen more. Crucially, the data that delivers their polar orbits is as important (and, in some cases, more important) to global weather models than it is to their American counterparts.
For a journalist who wants to get up close and personal with weather satellites looking for a simple report, EUMETSAT is a dream come true.
In the middle of our conversation in his office Buhler came too short and studied the big clock on his wrist. He spun around to the telephone on his desk. "Do you know when the pass is? Yes. That's perfect. That's perfect. "Bühler led us through the satellite-shaped building, clicking through electronic locks, shuffling through brightly lit staircases and telling scientists and engineers in French, English, German and Italian hellos.
Behind one last set of heavy double doors, the control room was a large room built like a Hollywood mission, with work chairs, dozens of screens, and large countdown clocks mounted high on the wall. The technicians have closely monitored the EUMETSAT LEOs and the GEOs of the adjacent control rooms. Each room had its own personality and rhythm, just like the satellites that were being watched. The technicians in the GEO control room kept a constant watch; If everything goes well, not much happens. The LEOs are more lively and their life is more syncopated.
Every 30 minutes one of their LEOs makes a "pass": the time into each orbit when the satellite flies over the North Pole to be in radio communication with its ground station. When Bühler and I entered, Nico Feldmann, a young ponytail plant engineer, jumped to his feet. "Twenty-three minutes; Metop-B; over Spitsbergen! He barked. It took me a moment to realize he was making a joke, Spock playing Bühler's Kirk, pretending we were on the Starship Enterprise bridge. But then I realized that he was only kidding. We were really there to meet a spaceship.
The plant in Darmstadt controls its polar railways via a fiber-optic link that leads across Europe and under the Barents Sea to Spitsbergen, the Norwegian island over the Arctic Circle. From there, a radio link is made from a 33-foot diameter dish antenna protected by an egg-shaped, dome-sized dome. The court that serves EUMETSAT is one of 31 on a plateau called Platåberget next to the Svalbard Global Seed Vault, which keeps seeds from around the world in the event of an apocalypse. [Bühler, Feldmann, and I talked in the LEO control room in Darmstadt.] The antenna in Spitsbergen swiftly and smoothly turned like a robotic arm on its spindles until the massive bowl aimed precisely at the point on the horizon where Metop-B emerged and rose like a speck of dust in a sunbeam.
Feldmann and his colleagues call this moment "AOS", an abbreviation for "acquisition of signals". Metop-B orbits the earth 14 times a day and flies almost north to south and then south to north (at an angle or incline of 98 degrees), each time directing the instruments down through a narrow swath of atmosphere , A polar orbiting satellite, by definition, passes the poles in each orbit. As the earth turns underneath, however, she crosses the equator at a different length each time.
Each orbit takes 102 minutes, and the satellite is visible only to the ground station on Spitsbergen between 12 and 15 minutes minutes from it. On the day I'm here, the shortest pass would come on the Norwegian night, at two or three in the morning, when the satellite on the other side of the globe was heading for daylight. The main task of each run is to download the gigabytes of observation data that would normally be collected as the satellite flies around the planet.
Technically, this is called a "full dump" and is similar to trying to download a movie over your neighbor's Wi-Fi while you drive past its house. (Unless it works.) "You need to get the data down, and you have to get it down quickly," Bühler said. In order to reduce the delay between observations of the satellite and the distribution of the data, flying over the McMurdo research station in the Antarctic by the satellite also produces a "half dump".
Each passage brings with it a mix of drama and routine. That's why I was interested in this control room and not in the next door. The geostationary satellites are just that: stationary. They seem to float lazily in their stability above us and to keep a watchful eye. This is of course an illusion; They actually fly through space at a speed of more than 6,700 miles per hour, orbiting an earth orbit once a day – in other words, at the same speed as the planet itself. The GEOs are always in contact. But with the LEOs every pass is exciting. If something goes wrong while the satellite is out of range – if an instrument malfunctions or a temperature or voltage parameter is out of bounds – an alarm sounds. Feldmann gave his own analysis of the geostationary spaceship managed by his colleagues next door. "GEO is boring," he said. Bühler was more diplomatic. "It's always interesting to watch what happened in those 100 minutes when the satellite flew, invisible to our location," he mused.
Metop-B's approach to Spitsbergen from the other side of the earth was indicated by a red marker. numbered LED countdown clock on the wall. "The first activity associated with a pass is usually 12 minutes before connecting to the ground station," Feldmann said. The moment came closer. We waited. A machine chirped. "There it is," said Feldmann. "Now we have 12 minutes to send orders to the spaceship."
"And to save the data," Bühler added, pointing his finger upwards. We all watched a box column turn green on the monitor. "And telemetry looks … nominal," Bühler said with relief, using the room language as "normal." "Telemetry" refers to the basic state of the satellite and its systems, e.g. For example, temperatures and voltages. The two key values monitored by Feldmann for each passage of the satellite were the duration of "TM" and "TC", which represent telemetry and signify the health data received from the satellite. and telecommand, indicating the ability to return commands. These transmissions occur over relatively low S-band frequencies.
The juicy stuff, that is the "scientific data", comes via the X-band, which is a higher-frequency microwave band. Feldmann pointed to another column of green rectangles. "If these are green, it means the scientific data is sinking." We watched the numbers increase bit by bit. Feldmann went through the list of acronyms of various instruments that measure things like temperature, humidity, cloud cover, and water vapor: ASCAT. GOME. GRASS. IASI. AMSU. Buhler softly whispered her name with him, like a father of a spider bee. At this time, we were 1.8 gigs in the dump. If the downloaded data was a movie, only an experimental filmmaker of the future could imagine: it consisted of 10,000 channels of infrared and radar soundings shot from space through the clouds. There were still five minutes left on the pass.
When Bühler, Feldmann, and I went through the details of the Metop-B routine, I was able to appreciate the satellite as a busy working tool and observe the atmosphere as attentively as any terrestrial weather station. It stashes its images in its solid state memory banks and then zaps them down onto the surface. The data itself is not a snapshot, but a single click in time, rather a ragged film strip as the soaring robot crosses the atmosphere and pushes its nose down like a bloodhound.
Before I & # 39; I had a chance to notice that Metop-B had finished his dump. "Now you see that the scientific data has been downlinked," Feldmann said in his best David Attenborough voice. "We have just over a minute left to send him orders."
But we had nothing to tell the satellite. Everything was green, everything was nominal. In another part of the building, EUMETSAT's computers had already begun sending observations of their data connections to the world. Special attention was paid to the most avid customers: the operators of the weather models who were starving for the latest measurements of the atmosphere. There was a pleasing symmetry: the satellite absorbed its observations of the whole earth and EUMETSAT sent them back to the whole earth.
When the first weather satellite, TIROS 1, was launched in the spring of 1960, President Dwight Eisenhower made a deceptively simple statement: "The earth does not look that big when you see that curvature." What seemed to surprise him and everyone , was the extent to which this new view of the entire planet belonged to the planet. Polar orbiters were the pioneering observatories of today's predictions. They were too small to be seen with the naked eye, but I now had a new vision of how they circled over them. Next to the clock, which counted down to the next passage, was the spacecraft's odometer: the number of orbits traveled. That afternoon, Metop-B was in the middle of its 10,754th turn around Earth, a journey that began in 2012. In less than an hour, she would return over the horizon. His rhythm is tied to our life, to the rotation of our planet that defines our hours.
Adapted to The Weather Machine by Andrew Blum. Copyright © 2019 by Andrew Blum. Reprinted with permission from Ecco, an imprint of HarperCollins Publishers.
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