Astronomie - A journey into the northern lights



Spider-2 is a scientific rocket project within a program funded by the Swedish National Space Agency for Swedish balloon and rocket activities from Esrange. Spider-2 kicked off in 2018 and is scientifically a collaboration between Swedish and German scientists from the KTH Royal Institute of Technology, Stockholm University, Swedish Institute of Space Physics of Stockholm and the Leibniz Institute of Atmospheric Physics. Photo by Marcus Lindh | SPIDER-2 Team.

Late February, close to midnight, a blast successfully sent off the one-stage rocket experiment Spider-2 from Esrange Space Center in northern Sweden. All previous attempts had been cancelled due to combinations of poor weather conditions, moonlight disturbing the optical instruments and most of all, the absence of Aurora Borealis, the central figure of the mission. Finally, the conditions were just perfect.

Named by Galileo Galilei in 1619, Aurora Borealis or northern lights has long fascinated mankind. Every year, thousands of visitors travel to the northern hemisphere to get a glimpse of this luminous spectacle which is the result of disturbances in the magnetosphere caused by solar wind.

Not surprisingly, scientists are still very interested in this phenomenon. More than usual this February night as a team in northern Sweden set course to investigate the phenomenon from the inside. The team is on a mission to gather data from within the northern lights in order to, among other things, study processes that interact and interfere with radio and GPS signals.

Krister Sjolander, project manager at Swedish Space Corporation, SSC, explains what went on in the skies above Esrange that clear winter night:

"Once launched into the Aurora Borealis, 125 kilometers up into space, the Spider-2 rocket ejected twelve free-flying measuring units in different directions, creating a multi-point system simultaneously registering data in the volume of the Aurora.

This will provide a huge amount of data, for example on plasma physics processes within the Aurora, for the project scientists to work with for years to come. The science team is specifically targeting a process called Farley-Buneman instability, amongst others.

After collecting data, the instruments re-entered the atmosphere in free-fall before finally slowly sailing down towards Earth in parachutes, for the final five kilometers, before landing in the snow of the vast landing area surrounding the space center.

"As for all projects, it was such a relief to see that everything worked as it was supposed to during the flight. Perhaps even more so this time due to all the launch constraints on a mission like this. The weather conditions had to be perfect, both for the actual launch but also for the recovery process of all the instrumentation. Also, launch was only possible around the new moon phase as to not saturate the optical instrumentation.

Lastly and most importantly, we also needed an actual northern light of the correct type to appear at the right time and in the nominal trajectory or flight path of the rocket. We waited for weeks for this to happen and then on this possibly last opportunity for hours until it did. I must admit it was a great relief, says Krister Sjolander.

An extensive localization process
Retrieving the payload after landing may not sound like a big deal and usually, it is not. The tricky part on Spider-2, however, is that there is not only one big payload to find but also 12 tiny instruments spread out in the vast unpopulated snow-covered forest and mountain area surrounding Esrange.

Several techniques were used to transmit all individual units' final GPS-position. Even with a perfect fix, these small devices are challenging to find in the terrain. And if there should be any issues with the positioning systems, as occurred during Spider-2, there is normally no back-up.

This time however, the team had introduced an innovative passive system as extra back-up and with some detective work, before scanning of the landing area, 9 out of the ejected 12 units were recovered which is considered a great success.

"For the science team it is a huge difference to be able to collect data from as many units as possible, in order to get the multi-point data set that they are looking for. As for the three remaining units, however, there is still time and hope. The measuring units' data storage can survive for extensive periods of time and when found will most likely be intact.

If they are not found in possible upcoming active scans of the area, they might still find their way home during the summer season when the area is also occupied by hikers, as all of the devices are tagged with contact information, says Krister Sjolander.

Making life on Earth benefit from Space
Helping scientists understand the secrets of Aurora Borealis is, one might say, just another day at work at SSC. Spider-2 is only one of many space operations conducted by SSC, aiming to find new ways of using space to facilitate everyday life and develop societies around the globe.

Since the first rocket was launched in 1966, Esrange har grown to be Europe's largest civilian space center. And while industry needs continue to grow, SSC aims to expand even more, creating new capacity for launching opportunities in Europe. The company is currently working intensively to establish a test bed for tests of reusable rockets, as well as developing a basic ability to launch small satellites by 2021.

The arctic location of Esrange Space Center also means an advantageous position for communicating with polar-orbiting satellites. Meanwhile, it is also one of the world's largest civilian satellite ground stations, acting as hub for SSC's global satellite station network, including Canada, Alaska, Hawaii, Chile and Australia. Consequently, the space center in northern Sweden has for more than fifty years been an attractive hub for the exploration of our immediate space - making life on Earth benefit from the opportunities that lie there.

"Since established, Esrange has been the scene for 572 rocket launches and 649 balloon releases. Add to that, years of managing and downloading data from satellites, used for providing valuable information to researchers and enabling various data driven functions of society. Using space technology for Earth observations, scientists from all over the world get access to huge amount of valuable data. Not least for environmental purposes where a global overview from satellite data might prove to be crucial for human existence on Earth, says Krister Sjolander.

It is not for nothing that Esrange is considered one of the world's most versatile space centers. Today, it is home to a wide range of space operations - launching sounding rockets for microgravity and atmospheric research, releasing high altitude balloons for astronomy, atmospheric research as well as executing drop tests of space and aerial vehicles, to name a few.

"By extension, all the projects that we are involved in have the same purpose - to make life easier for the people on Earth. Space research like the northern lights project helps us getting new insights on how processes up there affect us down here. This in turn creates a foundation for societies to evolve. That is how we help Earth benefit from space, says Krister Sjolander.

Quelle: SD

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