High-altitude balloon ride offers new perspective for CAIRT
A novel sensor that simulates the measurements that would be taken by one of the proposed satellites vying to be ESA's eleventh Earth Explorer, has endured an extraordinary journey.
Carried aboard a high-altitude balloon on a four-day voyage from Sweden to Canada, the sensor provides new data that could help to refine the CAIRT mission concept ? a mission that aims to unravel the complexities of Earth's atmosphere and enhance our understanding of climate dynamics.
CAIRT stands for Changing-Atmosphere Infrared Tomography. As a candidate satellite mission, it is currently in the feasibility study phase.
Next year, it will be pitched against the Wivern concept, before a final selection is made as to which of the two will be realised as ESA's Earth Explorer 11 mission.
If selected, CAIRT would provide the measurements needed to make a step change in understanding the links between climate change, atmospheric chemistry and circulation, gathering data between about five and 115 km above Earth's surface.
By observing the atmosphere from the mid-troposphere to the lower thermosphere simultaneously, CAIRT would provide critical and hitherto unavailable global observations of a host of important atmospheric trace gases, and of elusive gravity waves that all play key roles in the inner workings of the atmospheric system.
CAIRT would be the first limb-sounder with imaging Fourier-transform infrared technology in space. The CAIRT observing concept draws on well over a decade of airborne measurements with a prototype instrument named GLORIA.
Developed jointly between the Karlsruhe Institute of Technology and the Forschungszentrum Jülich, GLORIA had been deployed to all corners of the world on high-altitude research aircraft and more recently on stratospheric balloons.
These campaigns provided a wealth of robust scientific data and insight into many atmospheric research topics as well as technological aspects behind CAIRT's measurement technique.
Now, this workhorse of an instrument has evolved into a smaller, simpler, and more robust design. GLORIA-Lite may continue to support CAIRT in the future by simulating the measurements that CAIRT would take from space.
On its maiden flight, GLORIA-Lite was carried high into the stratosphere for a trans-Atlantic balloon ride.
The balloon was launched by the CNES French Space Agency team at Sweden's Esrange Space Center in Kiruna. It climbed to an altitude of 40 km, by which time it had expanded to a diameter of about 100 m, flew across the Atlantic Ocean, passed over Greenland, and after four days, landed on Canada's Baffin Island.
During this remarkable transit, the GLORIA-Lite imaging Fourier-transform spectrometer, which was fixed to the balloon's gondola, measured mid-infrared limb-emission spectra.
ESA Atmospheric Scientist, Alex Hoffmann, explained, "A limb-sounder works by measuring radiation that has travelled laterally through the atmosphere, by looking sideways through the layers of air above a planet, adopting a limb view. Like this, we can retrieve information about atmospheric constituents and properties with much finer vertical resolution than with other techniques.
"Combined with tomographic imaging, CAIRT would provide a unique three-dimensional view of the composition and temperature of the middle atmosphere. The GLORIA-Lite instrument uses the same measurement principles as CAIRT and offers comparable spectral resolution.
"The vertical and horizontal spectra gathered by GLORIA-Lite as it was swept across the Atlantic help to better understand this new instrument before deploying it on further campaigns. In the future, GLORIA-Lite could serve as a versatile tool to help us further develop CAIRT, and to demonstrate the value the mission would bring to science and climate research."
Michael Höpfner, from the Karlsruhe Institute of Technology in Germany added, "With GLORIA-Lite, we continue our legacy of developing and deploying advanced mid-infrared remote-sensing Fourier-transform spectrometers, enabling deeper exploration of the sparsely studied upper-atmospheric regions, which are undergoing unprecedented changes at an accelerated pace."
For GLORIA-Lite, the demonstration test flight was a great success, and the team is now busy analysing the data.
As for Earth Explorer 11, the decision between CAIRT and Wivern will be made after the public User Consultation Meeting in July 2025.
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