A green laser was used to guide the invisible infrared beam from La Palma to Tenerife as part of an experiment to test a new satellite concept for measuring atmospheric greenhouse gases and turbulence. Credits: ESA
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It may have looked like a futuristic scene from Star Wars, but ESA’s latest technique for aiding space exploration might shed some “green light” on greenhouse gases. A recent experiment involving the Spanish Canary Islands was conducted by shooting laser beams from a peak on La Palma to Tenerife. The two-week endeavor not only increased the viability of using laser pulses to track satellites, but increased our understanding of Earth’s atmosphere.
ESA runs an optical ground station in Tenerife for communications links with satellites. The facility is part of a larger astronomical installation Observatorio del Teide run by Instituto de Astrofisica de Canarias. Credit: ESAKnown as infrared differential absorption spectroscopy, the laser method is an accurate avenue to measure trace gases such as carbon dioxide and methane. It is accomplished by linking two Earth-orbiting satellites – one a transmitter and the other a receiver – and examining the atmosphere as the beam passes between the two. As satellites orbit, they both rise and set behind Earth and radio occultation occurs. It’s a time-honored way of employing microwave signals to measure Earth’s atmosphere, but new wave thinking employs shortwave infrared laser pulses. When the correct wavelength is achieved, the atmospheric molecules impact the beam and the resultant data can then be used to establish amounts of trace gases and possibly wind. By different angular repetitions, a vertical picture can be painted which stretches between the lower stratosphere to the upper troposphere.
While it all sounded good on paper – the proof of a working model is when it is tested. Enter ESA’s optical ground station on Tenerife – a facility built on a peak 2390 meters above sea level and part of a larger astronomical installation called the Observatorio del Teide run by the Instituto de Astrofisica de Canarias (IAC).With equipment placed on two islands, the Tenerife location offered the perfect setting to install receiver hardware grafted to the main telescope. The transmitter was then assigned to a nearly identical peak on La Palma. With nothing but 144 kilometers of ocean between them, the scenario was ideal for experimentation.
Over the course of fourteen days, the team of researchers from the Wegener Center of the University of Graz in Austria and the Universities of York and Manchester in the UK were poised to collect this unique data.
The Observatorio del Roque de los Muchachos on the island of La Palma housed the equipment to transmit the infrared signal and green guidance laser across the Atlantic Ocean to the receiving station in Tenerife. The experiment was carried out to test a new satellite mission concept for measuring concentrations of atmospheric carbon dioxide and methane. Credit: ESAWhile the infrared beam wasn’t visible to the unaided eye, the green guidance laser lit up the night during its runs to record atmospheric turbulence. Gottfried Kirchengast from the Wegener Center said, “The campaign has been a crucial next step towards realising infrared-laser occultation observations from space. We are excited that this pioneering inter-island demonstration for measuring carbon dioxide and methane was successful.”
Armin Loscher from ESA’s Future Mission Division added, “It was a challenging experiment to coordinate, but a real pleasure to work with the motivated teams of renowned scientists and young academics.” The experiment was completed within ESA’s Earth Observation Support to Science Element.
