The European Space Agency (ESA) has conducted a new experiment involving the firing of laser pulses between satellites to track greenhouse gases as part of the agency's need to understand global change, one of today's most pressing scientific challenges.

The Spanish Canary Islands played host to the two-week experiment that involved shooting laser beams from La Palma peak to Tenerife and made the night sky lit up with green pulses of light, like a scene from a Star Wars film.

During the two weeks, the core team of scientists from the Wegener Center of the University of Graz in Austria and the Universities of York and Manchester in the UK recorded the first data of this kind.

The ESA experiment tested the concept of using ‘infrared differential absorption spectroscopy' as a means to make extremely accurate measurements of trace gases such as carbon dioxide and methane.

The approach links two satellites orbiting Earth, one as transmitter and the other receiver, with the atmosphere being probed as the beam travels between them.. This new concept, however, uses shortwave infrared laser pulses.

The researchers placed the equipment on the two islands, taking advantage of ESA's optical ground station on Tenerife. The station offered the perfect location to install the receiver hardware, which was integrated into the main telescope.

At the right wavelength, the atmospheric molecules affect the beam and this information can then be used to calculate concentrations of trace gases, and potentially wind.
Perched on
these volcanic mountains and separated by 144 km of Atlantic Ocean, there is an unobstructed path between the two facilities, making them one of the best sites in the world to conduct such experiments.

"The campaign has been a crucial next step towards realizing infrared-laser occultation observations from space," said Gottfried Kirchengast from the Wegener Center. "We are excited that this pioneering inter-island demonstration for measuring carbon dioxide and methane was successful."

"It was a challenging experiment to coordinate, but a real pleasure to work with the motivated teams of renowned scientists and young academics," added Armin Löscher from ESA's Future Mission Division.

The experiment was carried out within ESA's Earth Observation Support to Science Element.