December 1, 2006

Calipso flying high

Orbited 28 April, the NASA/CNES Calipso satellite is designed to study the impact of clouds and aerosols on climate change. With the data validation phase of the mission drawing to an end, its 1st series of results is set to arrive this month. Calipso’s instruments have performed remarkably well since being switched on in May. “The instruments’ signal-to-noise ratio is even better than we expected,” confirms Jacques Pelon, Principal Investigator on the French side of the mission.

And the most innovative and complex instrument of all, the lidar—a sort of “optical radar” that uses a laser beam instead of microwaves—has functioned flawlessly for the last 6 months, whereas its predecessors experienced numerous hitches.

“The lidar is a complex instrument in which all of the optical parts must be perfectly aligned for the laser to work as intended. Getting this technology to operate durably in space is a real feat of engineering,” says Didier Renaut, in charge of meteorology and climate programmes at CNES.

Unprecedented complementarity

While the lidar is able to record vertical profiles of clouds and aerosols in very fine detail, it lacks a horizontal dimension. This is where the Infrared Imager Radiometer (IIR) developed by CNES comes in. “IIR is the 1st uncooled, multispectral infrared imaging radiometer to be operated in space,” enthuses Jacques Pelon. “It’s a very good instrument that is going to allow us to measure brightness temperatures to within 2/10ths of a degree while fully exploiting its complementarity with the other instruments.”
The combination of lidar and IIR data from Calipso will help scientists to probe the atmosphere in three dimensions.
Calipso data will also ideally complement those from its companion satellites in the A-Train constellation — A for “afternoon constellation”, since all the satellites cross the equator a few minutes apart at around 1.30 pm local time —, particularly CloudSat and Parasol, the latter carrying an imaging radiometer/polarimeter with a wider field of view than IIR.

Understanding long-term climate change

“Thanks to measurements from the A-Train, we hope to finally lift the veil on the role that clouds and aerosols play in global warming, and to ascertain if they tend to amplify or limit it overall,” explains Didier Renaut.
Jacques Pelon is convinced that the unique complementarity of the instruments on Calipso and its A-Train companions “is set to reveal for the 1st time ever a great deal more about the vertical dimension of the atmosphere and cloud and aerosol characteristics, which will be crucial to gain a clearer understanding of processes likely to affect climate in the long term. We all wish Calipso a long life.”

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Previous news

Calipso climbs aboard the train
6th june 2006

Calipso launch preparations
27th april 2006

Calipso ready to go
20th april 2006

Calipso to launch end October
26th september 2005

Calipso satellite arrives in the United States
3rd june 2005