French researchers said the five-member “A-Train” caravan of U.S. and French satellites studying the Earth’s atmosphere is delivering on its promise but is at risk of not being pursued further because it is no longer in the technology-innovation phase and

has not yet been endorsed by agencies responsible for providing operational weather and environmental services.

Officials said that 19

months into its mission, the A-Train has been operating without a major hitch despite the unusual

coordination required between the U.S. and French space agencies.

Orbiting at an altitude of 705 kilometers, the A-Train is led by NASA’s

Aqua spacecraft and followed, in the same orbit, by the U.S.-Canadian Cloudsat, the U.S.-French Calipso, the French Parasol and NASA’s Aura satellites.

A span of eight

minutes separates the first satellite from the fifth, and Cloudsat flies just 15 seconds ahead of Calipso. Ground teams must ensure that software uploads or other routine maintenance done on any one of the satellites is coordinated closely with the teams monitoring the others.

“If one instrument moves, the others have to take account of that,” said Didier Tanre of the French Institute for Sciences and the Universe (INSU), a principal investigator for the Parasol satellite. “We’d like to avoid being the ones who caused the first space accident in which CNES is involved.”

and other A-Train science managers spoke here Nov. 27 during a press briefing organized by the French space agency, CNES. They said indications are that all five satellites will exceed their nominal service lives.

The A-Train’s mission of assessing the components of aerosols

and cloud droplets

in the atmosphere inhabits a no-man’s land between applied science and the current borders of operational meteorology and environmental studies.

As is the case with the Jason series of U.S.-French ocean-monitoring satellites, assuring an A-Train follow-up mission is of little interest to CNES or NASA insofar as both agencies believe they should remain on the frontier of technology and steer clear of building recurrent models of the same satellite.

The Jason missions have secured at least medium-term funding via

support from both the French and U.S. navies, and from the U.S. and European meteorological organizations.


thus has emerged from what Didier Renaut, a manager of CNES Earth observation programs, said is known as the “valley of death,” a period during which successful missions lose the support of their original sponsors without having secured fresh financial backing.

That is where the A-Train is at the moment. “There is no current follow-on for A-Train, which is likely to end its mission in 2011,” Renaut said. “As is true for other space agencies, CNES’s policy is to focus on technological innovation, not to build the same instrument several times over.”

There is some overlap between A-Train’s measurements and two other missions being planned in Europe – ADM-Aeolus satellite, to be launched in 2009, and the Euro-Japanese EarthCARE satellite, scheduled for launch in 2012.

Jacques Pelon, co-principal investigator on the Calipso satellite, said ADM-Aeolus will measure fewer parameters in the atmosphere but will offer at least some data continuity to researchers working with A-Train data.