The French space agency, CNES, and prime contractor Alcatel Alenia Space have modified some manufacturing techniques for the Proteus satellite platform in response to NASA safety concerns, according to CNES officials.

 But these officials also defended the soundness of the platform's original design, and said they regret some of the conclusions of a NASA safety review conducted in preparation for the recent launch of the Calipso cloud-monitoring satellite. The review raised questions about CNES' cooperativeness with the safety inquiry.

CNES's Calipso satellite and NASA's CloudSat spacecraft were launched April 28 aboard a Boeing Delta 2 rocket from Vandenberg Air Force Base, Calif. Calipso was built by CNES using a Proteus platform produced by Alcatel Alenia Space.

The launch had been scheduled for mid-2005. NASA concerns that the Proteus platform's hydrazine fuel tanks could leak and pose a danger to satellite integration teams prompted a detailed review of the system by the NASA Engineering and Safety Center (NESC). The center's 181-page report criticized CNES for being slow in providing detailed documents relating to the hydrazine tanks' test procedures and other aspects of the Proteus platform.

Calipso's platform is identical to the one flying aboard the U.S.-French Jason-1 satellite, launched by a Delta 2 rocket in 2001.

The NESC was created in the aftermath of the loss of the Space Shuttle Columbia Feb. 1, 2003, to provide an independent technical review facility for NASA project managers. The Calipso review was requested by NASA's Goddard Space Flight Center, Greenbelt, Md., following concerns that hydrazine could leak from the mechanical fittings that are used instead of welding to hold certain propellant-tank components together.

The two-month review concluded the CNES design was solid and should be cleared for launch. But the document also says CNES was slow to provide information about its designs, and that some of the information provided was incomplete.

"[K]ey CNES information requested for this assessment was not provided," the NESC report says. "There was clearly confusion over certain safety requirements among the organizations involved in Calipso."

Philippe Goudy, CNES deputy director for orbital systems, said CNES was surprised to read the NESC conclusions - both because CNES officials had not been invited to comment on the report before its publication, and because CNES believed it had fully cooperated with its NASA partners.

"We had had several letters [from NASA] saying that the Jason-1 waivers applied to Calipso," Goudy said in an April 24 interview. "Safety is a concern for everyone, and among the major space agencies, the same rules apply in general."

Goudy also said that in those cases in which CNES did not provide information the NESC requested, it was because the information was not in CNES' possession. In addition, he said, CNES as a rule dealt with NASA's Calipso project team, which in turn interacted with NESC. "The NASA project team told us that the minor differences between the two agencies [relating to hydrazine-tank assembly] would be subject to a waiver. They ran the dialogue with NESC."

Goudy and CNES President Yannick d'Escatha said in separate interviews that CNES did not withhold information because of technology-transfer concerns or to protect industrial secrets. Goudy said NASA and NESC personnel visited the Proteus assembly facility at Alcatel Alenia Space's Cannes, France, site. The U.S. delegation during the visit had access to all the information it wanted, he said.

In part because of the launch delays - which had nothing to do with the Calipso satellite or the Proteus platform - Calipso's hydrazine tanks remained filled and in storage at the Vandenberg launch site for some 200 days - far longer than forecast.

CNES officials said no leaks were recorded by the electronic "sniffers" stationed near the satellite to detect hydrazine.

CNES and Alcatel Alenia Space nonetheless have decided to weld certain hydrazine tank segments in the future, in particular for the Jason-2 satellite, to be launched in 2008 aboard a Delta 2 rocket.