Amy Svitak London and Paris and Frank Morring, Jr. Washington

After a Taurus XL launch vehicle failed to loft the Orbiting Carbon Observatory (OCO) in February 2009, NASA used another Taurus XL to launch the Glory climate-monitoring spacecraft despite a recommendation from its own engineering safety office to ground the Orbital Sciences Corp. rocket until key components could be requalified.

The agency accepted a risk of a similar mishap on the March 2011 launch attempt that was calculated as high as 50%, a gamble that resulted in the loss of the $424 million mission when the vehicle's payload shroud once again failed to open and pulled the satellite into the ocean off Antarctica.

Since then, NASA has decided against using a Taurus XL to launch the replacement OCO-2 mission. Other Orbital vehicles, including the air-launched Pegasus and a new Antares rocket, use a version of the same fairing separation system that is most likely responsible for the combined $700 million loss of two key climate-study satellites. Orbital's original name for Antares was Taurus II.

So far, NASA has not accepted the Antares shroud-separation configuration for operational flights. Dulles, Va.-based Orbital says it has made a number of changes to its frangible joint fairing separation system in the wake of the Glory launch failure, including modifications to the frangible rail used on Antares. The company is developing that rocket under NASA's Commercial Orbital Transportation Services (COTS) program to carry cargo to the International Space Station (ISS).

The findings of a Glory Mishap Investigation Board review reached NASA headquarters in September 2011, but a public version will not be released until early next year. William Gerstenmaier, NASA's associate administrator for Human Exploration and Operations (HEO), says the failure analysis could not identify a root cause of the Glory accident, though investigative teams continue to explore possible root causes.

In the meantime, the fairing-separation system that currently equips Pegasus and Taurus—and which is planned to fly on Antares next year—has yet to be fully qualified, an issue that came to light in May 2010 when the NASA Engineering and Safety Center (NESC) recommended grounding the Glory mission until the frangible joint system could be sufficiently certified.

“The team recommends that the Glory mission not fly until the frangible joint system is adequately qualified per existing project requirements for its intended-use environments,” NESC stated in a May 27, 2010, report on its investigation into Taurus XL and other Orbital launchers that use similar frangible joint systems.