The failed launch of a scientific satellite last week has triggered an investigation by the National Aeronautics and Space Administration (NASA) to figure out exactly what went wrong. The Mishap Investigation Board is studying the abortive launch of the Orbiting Carbon Observatory (OCO) on Feb. 24.
The OCO, a climate satellite intended to take carbon dioxide (CO2) and oxygen (O2) readings in the atmosphere, crashed into the ocean near Antarctica only a few minutes after its liftoff from the Vandenberg Air Force Base in California.
Currently, the failure to reach orbit is being attributed to the fairing, described on NASA's Web site as "a clamshell structure that encapsulates the satellite as it travels through the atmosphere."
The Taurus XL, the launch vehicle for the OCO, is a four-stage rocket, meaning that its engines are ignited four times. During the third stage, the fairing is supposed to separate (like a clamshell) and fall away. This gives the rest of the rocket a burst of acceleration since the fairing is extremely heavy compared to the other parts of the vehicle.
During the OCO's launch, though, the fairing failed to separate. This prohibited the satellite from reaching its orbit because, though the third and fourth stages were successfully completed, the vehicle was carrying excess weight and therefore could not accelerate as much as was necessary.
Approximately three minutes into the flight, the vertical portion of the fairing is signaled to separate by four pulses, two primary and two redundant. Eighty milliseconds later, the base of the fairing receives four similar pulses. These steps in the sequence all appear to have gone according to plan.
"We have confirmation that the correct sequence was sent by the software. We had good power going into this event and we also had a healthy indication of our electronics box that sent the signal," Project Manager for the Taurus rocket program John Brunschwyler said. At the moment it is unclear why the fairing failed to respond.
The Taurus XL was manufactured by the Virginia-based Orbital Sciences Corporation. Since its construction in 1994, the Taurus XL has successfully completed six out of its eight missions and has put 12 satellites into orbit.
Its other failure occurred in 2001 when the second stage fuel tank rotated so that it was perpendicular to the flight path. This caused a temporary drop in acceleration that could not be overcome, even after the tank had righted itself.
Though the two satellites the Taurus XL was carrying were successfully deployed (and there were no problems with the fairing), they never reached their target orbits and seemed to be lost in space, until they were determined to be lost in the Indian Ocean.
Coincidentally, one of the two satellites the Taurus XL was carrying during its failed launch in 2001 was a NASA probe for studying the ozone layer.
The OCO mission cost more than $270 million and was intended to collect valuable data about CO2 and other forms of carbon in the atmosphere. Currently, the carbon cycle is not completely understood.
The failure of the OCO mission has implications for NASA's Glory satellite, which will also collect data about climate and the environment, and which is currently scheduled to use a Taurus rocket for launch in October.
