NASA's Juno spacecraft develops engine problems

Two valves failed to open when they should, and will be studied before the engine is next fired

NASA's Juno probe has developed engine troubles as it orbits Jupiter, leading to a delay in part of its mission.

According to a press release from the US space agency, the probe developed an issue in a set of valves that make up part of the spacecraft's fuel pressurisation system.

"Telemetry indicates that two helium check valves that play an important role in the firing of the spacecraft's main engine did not operate as expected during a command sequence that was initiated yesterday," said Rick Nybakken, Juno project manager at NASA's Jet Propulsion Laboratory in Pasadena, California.

"The valves should have opened in a few seconds, but it took several minutes. We need to better understand this issue before moving forward with a burn of the main engine," he added.

The probe was scheduled to fire its engines on Wednesday 19 October in order to decrease its 'orbital period', the time it takes to orbit the gas giant, from 53.4 to 14 days.

This engine burn can only happen at certain times however, if it is to be efficient. According to the release, the best time to perform such a burn is when the spacecraft is at the part of its orbit which is closest to the planet. The next opportunity for the burn will be during its close flyby of Jupiter on 11 December.

Before the engine problems had been discovered, the plan was for this part of the mission to utilise only some of the probe's scientific instruments, but perhaps fearing further failures, NASA has now decided that all instruments will be used to examine Jupiter after its next engine burn.

Experts remain hopeful that the mission will still prove successful.

"It is important to note that the orbital period does not affect the quality of the science that takes place during one of Juno's close flybys of Jupiter," said Scott Bolton, principal investigator of Juno from the Southwest Research Institute in San Antonio.

"The mission is very flexible that way. The data we collected during our first flyby on August 27th was a revelation, and I fully anticipate a similar result from Juno's October 19th flyby."