Problems with Juno’s engines change Jupiter mission plans

A maneuver designed to reduce the Juno spacecraft’s orbit around Jupiter from 53.4 days to 14 days has been postponed due to issues with a pair of helium check valves in the probe’s primary engine which are part of its fuel pressurization system, NASA officials have announced.

According to Engadget and Ars Technica, mission control personnel at the US space agency’s Jet Propulsion Laboratory (JPL) in Pasadena, California entered a series of commands late last week when they discovered via telemetry that the valves were not functioning correctly.

“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,” Rick Nybakken, Juno project manager at JPL, explained in a statement. “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.”

As a result, the orbital period reduction maneuver that had been scheduled to take place on Oct. 19 has been postponed for one orbital cycle, meaning that the maneuver will not take place until at least Dec. 11 – which likely means that Juno will not be able to complete the 36 flybys of the gas giant that it was originally schedule to perform over the next 20 months.

Scientific observations should not be affected, according to NASA

The maneuver’s postponement has also spurred NASA officials to make other changes to the spacecraft’s schedule. While mission planners originally intended to limit the number of science instruments being used during the Oct. 19 flyby of Jupiter, the plan now is to have the entire suite gathering data as it orbits the gas giant, JPL noted.

“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, Juno principal investigator at the San Antonio-based Southwest Research Institute (SwRI). “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.”

The period reduction maneuver is scheduled to be the final firing of the spacecraft’s main Leros 1b engine, which propelled it from its Aug. 5, 2011 launch through its arrival at Jupiter on July 4. Once the maneuver is complete, Juno will be powered by small, onboard thrusters for the rest of its mission, during which scientists hope to better understand the origins of the gas giant, map its magnetic field, observe its auroras and search for a potentially solid planetary core.

In late August, the probe successfully executive the first of its planned orbital flybys, capturing and beaming back the first-ever images of Jupiter’s north pole. Those images, NASA explained in a press release issued in September, revealed that the region was home to storm systems and weather activity unlike anything ever seen around a gas giant in our solar system.

“First glimpse of Jupiter’s north pole, and it looks like nothing we have seen or imagined before,” Bolton said at the time. “It’s bluer in color up there than other parts of the planet, and there are a lot of storms. There is no sign of the latitudinal bands or zone and belts that we are used to – this image is hardly recognizable as Jupiter. We’re seeing signs that the clouds have shadows, possibly indicating that the clouds are at a higher altitude than other features.”


Image credit: NASA