The final firing of Juno’s main engine will have to wait. On Friday, NASA announced the period reduction maneuver is being postponed after an issue with two helium check valves was identified.

A command was sent to open two helium check valves last Thursday. Usually, these valves open within a few seconds. But for some reason, it took several minutes. “We need to better understand this issue before moving forward with a burn of the main engine,” said Juno project manager Rick Nybakken.

Nybakken says the pair of valves plays “an important role in the firing of the spacecraft’s main engine.”

The delay will last for at least one orbit. The next opportunity to shrink Juno’s orbit comes on December 11th.

Juno’s mission will continue

While the delay is giving folks on the Juno team a headache, the mission will go on no matter what. Juno’s engine already did the hard part. Getting into Jupiter’s orbit.

Scott Bolton, principal investigator of Juno, explains the orbital period doesn’t affect the quality of science. Quantity? Sure. We’ll just have to wait a little longer for the jaw-dropping images. “The mission is very flexible that way,” says Bolton. “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.”

Wednesday’s flyby could be even better. Juno’s team initially planned to keep several science instruments switched off during this week’s close flyby. But since the main engine won’t be firing, all science instruments will be trained on Jupiter as it soars just a few thousand miles above the gas giant’s cloud tops.

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Those looking for awesome images will want to tap the brakes a little longer. I know we haven’t seen the stunning images New Horizons spoiled us with. But remember, Juno is conducting its mission over a series of flybys. Not just one. Many of the instruments aboard Juno were switched off during its short time at Jupiter as the Juno team worked to finalize the spacecraft’s orbit. With all instruments being on this week, we should see a few more images soon. Then we wait as the spacecraft takes another 50 odd days to get close to Jupiter again.

Also, JunoCam (the camera giving us spectacular images) will snap the best images during specific orbits. Some of the orbits are designed specifically for Juno’s Microwave Radiometer (MWR). Others are designed for Juno’s gravity science (GRAV) experiment.

MWR orbits will produce the best images of Jupiter. Juno will be oriented with the gas giant directly below and in a perfect position for JunoCam. For GRAV orbits, Juno will be pointed towards Earth to allow real-time downlinking. Great for science. Not so great for cool images.

The final burn delay raises questions

How does the delay affect the number of flybys? That’s the big one for me. Juno was expected to conduct 32 science orbits. NASA didn’t say how the delay would affect that final number.

According to the Juno press kit, the spacecraft will execute a deorbit burn on orbit 37. On February 20, 2018, Juno will fall into Jupiter’s atmosphere and burn up.

Hopefully, Juno engineers can figure out the issue by the time December 11th rolls around. Until then, we wait to see what kind of images JunoCam snaps on Wednesday.

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