[China Instrument Network Instrument Development] The NASA "Juneau" Jupiter Detector entered Jupiter's orbit around July 4, 2016 and will continue to operate in follow-up missions. The current cycle is 53 days. The orbit around the track, instead of the original planned cycle of 14 days, still fulfills the scientific goal of this mission. The main reason for NASA to make this decision is to avoid the risk of ignition of its engine used to reduce the orbital altitude.
As of now, "Juneau" has successfully circled Jupiter 4 laps and carried out exploration. It will begin the 5th overflight detection on March 27.
Since the distance from Jupiter is the same when each probe of "Juneau" is over, the orbital period will not affect the quality of the scientific results obtained. On the contrary, the long-period orbit enables Juno to detect the far side of Jupiter's magnetic field and enrich the detection results.
"Juneau" originally planned to follow-up exploration missions on the 14-day orbit after two cycles on the 53-day orbit. However, when "Juneau" pressurized the propulsion system in October 2016, the main engine's two check valves malfunctioned, failing to turn on for a few minutes as expected, and shutting off after the main engine was fired for a few seconds.
After a thorough inspection, NASA proposed multiple plans to reduce the orbital period. However, it is believed that the ignition of another main engine may not allow Juno to enter the expected orbit, and concluded that "engine ignition is the realization of the 'Juno' scientific goal. risks of".
The 53-day cycle has enabled Juno to achieve "additional scientific achievements." "Juneau" will probe the far side of Jupiter's magnetosphere (the space affected by Jupiter's magnetic field), including the magnetic tail, the southern end of the magnetic layer, and the magnetic top layer. One of the key scientific issues that the NASA Solar Physics Science Department (HSD) is concerned with is "understanding magnetic layers and their interaction with the solar wind."
Another advantage of the long-period orbit is that it reduces the time during which Juno is affected by Jupiter's strong radiation band during orbital operations, and radiation is the main reason that affects the life of Juno.
According to the current budget plan, "Juneau" will run until July 2018, orbiting Jupiter on 12 occasions. After that, NASA will evaluate the probe results that "Juneau" has achieved and is expected to obtain, and determine whether to expand the "Juneau" mission.
The "Juneau" scientific team analyzed the data obtained so far and found that Jupiter's magnetic field and auroras are larger and stronger than previously thought. The JunoCam camera carried by Juno will also determine the shooting target based on public voting results during each flight.
(Original title: NASA Project "Juneau" Jupiter Detector Continues to Run on Long-Range Surrounding Tracks)