Juno update: 53.5-day orbits for the foreseeable future, more Marble Movie
Posted By Emily Lakdawalla
03-11-2016 9:44 CDT
Juno suffered two setbacks in October. First, a problem with check valves in the main thruster system prevented a planned rocket burn during its October 19 close pass by Jupiter. The science team raced to use the burnless perijove pass to do some science, but then the spacecraft went into safe mode on October 19, before perijove, and before the science sequences could kick in. Juno exited safe mode on October 24 and performed a half-hour burn with its maneuvering thrusters -- not its main thrusters, which were still not being used, pending the outcome of the investigation into the check valve problem. An article at Spaceflight Now goes into much more detail about the investigation into both engine problem and safing event.
At the DPS/EPSC meeting last week, principal investigator Scott Bolton spoke about keeping Juno in its long, 53.5-day orbit for a long time, not ruling out the possibility of performing the entire mission in such an orbit. Juno only gets exposed to dangerous radiation when very close to Jupiter, so the spacecraft wouldn't be exposed to any additional radiation by doing this, though it would seriously prolong the mission. If the mission has not ended by September 2019, Jupiter will have traveled far enough around the Sun that Juno will pass into Jupiter's shadow for several hours on every orbit, a condition that it was not designed for and which could harm its power system; the mission would need to develop a solution to that problem.
At present, the future orbital path of Juno is still uncertain. For the time being, it will stay in its 53.5-day orbit. According to JunoCam team member Glenn Orton, the next planned perijoves in that orbit would be:
|Perijove||Date/time (UTC, SCET)||longitude of equator|
crossing (System III)
|PJ2||2016 Oct 19 18:12:01||348.83 deg W|
|PJ3||2016 Dec 11 17:05:08||7.03 deg W|
|PJ4||2017 Feb 2 12:59:12||277.00 deg W|
|PJ5||2017 Mar 27 08:53:20||187.00 deg W|
|PJ6||2017 May 19 06:01:51||142.00 deg W|
|PJ7||2017 Jul 11 01:55:56||52.00 deg W|
|PJ8||2017 Sep 1 21:50:01||322.00 deg W|
|PJ9||2017 Oct 24 17:44:04||232.00 deg W|
|PJ10||2017 Dec 16 17:58:48||299.50 deg W|
|PJ11||2018 Feb 7 13:53:23||209.50 deg W|
|PJ12||2018 Apr 1 09:47:24||119.50 deg W|
|PJ13||2018 May 24 05:41:25||29.50 deg W|
|PJ14||2018 Jul 16 05:18:44||74.50 deg W|
|PJ15||2018 Sep 7 01:13:46||344.50 deg W|
|PJ16||2018 Oct 29 21:07:49||254.50 deg W|
|PJ17||2018 Dec 21 17:01:52||164.50 deg W|
|PJ18||2019 Feb 12 17:36:13||243.25 deg W|
|PJ19||2019 Apr 6 13:30:13||153.25 deg W|
|PJ20||2019 May 29 09:24:18||63.25 deg W|
|PJ21||2019 Jul 21 05:18:43||333.25 deg W|
|PJ22||2019 Sep 11 20:14:43||61.87 deg W|
At any perijove, of course, they could decide to go ahead and shift Juno to a shorter orbit with a main engine burn -- we'll just have to wait and see.
In the meantime, JunoCam imaging scientist Candy Hansen told me that the camera has not been turned on since the sticky-valve problem reared its head, and will not be turned on until perijove 3, on December 11. I've now updated my Marble Movie index page with all the JunoCam images received on Earth to date. Below is the near-final version of the JunoCam Marble Movie, covering July 10 through October 14, 2016, between perijoves 0 and 2; all that is missing is the extra-close frames of perijove 1.