Juno development, launch, and cruise, Including Earth flyby imaging Oct 9 2013 Options

[Paolo]

from NASA's Juno site:

Juno's first deep space maneuver took place Aug. 30. The maneuver, as planned, changed the spacecraft's velocity by about 770 mph (344 meters a second) and lasted 29 minutes 39 seconds. Upon review of mission data following the burn, the team determined that although the first maneuver was completely successful, one of the propellant pressures within the spacecraft's propulsion system was higher than expected. The team has decided to take an extra 10 days to analyze this increase and consider mitigation options, placing the second deep space maneuver on Sept. 14. There will be no impact to the mission's timeline or science.

[B Bernatchez]

Second DSM executed successfully.

http://www.nasa.gov/mission_pages/juno/new...no20120914.html

Link fixed - admin

[Paolo]

more details on the second burn
http://www.nasa.gov/mission_pages/juno/new...no20120917.html

[propguy]

Sorry I have not posted lately, but I have been laid up (crashed my road bike and broke both my clavicle and scapula). The burn went nearly perfect (missed the predicted burn time by only 1.7 seconds). Now we are on track for Earth Fly By in Oct 2013. Have burned ~45% of the loaded propellant, so right on plan. Nav says closest approach will be near South Africa (no idea how firm this is, so don't book your travel yet). The concern the program had after DSM1 (that caused the DSM2 delay to assess the impacts) did not reoccur, so no anomalies during burn. Go Juno!

[Explorer1]

Are there any plans for any activity during the flyby (imaging, other burns, etc.)?

[Paolo]

thank you for the update Propguy, and heal fast!
do you have any details on the "anomaly" that caused the second burn to be delayed and that you can share with us?

[propguy]

Are there any plans for any activity during the flyby (imaging, other burns, etc.)?

While I work spacecraft ops not instruments, there definitely are plans to use the instruments before, during, and after EFB. The ops plan says they will focus on a 11 days period straddling EFB (just like one science orbit). Note though that one of the main instruments MWR will have limited use as EFB since terrestrial microwave radiation could damage the instruments. We had to be very careful in ATLO to protect MWR.

[propguy]

thank you for the update Propguy, and heal fast!
do you have any details on the "anomaly" that caused the second burn to be delayed and that you can share with us?

It is always difficult to answer questions without dumping too much data and boring folks (and also violating export control rules either). Never the less here is my try. At the end of DSM1 when we closed the liquid latch valves to isolate the main engine, on one of the propellant legs the pressure rose higher than we expected. This pressure was not above anything the system had not been already tested to, but it was an issue in the otherwise perfect burn. We changed the sequence to lower that section of line's temperature control point to avoid excessive pressures after engine shutdown. This new sequence worked great. Just one of the things you get when you use a new propulsion system design for the first time.

[climber]

Yep, better crash a bike! I hope you'll recover fast

[B Bernatchez]

It is always difficult to answer questions without dumping too much data and boring folks

ITAR issues aside, you'd be hard pressed to bore people on THIS forum.

[nprev]

ITAR issues aside, you'd be hard pressed to bore people on THIS forum.

Hear, hear!!! Propguy, please feel free within of course the constraints of ITAR and proprietary information...we love it!!!

[Paolo]

thanks for the info Propguy!

[Doug M.]

Eyeballing Juno's trajectory over at Space101, it looks like Juno is either just at, or just past, aphelion for this orbit. It's currently about 2 au from the Sun, which puts it just inside the inner edge of the main asteroid belt. So now it'll start falling inward for its October 2013 rendezvous with Earth. It'll cross Mars' orbit in April, cross Earth's orbit in July, and reach perihelion at 0.88 au at the end of August. There are three planned Trajectory Correction Maneuvers somewhere in there. (Is there any difference between a Trajectory Correction Maneuver and a Deep Space Maneuver? It's just a question of where each one takes place, right?)

Apparently the Earth flyby is scheduled for October 9, with a closest approach of 541 km. The lowest pass is currently scheduled to be over SW Australia, though that's subject to some fine tuning. It'll be at 1400 GMT, which would be about 11 pm Sydney time.

Which leads to a question: has anyone calculated Juno's apparent magnitude at closest approach? I'm wondering if our friends in Australia will have a chance to see it (assuming clear skies and so forth).


Doug M.

[gwiz]

Is there any difference between a Trajectory Correction Maneuver and a Deep Space Maneuver? It's just a question of where each one takes place, right?

My impression is that a DSM is intended to alter the trajectory into a new one, while a TCM is intended to bring the trajectory back to the target one.

[propguy]

My impression is that a DSM is intended to alter the trajectory into a new one, while a TCM is intended to bring the trajectory back to the target one.

Actually it is simpler than that. The two DSM burns could have been called TCM 3 & 4 (and infact there are no TCM's with those names) but to point out that it is a large manuever the names were changed to be DSM 1 & 2. Large manuevers use the bipropellant system, whereas all others use the monopropellant thrusters. The only two others uses of the bipropellant system are the JOI and PRM manuvers.