Discussing Juno/JunoCam Mission and Jupiter Data

[Clever Penguin]

I hope we find out what the core is made of.

 

[1oldman2]

I hope we find out what the core is made of.

I'm not sure if the actual material will be determined however I believe the main focus there is determining whether or not it's solid. I'll look into that and see what they are expecting to find.

 

[1oldman2]

how does Juno navigate

I've asked the folks at JPL in an email which I may or may not get a response to, I'll keep you posted if a response is forthcoming. The only information readily available is the line about uploading commands for the insertion maneuvers about a week before arrival. It could be that the actual navigation to Jupiter has become so routine that JPL doesn't take time to mention the details, all I see so far is the mention of certain "deep space maneuvers. One things for certain they are getting very good at ending up in the "right place at the right time"

 

[D H]

I'm not sure if there is any secrecy, why would there be?

See page 4 of this briefing by the Software Engineering Institute, who apparently were validating parts of the Juno flight software. It's "export controlled and proprietary." JPL used to be much more open in the past. If they had their druthers, I suspect they would now classify $\mathbf F=m\mathbf a$ as Secret//NOFORN.

 

[D H]

I believe things will be a little slow while Juno completes the first two orbits.

That's correct. We should expect to see some stuff after the closest approach (perijove) on August 27, but then not much until November 2. All scientific instrumentation will be turned off for the October 20th closest approach, just as it was for orbit insertion. Patience is a virtue here. The science starts in early November.

JunoCam is not one of the primary scientific instruments on this spacecraft . The mission will be declared a complete scientific success if JunoCam fails early but all of the other scientific instruments work as good or better than expected. On the other hand, JunoCam is the primary public outreach instrument on this mission. The public will not look highly on JunoCam failing early. So, break a leg, JunoCam!

Because it is primarily for public outreach rather than science, the JunoCam data will not be treated in a manner similar to other recent missions (*cough* Kepler *cough*) where the data have been held closely until the principal investigators have a chance to sift through the data first and publish papers. The JunoCam data will instead be automatically released shortly after being received and processed.

 

[The Bill]

Approximately what will Juno's orbital speed be at periapsis of its science orbits?

 

[dragoneyes001]

37 orbits at about 23 days each how much time will they be active in close orbit? 1-2 days per? what's surprising me is the lack of a new planetary pic from the first close pass from Jul 4th everything I've seen so far are renderings.

 

[Dotini]

I found this interesting tidbit on todays's edition of spaceweather.com. Jupiter's magnetosphere and moons have some amazing properties to be explored. Let's get going.

RADIO BEAMS FROM JUPITER HIT EARTH: Yesterday, a series of narrow radio beams from Jupiter reached Earth ... but they weren't from NASA's Juno spacecraft . They came from Jupiter itself. Natural radio lasers in Jupiter's magnetosphere send shortwave signals into space and occasionally they sweep past Earth. "I picked them up in broad daylight," says Thomas Ashcraft, who operates an amateur radio telescope in rural New Mexico. Click on the image to hear the static-y sounds that emerged from his loudspeaker:

Each pop and click is the sound of a single beam washing over our planet. "The interesting thing to me," says Ashcraft, "is that unbeknownst to us Jupiter radio beams are often sweeping over us, actually washing over our bodies if we are outside at the time."

The lasers are powered, in part, by electrical currents flowing between Jupiter's upper atmosphere and the volcanic moon Io. When the geometry is just right, and Earth is in line with the beams, they are easily detected by ham radio antennas on Earth. Jovian "S-bursts" (short bursts) and "L-bursts" (long bursts) mimic the sounds of woodpeckers, whales, and waves crashing on the beach. Here are a few audio samples: http://radiojove.gsfc.nasa.gov/observing/samples/sbursts1.wav, http://radiojove.gsfc.nasa.gov/observing/samples/sbursts1_slowed.wav (slowed down 128:1), http://radiojove.gsfc.nasa.gov/observing/samples/lbursts1.wav

Now is a good time to listen to Jupiter's radio storms. The giant planet is high in the sky at sunset and, thanks to the crashing solar cycle, background noise is low. There are few solar radio bursts to overwhelm Jupiter and terrestrial stations are having a hard time bouncing over the horizon as ionizing radiation from the sun ebbs. Ready to start taking data? NASA's Radio Jove Project explains how to build your own receiver.

 

[1oldman2]

Approximately what will Juno's orbital speed be at periapsis of its science orbits?

I'm not finding that info anywhere yet, but will watch and post if I do. I have read the close aspect of the orbit is actually very brief, in the neighborhood of two hours each time so that would make the speed very high considering how much real estate they are covering.

 

[1oldman2]

37 orbits at about 23 days each how much time will they be active in close orbit? 1-2 days per? what's surprising me is the lack of a new planetary pic from the first close pass from Jul 4th everything I've seen so far are renderings.

As far as I can tell JPL plans to be gathering data constantly while in the science orbit phase. While in the "capture orbits' all unnecessary equipment is shut down to free up processing power in case of a glitch, no cam or anything running that is not vital to the control of Juno, thus no imaging or any experiments until science orbits begin, aside from a couple of instrument check outs to make sure the science equipment is functioning normally, no "cam" images are expected until early November. This site is one of the best I've found for mainstream info and are worth bookmarking for the duration of the project. http://www.planetary.org/
http://www.planetary.org/blogs/emily-lakdawalla/2016/07042245-juno-has-arrived.html

 

[1oldman2]

I found this interesting tidbit on todays's edition of spaceweather.com. Jupiter's magnetosphere and moons have some amazing properties to be explored. Let's get going.

Very cool, Your right there is a lot of work to do before deorbit and I'm hoping the radiation doesn't bake Juno earlier than they expect, That is one incredibly energetic system and I expect we are going to learn a lot more about it in the near future. The magnetosphere alone is incredibly powerful (as I was saying the reconnect must be unbelievable). Thanks for the post.

 

[D H]

Approximately what will Juno's orbital speed be at periapsis of its science orbits?

About 56 km/s to 57 km/s. This does not take into account Jupiter's rapid rotation rate (12.6 km/s at the equator) or Jupiter's large equatorial bulge.

Different orbits will have slightly different periapsis distances, by design, from 4200 to 7900 km above the cloud tops. These values, combined with Jupiter's 71492 km equatorial radius, Jupiter's 126686534 km^3/s^2 standard gravitational parameter, and the orbital period of 13.965 days, Kepler's third law, and the vis viva equation yield the above range of periapsis velocities.

37 orbits at about 23 days each how much time will they be active in close orbit? 1-2 days per? what's surprising me is the lack of a new planetary pic from the first close pass from Jul 4th everything I've seen so far are renderings.

The science phase orbits will be 13.965 days long, not 23 days long. That period allows the NASA Goldstone DSN complex to receive data from each and every one of the closest approaches.

There was no science return from the orbit insertion operation because all of the scientific instruments, including JunoCam, were powered off during that extremely critical operation. All of the electrical power and all of the computing power of the spacecraft were dedicated to one task during orbit insertion, and that one task was of course orbit insertion.

 

[1oldman2]

Very good write up here>>> http://www.planetary.org/blogs/guest-blogs/2016/0708-jupiters-clouds-a-primer.html

 

[dragoneyes001]

About 56 km/s to 57 km/s. This does not take into account Jupiter's rapid rotation rate (12.6 km/s at the equator) or Jupiter's large equatorial bulge.

Different orbits will have slightly different periapsis distances, by design, from 4200 to 7900 km above the cloud tops. These values, combined with Jupiter's 71492 km equatorial radius, Jupiter's 126686534 km^3/s^2 standard gravitational parameter, and the orbital period of 13.965 days, Kepler's third law, and the vis viva equation yield the above range of periapsis velocities.
The science phase orbits will be 13.965 days long, not 23 days long. That period allows the NASA Goldstone DSN complex to receive data from each and every one of the closest approaches.

There was no science return from the orbit insertion operation because all of the scientific instruments, including JunoCam, were powered off during that extremely critical operation. All of the electrical power and all of the computing power of the spacecraft were dedicated to one task during orbit insertion, and that one task was of course orbit insertion.

13.6 days then how is it 37 orbits in that total length of time what I was seeing in the orbit simulation was mostly identical orbits with changing angles in relation to the planet i have to have missed something

 

[Hoophy]

This is not meant to be a dig at you, 1oldman2. It is a dig at JPL, Lockheed Martin, and SWRI.

There is no meat in that link. There is no meat, anywhere, on any of the web pages that describe Juno. It's all fluff, no substance. Compare that to the incredible technical details released with regard to the New Horizons mission to Pluto or the Rosetta mission to Churyumov-Gerasimenko. At a $1.1 billion dollar price tag, answering how does Juno navigate should not be hidden in secrecy. I have looked. There is no answer to that question.

http://whqr.org/post/star-trackers-help-juno-find-its-way

"To find the position when you go to deep space, like on Juno, you need to have help," says Jørgensen.

These days the help comes from NASA's Deep Space Network — three large radio antennas in California, Australia and Spain. They receive radio signals from Juno and use those to figure out where the probe is and how fast it's moving.

"That works beautifully for deep space spacecraft ," says Jørgensen. "It's just that it is relatively expensive to track with a big dish antenna, so people have been looking for different ways of navigating, and that's a problem you also can solve with the star tracker."

How exactly does this 'Deep Space Network' determine the position of Juno? Could someone please try to explain this to me?

 

[rootone]

How exactly does this 'Deep Space Network' determine the position of Juno? Could someone please try to explain this to me?

I guess something like conventional triangulation, (the scopes are located at different positions on Earth).
combined with received flight data from the craft, which knows where it is in relation to planets and their moons.

 

[1oldman2]

13.6 days then how is it 37 orbits in that total length of time what I was seeing in the orbit simulation was mostly identical orbits with changing angles in relation to the planet i have to have missed something

The first two orbits are "capture orbits" each having a duration of 53.4 days, this is followed by the science orbits with the roughly 14 day duration.
https://www.missionjuno.swri.edu/ne...t-team-begins-powering-up-science-instruments

 

[dragoneyes001]

The first two orbits are "capture orbits" each having a duration of 53.4 days, this is followed by the science orbits with the roughly 14 day duration.
https://www.missionjuno.swri.edu/ne...t-team-begins-powering-up-science-instruments

ok thanks I was under the impression the captures were already accounted for before the two year-ish science period

 

[1oldman2]

I'm beginning to like the "extended mission" aspect. From http://spaceflight101.com/outline-junos-capture-orbits-around-jupiter/
If everything goes according to plan, Juno will finish the final orbit of the primary mission with perijove on
February 6, 2018. The primary mission is expected to end with a destructive entry into the Jovian atmosphere
on February 20, a date that previously seemed to be set in stone as an extended mission was ruled out for
planetary protection reasons. Newer information shared by the mission team indicates that a mission extension
is at least on the table, pending Juno’s performance in Jupiter’s extreme radiation environment.

 

[1oldman2]

While reading up on the orbital aspect of the mission I came across the mention early in the planning stages of the possible use of orbital tethers, while I can see the polar orbit may not be optimum for power generation, I'm wondering if the tether system might be used for deorbiting the craft at the end of the mission. If anyone comes across info regarding Juno and tethers could they please mention it in a post, I'm not finding anything in the current writings concerning this.
http://www.tethers.com/TT.html?gclid=CODTk-rD6c0CFQ6GaQodSaUNwQ#TermTether
http://www.sciencedirect.com/science/article/pii/S0273117709007546
http://onlinelibrary.wiley.com/doi/10.1029/2011JA016951/full https://www.researchgate.net/publication/258496579_Tether_radiation_in_Juno-type_and_circular-equatorial_Jovian_orbits http://oa.upm.es/23242/1/A90L.pdf
http://adsabs.harvard.edu/abs/2011JGRA..11612226S
http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/44421/1/13-3066_A1b.pdf

Also here is an interesting article on the orbital gymnastics of deep space maneuvers. http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/45612/1/14-2698_A1b.pdf Not much going on aside from an orbital clean up maneuver on the 13th and instrument check out, however I'll post anything new that's of interest.
I would like to thank D H and dotini for the technical info they posted, you guys have much better sources than myself so it's much appreciated.

 

[1oldman2]

From https://www.missionjuno.swri.edu/news/juno_sends_first_in-orbit_view

 

[1oldman2]

A backlit view (not Junocam)

And from http://www.jpl.nasa.gov/spaceimages/details.php?id=PIA20178

I haven't noticed any Juno studies on this, any thoughts?

 

[Clever Penguin]

(SNIP) And from http://www.jpl.nasa.gov/spaceimages/details.php?id=PIA20178
(SNIP)
I haven't noticed any Juno studies on this, any thoughts?

I haven't noticed any Juno experiment designed to look for dark matter.

 

[1oldman2]

I haven't noticed any Juno experiment designed to look for dark matter.

Same here, I don't even know how one would detect it, just thought I'd mention the theory.

 

[Clever Penguin]

Same here, I don't even know how one would detect it, just thought I'd mention the theory.

You would probably need a much larger spacecraft

Here is a detector designed to detect dark matter using xenon, but whether it will work I don't know
http://phys.org/news/2015-12-results-world-sensitive-dark-detector.html

 

[lpetrich]

Some pages on spacecraft navigation:

The Navigators: How We Fly Spacecraft Around the Solar System - Universe Today
How do space probes navigate large distances with such accuracy and how do the mission controllers know when they've reached their target? - Scientific American
Basics of Space Flight Section II. Space Flight Projects
Spacecraft Navigation

There are several sorts of data that spacecraft navigators use.

• Pictures of the spacecraft . That's mainly useful in low Earth orbit. It gives the spacecraft 's direction relative to the stars from the observation site.
• Radio ranging. A round trip of a signal gives the spacecraft 's distance.
• Radio range rate. Doppler shift of the signal frequency gives the spacecraft 's radial velocity.
• Radio ranging with receivers in different positions, like on different continents. The relative arrival times and radial velocities can be combined to find the spacecraft 's direction.
• Optical navigation. The spacecraft takes an overexposed picture of a nearby celestial body, the overexposure being for seeing stars in nearby directions. This gives the body's direction, and if the body was resolved, its distance.

They then compare their data with their calculated positions and velocities for the spacecraft , and improve their calculations with it.

For doing the calculations, they typically do numerical integration, though analytic approximations are often good starting points. Approximations like the Newtonian two-body problem. For going from the Earth to Mars, one starts with geocentric calculations, then switches to heliocentric calculations for most of the trip, then switches to areocentric calculations at Mars.

They have to take into account not only celestial bodies' gravity, but also the pressure of sunlight and the solar wind. But they have gotten very good at that, and they also maintain very precise ephemerides, tables of the celestial bodies' positions. One can use spacecraft navigation data as inputs for those also.

 

[lpetrich]

One can get not only planets' masses with spacecraft , but also planets' departures from sphericity. Planets' equatorial bulges pull on spacecraft , and this causes their orbits to precess. How much precession gives how much material is in the bulge, and that in turn gives clues as to the planets' internal structures. One can get more fine-grained gravity data in this way, data that revealed the presence of mass concentrations or "mascons" in the Moon.

However, such gravity data is essentially 2D and not 3D, so it has limits.

A planet's gravitational field can be given by a multipole expansion, where one finds the expansion's coefficients. One then finds those coefficient values from how the planet fields affect spacecraft orbits.

$$V = - \frac{GM}{r} \left( 1 - \sum_{l=2}^\infty J_l \left( \frac{R}{r} \right)^l P_l(\hat r \cdot n) \right)$$

for mass M, equatorial radius R, spin-axis direction n, and Legendre polynomials P. There are additional terms with variation in the azimuthal coordinate.

One of the purposes of the Juno mission is to try to get improved values of Jupiter's gravity's multipole coefficients. These values can then be compared to the results of internal-structure calculations.

 

[1oldman2]

Awesome posts ! Thanks.

 

[1oldman2]

The first raw images have been released, If anyone is planning on using the processing aspect of Junocam this might be good practice. they can be downloaded at. https://www.missionjuno.swri.edu/media-gallery/jupiter-approach

 

[dragoneyes001]

like the first pic from juno just one question being out in space without any light wouldn't the star field be super visible in the background?

 

[OmCheeto]

like the first pic from juno just one question being out in space without any light wouldn't the star field be super visible in the background?

From my experience of the Dawn mission photographing Ceres, my guess is no.
The only time I remember seeing stars was from a composite image.

Good question though.
I asked the same thing last year about Ceres, and got the following response:

June 4, 2015
Marc Rayman, director and chief engineer for NASA's Dawn mission; "... For the approach phase images, we used two different camera integration times (what most people call exposure times). One value was chosen to ensure Ceres was correctly exposed and the other was chosen to bring out the background stars. The images alternate, so we interpolate to get Ceres' location relative to stars. ..."​

[ref: PF]

Ah ha! Just found the explanation of the image I was referring to.

But, I'm afraid I'm not much of an astronomer, so I don't quite understand how "apparent magnitude" works.
Does Jupiter get brighter as you get closer?

Anyways, here's a list of the "apparent magnitude" of Jupiter and the 4 brightest stars:

Jupiter at brightest: -2.7
Sirius: -1.46
Canopus: -0.72
Rigil Kentaurus: -0.27
Arcturus: -0.04​

My guess is, that Sirius would probably show up, if the camera were pointed in the right direction.

 

[dragoneyes001]

From my experience of the Dawn mission photographing Ceres, my guess is no.
The only time I remember seeing stars was from a composite image.

Good question though.
I asked the same thing last year about Ceres, and got the following response:

June 4, 2015
Marc Rayman, director and chief engineer for NASA's Dawn mission; "... For the approach phase images, we used two different camera integration times (what most people call exposure times). One value was chosen to ensure Ceres was correctly exposed and the other was chosen to bring out the background stars. The images alternate, so we interpolate to get Ceres' location relative to stars. ..."​

[ref: PF]

Ah ha! Just found the explanation of the image I was referring to.

But, I'm afraid I'm not much of an astronomer, so I don't quite understand how "apparent magnitude" works.
Does Jupiter get brighter as you get closer?

Anyways, here's a list of the "apparent magnitude" of Jupiter and the 4 brightest stars:

Jupiter at brightest: -2.7
Sirius: -1.46
Canopus: -0.72
Rigil Kentaurus: -0.27
Arcturus: -0.04​

My guess is, that Sirius would probably show up, if the camera were pointed in the right direction.

thanks

 

[1oldman2]

From my experience of the Dawn mission photographing Ceres, my guess is no.
The only time I remember seeing stars was from a composite image.

Hi Om, Marc pretty well described what's going on in the paragraph quoted from your link,
"Ceres is the bright spot in the center of the image. Because the dwarf
planet is much brighter than the stars in the background, the camera team
selected a long exposure time to make the stars visible. The long exposure
made Ceres appear overexposed, and exaggerated its size; this was
corrected by superimposing a shorter exposure of the dwarf planet in the
center of the image."
The brightness of background objects (stars etc. is relative to the object being targeted as far as "brightness", kind of like how Occator glowed so brightly in the earliest images. It's also why in the feed from the ISS no stars are visible.

 

[D H]

But, I'm afraid I'm not much of an astronomer, so I don't quite understand how "apparent magnitude" works.
Does Jupiter get brighter as you get closer?

Yes, it does. That's the reason for using apparent magnitude as opposed to absolute magnitude. Absolute magnitude does not change with distance. Apparent magnitude does change with distance, in an inverse square manner.

 

[1oldman2]

Finally ! Juno's about to go inbound for a practice run with the science payload operating,
http://www.nasa.gov/feature/jpl/five-years-post-launch-juno-is-at-a-turning-point
Juno's science instruments were turned off during orbit insertion, to simplify spacecraft
operations during that critical maneuver. In contrast, all the instruments will be collecting data
during the Aug. 27 pass, which serves as a trial run before the mission gets to work collecting
the precious data it came for.