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NASA’s Juno Spacecraft Sends First In-orbit View

nasa.gov

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Re: NASA’s Juno Spacecraft Sends First In-orbit View

#61

Post by mturmon »

valarauca1 wrote: post #22
neals wrote: post #17

Are we going to get amazing Pluto-like images, like that chilling closeup? They really impressed me A LOT. Or is Jupiter close enough for us to already know enough about its surface?

>Are we going to get amazing Pluto-like images, like that chilling closeup? No. The camera on Juno was literally an after thought. Originally it wasn't even going to have one. It's main job is studying magnetic fields and radiation belts.

Yes, the optical-wavelength camera was not a science driver for Juno. It's just making images of cloud tops. The cloud tops aren't that interesting, it's what's going on underneath or beyond.

In addition to fields and radiation instruments you mention, there are two other imaging spectrographs, one an IR instrument and one in UV. The IR camera can look ~70 km down below the cloud tops.

Importantly, there is a microwave radiometer, which can peer ~500km beneath the clouds to determine atmospheric composition as a function of time and space.

They have put Juno in a polar orbit, so it will scan the atmosphere through dozens of orbits before the radiation kills the instruments.

Re: NASA’s Juno Spacecraft Sends First In-orbit View

#62

Post by mturmon »

kchoudhu wrote: post #26

I understand the importance of this mission, but after the Curiosity skycrane, the Pluto flyby and the Rosetta orbiter, I'm really jonesing for something cool . What else is in the pipeline?

Mars helicopter for the upcoming Mars 2020 mission -- (http://www.jpl.nasa.gov/news/news.php?feature=4457)

Asteroid redirect mission -- (https://www.nasa.gov/mission_pages/asteroids/initiative/inde...)

Re: NASA’s Juno Spacecraft Sends First In-orbit View

#63

Post by mikeash »

drzaiusapelord wrote: post #34
cornholio wrote: post #7

I understand JunoCam is a public outreach tool. But if it provides much worse resolution than Hubble from inside Jupiter's orbit, it's basically useless even for that. I don't know if the cam is the problem or the transmission bandwidth, one thing is clear, when serios science starts there will be much less bandwidth available to send sharp and cool photos. That's what you get from a solar powered probe. We waste bil…

>gotten in their minds that RTG power is evil and dangerous RTG usage is curbed due to NASA's low supply of plutonium-238. Until more is made it makes sense to design for solar powered systems. Also these are risky missions with high pricetags and erring on the side of caution using well known technologies isn't some big conspiracy. Its to avoid high-profile fails. We can try new and risky stuff in lower profile miss…

Juno is the first use of solar panels for a probe going that far out. You're right that they want to err on the side of caution using well-known technology to minimize risk. But you're missing the fact that RTGs are that well-known risk-minimized technology.

If solar panels saved weight, they would have been used on past missions like Galileo. Better solar panel technology will eventually shift the balance, but we're not there yet. Juno's panels weigh 340kg. Galileo's two RTGs, which produced about the same amount of power at Jupiter, weighed 57kg each.

Re: NASA’s Juno Spacecraft Sends First In-orbit View

#64

Post by mikeash »

dredmorbius wrote: post #13
cornholio wrote: post #7

I understand JunoCam is a public outreach tool. But if it provides much worse resolution than Hubble from inside Jupiter's orbit, it's basically useless even for that. I don't know if the cam is the problem or the transmission bandwidth, one thing is clear, when serios science starts there will be much less bandwidth available to send sharp and cool photos. That's what you get from a solar powered probe. We waste bil…

The probe is 2.7 million miles from Jupiter, headed further out (its orbit is highly eccentric). That's nearly 11 times the distance from the Earth to the Moon. At closest approach, Juno will be 2,200 miles from Jupiter, less than 1% of the distance between the Earth and Moon. Space exploration is expensive, and a very large part of that expense is mass. Putting a 2.7 million mile scope on a probe that's going to be…

Strictly speaking, the probe will be spending most of its time at distances like these. That's the nature of elliptical orbits. But it'll spend enough time up close to get some great pictures.

And yes, photos weren't a priority at all. If it were just a matter of returning scientifically useful data, they wouldn't have included this camera at all. But NASA likes pretty pictures too, so they included one.

Re: NASA’s Juno Spacecraft Sends First In-orbit View

#65

Post by mikeash »

cornholio wrote: post #7

I understand JunoCam is a public outreach tool. But if it provides much worse resolution than Hubble from inside Jupiter's orbit, it's basically useless even for that. I don't know if the cam is the problem or the transmission bandwidth, one thing is clear, when serios science starts there will be much less bandwidth available to send sharp and cool photos. That's what you get from a solar powered probe. We waste bil…

Juno's solar panels produce as much power at Jupiter as Galileo's RTGs did. The quality of this picture has nothing to do with solar power. It's a bad picture because Juno is on a highly elliptical orbit for reasons of efficiency and longevity (there's tons of radiation closer in) and this picture was taken when the probe was very far away.

Re: NASA’s Juno Spacecraft Sends First In-orbit View

#66

Post by nitrogen »

drzaiusapelord wrote: post #35
KnightOfWords wrote: post #10

Glad Juno has made it and appears to be working OK. Not the most amazing image, better ones are routinely taken by amateurs from earth, but the crescent can only be seen by going there as Jupiter lies outside our orbit. We'll see much closer views from Juno when it's moved to a closer orbit in October. I came across this on Reddit the other day, taken with a smartphone and 8" telescope: https://www.reddit.com/r/astro…

>Stacked 400 best in Autostackert This isn't a photo. It a photoshop fiction of 400 different photos blended together. There's a big difference between that and a single frame from a spacecraft. Comparing the two seems silly.

To complement what others have said, stacking photos is mathematically the same thing as using a long exposure time and blocking the iris whenever the image would have been fuzzy, so it doesn't seem any less of a "photo" than anything else. You are still integrating across the stream of photons you want while discarding ones you don't.

Re: NASA’s Juno Spacecraft Sends First In-orbit View

#67

Post by jonknee »

jessriedel wrote: post #38
jonknee wrote: post #32

Earlier quoted context omitted.

> It's a wide-field of view and only a few megapixels, so basically a cell-phone camera. It's not similar to a cell phone camera at all. Cell phone cameras are usually much higher resolution (current iPhone is 8 megapixels vs the 2 for Juno), but with a much smaller sensor (iPhone cam has a 1.5µm pixel size vs 7.4µm for Juno).

Um, so the best cell phone camera on the market is within a factor of 2 in linear resolution? I think that qualifies as "basically".

Resolution has very little to do with it. Many images from NASA are stitched, even the ones from New Horizons. The important part is light sensitivity (in the correct wavelengths!) and making sure that it can work in the radiation of Jupiter.

You can go buy a camera with the same sensor if you'd like, but they're expensive:

http://www.qsimaging.com/620-overview.html

I believe it's the same sensor that flew on the Curiosity mission and we all know those photos are fantastic. They are also flight tested, invaluable for missions like this where you only get one shot at it.

Re: NASA’s Juno Spacecraft Sends First In-orbit View

#68

Post by drzaiusapelord »

mikeash wrote: post #64
dredmorbius wrote: post #13

Earlier quoted context omitted.

The probe is 2.7 million miles from Jupiter, headed further out (its orbit is highly eccentric). That's nearly 11 times the distance from the Earth to the Moon. At closest approach, Juno will be 2,200 miles from Jupiter, less than 1% of the distance between the Earth and Moon. Space exploration is expensive, and a very large part of that expense is mass. Putting a 2.7 million mile scope on a probe that's going to be…

Strictly speaking, the probe will be spending most of its time at distances like these. That's the nature of elliptical orbits. But it'll spend enough time up close to get some great pictures. And yes, photos weren't a priority at all. If it were just a matter of returning scientifically useful data, they wouldn't have included this camera at all. But NASA likes pretty pictures too, so they included one.

>But NASA likes pretty pictures too, so they included one.

Well, everyone does. If it wasn't for this photo we wouldn't be discussing Juno here on HN nor would this mission be in the press right now.

It seems crazy to me not to put a camera on deep space missions. The cost is trivial in the grand scheme of things.

Re: NASA’s Juno Spacecraft Sends First In-orbit View

#69

Post by mikeash »

drzaiusapelord wrote: post #68
mikeash wrote: post #64

Earlier quoted context omitted.

Strictly speaking, the probe will be spending most of its time at distances like these. That's the nature of elliptical orbits. But it'll spend enough time up close to get some great pictures. And yes, photos weren't a priority at all. If it were just a matter of returning scientifically useful data, they wouldn't have included this camera at all. But NASA likes pretty pictures too, so they included one.

>But NASA likes pretty pictures too, so they included one. Well, everyone does. If it wasn't for this photo we wouldn't be discussing Juno here on HN nor would this mission be in the press right now. It seems crazy to me not to put a camera on deep space missions. The cost is trivial in the grand scheme of things.

I don't know that the cost is trivial. The camera is cheap, sure, but that's weight and power and bandwidth that could be spent on something else.

However, I totally agree that it would be crazy not to include one, and whatever it costs, it's well worth it.

Re: NASA’s Juno Spacecraft Sends First In-orbit View

#70

Post by jonknee »

jessriedel wrote: post #51
pwthornton wrote: post #45

Earlier quoted context omitted.

It's the opposite of cellphone camera. It has low megapixels and a large sensor size. This will allow a lot of light onto the sensor and it won't suffer from the noisiness that high megapixels on a smaller sensor suffer from.

The point is that, on the spectrum of all imaging devices you might put on a satellite, both Juno and a cell phone camera are in the same rough neighborhood. They are dwarfed by telephoto lens, or 200 megapixel sensors. Remember especially that the topic we are discussing is the resolution (km/pixel) at a particular distance (see above), and for this the lens are much more important than the particular CCD chosen.

So now it's the lens that you don't like, not the sensor? The imaging camera has a wide angle (11.7mm) because it's going to be so close to the surface that a wide angle is optimal. That's actually a lot wider than cell phones (iPhone 6s is 31mm equivalent). There are also other instruments on board that look through the gas with telescopic reach.

td;dr Juno has a fine sensor and lens

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