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Decoding James Webb Space Telescope

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Re: Decoding James Webb Space Telescope

#51

Post by Twisol »

ufmace wrote: post #37
mhh__ wrote: post #33

Earlier quoted context omitted.

Science in general still basically operates on the "NASA invented xyz while going to the moon"-model from the 20th century. Things get developed and then trickle into industry via back-channels (or people moving) but the idea of open-source is still both culturally alien and legally suspect. Even in CS papers directly dealing with a piece of software there is no obligation to publish code.

After seeing plenty of code and projects by people who weren't professional software engineers used to working on teams, part of the problem is likely that code written for this sort of thing often depends on a ton of dependencies and system-specific configuration bits that are documented poorly or not at all. Getting such projects to a state where a random person could git pull it and make sense of it and use it is…

On top of that, missions are heavily incentivized (in an "our success depends on this" way) to solve only the problems they absolutely need to solve, due to constraints on time, budget, and manpower. It's an incredible feat to achieve what they do, but reuse and non-specialist use are non-goals.

Re: Decoding James Webb Space Telescope

#52

Post by Animats »

boardwaalk wrote: post #24
Beltiras wrote: post #18

I'm a bit shocked at how low bandwith was allocated. 421 Megabytes per day is the theoretical upper limit. 16 Terabytes for the entire mission. I have more bulk storage in my desktop.

This is just the telemetry data. They deployed the high data rate antenna yesterday which can do many GB per day.

Oh, good, that unfolding worked.

The amount of unpacking involved as this thing deploys is insane.

On the data rate thing, satellites usually have a low data rate system with omnidirectional antennas, used for command and positioning. Then they have a high data rate system with directional antennas for whatever it is they do.

(The USAF used to have a strict separation between the two. This reflects the USAF's pilot-oriented mentality. The USAF is pilots, and then everybody else. The low data rate system belonged to the piloting operation, which used to be in the Blue Cube in Sunnyvale CA and is now at Schriever Space Force Base, formerly Falcon AFB, in Colorado Springs CO. They "drive the bus", managing orbital insertion and station keeping. The high data rate system belonged to the payload, and once the piloting operation had it turned on and aimed, it was turned over to the agency that owned the payload. Private satellite operators usually don't make that distinction.)

Re: Decoding James Webb Space Telescope

#53

Post by dividedbyzero »

londons_explore wrote: post #27
semi-extrinsic wrote: post #19

Earlier quoted context omitted.

> the data sent back would be sitting on an FTP server somewhere for anyone to download and use I'm sure they could actually do that without too much fuss. But it would require significant amounts of scientist time to document those datasets to enable others to use them for any arbitrary dataset . I'm sure we'll see fully open data sets from JWST appear, but lots of the stuff it collects isn't going to be interesting…

I think there needs to be a distinction between something that a project "publishes", and something that is "made available". Something published has been checked by a few team members, written with care, and represents the opinion of the authors and project. Something made available has no guarantees of correctness, might not represent the projects opinion, and might just be random matlab scripts made by a JWST scie…

That's a pretty bad idea IMO. Putting people in a panopticon has a strong chilling effect, no matter what disclaimer you put on the recordings. Creative, deep work needs space to make blunders in private, scientists are no exception. They'll just use their personal laptops or document every experiment and mistake and script to death, getting done a lot less actual research.

Plus, it will be pretty much useless im practice since you'd have to be an expert in that niche yourself to know what's correct (you're not getting any extra docs or context) and probably most of it will be some kind of incorrect, possibly very subtly. The only people who could profit tremendously are the competition who aim to snipe that particular paper. Science is pretty dirty and ruthless often as not, I totally could see this happen.

Re: Decoding James Webb Space Telescope

#54

Post by iszomer »

cycomanic wrote: post #17
andruby wrote: post #3

Earlier quoted context omitted.

I actually don’t know if they want to protect the data. I can imagine they might not want China or other countries listening in and potentially sending commands to the craft. Does anyone know if there is typically encryption on the downlink? How about uplink commands? I guess we want those to be secured so only authenticated control can send commands

I highly suspect that China (and almost every other country) are not the issue. Chinese and the whole international scientific community will profit immensely from the data coming from James Webb, so I don't think the Chinese have any interest in sabotaging the project. More dangerous would be some average joe, somewhere who would try to mess with it for the lulz.

Or frame the average Joe for the lulz for political points.

(sorry, I'm just now reading into the drama with the fbi and gov. whitmer..)

Re: Decoding James Webb Space Telescope

#55

Post by foobarian »

Animats wrote: post #52
boardwaalk wrote: post #24

Earlier quoted context omitted.

This is just the telemetry data. They deployed the high data rate antenna yesterday which can do many GB per day.

Oh, good, that unfolding worked. The amount of unpacking involved as this thing deploys is insane. On the data rate thing, satellites usually have a low data rate system with omnidirectional antennas, used for command and positioning. Then they have a high data rate system with directional antennas for whatever it is they do. (The USAF used to have a strict separation between the two. This reflects the USAF's pilot-o…

And according to this chart it's about to pass the Moon in distance in a few hours. https://jwst.nasa.gov/content/webbLaunch/whereIsWebb.html

Re: Decoding James Webb Space Telescope

#56

Post by dividedbyzero »

dylan604 wrote: post #13
gjsman-1000 wrote: post #4

Earlier quoted context omitted.

There would have to be some sort of encryption or passkey or digital signature on commands, for sure. Otherwise some hobbyist in the middle of the Ocean on his yacht could be messing with the craft and taking pictures and there'd be no easy way to shut him down.

"Torpedo in the water!" would probably be sufficient.

The US government being able to discreetly torpedo everyone everywhere within what would have to be a few minutes at most, that would be pretty pretty scary. Imagine the number of drones they'd need to have deployed and armed at all times, and the potential for abuse.

Re: Decoding James Webb Space Telescope

#57

Post by iszomer »

manquer wrote: post #16
gjsman-1000 wrote: post #4

Earlier quoted context omitted.

There would have to be some sort of encryption or passkey or digital signature on commands, for sure. Otherwise some hobbyist in the middle of the Ocean on his yacht could be messing with the craft and taking pictures and there'd be no easy way to shut him down.

It is not necessary really. There is unlikely any non-state actors[1] that has the ability to transmit signals to L2 . Just receiving signals even now (only 2 out of 30 days to l2) the OP used a 6 meter dish. Most of interplanetary mission signals are handled by the DSN. Any sort of encryption will add both b/w requirements and compute requirements . The CPU/network budgets on such missions are very very limited. Eve…

I'd imagine the specs are rated and hardened for radiation first, as seen on all previous NASA satellite and probe missions before getting into the weeds of overhead and encryption.

Re: Decoding James Webb Space Telescope

#58

Post by astroflask »

Twisol wrote: post #50
colechristensen wrote: post #9

Earlier quoted context omitted.

This is just telemetry data which doesn’t have much general or scientific interest, i guess they could publish the protocol spec (honestly it probably is aquirable) but most of the fun for the kinds of people who want this data is going to be doing this reverse engineering themselves. The real imaging data would require a much more significant dish to even receive (i can’t immediately find what it’s going to use, but…

Most of the public specifications are distributed freely by the CCSDS (Consultative Committee for Space Data Systems): https://public.ccsds.org/Publications/BlueBooks.aspx The mission-specific parameters ("managed parameters") used by any given mission are usually more tightly controlled, as are the payload specifications for each telemetry channel. > This is just telemetry data which doesn’t have much general or sci…

Gonna chime in here to comment that most NASA missions (and ESA too) provide the scientific data for download free of charge, under Public Domain or CC licenses. If it's for scientific purposes, it's not just good manners, but rather a requirement to cite the proper dataset (that also gives you the bonus of citing a respected source, so it's a win-win). Thing is that many people doesn't even know where to look for!

And it doesn't help that some missions manage their own archives differently, and there's a lot of terminology to learn on your own. One of the complete opposites of that, which was a joy, was the New Horizons archive which, at one point, you could download from a torrent! For example, if you wanted to see V3 of the Arrokoth encounter from 2019, you'd go to: https://pdssbn.astro.umd.edu/holdings/nh-a-lorri-3-kem1-v3.0...

Again, New Horizons is a bit of a rare case in which they went for super accessible data for everyone. PDS itself is a great system, but many missions will just upload a bit of data to PDS and then manage the rest some other way (Cassini for example has only a couple of instruments on PDS, and you have to go to some other URL if you want uncalibrated but automatically processed images on JPEG format[0], but yet another place (to which I've lost the link to and I can't find on mobile) for the full, science-grade dataset).

A great resource is OPUS[1] too, however I find it's UI a bit difficult, and in the end I prefer to download full datasets and just explore them on my own rather than going with those online browsers. For example, if you wanted to check the Voyager images of Neptune, you'd go to this massive URL[2]. Quick tip: once you've configured the filter you want to apply, the Search button is on the top left -- this is the kind of usability thing I mentioned, buttons and links aren't quite where you'd expect them. Oh and there's a limit to how many things you can select for download at once. And it's all dynamically loaded, and on and on and on. Which is why, as I said before, I generally prefer to just download the full GB sized dataset and explore it on my own.

[0] https://solarsystem.nasa.gov/raw-images/raw-image-viewer/?or...

[1] https://opus.pds-rings.seti.org/opus/

[2] https://opus.pds-rings.seti.org/opus/#/instrument=Voyager+IS...

Re: Decoding James Webb Space Telescope

#59

Post by cfraenkel »

Animats wrote: post #52
boardwaalk wrote: post #24

Earlier quoted context omitted.

This is just the telemetry data. They deployed the high data rate antenna yesterday which can do many GB per day.

Oh, good, that unfolding worked. The amount of unpacking involved as this thing deploys is insane. On the data rate thing, satellites usually have a low data rate system with omnidirectional antennas, used for command and positioning. Then they have a high data rate system with directional antennas for whatever it is they do. (The USAF used to have a strict separation between the two. This reflects the USAF's pilot-o…

There are completely practical reasons.... The omni-directional antenna typically doesn't have the gain, or bandwidth, or power of the high bandwidth antenna, but does have the useful property of being usable when the vehicle might be tumbling.

Re: Decoding James Webb Space Telescope

#60

Post by Animats »

cfraenkel wrote: post #59
Animats wrote: post #52

Earlier quoted context omitted.

Oh, good, that unfolding worked. The amount of unpacking involved as this thing deploys is insane. On the data rate thing, satellites usually have a low data rate system with omnidirectional antennas, used for command and positioning. Then they have a high data rate system with directional antennas for whatever it is they do. (The USAF used to have a strict separation between the two. This reflects the USAF's pilot-o…

There are completely practical reasons.... The omni-directional antenna typically doesn't have the gain, or bandwidth, or power of the high bandwidth antenna, but does have the useful property of being usable when the vehicle might be tumbling.

Right, but didn't want to go into that much detail.
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