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Decoding James Webb Space Telescope

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Re: Decoding James Webb Space Telescope

#41

Post by monocasa »

shagie wrote: post #10
rodiger wrote: post #5

Does anyone know offhand when we should receive the first images?

About six months. https://webbtelescope.org/quick-facts/mission-launch-quick-f... > After reaching its orbit, Webb undergoes science and calibration testing. Then, regular science operations and images will begin to arrive, approximately six months after launch. However, it is normal to also take a series of "first light" images that may arrive slightly earlier. It will take about a month for it to get out to the Sun…

We'll probably get the calibration images before the six months from now when regular science missions start if they go according to plan as it's great press. Also there's a chance that there's a delay on the science mission images to allow for academic publishing.

Re: Decoding James Webb Space Telescope

#42

Post by xioxox »

jandrese wrote: post #36
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…

It seems like it should all be automated. Some scientist generates a mission request for the JWST techs. If accepted the mission is added to the timeline with all of the metadata the original scientists had in their proposal. Stuff like the area being imaged, the sensors in use, duration of capture, etc... Once the data is collected and downloaded it is added to the catalog with all of that metadata attached. Then it…

The data from the mission will be made public after proprietary periods [1]. They have an archive [2]. I don't expect that the raw telemetry will be made available, but the raw science data in FITS format appears will be available.

[1] https://jwst-docs.stsci.edu/jwst-opportunities-and-policies/... [2] https://archive.stsci.edu/missions-and-data/jwst

Re: Decoding James Webb Space Telescope

#43

Post by jacquesm »

dylan604 wrote: post #14
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…

Aren't they using the Deep Space Network for this?

Yes, all communications are routed through DSN.

Re: Decoding James Webb Space Telescope

#44

Post by wongarsu »

foobiekr wrote: post #32
cycomanic wrote: post #17

Earlier quoted context omitted.

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.

Embarrassing the US is high value.

If somebody like China is caught sabotaging JWST the fallout could be immense. They would be accused of trying to hold back human progress, and I could easily imagine high profile Chinese scientists leaving the country and science institutions boycotting China. It's not worth the risk.

Re: Decoding James Webb Space Telescope

#45

Post by smccully »

TedDoesntTalk wrote: post #21
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.

That’s insane. Where did you read that?

Astronomical Images are calculated in Hours, and I have no idea how long the average image will be for NIRCam on JWST, but your average Space Photo from Ground Telescopes is usually a combination of 5 to 15 minutes images, with a total imaging time from 10 - 40 hours.

Re: Decoding James Webb Space Telescope

#46

Post by Sporktacular »

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…

"It is not necessary really."

Authentication of commands to satellites is very, very necessary

Re: Decoding James Webb Space Telescope

#47

Post by Thorentis »

aunty_helen wrote: post #29
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…

From: https://ntrs.nasa.gov/api/citations/20080030196/downloads/20... >To keep up with the high downlink, the recorder data gets sent directly to the Ka-band transmitter Currently aws groundstation doesn't support KA band so no luck there. It's apparently going to do a transmission once a day so you would need to time it right with the ground station.

Groundststion as a Service. I had no idea this existed. I am continuously amazed at how many things Amazon churns out "as a service".

Re: Decoding James Webb Space Telescope

#48

Post by hayanno »

aunty_helen wrote: post #29
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…

From: https://ntrs.nasa.gov/api/citations/20080030196/downloads/20... >To keep up with the high downlink, the recorder data gets sent directly to the Ka-band transmitter Currently aws groundstation doesn't support KA band so no luck there. It's apparently going to do a transmission once a day so you would need to time it right with the ground station.

Nice link, very informative, here's a funny excerpt : "It [JSWT] is currently planned to be launched in 2013 from French Guiana aboard an Ariane 5 launch vehicle".

Re: Decoding James Webb Space Telescope

#49

Post by leephillips »

wongarsu wrote: post #44
foobiekr wrote: post #32

Earlier quoted context omitted.

Embarrassing the US is high value.

If somebody like China is caught sabotaging JWST the fallout could be immense. They would be accused of trying to hold back human progress, and I could easily imagine high profile Chinese scientists leaving the country and science institutions boycotting China. It's not worth the risk.

I also don’t think they would want to do this, but I think you’re overestimating the risk. Genocide, stealing the entire South China Sea, and threatening the sovereignty of other nations haven’t inspired such boycotts.

Re: Decoding James Webb Space Telescope

#50

Post by Twisol »

colechristensen wrote: post #9
gjsman-1000 wrote: post #2

One would wish that for budget-exponentially-overrun taxpayer-funded infrastructure, there would be open-source decoding information available.

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 scientific interest

My understanding is that "telemetry" and "telecommand" stand for the downlink and uplink directions of a space link. I mostly worked upstream of telecommand, but I understood "telemetry" to refer to received data of any kind -- e.g. in CCSDS 130.1-G-3, an informational report on the design of the CCSDS telemetry system. https://public.ccsds.org/Pubs/130x1g3.pdf

By the by, I've been continually impressed with the quality of the CCSDS' documents. The "green books" (informational reports, like the one above) are extremely approachable and well-written.

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