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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

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.

TedDoesntTalk 5y ago
That’s insane. Where did you read that?
- jandrese 5y ago
  It's in the article, but the OP was confused because this isn't the imaging data. It's the telemetry, things like thruster temps, gyro speeds, etc... The metadata that NASA uses to make sure the spacecraft is healthy, not the mission payload.
- smccully 5y ago
  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.
boardwaalk 5y ago
This is just the telemetry data. They deployed the high data rate antenna yesterday which can do many GB per day.
- Animats 5y ago
  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.)
  - foobarian 5y ago
    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 https://jwst.nasa.gov/content/webbLaunch/whereIsWebb.html
  - cfraenkel 5y ago
    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.
    - Animats 5y ago
      Right, but didn't want to go into that much detail.
- frakkingcylons 5y ago
  And to tag on, there's even a 6-second 4K video of that deployment step: https://svs.gsfc.nasa.gov/vis/a020000/a020300/a020339/WEBB_HGA_4k_30fps_h264.mp4 https://svs.gsfc.nasa.gov/vis/a020000/a020300/a020339/WEBB_H... That's from this link: https://www.jwst.nasa.gov/content/webbLaunch/deploymentExplorer.html https://www.jwst.nasa.gov/content/webbLaunch/deploymentExplo... I feel so spoiled that NASA provides video clips of each specific deployment step.
  - naikrovek 5y ago
    I would feel more spoiled if it were actual video from the spacecraft.
deleted 5y ago
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halfdan 5y ago
You have to take into account that it was originally scheduled to launch in 2007, then in 2014. Development began as early as 1996.
Yes_and 5y ago
Yes, please provide a source! Based on this [0], with the High-Gain antenna (Ka-band), they can do 3.5 Mbyte/sec (28 Mbit/sec), which is about 295 Gbyte/day. Even if only assuming 16 hours/downlink/day, that is ~200 Gbytes/day. Also, with the S-Band Medium gain antenna, JWST is capable of accomplishing true duplex communication, which means they can uplink on the S-band and simultaneously downlink on Ka-band. For reference, MRO is capable of downlinking at up to 5 Gbit/sec with a 3.0-meter HGA [1]. [0] https://jwst-docs.stsci.edu/jwst-observatory-hardware/jwst-spacecraft-bus/jwst-communications-subsystem https://jwst-docs.stsci.edu/jwst-observatory-hardware/jwst-s... [1] https://descanso.jpl.nasa.gov/DPSummary/MRO_092106.pdf https://descanso.jpl.nasa.gov/DPSummary/MRO_092106.pdf, table 4-7
- basementcat 5y ago
  That is 5 Mbps, not Gbps :) In Reed-Solomon only mode, MRO can transmit about 6.6 Mbps but at typical Mars-Earth range the data rate is much lower.
semi-extrinsic 5y ago
The instruments aren't really high bandwidth. If you take NIRCam as an example, it's 40 megapixels with an observation time per image that is from 4 minutes up to 3 hours.
- nullc 5y ago
  Only the NIRcam has that many pixels, the other instruments have far fewer I believe. They will make up for the smaller numbers of pixels per (long) exposure by running the thing constantly. Check out the sort of images they produced with the 128x128 pixel sensor on spitzer: https://upload.wikimedia.org/wikipedia/commons/a/a5/Andromeda_galaxy_Ssc2005-20a1.jpg https://upload.wikimedia.org/wikipedia/commons/a/a5/Andromed...
deleted 5y ago
[deleted]
walrus01 5y ago
It's fairly typical for the S/L-band telemetry and command and control antenna (omnidirectional, in case of pointing/station keeping error) on a satellite to be a very low data rate, and narrow channel. The narrower the channel is, the easier it is to pick it out of noise, and aim medium sized earth station dishes at it.

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.

TedDoesntTalk 5y ago

That’s insane. Where did you read that?

jandrese 5y ago
It's in the article, but the OP was confused because this isn't the imaging data. It's the telemetry, things like thruster temps, gyro speeds, etc... The metadata that NASA uses to make sure the spacecraft is healthy, not the mission payload.
smccully 5y ago
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.

boardwaalk 5y ago

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

Animats 5y ago
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.)
- foobarian 5y ago
  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 https://jwst.nasa.gov/content/webbLaunch/whereIsWebb.html
- cfraenkel 5y ago
  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.
  - Animats 5y ago
    Right, but didn't want to go into that much detail.
frakkingcylons 5y ago
And to tag on, there's even a 6-second 4K video of that deployment step: https://svs.gsfc.nasa.gov/vis/a020000/a020300/a020339/WEBB_HGA_4k_30fps_h264.mp4 https://svs.gsfc.nasa.gov/vis/a020000/a020300/a020339/WEBB_H... That's from this link: https://www.jwst.nasa.gov/content/webbLaunch/deploymentExplorer.html https://www.jwst.nasa.gov/content/webbLaunch/deploymentExplo... I feel so spoiled that NASA provides video clips of each specific deployment step.
- naikrovek 5y ago
  I would feel more spoiled if it were actual video from the spacecraft.

deleted 5y ago

[deleted]

halfdan 5y ago

You have to take into account that it was originally scheduled to launch in 2007, then in 2014. Development began as early as 1996.

Yes_and 5y ago

Yes, please provide a source! Based on this [0], with the High-Gain antenna (Ka-band), they can do 3.5 Mbyte/sec (28 Mbit/sec), which is about 295 Gbyte/day. Even if only assuming 16 hours/downlink/day, that is ~200 Gbytes/day. Also, with the S-Band Medium gain antenna, JWST is capable of accomplishing true duplex communication, which means they can uplink on the S-band and simultaneously downlink on Ka-band. For reference, MRO is capable of downlinking at up to 5 Gbit/sec with a 3.0-meter HGA [1]. [0] https://jwst-docs.stsci.edu/jwst-observatory-hardware/jwst-spacecraft-bus/jwst-communications-subsystem https://jwst-docs.stsci.edu/jwst-observatory-hardware/jwst-s... [1] https://descanso.jpl.nasa.gov/DPSummary/MRO_092106.pdf https://descanso.jpl.nasa.gov/DPSummary/MRO_092106.pdf, table 4-7

basementcat 5y ago
That is 5 Mbps, not Gbps :) In Reed-Solomon only mode, MRO can transmit about 6.6 Mbps but at typical Mars-Earth range the data rate is much lower.

semi-extrinsic 5y ago

The instruments aren't really high bandwidth. If you take NIRCam as an example, it's 40 megapixels with an observation time per image that is from 4 minutes up to 3 hours.

nullc 5y ago
Only the NIRcam has that many pixels, the other instruments have far fewer I believe. They will make up for the smaller numbers of pixels per (long) exposure by running the thing constantly. Check out the sort of images they produced with the 128x128 pixel sensor on spitzer: https://upload.wikimedia.org/wikipedia/commons/a/a5/Andromeda_galaxy_Ssc2005-20a1.jpg https://upload.wikimedia.org/wikipedia/commons/a/a5/Andromed...

deleted 5y ago

[deleted]

walrus01 5y ago

It's fairly typical for the S/L-band telemetry and command and control antenna (omnidirectional, in case of pointing/station keeping error) on a satellite to be a very low data rate, and narrow channel. The narrower the channel is, the easier it is to pick it out of noise, and aim medium sized earth station dishes at it.