5 ms·

JWST is not serviceable. If the ssd dies, then it's dead. There's no replacing it.

zimpenfish 4y ago
> If the ssd dies, then it's dead. Presumably they could operate in a reduced mode where it does live transmission of the data when it's in contact with Earth?
- Sporktacular 4y ago
  Depends if the sensor readout is slower than 28 Mb/s.
  - zimpenfish 4y ago
    If it generates, at most, 57GB per day[1], assuming 22h operation (2h for transmission), the sensors are generating 2.6GB/h or about 750kB/sec which is just about 6Mb/s (unless my math is wonky.) [1] "JWST can produce up to 57 GB each day (although that amount is dependent on what observations are scheduled)."
    - Sporktacular 4y ago
      That is the average rate over a day. If storage is not available to buffer it, then a sensor's peak readout rate could easily exceed the transmission rate.
      - Sporktacular 4y ago
        Edit: Which apparently it does, which is why the SSD can ingest up to 48 Mb/s to be read out more slowly later (https://jwst-docs.stsci.edu/jwst-observatory-hardware/jwst-solid-state-recorder https://jwst-docs.stsci.edu/jwst-observatory-hardware/jwst-s...).
        zimpenfish 4y ago
        But also "The actual data rate depends on the number of detectors simultaneously in use, their exposure parameters, and the precise timing of when their exposure readouts arrive in the ICDH for processing" - in a reduced operation mode, they can turn down the number of sensors, etc., to keep the data rate below the live transmission rate.
AngryData 4y ago
It isn't meant to need servicing, but it does have a docking port if it ever does need it and we have the desire to do so.
- dr_orpheus 4y ago
  Yes, but a servicing mission for replacing the memory would still be an unlikely operation to be able to do. The most likely use for the docking port is if the electronics onboard exceed their design life, but JWST is running out fuel (to maintain its position at the Lagrange point) so they basically strap a "jet pack" on to the satellite to keep in operation. This has been the business case of some companies trying to do this for GEO satellites: https://astroscale.com/astroscale-u-s-enters-the-geo-satellite-life-extension-market/ https://astroscale.com/astroscale-u-s-enters-the-geo-satelli...

> If the ssd dies, then it's dead. Presumably they could operate in a reduced mode where it does live transmission of the data when it's in contact with Earth?

Sporktacular 4y ago
Depends if the sensor readout is slower than 28 Mb/s.
- zimpenfish 4y ago
  If it generates, at most, 57GB per day[1], assuming 22h operation (2h for transmission), the sensors are generating 2.6GB/h or about 750kB/sec which is just about 6Mb/s (unless my math is wonky.) [1] "JWST can produce up to 57 GB each day (although that amount is dependent on what observations are scheduled)."
  - Sporktacular 4y ago
    That is the average rate over a day. If storage is not available to buffer it, then a sensor's peak readout rate could easily exceed the transmission rate.
    - Sporktacular 4y ago
      Edit: Which apparently it does, which is why the SSD can ingest up to 48 Mb/s to be read out more slowly later (https://jwst-docs.stsci.edu/jwst-observatory-hardware/jwst-solid-state-recorder https://jwst-docs.stsci.edu/jwst-observatory-hardware/jwst-s...).
      - zimpenfish 4y ago
        But also "The actual data rate depends on the number of detectors simultaneously in use, their exposure parameters, and the precise timing of when their exposure readouts arrive in the ICDH for processing" - in a reduced operation mode, they can turn down the number of sensors, etc., to keep the data rate below the live transmission rate.

AngryData 4y ago

It isn't meant to need servicing, but it does have a docking port if it ever does need it and we have the desire to do so.

dr_orpheus 4y ago
Yes, but a servicing mission for replacing the memory would still be an unlikely operation to be able to do. The most likely use for the docking port is if the electronics onboard exceed their design life, but JWST is running out fuel (to maintain its position at the Lagrange point) so they basically strap a "jet pack" on to the satellite to keep in operation. This has been the business case of some companies trying to do this for GEO satellites: https://astroscale.com/astroscale-u-s-enters-the-geo-satellite-life-extension-market/ https://astroscale.com/astroscale-u-s-enters-the-geo-satelli...