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The article didn't go into it I think, but I recall in many satellite missions of this type, there are not only data storage and transmission issues (normal iss

The article didn't go into it I think, but I recall in many satellite missions of this type, there are not only data storage and transmission issues (normal issues you would expect), but also considerations that the antennas and transmission hardware themselves have a certain duty cycle or lifetime that is finite. As in transmission of data consumes that margin. So you have to quite deliberate in considering how much data to be sending, which data, etc. because every GB eats a chunk of the satellite's expected life. (Again, I believe.)

foobarbecue 4y ago
Really? I've never heard of transmitter or antenna being considered a consumable (and I work in the space industry). Any idea where you got this idea from?
- supernova87a 4y ago
  I will try to find a link, although it's of course quite specialized info that is not often written about. But for example, I recall that for Spitzer space telescope (I believe) every activation of the transmission hardware consumed it's usable lifetime, or the finite amount of liquid helium coolant that was needed for the operation of the telescope (which only had an expected lifetime of 2.5 years, for the key instruments that relied on coolant).
  - foobarbecue 4y ago
    Helium, for sure. Coolant, propellant, battery charge cycles, flash write cycles are all consumables. Maybe even solar panels -- they wear out. The radio? I doubt it.
  - foobarbecue 4y ago
    BTW this is what Spitzer was using: https://en.wikipedia.org/wiki/Small_Deep_Space_Transponder https://en.wikipedia.org/wiki/Small_Deep_Space_Transponder . I haven't been able to find info on what Webb is using.
  - foobarbecue 4y ago
    I know I'm beating a dead horse here, but I thought I'd mention that the idea this isn't written about is incorrect. There are hundreds of papers and publicly available engineering documents about deep space transponder design. I did a little more research and found that JWST is using the radios on its Raytheon ECLIPSE bus. There's a lot of conference papers and specs available. I haven't found any lifetime estimates yet, presumably because it's just not a concern.
    - supernova87a 4y ago
      Sorry, I meant the aspect that for example, Spitzer, only had so much margin to transmit data (or other heat-causing) activities else its lifetime would be shortened. That was not much written about (outside of detailed technical circles).
      - foobarbecue 4y ago
        ??? helium cools the detector, not the radio...
    - Sporktacular 4y ago
      On that, could you explain the term transponder when I would have thought transceiver would be a more apt description. From the SDST and Iris info out there they handle up and downlinks, telemetry and commands etc. which all seem like transceiver functions.
      - foobarbecue 4y ago
        Hm, yeah, I would have called it a "transceiver", but SDST uses "transponder" in the name so I started using that term without thinking. I guess the terms are used interchangeably in this context... Edit: what's Iris? Also now I'm not sure SDST was sending the data -- was that on a different radio?
        Sporktacular 4y ago
        Iris is another transponder/transceiver package for smaller satellites. Supports Turbo codes too btw. https://en.wikipedia.org/wiki/Iris_(transponder) https://en.wikipedia.org/wiki/Iris_(transponder)
- foobarbecue 4y ago
  I thought about this some more and remembered that we do do "trending" of just about every subsystem on the spacecraft, and comms is one of them. Pretty sure there's a slide in a presentation every few months looking at how many times the radio has been turned on compared to the number of times it was designed to be turned on, but I assume the component in question is just the relay that switches it on. We have similar plots for everything that can be turned on and off. I think the point of these presentations is just to think about what's likely to die first and to make it obvious if we suddenly change how often we use things.

foobarbecue 4y ago

Really? I've never heard of transmitter or antenna being considered a consumable (and I work in the space industry). Any idea where you got this idea from?

supernova87a 4y ago
I will try to find a link, although it's of course quite specialized info that is not often written about. But for example, I recall that for Spitzer space telescope (I believe) every activation of the transmission hardware consumed it's usable lifetime, or the finite amount of liquid helium coolant that was needed for the operation of the telescope (which only had an expected lifetime of 2.5 years, for the key instruments that relied on coolant).
- foobarbecue 4y ago
  Helium, for sure. Coolant, propellant, battery charge cycles, flash write cycles are all consumables. Maybe even solar panels -- they wear out. The radio? I doubt it.
- foobarbecue 4y ago
  BTW this is what Spitzer was using: https://en.wikipedia.org/wiki/Small_Deep_Space_Transponder https://en.wikipedia.org/wiki/Small_Deep_Space_Transponder . I haven't been able to find info on what Webb is using.
- foobarbecue 4y ago
  I know I'm beating a dead horse here, but I thought I'd mention that the idea this isn't written about is incorrect. There are hundreds of papers and publicly available engineering documents about deep space transponder design. I did a little more research and found that JWST is using the radios on its Raytheon ECLIPSE bus. There's a lot of conference papers and specs available. I haven't found any lifetime estimates yet, presumably because it's just not a concern.
  - supernova87a 4y ago
    Sorry, I meant the aspect that for example, Spitzer, only had so much margin to transmit data (or other heat-causing) activities else its lifetime would be shortened. That was not much written about (outside of detailed technical circles).
    - foobarbecue 4y ago
      ??? helium cools the detector, not the radio...
  - Sporktacular 4y ago
    On that, could you explain the term transponder when I would have thought transceiver would be a more apt description. From the SDST and Iris info out there they handle up and downlinks, telemetry and commands etc. which all seem like transceiver functions.
    - foobarbecue 4y ago
      Hm, yeah, I would have called it a "transceiver", but SDST uses "transponder" in the name so I started using that term without thinking. I guess the terms are used interchangeably in this context... Edit: what's Iris? Also now I'm not sure SDST was sending the data -- was that on a different radio?
      - Sporktacular 4y ago
        Iris is another transponder/transceiver package for smaller satellites. Supports Turbo codes too btw. https://en.wikipedia.org/wiki/Iris_(transponder) https://en.wikipedia.org/wiki/Iris_(transponder)
foobarbecue 4y ago
I thought about this some more and remembered that we do do "trending" of just about every subsystem on the spacecraft, and comms is one of them. Pretty sure there's a slide in a presentation every few months looking at how many times the radio has been turned on compared to the number of times it was designed to be turned on, but I assume the component in question is just the relay that switches it on. We have similar plots for everything that can be turned on and off. I think the point of these presentations is just to think about what's likely to die first and to make it obvious if we suddenly change how often we use things.