back to article Could a leaky capacitor be at fault on ESA's Sentinel-1B?

Attempts to recover ESA's stricken Sentinel-1B satellite are continuing and one of the failure scenarios engineers are considering will be familiar to some of us: possible leakage of a ceramic capacitor. The satellite, launched in 2016 aboard a Russian Soyuz rocket from the Arianespace facility at Kourou in French Guiana, …

  1. Yet Another Anonymous coward Silver badge

    This particular capacitor is part of the main and redundant regulators

    “You keep using that word. I do not think it means what you think it means.”

    1. Snowy Silver badge

      Re: This particular capacitor is part of the main and redundant regulators

      Maybe they mean redundancy but it still does not make sense.

      It can be in one of the other but not both. If it is in both then there is no redundancy!

      Could be they have a broken capacitor but they do not know which one and there is a number of them being used. Some are used in the by the main regulators and some other ones are used in the backup regulators so the system has some redundancy.

      1. This post has been deleted by its author

      2. Trigonoceps occipitalis

        Re: This particular capacitor is part of the main and redundant regulators

        Perhaps "particular capacitor" is a reference to the type, ie one of the type in each regulator as opposed to one capacitor bridging both regulators? Not clear writing.

    2. Anonymous Coward
      Anonymous Coward

      Re: This particular capacitor is part of the main and redundant regulators

      Now why did I think "offcom"?

  2. Yet Another Hierachial Anonynmous Coward

    squirty can

    A can of squirty freezer spray and a soldering iron tip in close proximity will quickly locate the failed part. Oh hang on, that might not be so easy.

    1. Yet Another Anonymous coward Silver badge

      Re: squirty can

      It should already be pretty cold up there. Just take your helmet off and breathe on it and see which part doesn't get frosty - errm perhaps not.....

  3. This post has been deleted by its author

  4. Kevin McMurtrie Silver badge

    Leaky ceramic?

    Ceramic capacitors have nothing to leak since they're metal and ceramic. Maybe they mean shorted? Hopefully there's more than one cap on the power supply. If they can get the shorted cap hot quickly it might pop itself off the board.

    I'd bet it's a damaged switching transistor. The symptoms are similar but with no chance of fixing it. Hopefully there's another power supply too.

    1. ashdav

      Re: Leaky ceramic?

      Leaky in this context means it has parallel internal resistance so there is a DC current flow.

      This is common in ceramic and tantalum capacitors.

      Nothing to do with your perception of an electrolyte leak in an electrolytic capacitor.

      (Speaking as a former capacitor design engineer).

      1. Anonymous Coward
        Anonymous Coward

        Re: Leaky ceramic?

        'Leaky in this context means it has parallel internal resistance so there is a DC current flow.'

        Exactly this!

      2. John Robson Silver badge

        Re: Leaky ceramic?


      3. Kevin McMurtrie Silver badge

        Re: Leaky ceramic?

        I figured that when I said shorted. That's why you can maybe get it to pop off the board. Once the solder melts, various organic vapors will either pop it off or blow the solder away.

        MLCC caps cap pop off by burning their adhesive dot. Tantalum caps need no help.

      4. ThatOne Silver badge

        Re: Leaky ceramic?

        > (Speaking as a former capacitor design engineer)

        "Speaking in my capacity as a former capacitor design engineer"

        Sorry, couldn't resist...

        1. MyffyW Silver badge

          Re: Leaky ceramic?

          Please don't make me giggle, I'll be dealing with a different kind of leakage...

  5. MachDiamond Silver badge


    If you think of all of the electronic devices you have the only went through a cursory functionality test at the factory using parts from a huge bin. Now look at the process to build a satellite where every component is hand selected and systems tested multiple ways to verify operation and they still get a higher percentage of failures than in the consumer world (quantities of satellites being rather tiny). These parts are also the highest spec from a quality vendor, not sourced on price alone or at all in most cases. I have to wonder if the process is flawed. Space is a difficult environment to design for, but it's not that hard.

    I'll admit that MLCC caps can be a PIA.

    1. yetanotheraoc Silver badge

      Re: Strange

      "higher percentage of failures than in the consumer world"

      All hardware eventually fails so in both cases it's 100%. The difference is when it's some expensive satellite then you read about it.

      "quantities of satellites being rather tiny"

      You are measuring it wrong. A satellite has millions of parts compared to a consumer piece of kit having thousands. And still the mean time to failure for a satellite is in decades (granted some is DOA) versus for the consumer kit in years (granted some lasts decades).

      1. MrBanana

        Re: Strange

        I have a pre-amp from the late 1980s that still works flawlessly, and has been permanently powered on for most of that time. It was build with discrete transistors and diodes, and polystyrene and polypropylene caps. No ceramics or electrolytics. It cost an arm and a leg back then, but I've never regretted it.

    2. LateAgain

      Re: Strange

      Don't they still make them on pairs?

      One to test, one to send ip.

    3. Anonymous Coward
      Anonymous Coward

      Re: Strange

      I remember seeing a satellite in the London Science museum many moons ago, and being rather suprised that the connector on the PCB had the RS logo on it. Just seem so mundane some how....

      The main problem that I have seen with MLCC (never knew till today about MLCC, just called them sufrace mount ceramic caps) is that when the kit gets dropped and they get knocked off - then trying to find a) where they dropped off from and b)if I can solder it back on - hopefully the solder pad is still on the board, or I can solder it to something else or part of the silver bit of the end is missing and I can turn it over and use the other side.

      (Came from electronic background, drifted in IT, apart from visually looking at stuff and poking it with a soldering iron if it's obvious fault. My Yorkshire boss ("How much????") was pleased that I was fixing out of warranty monitors with leaking electrolytic caps for about £2 rather than buying new monitors.


      1. Anonymous Coward
        Anonymous Coward

        Re: Strange

        Not so easy to solder the stuff back on now.

        A few years ago, I got a new piece of kit out of the box and it rattled. Opened the box and a capacitor dropped out. Found the bare spot where it should have been, blew the dust off my trusty but not recently used soldering iron and tried to solder it back... it was near impossible as the modern lead-free stuff has a higher melting point and this was a temperature-controlled iron for traditional solder

  6. Sparkus

    check the supply chain...

    see if the dodgy components came from the same source, factory, lot #......

  7. Mavis Grind

    Can ceramic capacitors leak?

    1. james 68

      If you consider electrons moving from one point to another where or when they aren't supposed to go, then yes.

  8. Zenco

    I was under the impression that only polarised capacitors could leak. In my experience the only fault mode of a ceramic capacitor is mechanical failure, where it goes open circuit.

  9. Electronics'R'Us

    Power supply failures

    It depends on the specifics, but here is my list of things that go wrong that are caused by capacitors. It is not just the capacitance, though. The parallel leakage resistance and effective series resistance are also critical design considerations. Effective series inductance is not usually an issue with regulators.

    Soft start. Virtually every regulator that feeds a capacitive load (just about all of them) either have a soft start or short circuit sense inhibit at power up. For many of the switch mode devices that soft start is defined by a capacitor. If that device has become a smaller capacitance (a very common fault mode for ceramic devices), then the soft start won't be as soft and a start up short circuit would be detected, which can stop the start up process.

    Loop compensation. All regulators require loop compensation to prevent them being oscillators (which can often let the magic smoke out of the regulator itself). This can be tricky to get right as a dynamic load transient that is not corrected quickly enough (over compensated) can be just as bad as too fast (under compensated). Those compensation networks are made from resistors and capacitors.

    There are several poles and zeros in a typical regulator which all interact and a fault may not be apparent immediately for various reasons. Note that even linear regulators require loop compensation although some are easier to implement than others.

    Output ripple filters. This is an interesting one because the ripple filter is often part of the loop compensation network (or more properly, the loop compensation network compensates for the output pole and zero for a particular topology). If there is excessive output ripple, then downstream devices may not work properly, which might trigger a shutdown.

    A typical regulator has a dozen or more components depending on the details and a passive component is more likely to fail than the silicon controller device(s).

    Lots of possibilities.

  10. Grivas Bo Diddly Harm

    Ail C-SAR.

  11. NXM Silver badge


    One favourite trick somewhere I worked was to give the trainee some piece of hardware to fix after sellotaping a low voltage electrolytic to the back with a long wire to the prankster's desk.

    Turn the mains on to it, and watch the trainee run for a new pair of undercrackers.

  12. Sandstone


    It's Putin's fault!!!

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