> Data gathered from its scientific instruments, once collected, is stored within the spacecraft’s 68-GB solid-state drive (3 percent is reserved for engineering and telemetry data)
Hope the SSD does not fail after 32768 or 40000 hours of operation.
Also likely that they are already super experienced with that particular SSD. I read an article a long time ago that talked about a spacecraft with some camera on it. They said the camera was 10 years old when it was installed and although their were better cameras out there, they picked this one specifically because of reliability.
Chances are they or the manufacturer have a room full of those cameras clicking away on a schedule for the last ten years, too, as an early warning system.
Could it perhaps be this? Interesting read about the level of effort and process invested in the Space Shuttle's software (~1996) [0]
For a TLDR, this answer [1] is great.
My favorite excerpt: The Shuttle software consists of ca. 420,000 lines. The total bug count hovers around 1. At one point around 1996, they built 11 versions of the code with a total of 17 bugs.
Data at-rest in SSDs isn't really at rest. The controller is constantly scrubbing and correcting errors.
The real hazard with SSDs is leaving them unpowered. I know of a story of several systems purchased a decade before they were needed and by the time they were used the boot drives were corrupted.
Huh. Interesting. That explains why my SSD died at boot time. I thought it was just coincidence, and that it had died the night before or something, but that obviously doesn’t make sense.
They are pretty awesome. Once got some data that seemed to be bad out of one and realized that the entire error was exactly accounted for by the Coriolis effect from the rotation of the earth.
I believe that the tech you mention is the same tech as used by the flat-earthers in Behind The Curve in the $20k gyroscope they bought, to try and prove that the Earth did not rotate (except they found it picked up a 15-degree-per-hour drift, debunking themselves, so then doubted the technology, heh) [1].
But, aside from the laser/fibre-optic tech, there are also MEMS [2] gyroscopes also — which is almost nanotech IMO — which are used as sensors in modern phones/tablets, and also on drones (to assist with navigation), plus various other robotics uses, and more.
MEMS gyros — often with an accelerometer (aka IMU / inertial measurement unit) and maybe a magnetometer (compass) — can be bought from folk such as Adafruit [3], SparkFun, etc. (I've got a few different ones myself), and hooked up to e.g. an Arduino or similar MCU (or indeed anything else that speaks can speak the appropriate protocol, e.g. I2C/SPI/etc depending on the board in question).
Hmm, just looked for a good image of how a MEMS gyro works, and didn't come up with what I was looking for / recall seeing before (I'm a bit pushed for time), but there's a diagram on this WP page [4].
I've done some projects myself with MPU6050 and some with its 9-axis "bigger brother" the MPU9250 (same as 6050, but with added 3-axis magnetometer/compass). I've also used the LSM9DS1 — another 9-axis IMU, just a different chip.
— Yeah, definitely amazing tech for the price. Cheap as chips! /me gets coat.
Ingenuity, the Mars helicopter/drone, apparently includes a bunch of off-the-shelf kit like this — IIRC I think a bunch of the parts are made by SparkFun. I don't recall any specifics though.
You could almost invert your logic too. Perhaps the spinning on the HD throws off the telescope enough to be troublesome. I'm not sure how stable the lagrange point orbiting is, but it can't be super stable.
Any moving mechanism is potentially a source for disturbance to the telescope. Not something that affects the stability of the orbit. But the small vibrations can translate to small vibrations in the instruments and secondary mirror which then cause distortion over the integration time of the image.
I don't know that that is the primary reason HDD's have been avoided. But any moving part is another source of failure so my guess is the HDD's life is not as long.
As far as I'm aware I don't know of any spacecraft that has flown a HDD (but there certainly could be). However, some early spacecraft did use tape drives. Hubble originally used tape drives and was replaced with solid state memory during one of the servicing missions.
Shielding adds significant weight, which isn't good for space-bound components.
I would guess they just use RAID, do round-trip data verification before writes succeed, and then reinitialize and scrub any storage module behaving improperly.
For bits stored on SSDs which already rely on error correction, if they were willing to make custom hardware rather than use something off-the-shelf, they could add more chips and scale up the error correcting code to deal with more errors.
Technology for space lags behind consumer technology by 10-20 years. There are a few reasons for this:
- Long lead time to test and certify hardware.
- Higher reliability requirements (e.g. must work non-stop for 10 years)
- Must be able to operate in a higher radiation environment with little to no cooling. In a vacuum, and in zero gravity, cooling works very differently to how it does on Earth.
- These missions often take a decade or more to come together, and changing requirements throughout that process is hard, costly, and risky, so often they stay the same from the beginning.
Notably, SpaceX are bucking this trend a bit with their avionics which just runs on standard Linux machines rather than specialist machines or with a realtime OS, but they have mission lengths measured in minutes to hours, not decades.
Didn’t JWST use some kind of grivitational breaking to stop at the LGPoint?
A manned mission would require much more fuel to shorten the time of the trip and fuel for returning.
I think the engineering that would go into a mission to do maintenance/repair would be quite valuable and help with many other missions. It’s far enough to be far, but not so far that other factors like communication is extremely delayed. Getting that far out of LEO has a huge set of new challenges, I assume, we should be able to learn about.
Even if a crewed spacecraft could be sent to it (honestly not that crazy given JWST's predicted lifespan of 20 years. Starship should be crew rated in 10 years at most and if not, Orion could be sent with some sort of expanded service module for the trip) the issue would be that docking to or even approaching the telescope is extremely risky.
You don't want to fire any thrusters in its direction to avoid damaging the sunshield or the mirrors, but of course to slow down at it you would need to do that at some point.
If the SSD failed and a constant connection to Earth cannot be maintained, the more realistic solution would probably be to launch a satellite to a high orbit to maintain permanent connectivity with JWST which can act as a store-and-forward relay, effectively replacing the SSD without having to actually go to the telescope.
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:
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)."
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.
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.
It's "Starship", and it's unlikely to be able to get to where the JWST is in the next few years due to needing to be refuelled in orbit. Plus they have no payload bay design. Then there's the robotics necessary for doing a repair, or human-rating Starship, either of which is years worth of time.
Hope the SSD does not fail after 32768 or 40000 hours of operation.