Basically, the spacecraft needs a transponder to communicate with Earth. The transponder is attached to a circuit breaker. For various reasons, the circuit breaker can flip off. When this happens, it sends an "I'm off" status bit to the spacecraft's power control computer, which in turn flips the circuit breaker back on.
The problem is that the transponder circuit breaker, if it switches rapidly, turns itself off without setting the "I'm off" status bit. Since the spacecraft computer doesn't know the transponder circuit breaker is off, it never commands it back on. Consequently, the spacecraft can't send or receive commands and becomes useless.
The paper speculates that one way to break out of this state might be to wait for an eclipse that lasts long enough to drain the onboard batteries, causing the whole spacecraft to lose power. When the spacecraft boots up again after exiting the eclipse restores power, the power control computer will unconditionally command the transponder circuit breaker on, restoring connectivity --- basically, waiting for orbital geometry to turn the whole thing off and on again.
There's more. You might think: "Well, just add a bit of code to the main onboard computer to unconditionally reset the circuit breaker every so often. Hacky, but it works, right?"
Nope. If I'm understanding this right, the power display computer (which doesn't appear to be programmable) is designed to ignore transponder power control commands from the main computer. The paper doesn't explain the reasoning for this resign, but I suspect it's probably to guard against software bugs causing exactly the scenario that the circuit breaker hardware bug caused. So in an attempt to guard against a software bug, the designers lost the ability to work around a hardware bug.
Maybe you could program the software to notice that it hasn't gotten commands for a while and deliberately rotate itself into an orientation that causes a power loss and reset? I'm guessing that the solar panels are arranged in such a way that it wouldn't work, and the attitude control fuel consumption might be excessive.
heh, some spacecraft buses are designed to do the opposite. they'll go into a spin during emergencies just to guarantee that their solar panels are hit at least occasionally.
> I'm guessing that the solar panels are arranged in such a way that it wouldn't work,
plenty of spacecraft have solar panel arrangements where it is possible for them to not receive any light.
> and the attitude control fuel consumption might be excessive.
spacecraft can (if designed to include them, which is common AFAIK) control their orientation with reaction wheels, no propellent required. (the reaction wheels will become saturated sooner or later, though. when orbiting bodies with significant magnetic fields they can be desaturated through the use of magnetic torquer bars. otherwise they have to use propellent to do it.)
(I don't think reaction wheels are capable of gross orientation changes at all -- only very minor alignment corrections.)
precisely. angular momentum.
> I don't think reaction wheels are capable of gross orientation changes at all -- only very minor alignment corrections.
nah. as an example, SORCE has nothing but wheels and a torquer bar (or two?), and aims all over the sky.
NASA calls Dell Support, too?
(I don't mean this as a spammy ad, just in case other people have as terrible Internet access as Chunghwa is giving me)
They turned it off and on again, and it worked (of course). So they refused to replace it.
And I can't schedule reboots, because it usually fails a few minutes after I start using it when I return to my house (not at a consistent time every day).
Even if it's really two "applications" running on the same CPU I don't see how spectre/meltdown would help since it's all about getting read-only access to "forbidden" memory. Clearly they don't need that (they know full well what's in memory), they want to be able to modify it.
In such a situation RowHammer might be used to modify the state of an other program sharing the same RAM in the right conditions but if there's one piece of hardware I expect to be hardened against spurious bitflips it's a space probe. We're talking about radiation-hardened ECC-protected RAM after all.
It also had a branch predictor, however, this line is notable:
> Note that the RSC never speculatively executes prefetched instructions.
This means that the branch predictor only did fetch/decode, and so the chip would not have been susceptible to Spectre, as the pipeline would have been flushed and the correct instructions reloaded as soon as the condition evaluated false, before the branch would have been actually executed.
That was the Pentium 4 not yet in existence so there is no chance of there being an x86 able to be 'Meltdowned' in space. However you are most definitely thinking along the right lines, but I am sure the NASA boffins would have tried all the hacks they could back in 2007. Or maybe the management made sure this was not possible, much like how the Voyager missions were not supposed to go beyond Saturn yet behind the backs on management everyone made sure those spacecraft could get past the edge of the heliosphere.
Edit: I read the wiki, very interesting
> A number of articles published by the amateur satellite tracking community state that if the satellite is still in orbit and operating covertly, they will attempt to locate it visually
I’ve only managed to receive so far due to a cruddy antenna but that was with a $30 Baofeng radio from Amazon.
Note: you need a license but it’s pretty easy to get, at least in the UK and you learn a lot while getting it. It also tends to cost you a lot of money in the end because it’s really interesting :)
Not in one sitting, IIRC went from tech to expert on the second trip.
He had a giant dish in the back yard hooked up to a computer with a monochrome monitor. I think he got weather data from it.
Edit: Storytime. Several weeks ago, about 2:00am local time, I was letting the dog out into the back yard and saw a very bright object (somewhat brighter than the stars around it) passing from NW to SE, almost overhead. It had a bright-dim-bright frequency of about 10-15 seconds. A satellite is the only option that comes to mind, but I checked several "what's overhead now" websites with no luck.
"Meet the amateur astronomers who track secretive spy satellites for fun"
If it is the case that no one remembered about this satellite, then this really is an amazing find.
I have a sudden urge to somehow make DSN Now my desktop background.
> I have attached the TLE I got this morning from JSPoC/CARA. Looks like a close match. We are in the process of engaging the Deep Space Network to see if they can get a signal lock. They (JPL/DSN) are in the process of digging up 13-year old configuration files for that attempt. The DSN has evolved since then so some adjustments to their system setups will be required.
> I have no schedule estimate yet for when that first attempt will be made. If we are able to get signal lock and verify that it is IMAGE, we will setup a MINIMAL ops setup to verify telemetry/command and make an initial assessment of the health and viability of the spacecraft bus. I don't have a credible schedule prediction yet for that step either.
> Thank you for all of your efforts for IMAGE. IMAGE made ~39 new discoveries about the Earth's magnetosphere and plasma-sphere. At the time it stopped radiating, NASA HQ ranked IMAGE as the 2nd most valuable space-physics mission flying. A follow-on mission called MMS, with a 4-spacecraft constellation is currently flying, in part, to follow up on these discoveries.
> I just received official confirmation from NASA that IMAGE is indeed alive! See Below!
> Engineers at GSFC have acquired the suspect S-band source using the 4m CTA (Compatibility Test Antenna) here at GSFC (.jpg attached and no I’m not in the picture). They acquired the signal while the target was on ascent at about 2RE. Center frequency (CF) was between 2272.478 and 2273.418. The difference between IMAGE documented CF of 2272.5Mhz can be attributed to expected Doppler. Subcarriers are visible as well 1.7Mhz from CF as expected. The signal strength was oscillating. Plots will be forthcoming. The oscillation is not unexpected given IMAGE’s loss of spin balance.
> All indications so far suggest that this is, in fact, IMAGE.
Not sure your OS, but if you're a Mac user you can do this pretty easily with GeekTool. I used it for some years as a quasi dashboard on desktop setup and it was pretty nice.
What replaces the expensive satellite tracking system? A top notch neural network with high endurance myelin-actuated 6-dof arm. You.
And who might 'the wrong hands' be?
And how does proving that it works prevent it from falling into the wrong hands?