14 ms·
Receiving SpaceX Falcon 9 Telemetry with a HackRF and 1.2m Satellite Dish
- ex3ndr 6y agoI feel that this data is trade secret - why it is not encrypted?
- gmueckl 6y agoLooks like this is just data from the GPS receiver, mostly about where the rocket thinks it is at the moment. This doesn't strike me as particularly sensitive. Data from, say, sensors embedded in the engines would be much more interesting.
- chrisseaton 6y ago> This doesn't strike me as particularly sensitive. I'm no rocket scientist but I would have thought you'd want to encrypt and sign everything... by default. Otherwise how do you stop spoofing as well?
- verelo 6y agoEncryption takes time, and energy. I suspect they are trying to avoid adding latency to anything that’s not super sensitive.
- mikepurvis 6y agoThose final gasps of data while a vehicle is breaking up could be critical for understanding what went wrong with it. I can definitely see how missing out on the final milliseconds of telemetry because some encryption buffer wasn't full enough to trigger a frame or something would be unacceptable.
- myself248 6y agoI think this is the true reason that telemetry is as raw as possible. The happy-path telemetry tells you very little you didn't already know, but when something goes wrong, those last few bits before the transmitter went silent can make or break your analysis. Sitting on bits until you have enough to run a block through the cipher seems like a terrible idea, even if that's only a few microseconds. Things happen mighty fast when you're trying to get data that might represent the structural collapse or propagation of a blast wave through the body of a hypersonic vehicle.
- vardump 6y agoYou don't need any buffering if you pick your encryption mode correctly. That is, use a stream cipher.
- mikepurvis 6y agoHow much would that affect the ability to recover a partially-corrupted stream, though? I feel like that's part of this too— where the last few seconds might have an increasing amount of the content scrambled, and encryption would render that completely unusable, whereas having it in plaintext would still permit some degree of inference about the fragments you do have.
- vardump 6y agoIt would not affect at all. Flipped bits / transmit errors have no avalanche effect, unless the bit was flipped in the encryption module.
- mikepurvis 6y agoWhat if you have gaps in your stream with uncertain length, though? Based on quick read about stream ciphers, it seems like the alignment of the key and data is pretty critical.
- 6y ago
- toomuchtodo 6y agoI can't speak to SpaceX's decision, but in FCC rulings, they have proposed encryption when commanding vehicles, not for telemetry or tracking comms (satellites, specifically, although I'd assume similar guidance for vehicles, with the only command you're going to send to the vehicle would be boom for range safety).
- toomuchtodo 6y agoFor historical purposes, range safety on SpaceX vehicles has been autonomous and onboard since 2017. Vehicles emit telemetry, but do not receive commands. https://www.spaceflightinsider.com/space-centers/ccafs/automated-flight-safety-improving-space-access/ https://www.spaceflightinsider.com/space-centers/ccafs/autom...
- BenjiWiebe 6y agoSpoofing is extremely difficult when you are pointing a highly directional dish antenna up into the air at a rocket.
- dylan604 6y agoNot if you're SR Hadden. I have been curious on what it would take to do a Contact like signal fake. Would it be possible for a satellite to be launched into a direction in space that for all intensive purpose make it look like it is coming from somewhere else further away? Would it be easy to tell that it is originating much closer than what it is simulating? How far would it need to be away from earth before it was believable, and then would the fact the signal's source is constantly moving futher away be discernible from the signal itself? Basically, think along the lines of a fanfic premise told from Michael Kitz' perspective.
- sandworm101 6y ago>> Would it be possible for a satellite to be launched into a direction in space that for all intensive purpose make it look like it is coming from somewhere else further away? Anything is possible but it would be very hard. You would have to fake the doppler shifts. With massive scrutiny you might even have to fake some absorption lines. Then, if the signal was longer than a few days/weeks, you would need to place the emitter far enough away that parallax, relative motion against the stellar background, was undetectable. That distance is probably measured in light-years.
- rrmm 6y agoIf they were carrying a national security payload, then having a gps feed of the second stage trajectory and target orbit would be less than ideal.
- ceejayoz 6y agoAmateur astronomers are very good at spotting national security payloads after launch. https://www.theatlantic.com/technology/archive/2016/06/mapping-clandestine-moons/485915/ https://www.theatlantic.com/technology/archive/2016/06/mappi...
- rrmm 6y agoYup. Easy to do for most adversary nation-states as well, but the NRO still doesn't allow the SpaceX livestream to follow stage 2.
- _Microft 6y agoMaybe it's possible to detect radio echoes off the rocket exhaust trail (passively) like it is possible to do with meteors [0][1] and roughly tell where the second stage is (just for the sake of doing it this way). [0] https://www.electronics-notes.com/articles/antennas-propagation/meteor-scatter-burst-communications/meteors-trails-radio-signals.php https://www.electronics-notes.com/articles/antennas-propagat... [1] https://en.wikipedia.org/wiki/Meteor_burst_communications https://en.wikipedia.org/wiki/Meteor_burst_communications
- ceejayoz 6y agoYeah, over-classification is definitely a thing. I suspect they don't want close-up video imagery of the payloads out there, either.
- Cthulhu_ 6y agoAnd if amateur astronomers can do it, a well-funded national space agency can do it even better. I'm 100% sure that any launch is picked up via radar and sattelites and the like when they happen, and various properties extracted and extrapolated to determine their target orbit. That said, I wouldn't be surprised if some known launches also contained some unknown payloads. Stealth technology on a satellite would probably thwart detection in space well enough.
- ylere 6y agoPeople have been running full simulations of SpaceX vehicles just of on-screen telemetry and videos [0]. In the past, SpaceX has been very open towards these kind of efforts, they don't seem to mind at all. [0] Example for SN9: https://www.youtube.com/watch?v=UeBtBidjlvk https://www.youtube.com/watch?v=UeBtBidjlvk | https://flightclub.io/result?code=SN91 https://flightclub.io/result?code=SN91
- magicalhippo 6y agoI imagine it adds latency, which at the very least means more data is lost in case of accident, which can make it harder to know what went wrong. It also adds an additional failure point, as a single bit error during encryption can scramble an entire data packet or worse, rather than just invalidating a single sensor reading.
- de6u99er 6y agoYou can do this with FPGAs in real-time. https://www.google.com/search?q=fpga+encryption+serial+data+real+time https://www.google.com/search?q=fpga+encryption+serial+data+...
- cedivad 6y agoThis is just a guess, but having read the FCC regs in the past, maybe it's because it's so much easier to be complaint when your link is unencrypted (and your rf standard published).
- robin_reala 6y agoSerbia and Siberia are substantially different places. Let’s hope it’s just a typo and not a bug :)
- londons_explore 6y agoI really want to visit /S.*ia/ sometime!
- Lev1a 6y agoI personally don't have the kind of time to visit all of /S.*ia/, I'll have to make to do with just /S\w+ia/. Shame, really...
- function_seven 6y agoNot sure what you have against Sia, Cypress. I, for one, will try to make it to /S\w*ia/.
- bigiain 6y agoSouth East Asia are ramping up the hospitality as we speak...
- fastball 6y agoMight want to use /S[beir]+a/, otherwise you're gonna end up visiting a famous singer!
- rsj_hn 6y agoOr Silesia
- darknavi 6y agoSouth Africia is really pretty this time of year!
- ro2nie 6y ago
- _Microft 6y agoSome sleuths repaired/decoded a corrupted video file from (the first?) splashdown of a Falcon 9 in the ocean a few years ago [0], so maybe someone is able to tease out some information from the recorded binary data as well? They only searched for obvious string data so far. It's a different beast of course, as the structure and meaning of the data is basically unknown in contrast to the known format of a video file. Maybe some meanings can be inferred, let's say that a value in the possible range of rpms of a turbopump is correlated with acceleration or so? [0] https://www.nasaspaceflight.com/2014/06/recovering-falcon-9-ocean-landing-video-done/ https://www.nasaspaceflight.com/2014/06/recovering-falcon-9-...
- Cthulhu_ 6y agoI'm kinda hoping they'll publish some specs about at least part of their transmission data, I mean given that it's not encrypted either means it's not critical, or encryption is too costly. I can imagine that commands the other way do have some kind of encryption.
- TeMPOraL 6y agoI'd assume so. It's standard practice with space hardware to keep the downlink unencrypted, and secure just the command channel. Saves on complexity and power use (the latter matters a lot for satellites).
- sandworm101 6y ago>> commands the other way do have some kind of encryption. I'm betting that they don't. The reason that this stuff isn't encrypted is likely the same reason that fighter jets and airliners don't have keys. Yes, someone could jump in and do something bad, but the greater danger is the encryption/lock system causing an accident by getting in the way of legitimate commands. This is the launch vehicle, not the spy satellite. It is likely that physical realities offer sufficient protection. The rocket might be designed to ignore commands coming from the wrong direction and/or signal strength. It might be that to send a command you would have to be physically co-located with the legitimate antenna array, or be ridiculously more powerful, something that would be very easy to detect.
- shmerl 6y agoDoes HackRF require soldering an RF shield to it? Apparently it comes without it by default.
- marcodiego 6y agoHow likely is the possibility of sdr freeing us from wifi chips or cell modems that need proprietary firmware?
- namibj 6y agoThe latter already exists, at least for LTE. Well, SDR-based clients that you could package in a smartphone form factor. They're fairly power-hungry, though.
- newman8r 6y agoIt would be cool but I don't see it happening any time soon. Plenty of demos have been created, but the ASICs that the SDR would be competing with are much more efficient at doing their particular job, and they're very cheap.
- sgtnoodle 6y agoI vaguely understand that modern high performance rf chipsets are largely software defined anyway, which is why they require binary firmware blobs. The modulations have gotten so complex that there's really no chance of a CPU or even a general purpose FPGA keeping up in real-time. Someone unencumbered by an NDA would need to be smart enough to design a specialty FPGA with the right sort of accelerators in silicon. They would also need to avoid any active patents. Like pretty much anything, I imagine someone will figure it out for any given technology a decade or two after it's mostly obsolete.
- marcodiego 6y agoAre patents a problem for software distributed in source code form? I don not think so. I remember something related to font hinting and apple patents that could be circumvented by simply uncommenting part of the code recompiling.
- sgtnoodle 6y agoI specifically mean patents for the "generalized" accelerator hardware implemented in silicon that would presumably be needed to make a specialty FPGA that's fast enough to handle modern RF modulations, even in a vaguely software-defined way. That's presumably companies like Qualcomm's secret sauce, and you can bet they have it locked down with patents and NDAs. If someone came up with a general purpose CPU powerful enough to actually do everything fast enough purely in software, then that might be different (but would likely have plenty of its own patent issues!)
- danbr 6y agoThis is something I’ve always thought about doing, but lack the in-depth RF/demodulation knowledge to undertake. Glad to see the SDR community is already on top of it!
- koolk3ychain 6y agoI wonder if this telemetry is also unencrypted for launches carrying sensitive government payloads? Very cool stuff though, rtl-sdr.com has been a great source of entertainment for many years!
- macmcleod 6y ago> Usual CCSDS frame format is not used, instead custom framing protocol is employed I've worked with this before, and it can be a pain.