That brings up some weird memories.. I saw 2 different researchers do bit manipulation in Matlab by printing the binary data as hexadecimal string, doing string manipulation on it and convert it back to binary
There's a strong indication that SpaceX does use software receiver in Falcon 9 and Starlink: when they didn't encrypt the downlink telemetry someone captured the signal and found some plain text: https://www.rtl-sdr.com/receiving-space-x-falcon-9-telemetry...
> PpRx has been licensed through the Radionavigation Lab to multiple commercial companies, but notably a major aerospace
company that uses the technology across their suite of advanced spacecraft and satellites. The SDR is deployed across the
company’s mega-constellation of satellites used for broadband Internet
For L1 I think a raspberry pi can have a reasonably fast time to first fix, for offline processing you can go faster than real time. L2/L5 need large sampling rate and a pi is probably not fast enough.. unless if you ditch float32 processing and do 2 bit signal processing, a uni commercialized that: https://radionavlab.ae.utexas.edu/wp-content/uploads/2022/10...
> remove bit twiddling — System programming languages like C, C++, Odin, and Zig need to manipulate bits, but a scientific DSL like Fortran does not need bit twiddling operators like &, |, ~, and so on. Bits are, after all, hardware-level concepts.
Yeah no, your language will be DOA if you don't have bit twiddling, because you can't write arbitrary binary file parser / writer without some sort of bit manipulation.
Because ITAR only applies to US companies, non-US companies can do and sell whatever they want. My favorite example is CRPA antenna, where they can block the jamming signal, so it was on ITAR. Other countries like Turkey and China doesn't care so you can even buy one of them in alibaba. They got all the money while the US company can't compete because they're not allowed to, so after several lobbying efforts, that technology got downgraded from ITAR, very toxic export control, to EAR, your normal export control.
Another example is high frame rate thermal camera, US companies are banned from exporting cameras above 9 fps, while chinese companies freely sells 50 fps cameras
Its an active research topic called signal of opportunity navigation, and papers has been written saying this is possible, some of the uses the idea you mentioned. I used to be involved in using starlink signals for positioning and there are problems:
1. Public ephemeris from space-track (celestrak) is notoriously inaccurate after a while. Less of a problem for starlink as they give free access to high accuracy ephemeris from their onboard GPS receiver: https://starlink.com/satellite-operators
2. For proprietary signals like starlink they can change signals whenever they want without telling you and break your positioning algorithm. For example, starlink used to transmit some sort of narrowband CW wave at their frequency band, which can be received by cheap ($20 ish) RTL-SDR dongle and satellite TV antenna: https://www.rtl-sdr.com/receiving-starlink-signals-with-an-r... . Everyone speculates that its a beacon signal, research papers were written trying to exploit doppler positioning from those signals. Then the signal disappears, as its possible that they don't intentionally transmit those signal. They you can't use cheap hardware to capture the signal, you need expensive hardware that can capture the full 250 MHz bandwidth. This is not a problem if you use standardized signals where they can even intentionally add positioning signals like 5G or digital TV
My pedantic self says GNSS includes other non-US constellations such as GLONASS, Galileo and Beidou, and they flew those satellites because they don't fully trust US GPS
I wish... I'm on Windows 11 Enterprise with corporate Teams, definitely 100% Microsoft approved combination and:
- on one channel my message never got sent, while on another channel it does work
- sometimes when I scrolled up the old messages doesn't show up, with a 'message removed by organization retention policy' text.. but those are messages from yesterday and sometimes when I restarted Teams it shows up again.. sometime it doesn't but when I opened web Teams it does show up
- sometime I can't connect to Teams for no reason, restarting Teams and computer doesn't help either, went to the IT helpdesk and they spent several minutes redoing what I did until they just googled it and delete the cookies or something
I also used slack and from my perspective its 100% reliable at delivering text messages
- They don't use GPS frequencies because there is receiver on the moon that receives GPS L1 signals (LuGRE and potentially more in the future)
- Make it easy to acquire for low complexity hardware
- Use 5G forward error correction code to reuse existing hardware implementation
- Design the signal in a way so that the user can easily find start of a data frame
And those are RF level considerations... there will be more considerations needed for the data transmitted over those navigation signal that the receivers need to use to determine navigation satellite position as lunar orbit is much more complicated than Earth orbit
Sometimes its not instant though.. sometime web search completes faster then locally installed software and because of muscle memory I accidentally opened a bing page about scrcpy (where the first result is an unaffiliated web page instead of official github page!) instead of my locally installed scrcpy
unfortunately the FPGA verilog source code isn't open source.. and I can't see any RF block diagram in the website
Some more questions because the website isn't clear:
- does the FPGA handle digital beamforming in the FPGA fabric? or it controls RF phase shifters for analog beamforming?
- will we have access to FPGA pin constraint file so we can write our own verilog
- can I get IQ samples from the antenna elements and run my own beamforming algorithm / calibration in a separate PC with possible GPU acceleration? or it will be bottlenecked by rpi5 gigabit ethernet?
You do need access to a large telescope (at least 1.2m based on the wiki article), a sensitive detector (is photomultiplier tube sensitive enough??) and most importantly, access to your local laser clearinghouse so you don't accidentally shoot an airplane, blind the pilot and got arrested, or a satellite and start a war (if you believe some guy on quora). Probably the last part is the hardest thing for an amateur
And to run windows only apps like some embedded toolchains. Although that gives a motivation for us to move on to gcc because windows is annoying to be used on CI/CD and gcc is good enough compared to that other toolchain
A bit pedantic here.. I think you might be thinking about space tether propulsion. I don't know if that has been deployed yet. Magnetorquers, as in a device that uses magnets to rotate the satellite are very common in cubesats, you can buy it off the shelf