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I worked on the software for the star trackers in these. Glad to hear they have already made contact. :-)
by planteen 10y ago
I worked on the software for the star trackers in these. Glad to hear they have already made contact. :-)
- bootloop 10y agoGreat! You didn't fuck it up than right? Or does it take some time to tell? I guess we will see soon. I will come back to you and this comment if they go down!
- devnonymous 10y agoYeah, we'll downvote the comment, that'll serve 'em right! :-)
- bootloop 10y agoI thought its funny... People are too serious. At first it even got some upvotes.
- comboy 10y agoI can't get my head around how this thing works. Apart from the direct GPS signal it's able to also receive the part of it that was reflected by the ocean? How does the reflected signal tell anything about the wind speed? And btw what are star trackers used for? As a fallback for GPS?
- wrigby 10y agoIIRC, star trackers are used as both a position and an attitude reference. GPS gives you only position (though more sophisticated systems can be used to determine attitude). While a GPS outage is a minor inconvenience for most of us, it could be pretty catastrophic for spacecraft if they didn't have another position reference. EDIT: See below - I was off; they're just attitude, not position
- planteen 10y agoStar trackers are usually just used for attitude, not position. I've heard of research to use them in conjunction with a camera pointed at Earth to resolve coastlines to get position, but it's very theoretical at this point AFAIK.
- phamilton 10y agoFor those of us just watching, what is attitude? At first I though spellcheck might have corrected it from altitude, but 3 times among 2 differently people I see attitude.
- andrewflnr 10y agoIt's orientation, AFAIK, what direction it's facing.
- planteen 10y agoYep. Think of it like right ascension, declination, and roll from astronomy. Given attitude, your position, and the time, you can know where you are pointing on the Earth (lat/lon).
- oh_sigh 10y agoAltitude is how high your body is. Attitude is which direction your face is pointing. Imagine a satellite meant to photograph the earth at the right altitude but the wrong attitude could just be taking nice shots of outer space.
- toomuchtodo 10y agoWhat's the difficulty level of writing star tracker software for consumer grade CCD devices? I've always had writing and open sourcing a star tracker on my bucket list, similar to how this person did the same for a from-scratch GPS receiver [1]. Same for determining your position in space using pulsars as beacons [2]. [1] http://www.aholme.co.uk/GPS/Main.htm http://www.aholme.co.uk/GPS/Main.htm [2] https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20150001327.pdf https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/201500...
- trailbits 10y agoThe earth is bathed in radiation from GPS transmitters and these clever satellites are using doppler radar techniques to see how those signals are being reflected from ocean waves. From the doppler shift you can infer wind fields. Consumer GPS receivers only compute position from these signals, but there is a lot of interesting science you can do from the raw signals with a hacked GPS receiver.
- comboy 10y agoWhoa, doppler shift from this mess from ocean waves, that's amazing. Looks like you registered just to reply, thanks a lot.
- lobster_johnson 10y agoCan you tell us some more? What the software is, what language, what hardware they're based on, etc.?
- planteen 10y agoIt's a LEON CPU (SPARC architecture) with a FPGA for hardware acceleration. Languages are C, MATLAB, and VHDL. The function is to take a picture of stars and return where you are pointed in inertial space with lots of accuracy.
- lobster_johnson 10y agoVery interesting, thanks.