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What materials and coding would be needed? And what are the necessary instructions should someone follow? I heard that you don’t need to be apart of NASA to build a satellite, but it just costs a lot of money to build and launch it (from NASA’s launcher). How would I get it to send me data from space?

Something similar to this video. How would some one build something like it?

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    $\begingroup$ The hard part is the super accurate clock. These are not cheap devices, and probably not easily built in your garage. Counting vibrations of an atom is 'tricky'. $\endgroup$ – geoffc Jun 12 '18 at 14:10
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    $\begingroup$ I'm not sure what you want to do. Do you really mean GPS? (Global Positioning System) An individual GPS satellite isn't much use, you need dozens of them, and all the data they send you is timing signals that you can use to locate yourself. A satellite for TV broadcasting, say, or internet, would be a different story. $\endgroup$ – Steve Linton Jun 12 '18 at 14:26
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    $\begingroup$ This is not a GPS satellite. Please improve your question. Do you really mean to build a satellite that could be part of a GPS constellation (and why would you want to)? or do you mean to build a cubesat that performs some function? If so, what function is that? The answers are wildly different. $\endgroup$ – Ross Millikan Jun 13 '18 at 3:16
  • $\begingroup$ @geoffc I dunno...1500USD certainty seems pretty cheap to me. popsci.com/technology/article/2011-05/… $\endgroup$ – Aron Jun 13 '18 at 6:06
  • $\begingroup$ @Emily - 2 minutes of googling and I get something ;). Short video of GPS III series satellite construction youtube.com/watch?v=MysI2_Sbmsg. For basics of GPS satellites you can start at Wikipedia page or tons of videos on Youtube. $\endgroup$ – Heopps Jun 13 '18 at 7:14
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This type of satellite is called a CubeSat. They're a standard size and mass, and can be launched relatively cheaply (perhaps \$100000) using spare capacity on a rocket whose main job is to launch something else. The Wikipedia page I've linked to outlines some of the things that need to be addressed in designing a cubesat and links to lots of further resources. As the video suggests it's still not a home workshop job -- you need a good electronics lab and quite a few skilled people.

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GPS satellites are not from NASA, they are from the U.S. Department of Defense. A functional GPS satellite is much bigger than such a tiny cubesat. The information about generating the military part of the GPS signal is classified. Each GPS satellite's position is determined from special ground stations, without precise and actual orbit information the system would not work. There is no place in the system for additional GPS satellites from a third party.

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  • $\begingroup$ Ehhh... this answer only covers where GPS sats come from in terms of the USA, not internationally. Then again, same with the other one. $\endgroup$ – Magic Octopus Urn Jun 12 '18 at 18:26
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    $\begingroup$ GPS is an US satellite navigation system, there are other satellite navigation system from other nations, but they are not called GPS. $\endgroup$ – Uwe Jun 12 '18 at 18:51
  • $\begingroup$ Oh really? That's neat. My original confusion came from the link being a UK-based satellite, thank you for clarification on diction. Any wiki links on what other nations call their versions of GPS? $\endgroup$ – Magic Octopus Urn Jun 12 '18 at 18:56
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    $\begingroup$ @MagicOctopusUrn At least at one point, the US constellation was actually called NAVSTAR, and GPS was a generic term, but NAVSTAR was the only constellation built up. The EU equivalents are the Galileo constellation IIRC, and Russia's is GLONASS. $\endgroup$ – Erin Anne Jun 12 '18 at 19:13
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    $\begingroup$ This may be literally true in the sense that nothing else would be a "GPS satellite", but it is not as practically true as it sounds - there are receivers going back to the 1990s that use satellites from multiple navigation constellations, and also systems which augment the GPS signal with terrestrial sources transmitting similar signals. There have also been documented instances of unauthorized signals spoofing GPS receivers. $\endgroup$ – Chris Stratton Jun 12 '18 at 21:34
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If you intend this as a method of learning about GPS, you don't really need to build satellites to do that. The principle of using 3 or 4 base stations to calculate location works just as well on the ground. And is much cheaper than launching the stations to the space.

This article could be one place to start from: https://www.rtl-sdr.com/localizing-transmitters-to-within-a-few-meters-with-tdoa-and-rtl-sdr-dongles/

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Now, on the other hand, if you wanted to learn about satellites, you should probably find your way into some university with a space technology department. It is quite common for them to have cube satellite research projects going on.

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As far as the "how does it send me data from space?" goes, the GNSS constellations that exist today broadcast a pseudorandom sequence of digits that allows a receiver to determine the exact time the satellite broadcast the signal. GNSS receivers measure the delay in the signal reception and combine this with information about the satellites' orbit to determine its position relative to the satellite. You would need a method of generating your own pseudorandom sequence that is long and unique enough to ensure there is no chance of cross-correlation (locking on signal believing it to be an incorrect time or from a different satellite).

The current GNSS constellations operate at Middle-Earth orbit (roughly 20,000 km away). Even at this distance there is enough drag from the remnants of the atmosphere to slow down the satellite, this error (called 'ephemeris error') needs to be measured and your satellite would occasionally need to have its orbit boosted.

The satellite in the photo would be far too small to broadcast a powerful enough message to be heard on Earth at MEO (keep in mind GNSS sats are roughly the size of a economy-sized car), and even at that size the received signal power on earth is around -135 dBm. You could use something smaller (a la the Iridium Constellation), and bring them in closer, but you need more units to cover the Earth at this point.

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