Any RF you can receive from low earth orbit is up for grabs. What would you do with a global satellite constellation of software defined radios?
An astronomical interferometer with the receiver the size of Earth, capable of observing in multiple directions simultaneously.
(Though first, help me validate it actually makes sense. I know very little of interferometry - enough to imagine this could work, but not enough to be sure an equivalent result won't be achievable through a bunch of ground stations on opposite ends of the globe.)
New (but slower) internet? (https://i.ytimg.com/vi/Km5XQxRrQvw/maxresdefault.jpg)
I’m also curious if anyone can explain everything which goes into something like this and the costs.
There are quite a few constellations that you can benchmark by: - Astrocast (IoT) [1] - Fleet (IoT) [2] - Iceye (Earth Obs) [3] - Planet (Earth Obs) [4] - Spire (Earth Obs, Navigation) [5] - Capella Space (Earth Obs) [6]
And many more ...
Cost of the satellite itself depends on the payload and on the attitude-control requirements - you can get a feel for rough costs by looking at the parts costs from suppliers like [1], adding in highly-skilled labor costs, etc. Numbers I've heard for simpler, smaller RF-only sats can be about $50K, while fancier things like Planet's Dove earth-observation sats (custom-built telescopes, precise pointing, high-bandwidth ground links) can run in the hundreds of thousands of dollars. (This is from what they've said to the press; Planet is very cagey about revealing precise cost numbers.)
Once you've built them, it's about $100K-$500K to launch them to LEO, depending on size (e.g. Nanoracks [2] will launch a 1U via the ISS for $85K, while Spaceflight Inc. [3] launches a 3U for $300K, or a 6U for $550K, or a 12U (who even builds those??) for about $1M).
So let's say a moderate-cost example would be a 3U with off-the-shelf payload hardware. Construction cost ~$100K, launch cost $300K, so $400K per satellite. You want a constellation of 50, that puts you at $20M.
For a more general Fermi-esque estimate, I'd say $2M-$200M depending on size and complexity of your constellation. Compare this to the cost of a single Falcon 9 launch at ~$60M, or to the $3.5B total cost of the Iridium NEXT constellation that SpaceX just finished launching.
[1] https://www.isispace.nl/products/
[2] pricing buried in http://nanoracks.com/resources/faq/, description of the service is at http://nanoracks.com/products/iss-cubesat-deployment/