Likely bit rate from low Earth orbit

DSS TV has to offer some clue about what's feasible. "Lots", I suspect.

With a 25m dish on the ground I'd not be surprised if they get comparable bandwidth to communications satellites like the one sky uses.

But, to invoke another cliche, I suspect anyone that could tell you he real figure would subsequently have to kill you.

On a sunny day (Mon, 17 Mar 2014 15:20:46 +1100) it happened Sylvia Else wrote in :

Digital tv broadcasting, 12 transponders at 32 megabits / second each per sat, of which there are hundreds geostationary working in the 10 GHz range

But recently things have gone optical, they use lasers from one sat to the other to ground. Now we are talking terabits/second.

IIRC they are just trying it from a moon orbiting sat too.

Look at the specification for some of the recent TDRS satellite. The TDRS satellites are geosynchronous and receive data from low orbit satellites and sends the data back to fixed ground stations.

Not sure the geosynchronous satellites tell us that much.

The low Earth orbit satellites move across the sky (quite fast, indeed), so the higher the antenna gain (both on Earth and on the satellite), the more accurately it must be pointed at a moving target.

On the other hand, it's a lot closer, which helps with the signal strength.

Sylvia.

At least the early TDRS satellites had multiple antennas and receivers for a specific band. The individual antenna signals were then moved with frequency translator to a big downlink.

On the ground station, individual signals from the different antennas were then extracted and frequency translated from the big downlink and combined with various delays to create an electrically steerable antenna lobe. Such electronic beam forming does not have problems tracking the LEO satellite, which is in the field of view for about 30 minutes.

Depending on the ground equipment capability, multiple satellites can be simultaneously tracked, even if they fly in the opposite direction i.e. N->S vs. S->N.

Exactly, so coverage Vs detail is what you have to decide.

Once upon a time, NASA had tracking stations scattered around the world in the STADAN network tracking near earth satellites. In order to save money and give real time control of the birds, NASA launched the TDRSS network to relay the data direct to the US no matter where they are in orbit, and shut down the STADAN stations including Orroral Valley in the ACT.

622Mbps from Lunar orbit during tests.

This post reminds me of a young Australian entrepreneur I heard about on ABC radio recently who is implementing a "flock of dove" satellites (not much bigger than bread box) to map a continuous up to date image of the entire earth.

The satellites were prototyped with off the shelf smart phones, but the production models are more sophisticated able to be repositioned in orbit.

Satellites being released into orbit from International space station

I found the specs for Digital Globe's satellites.

Their two most recent satellites have 800 Megabits/second.

Sylvia.