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Actually, the closest approach doesn't necessarily matter, especially for the inner planets as the traveled path usually uses gravity assists. Here is an example of Parker's path to get close to the sun:
https://directory.eoportal.org...

And one for Messenger going to Mercury:
http://messenger.jhuapl.edu/Ab...

It's not like you can take a direct route without using a shitload of fuel.

Objects about 10 cm and larger can be tracked in low orbit. That means the radar can follow an object long enough to derive orbital elements, allowing reliable predictions of where the object will be later. Objects about 2 mm and larger can be sampled by high-power radars. That means the radar helps build a statistical population based on whatever zips across a fixed beam.

I found a couple of figures (Fig. 1 and Fig. 24) showing the gap between tracking (Space Surveillance Network) and other sampling data sources. Also a recent presentation.

WTF are you talking about? M-2 isn't offline. It just launched in 2014:

https://directory.eoportal.org...

This band is not useful for long haul carriage due to atmospheric water vapor absorption. According to this chart, absorption between 200 and 280 GHz varies between 3 and 40 dB/km. That means at the low end only 50% of your signal is absorbed every km. At the high end, only 1/10,000th of your signal remains after each km.

this post speaks to similar issues including refraction.

That has not and will NEVER stop $TELCO from selling services across this with "UP TO" marketingspeak which means "we fuck you royally for a service which is online but effectively unuseable".

This band is not useful for long haul carriage due to atmospheric water vapor absorption. According to this chart, absorption between 200 and 280 GHz varies between 3 and 40 dB/km. That means at the low end only 50% of your signal is absorbed every km. At the high end, only 1/10,000th of your signal remains after each km.

this post speaks to similar issues including refraction.

There are no commercial European satellites with .5 metre pixel capability. The only commercial European Remote Sensing mission currently is SpotImage -- Spot 5 has a 2.5 m capability.

For all those who ask 'how hard can it be?' (shades of Top Gear...) entry level into the commercial Very High Resolution satellite business starts at around half a billion -- don't forget the ground segment. Even future missions are not planning to go much below .4 metre: the problems of handling huge data volumes, programming the satellite acquisitions, and the trade-off in covereage are not worth the gains in sharpness for most commercial users. The US military can get down to about 10 cm (allegedly), but are believed to use highly elliptical orbits (and huge, Hubble-sized telescopes) which would be inmpractical for commercial operators. 10 cm is not as good as Hollywood has got: the last episode of '24' showed what was supposed to be a Landsat image - only it was thermal infrared at about 1 cm updated once a second (as opposed to 15 m every two weeks or more...)

The Man may well have bought 'all the coverage of Afghanistan' -- from a single operator. The Ikonos mission (1m pixel) was the only one operating at the time. The US Govt. does retain 'shutter control' rights of all the VHR missionslicensed by them - which is all the current VHR missions. That will change - especially with COSMO-SkyMed, a constellation of all-weather radar satellites with a max. resolution of >1m, coming soon.

There's a intro to VHR satellite imagery here.

These students got theirs into space for $120,000. Sure, that doesn't include "donated material, equipment and expertise", or the estimated $40,000 launch cost, but let's be optimistic and call it $250,000 all told. Well, get 50 people in and it's only $5000 each -- less than a good used car. Make it 500 people and you've got the cost down to less than a trip for two to Vegas. And for this I get to help send a satellite running Linux into space -- as close as I'm likely to come to making the trip myself.

I know that ham radio folks are already doing this sort of thing, but they've got their own goals. I admit, mine are a bit fuzzy beyond "put this L33+ satellite into space", but that's kind of appealing too. What could we cram on a picosatellite? What imaging can you do for cheap -- what resolution, what wavelengths? And of course, the question everyone wants answered: Can you host a webserver in space, and could it survive a Slashdotting?

I think something like this would be cool beyond measure. Who's in?