KH-11 KENNEN

[Scott Kenny]

a. SOFIA doesn't have a radar,

Sofia has the usual 747 radars. Weather, etc.

c. NASA probes have around 1m mirrors and use the main comm antenna as radar or attach radar to solar arrays.
d. KH-11 has 2.5 to 3 m mirrors and radar sats have dishes around 50 feet.

Sweet, let's attach a 50ft radar array to the solar panels on an optical satellite.

a 96 minute sun synchronous orbit (15 orbits per day) would have a repeating ground track. This means for coverage at the equator (528 miles between ground tracks), there needs to be 6 satellites per orbit for 105 total.

I'm not asking for 6 birds per orbit. Only enough birds to put one of 3 tracks per 1056 miles staggered to have one of those 3 tracks able to point at a target within 15 min. I think that's 3 birds per orbit, if we can stagger the orbits. 45. More than I thought, admittedly.

Slant images!

 

[Byeman]

Sofia has the usual 747 radars. Weather, etc.

Do they "see" cars and trucks and other vehicles without transponders?
A space based radar needs a large antenna because it is far away

Sweet, let's attach a 50ft radar array to the solar panels on an optical satellite.

Not feasible. It isn't a science probe looking for water beneath ice for a few hours of a 2 to 3 week orbit. Radar and solar array will have conflicting pointing requirements on spy sat.

I'm not asking for 6 birds per orbit. Only enough birds to put one of 3 tracks per 1056 miles staggered to have one of those 3 tracks able to point at a target within 15 min. I think that's 3 birds per orbit, if we can stagger the orbits. 45. More than I thought, admittedly.

Slant images!

Slant image won't be any better than Starlink. To get the best images, the optical path through the atmosphere has to be minimized. 528 miles between ground tracks the same as the max swath for each satellite. max slant range is around 500 miles.

 

[Desertfox]

Sweet, let's attach a 50ft radar array to the solar panels on an optical satellite.

It can be done but you get the "too many eggs in one basket" problem. With launch costs dropping significantly, its just better to do multiple small sats than one big one.

 

[Josh_TN]

Tangentially related, but NRO has put up 140+ of its proffered constellation in 7 launches starting last May. We are just about due for an eighth, unless the first increment has wrapped up.