Every satellite I've seen crosses the sky in seconds. How does an orbiting mirror provide consistent illumination? Can it orbit as show as the rotation of the Earth and still maintain an orbit?
I copied that totally not critically from the article. I'm beginning to believe that this article may be missing some important information.
edit: One might also take care of it if it could be far enough east. Would need to do the trig though.
Geosynch is 36,000 Km out.
The Moon's albedo is 0.12.
Let's assume we can get a mirror of albedo 0.96 -- this is a little better than polished silver. It's also conveniently 8 times as reflective as the moon.
The Moon's angular diameter is about 0.5 degrees. To match that angular diameter at 36,000 Km, we need a 5.4 Km wide object.
That doesn't sound like it's within the current state of the art. Maybe in another 10 years?
23 million square meters at 2 g/m^2 (aluminized mylar) is 46,000 Kg -- about two Falcon Heavy trips. That doesn't count any framework or booster or other infrastructure.
The article doesn’t say it’s going to be as big as the moon - it only says it’ll be 8x brighter. You’re also forgetting about the relative shapes of the objects: the moon, being round, reflects what light it does in all directions, while a designed mirror can be made to reflect it all in one specific direction.
All that said, I don’t think this will work, but not be of your math.
The relative sphericity of the moon is nearly immaterial here: when the moon is in full phase, do you see notable dimness around the edges where less sunlight is reflected away from you? Increasing the albedo to a near-perfect mirror cancels it all out.
Now, reflection won't be perfectly coliminated, but if you assume it is, then the mirror essentially becomes a piece of sun. Since the sun is about 400 000 times as bright as the moon, you'd need to scale the diameter of the sun by sqrt(400 000 / 8) =~ 223. Applying that scaling to your 5.4Km yields about 24m of diameter, which seems waaaay to small to me, so I am probably wrong.
That feels really
> about two Falcon Heavy trips
This does sound like it's within the state of the art! The mirror doesn't have to be one solid piece, it can be assembled from many smaller-ish satellites.
Of course you have overhead, so ... 5 Falcon Heavy trips? This is still very fine, if you're willing to put in the money.
https://space.stackexchange.com/questions/10837/why-are-the-...
https://en.wikipedia.org/wiki/Geosynchronous_orbit Popularly or loosely, the term geosynchronous may be used to mean geostationary.[2] Specifically, geosynchronous Earth orbit (GEO) may be a synonym for geosynchronous equatorial orbit,[3] or geostationary Earth orbit.[4] Communications satellites are often given geostationary or close to geostationary orbits so that the satellite antennas that communicate with them do not have to move, but can be pointed permanently at the fixed location in the sky where the satellite appears.
Certainly the comment I responded to (which has been edited to be non-sensical since) meant geostationary. In any case, GPS are not geosynchronous in the general sense of the term, but rather semi-synchronous (period of half a sidereal day). These orbits were historically chosen for convenience, but the syncronicity is not at all a requirement for global positioning satellites: e.g Galileo, GLONASS.
Geosynchronous satellites can and do modify their inclinations and eccentricities to increase their coverage beyond one spot over the equator.
You may find this helpful:
http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit5/gps....
The nominal GPS configuration consists of a network of 24 satellites in high orbits around the Earth, but up to 30 or so satellites may be on station at any given time. Each satellite in the GPS constellation orbits at an altitude of about 20,000 km from the ground, and has an orbital speed of about 14,000 km/hour (the orbital period is roughly 12 hours - contrary to popular belief, GPS satellites are not in geosynchronous or geostationary orbits). The satellite orbits are distributed so that at least 4 satellites are always visible from any point on the Earth at any given instant (with up to 12 visible at one time).