Cosmos 1 will be about 100 feet in diameter,
and its material is over 99 percent reflective.

Now its orbit will vary, but at it's closest to Earthbound
observers it will have an apparent visual diameter of between
10 and 20 seconds of arc.

How bright will it appear?
This involves both mathematics and a bit of guess work but
It will easily be more than 40,000 times dimmer than the sun.
Considering the reflective material will wrinkle and warp abit,
and the Cosmos 1 will not form a perfect disc [composed of 8 fanlike panels],
it's more likely that it will be at least a 100,000 times dimmer than the sun.

So a 100,000 times dimmer means a positive Magnitude gain of between 12 and 13.
The sun has a brightness of about -26.4 Magnitude.

The Cosmos 1 would most likely have a visual Magnitude of nearly -14 Magnitude.
The full moon has a Magnitude of about -12.

Cosmos 1 could at times be several brighter than the full moon.
Awesome!

But! ...You amateur astronomers out there [Raoul, Phil, etc], be careful!

Don't look at the Cosmos 1 with binoculars....You may experience a blinding
surge of brightness from the reflected sunlight off of Cosmos 1.
Use discretion and indirect observation.

Jacob