The ISS and Tiangong-1 unmanned Chinese space module "pass" each other at around 10:15 UTC on 8th October 2011 when both will be traversing the Pacific Ocean off the coast of Japan. I have estimated that they will be somewhere between 1200 to 2000 kilometres apart ?
Tiangong-1 would be about 336.3 km altitude and ISS at 386.86 km at the time.
Will the ISS crew be able to view the Tiangong-1 module ?
Can other members check this please as this was a 'quick estimate' using current TLEs in satellite tracking programs ?
A-P
UK
These two images show the 'near flyby'pass on Saturday 8th October 2011
A-P
These two images show the 'near flyby'pass on Saturday 8th October 2011
A-P
There's got to be a time eventually where they pass much closer than that. Also, unless the time is near sun-rise or sun-set (but still night at the surface), it may be pretty difficult to spot Tiangong-1 from ISS. It should be far easier to see ISS from Tiangong-1 (heck, I can see ISS from my house... with a telephoto lens, I can even see details). But it's not likely to be too clear of a picture unless you use a very large lens, even if they pass within 100km.
I calculate, assuming the eye's angular resolution of about .02 degrees, that at 100km distance, you should be able to see the rough shape of ISS from Tiangong-1, but you're not likely to see much more than a dot if you look at Tiangong-1 from ISS. Unless, of course, you use a large lens (binoculars, telephoto lens).