I haven't found any rules in W:TA which address the physical realities of being in space. However, there are some sections that describe how to deal with the spiritual world. I'm also sticking to the Werewolf sources and ignoring Mage, which has its own cosmology and rules which may differ from Werewolf.
There is no direct correspondence between outer space and the Umbra.
Outer space is space - the empty area between things. Space is represented in the Umbra as the Aetherial Realms (Umbra: The Velvet Shadow). This realm includes representations of the sun, moon, and other celestial objects. There are both Incarna and lower-order spirits, which opens up a lot of possibility.
Umbra: The Velvet Shadow provides a list of rules for adventuring in the Aetherial Realms (pg.37-38). These largely describe how to adjust the difficulty for a variety of tasks that involve the relevant spirits (such as summoning lunes) or mundane activities that involve celestial objects (like the astrology skill).
In general, space itself doesn't correspond to any point in the Aetherial Realms. This prohibits you from stepping sideways between the two. There are some exceptions: the sun corresponds to the Hyperion and the moon corresponds to Phoebe, though stepping sideways into the sun or moon is a great way to die immediately.
If that isn't very satisfying to you, the same section also presents an optional rule which forces some kind of relationship between points in space and the Aetherial Realms. This allows you to step sideways ... into outer space. Another fantastic way to die.
Caerns and Moon-Travel
There are spirits in the Aetherial Realms that can be contacted like any other spirits. In fact, there is at least one caern in outer space - on the MIR space station (Book of the Wyrm). It is a level 3 caern of enigmas controlled by the Black Spiral Dancers.
The gauntlet rating of space (or the moon, etc.) is not explicitly described in any W:TA book I have access to.
Moon bridges connect caerns. A moon bridge has a maximum distance based on the rank of the caern it is opened from (Caerns, pg. 11). MIR has a maximum altitude of about 230 miles, which even a level 1 caern could reach. However, the moon has a distance of about 240,000 miles from earth - no caern on the table could reach anywhere close.
So how do you get to the moon? From earth, sidestep into the Umbra. Travel to the Aetherial Realms and Phoebe, then sidestep again. Alternatively, from MIR you could access the Aetherial realms directly and continue on. There are other possible routes.
What good does MIR do out there? It's a direct route to the dread realm of Malfeas. Normally this is a long and perilous journey through the Umbra, but MIR is effectively a shortcut.
Gnosis
There are no special rules for using or regaining gnosis in space. It's not clear why there should be, either, since gnosis can typically be used and regained in the realms of the Umbra without additional difficulty (special rules of any particular realm notwithstanding).
