How to pass users over to ASP.Net app seamlessly ?

It requires users to login. Is it easy/possible to generate the
appropriate request from Rails to seamlessly pass the user over to an ASP.NET app ?
I don't want users to have to log in twice.

Gary,
I found these wiki page to do single login from RAILS for php forum:

http://wiki.rubyonrails.com/rails/pages/HowToRenderProxiedPages

hope it helps,
Bojan