AX-235
From the Encyclopedia of Speculative Fiction - http://encyclopedia.wizards.pro
AX-235 was a Rebel outpost hidden in the asteroids of Cron Drift. It was the very outpost that intercepted the Imperial transmission with the schematics of the Death Star.
Behind the scenes
The scenario of the X-Wing is somehow inconsistent to the A New Hope opening crawl, according to which the plans were taken during a battle which was also 'the first victory' against the Empire.
According to the game, the Rebels had many victories before that event.
Dark Forces in turn contradicted the scenario of X-Wing by making Kyle Katarn phsyically stealing the plans from an Imperial Base on Danuta.