Instructions
Insert the game disc for "Call of Duty: Black Ops" into your console's disc tray and wait for the game to initialize. Select "Zombies" from the main menu once it has loaded onscreen.
Select "Ascension" from the map selection page and then wait for the map to load. As it loads you will see yourself being flown in on the first lunar lander module.
Begin by playing the game as you normally would until you reach the second lunar lander module (this one must be activated before you can use the first one again). Walk up to it and press the button indicated onscreen to activate it. You will now be flown back to the first lunar lander module area.
Continue playing the game as you normally would until you find the next two lunar lander modules. As with the second module, walk up to each module and press the button indicated onscreen to activate it. Once activated, you will be flown back to the original lunar lander module area again.