Wasteland Survival Guide - Mirelurks Walkthrough - Fallout 3 - Page No. 1
This quest can be picked up at Craterside Supply in Megaton. You will probably find this quest very easy. There are two ways to proceed that allow you to complete both objectives. The easiest is described below. If you prefer, you can clear the Memorial before taking this quest: Anchorage War Memorial Walkthrough - Fallout 3 - Page No. 1
You can find Anchorage Memorial in the middle of the river across from the Tepid Sewers.
The quickest and easiest way to complete this quest is to use the Anchorage War Memorial Service Entrance. This gives you immediate access to the lower levels where you need to place the Observation Device.
The Service Entrance is locked, but the lock is easy to pick. Keep low; you must remain hidden as long as possible.
Keep to the left and keep low.
You want to hide for a moment behind the rubble ahead on your left. You'll be turning right soon after you get there.