orbiter aerosurface profile test and main engine gimbal profile test

On 4 Jul 2006 11:58:16 -0700, "P" did carve unto the very living rock upon which we now stand:

Here's a link to the 'Countdown 101' pages at NASA:

In a nutshell, the two tests are basically the same except on different parts of the orbiter. The tests verify the range of motion for the respective elements (rudder and flaps for the areo surfaces, the three main engines on the latter).

NASA TV usually shows these test live when they are performed (at the T-3 min 55 sec mark). Usually you see the rudder move left, then centered, then right, then centered. Then the 3 main engines move from centered to up, down left, down right, then centered again.

The very next thing checked (though they never show this for some reason) is to verify the 'DOOR AJAR' and 'CHECK ENGINE' lights are both off. (see

for this and other humorous items).

Steve