This upgrade card reads:

"Action: Choose an enemy ship at Range 1-2. If you are inside the ship's firing arc, you may acquire a target lock on that ship. Then, you may perform a free boost action."

Three questions:

A) Are you allowed to measure the firing arcs of all the enemy ship within range, to see if you are within them, before picking the ship?

B) If you are not inside the firing arc of the ship you selected, can you then select another ship?

C) Or, if you are not inside the firing arc of the ship you selected, does it then count as an illegal move (like finding your choice of barrel roll impossible) and can you then take another action instead?

I am asking as my gut feeling that while some of these might be answered with a 'yes' under the basic (casual) rules, the answer to all three would be a 'no' when playing in a tournament, because of the sequence of choices.

You're generally not locked in to any decision made if it can't be completed. So the answers would be:

A) I would say only the ships that you can see that you might be in arc. If you started measuring ALL enemy ships arcs (including the ones well out of arc) that could be considered premeasuring.

B) Yes, of course you can.

C) If you aren't inside the arc, it does not count as an illegal move, it's just not possible, so you can declare a different ship or action.

First you declare you are going to use R7-T1 as your action, pick a ship that looks like you might be in their arc and measure range. If you're out of range, you can try another. If you're in range, then you can check his arc. If you're out of arc, you can try another. If no other ships are in range, you can take a different action instead.

If you're in range and arc, R7-T1 is now your action as it's requirements have been met. From here you can choose to acquire a target lock on that ship and you can choose to do a free boost action. Neither of those are compulsory. You "may" do either, both or none.