Would Emperor Palpatine trigger on a salvo? My thought is yes
as the the card reads
When
an
enemy
ship or
unique squadron
declares you as the
target
of an
attack
, it must
spend
1 of its
defense tokens
(if able).
As you would be the target of an attack. However, the other side of the coin is that does salvo declare you as an attacker?
Salvo reads
If the attack was made by a ship, the defender performs a salvo attack against the attacking hull zone using its printed rear battery armament. If the attacker was a squadron, however, the defender uses its printed anti-squadron armament.
So by using Salvo you are defaco targeting the other ship as when you spend the token you are targeting and declare the attack.