While secrecy and stealthiness are often desired in clandestine and covert operations, the terms secret and stealthy are not used to formally describe types of missions. Some operations may have both clandestine and covert aspects, such as the use of concealed remote sensors or human observers to direct artillery attacks and airstrikes. The attack is obviously overt (coming under attack alerts the target that he has been located by the enemy), but the targeting component (the exact method that was used to locate targets) can remain clandestine.