Official rule text
61.18 When scoring a secret objective, a player only score one objective during or after each combat. reveals the objective by placing it faceup in a A player can score an objective during both the space combat their play area. Then, they place one of their and the ground combat during the same tactical action. control tokens on that objective’s card and advances their control token on the victory
View official source
Source: Twilight Imperium: Fourth Edition - Living Rules Reference: Prophecy of Kings
Expansion: Prophecy of Kings
Version: 2.0
Reference: Rule 61.18