Resource Sampling:
The planet has some resource that may be of use to the Fleet, so the Troopers are to go in, secure a site for scientists to come down and do an analysis and take samples. Possible follow on mission may include safeguarding a prospecting operation.
Infiltration:
There is a powerful alien civilization on this planet, with space-faring capabilities. Your task is to go in as “embassadors” of Terra, and try to find out the extent of their empire so that a TEF-wide assault can be coordinated to take down this possibly legitimate threat to Terra. Conflicts will need to be kept small and covert, so as not to rouse the animosity of the civilization before their full power is gauged.
Beachhead:
You are the first unit to go in. Your mission is to locate and establish a suitable Landing Zone for the main effort of the assault. This could go many ways afterward, from the main body having a problem, to the PCs squad being put on LZ guard, or even being put at the point of the assault.
Rearguard:
The planet is too hot for 3:16 ground forces to cleanse, so they’re pulling out. You have been tasked with being the last ones off-planet, guarding the retreat and recovery of the rest of your unit. You’ll be pulled out, Troopers. Command values your expertise, and wouldn’t jeopardize you if it weren’t absolutely necessary. This is an opportunity for an iconic “fleeing the planet ahead of a nuclear explosion” scene.
Slash and Burn
The planet below is teeming with life- plants, insects, birds, a vast spectrum of non-threatening flora and fauna. Burn it all to the ground and salt the soil so that nothing ever thrives on the planet again.
Precise Instrument
Deploy your troopers for a surgical strike against a technologically advanced alien world. Orders dictate that the alien planetary infrastructure is the primary target- spaceports, industrial complexes, power generation facilities. Casualties are to be kept to a minimum- troopers are to engage only when directly attacked. Those returning to base with a minimum number (or no) kills are to be rewarded, while trigger-happy goons will come under scrutiny.
Code Name: AZATHOTH
Military Intelligence has discovered something unusual: a supermassive black hole that they believe to be intelligent. And hostile. The last two ships sent to destroy it indicated [CLASSIFIED] before they themselves were destroyed: so we’re going to try an experimental psychoactive counteragent on your Company’s troops when you’re sent to finish the job. Good luck!
(Run it as a Sentient Planet with Shadow Beast style minions (that may or may not just be psychic projections) and the Induce Weakness Special Ability, using emotional/mental attacks, and with a pretty high AA.)
((ETA: Just thought of an obvious alternative: “Corrupt” Trooper “minions” instead. Weirdly, this one is almost harsher if you use a low AA.))
Traitor
An officer seems to be conspiring with the aliens on the planets surface! Get down there and take her out before she sells out any secrets. Whoever brings her back alive gets a nice medal. Upon finding her with the aliens anyone can use their turn to roll FA to kill her instead of a threat token, she runs away after the first round. NFA to catch up to her and then NFA to capture her (she fights back, FA 5) or FA to kill her.