Atmo Systems in Warframe are a crafting item that you can earn by doing Heist bounties. These are the special bounties you can do for the Vox Solaris Syndicate on Fortuna and involve defeating the Orb Mother who guards the Vallis Orb.
You will need to reach the rank of Old Mate with Solaris United, then go to the secret room at the back of Fortunate and speak with Eudico. The best way to operate Atmo Systems is to play the second phase, or mission, multiple times. You'll have to steal the harmonic scheme of the Profit Taker's shield, and it's a quick and easy mission with a team. You will need to have completed the first phase to access the second phase.
Speak to Eudico and accept the mission, then head to Orb Vallis. Go to the Enrichment Labs and head all the way back to the top floor. You will have to kill three corpus directors. The first appears under the closed security room at the back of The Laboratories. If you kill the first, the second will spawn halfway through the lab, towards the entrance, and the third will spawn in the first main room, The labs.
When they're all dead, head back outside and two Terra Ambulas will appear to keep the pattern harmonic. Take them both out, grab the harmonic pattern that will fall into the room they were guarding and return to Fortuna. Once the mission is completed, you will hopefully get The Atmo systems in the reward pool. Just grind the mission until you have the number you need.
It should not take long to become very effective, especially with a full team. Three players have just taken up positions at the spawn points for the Corpus directors, with the fourth waiting outside with a sniper rifle. When each Tenno kills their target, they can join the player outside, then quickly kill any Terra Ambulas that appear. With a little practice, you can complete this mission in two to three minutes, making it a great way to farm Atmo Systems.
