The Union Aerospace Corporation is a global megacorporation based on Mars and is the main supplier of Argent Energy. The the leaders of organization included/Head of UAC Mars, Project Director of the Argent Facility/Chairman Samuel Hayden.
Note: Doom (2016)'s history may just be a rough continuation of Doom 3's timeline (see shared timeline) This article is concerned with the history of the UAC related within the soft-reboot series (though there remain links to the Doom 3 game's timeline within the soft-reboot games still).
In 2095, the UAC conducted a geological survey mission on Mars where they discovered the "Argent Fracture" and Argent Energy. Within a year, the UAC established an outpost to extract Argent plasma from the Fracture and producing Argent Energy, which became the primary power source for human civilization, and enriching the UAC. The UAC is wholly aware of the exact origins of Argent Energy in Hell and kept this knowledge hidden from the public, to ensure in exploiting Hell's resources in order for, in Samuel Hayden's words, "Humanity's best interest to do so."
The UAC conducted multiple explorations into Hell, where manned expeditions were utterly massacred by demons. Despite the costly losses, the UAC managed to recover artifacts such as the Corrax tablets, the Praetor Suit, and even the sarcophagus of the Doom Slayer. The UAC also captured demons to be experimented and turned into bio-weapons.
Over half a century since the discovery of the Argent Fracture, the UAC became slowly subverted by the corrupted influence of Hell. As a result, UAC personnel under Dr. Olivia Pierce formed a demon-worshiping cult within the corporate structure. Hayden and the UAC board of directors were aware of Pierce's cult, but initially tolerated it as long it benefits for the corporation's and mankind's progress. Inevitably, the cult grew beyond the UAC's control and leading to Pierce plotting to open the gates of Hell, unleashing its demons to invading the human realm.
In 2149, Pierce unleashed a wave of Lazarus energy that consumed the Mars facility and killed or converted many amongst Hayden's staff, opening a portal to Hell and allowing demons to invade the facility and brutalizing the rest. Hayden was forced to release the Doom Slayer from his sarcophagus, as the Slayer was the only being that would stand between Hell and Earth. The Demon Slayer had not initially allied with Hayden, refusing to trust the UAC, and waging his one-man war against the demons and leading to the destruction of the Argent Tower. Regardless, Hayden helped the Doom Slayer in locating The Crucible and giving him access to a BFG-9000 prototype. After another venture into Hell where the Slayer killed Pierce and sealed the portal from their side, Hayden confiscated the Crucible after teleporting him back to corporate headquarters so he could use it in future research before warping the Slayer to an unknown location, away from interfering the UAC's work.
Samuel Hayden returned to Earth with the Crucible in hand, intending to use it to restore his monopoly on Argent Energy. Earth, in chaos due to the loss of the power grid that had depended on the facilities on Mars, provided Hayden with access to all UAC facilities on Earth in the hope that he would quickly solve the energy crisis.
The UAC split following the opening of the Hell Portals on Earth, with those forces loyal to Samuel Hayden forming the Armored Response Coalition while the section still identified as UAC (generally identified as "UAC Cultists") mostly pledged their loyalties to the invaders, with the three Hell Priests assuming leadership roles.
UAC's automated factories on Earth are similarly split, with some turning out war machines for ARC while others have been converted into labs for the production of powerful, technologically enhanced demons.
Some elements of the UAC appear caught between loyalties to the two factions, such as those in the base on Phobos. Phobos base was ordered to stand down and allow their personnel to be consumed by demons, but at the time of the Slayer's arrival was still engaged in active combat with Hell's forces, repeatedly firing the BFG-10000.
There are a number of UAC related Logos in the 2016 reboot, including versions of classic Doom UAC logo (sometimes with Union Aerospace Corp written underneath, and sometimes without) and variations based off the Doom 3 UAC logo. The new design of the logo crest actually looks like its highly inspired by the Doom (film) logo crest, as well as the use of U Logo C design looks highly inspired by the film logo..
The new UAC logo appears to take elements from the classic logo (which can still be seen on various UAC products throughout the base) The discs have become stylized U and the C, and the Doom 3 triangular shape becomes a stylized "A" in the center where the triangle is in the classic logo.
There is yet another logo that appears on space related vehicles which basically a ringed planet with an orbiting satellite or moon, with the older style Doom 1 triangle/arrow in the center of the planet.
There is at least one Logo where there is a highly stylized word "Union" listed bold block letters. Some versions where Union Aerospace (without the Corporation attached).
Beyond that there are many other logos with their own unique designs.
It may suggest that the different logos refer to different divisions and sub-corporations of UAC.
The UAC in Doom is more tongue-in-cheek compared to many past versions of the Union Aerospace Corporation (with exception of perhaps the Doom RPG series and some of Doom 3). That is to say it is filled with a lot of self-referential humor about the Doom series in general (Doom 3 was more ironic, for example the poster at the beginning suggesting that UAC was unlocking the secrets of "Heaven", while in fact they were actually researching Hell).
If the 2016 reboot exists in the same universe as the rest of the games, by the time Doom 2016 takes place UAC isn't even bothering to 'cover-up' the fact that they are experimenting on hellish creatures, and artifacts and travelling to Hell. In fact the new business model is clearly inspired on a occultist Satanic religion, somewhat like a secret society (of both science and mysticism). at least its the case with the settlments around the Argent Facility (it's possible thinngs run different back in Mars City if Mars City was rebuilt).Whereas earlier games and in particular Doom 3, no one except maybe the top researchers knew what was going in the advanced research, everyone seems to know, even possibly people on Earth by this point (or at least its brushed away as rumors and is the source of popular entertainment 'games' of the day, and in the past). That's not to say that some details are still classified, but no one seems to be shocked about existence of Hell in the game. Whereas only a few years before (if Doom 3 is part of Doom 2016's universe), they were still covering up all events of incursions from Hell, and the actual nature of their research.
Due to this self-knowing nature of everyone and everything in this universe its hard to say what are clear easter eggs in some instances, or actual artifacts to make this self-referential world more consistent with itself.
Many elements of the base seem like highly stylized versions of the Doom 3 style architecture, logos and companies included, but further updated even more technologically advanced. You can find other elements that seem to link to Doom 3 including the basic date of when artifacts were found on Mars and later in Hell (Doom 3 used the date of 2104 for finding in a cavern on mars, one of which allowed them to unlock secrets of portals to hell, and the 2016 reboot maintains that date), as well as roughly sharing the 2095 date for start of some of the main research on Mars (Alpha Labs and Argent Energy respectively).
Finally there are other minor references such as copies of Super Turkey Puncher 3 existing in both Doom 3 and Doom. Like in Doom 3 and in Doom RPG, "Doom" (original series exists as a kind of known video game series to the people of the future, that mysteriously mirrors the 'accidents/incidents'), likewise a classic Doom movie poster can be found in a locker room in the entrance to the Administration building of the Advanced Research Labs.
Finally many of the details surrounding the mysterious main character the DOOM Marine seem to be self referential of the main character of most of the Doom series, but of someone who decided to remain in Hell (he is after all the same marine from Doom 64/The Lost Levels, and there may be other Doom 64 references in the game as well, including the references to the mother demon from that game and The Hero). There are other references to original Doom and Doom II including the Icon of Sin.