The expedition lead by Misato Katsuragi's father, Dr. Katsuragi, to the South Pole to research and experiment with Adam - the being that was found there. The expedition led to the cataclysm of the Second Impact. The events have been largely covered-up, both to the public and lower-ranking employees of Nerv.
In Mid-September, SEELE was funding the project for ambitious scientist Dr. Katsuragi, attempting to prove his theories on S² Engine in order to create one. The only person not part of the crew was Dr. Katsuragi's daughter, Misato.
In September 13th, the crew discovered Adam. The crew successfully extracted the being out of the ground, but through it brought upon the world Second Impact, nearly destroying the world and ravaging the the countries that survived through it. During Adam's awakening, the doctor sacrificed his life, sending his daughter in an escape capsule to sea. The events left Misato mute for nearly four years.
Save for a scientist named Gendo Ikari (Then known as Gendo Rokubungi), no one from the crew made it out alive.
While Katsuragi saw this as an opportunity to advance his research, he was backstabbed by SEELE, using the expedition to further their plans on the Human Instrumentality Project by retrieving Adam (Now fossilized).
This article bears the unpleasant designation of "Stub." This is a Bad Thing. Provide a great service to NGE fan-geeks everywhere by making it awesomer!