From Halopedia, the Halo wiki
Some time between 2540 and 2551, Cortez and his fireteam were tasked with a high priority mission on the Covenant-controlled planet Heian. The team was ordered to assassinate a Prophet to interrupt Covenant's supply lines. This mission was unusual in that a SPARTAN, Cal-141, was given command over the mission. His team was deployed via SOEIV during a meteor storm to mask their approach. One of Cortez' squad members, Checkman, was killed during atmospheric entry following a collision with an asteroid. After landing, Cortez nearly lost a second ODST, the team's secondary sniper, O'Brien, whose pod began to sink in the thick mud of a swamp he had landed in. Cortez and Dutch were about to assist O'Brien when the SPARTAN hurled the pod from the swamp. The team then began its day-long march to their intended destination. During their march, they neutralized several Unggoy and a Jiralhanae chieftain.
Upon reaching their destination, Cortez and his fellow ODSTs set up a loose perimeter around the SPARTAN as she adjusted her sniper rifle for the assassination attempt. However, they were caught unawares by the Brute they had previously engaged, who had hunted them since its defeat. The Brute, wielding a gravity hammer, attempted to smash O'Brien, but the SPARTAN managed to push him out of the way and take the brunt of the blow herself. After he and his fellow troopers knocked down and killed the Brute, O'Brien finished the mission himself. With her last words, Cal-141 handed Cortez the data she had gathered from the strange ruins scattered about the planet and asked him to take them to Dr. Halsey. It is unknown whether he fulfilled this request.
After the mission, Cortez, Dutch, and O'Brien were returned to the destroyer. There, they were accosted by a Marine, Berger, who mocked the death of the SPARTAN. Rather than holding antipathy for the SPARTAN, as most ODSTs would do, Cortez and his squadmates scolded Berger.
List of appearances