Star Trek: The Cantabrian Expeditions Wiki

The 27th century starship (also known as alien ship) was a Federation starship of unknown class staffed by 27th century historians and scientists.

The ship, under the command of Amila Thon, traveled back in time to late 2366 and early 2367 to witness the Battle of Wolf 359. Thon went so far as to send six historians to the Borg cube for surveillance purposes.

The USS Prospect, arriving moments too late to assist in the battle, discovered the 27th century starship and, after thinking it was aiding the Borg, pursued it, knocking out its communication beam. As a result, the historians on the cube were most likely assimilated.

Prospect Captain John Greene led an away team to the future starship, finding a mix of crew and technology from several species and cultures, including, but not limited to, Vulcan, Cardassian and Bajoran. Science officer T'Prain, a Vulcan-Cardassian hybrid, took Greene and his team to meet Thon, who gave them a few cryptic clues about their future and showed them the USS Enterprise-D stopping the Borg cube over Earth.

Once Thon was finished with the Prospect away team, she snapped her fingers, activating the transporter system to whisk Greene and his team back to the Prospect within an instant. The future starship also replaced and repaired damage to the Prospect (which, later, according to Thon, was not supposed to happen) and temporarily upgraded their sensors.

The 27th century starship then disappeared. (Star Trek: The Prospect Chronicles: "The Burnt Child")

While the crew wore uniforms, they might not have been Starfleet. Thon stated to Greene her future Federation was much different than the 24th century Federation, and because Greene hadn't realized his potential, the Federation was not as cohesive or grand as it once had been.