NASA’s mission to the Hubble Space Telescope may be compromised by orbital debris, shuttle program manager John Shannon revealed on Monday. It appears that the chances for a catastrophic collision with debris are 1 in 185, compared with the usual 1 in 300.

This is the biggest risk yet, forcing the shuttle to enter a higher orbit than for the International Space Station Mission, thus increasing the risk of an unwanted incident. Shannon also explained that some of the vehicle breakups in the past may also contribute to the debris environment.

Over the past year, two such incidents contributed to the space debris floating around Earth, one of them involving a Chinese missile that reportedly shot an old satellite out of orbit, and a Russian satellite orbiting around Earth said to have self-destructed.

Although space missions are known to have their share of danger, from launch to landing, the orbital debris increase the risk like never before, making the mission even more complicated.

NASA doesn’t afford another loss like on the Columbia space mission, when seven astronauts lost their lives as the space shuttle disintegrated during re-entry into Earth’s atmosphere, above Texas. The disaster took place in 2003, when the shuttle’s left wing was hit by debris, which destroyed its thermal protection system.

According to USA Today, the astronauts participating in the Atlantic mission are well aware of the risks: “That comes with the mission,” Atlantis commander Scott Altman said. “Hubble is where it is… We’ve got to go where the work is.”

The seven astronauts on the STS-125 mission are Scott Altman, who will command the final mission to Hubble, Navy Reserve Capt. Gregory C. Johnson, who will serve as pilot, mission specialists John M. Grunsfeld and Michael J. Massimino and first-time space fliers Andrew J. Feustel, Michael T. Good and K. Megan McArthur.