A panel of experts again reiterated that orbiting space junk can pose an even more serious risk to manned shuttle launches, satellites, and the International Space Station (ISS).

"The threat posed by orbital debris to the reliable operation of space systems will continue to grow unless the sources of space debris are brought under control," according to Nicholas Johnson, NASA chief orbital debris scientist.

NASA, ESA, and other space agencies are increasingly concerned of micrometeroid or orbital debris (MMOD) impacting shuttles or the International Space Station (ISS).  In the past 30 years, the amount of space traffic has quadrupled -- only helping to increase space debris as more satellites and other technology orbits Earth.

Most notably, China destroyed an aging weather satellite in 2007 during an anti-satellite test, while a crash between a Russian and American satellite in February helped increase space debris.

Space experts recently said the chance of space junk hitting shuttle Atlantis on its journey towards the Hubble Space Telescope is 1 in 221, with a 1 in 185 chance of debris estimation last October.  Any mission that has a risk higher than 1 in 200 requires a special waiver to be approved of and signed before the mission can launch.

The risk of space junk is higher than a normal trip to the ISS because Hubble is further away from Earth than the ISS.  Furthermore, it's located in a space environment area that is more densely crowded than the ISS, space experts warned.

The U.S.'s Department of Defense's Space Surveillance Network is actively tracking more than 19,000 objects at least four inches in size, though there are as many as 300,000 total objects about a half-inch in size or larger circling Earth.  The ESA is interested in launching its own service to help aid NASA in its efforts to track space junk.