A wayward piece of space junk belonging to a former Chinese satellite zoomed harmlessly past the International Space Station (ISS) yesterday, July 29. Experts at NASA decided not to take any actions concerning the six astronauts currently making up the Expedition 24 crew, as they calculated the orbit of the junk with great accuracy. There were however a few moments of tension a couple of days ago, when ground radars first detected the shard. The object zoomed past the ISS at 1:47 pm EDT (1747 GMT), Space reports.

Initially, experts at NASA Mission Control, in Houston, Texas, took into account ordering the astronauts into the two Soyuz capsules that act as lifeboats for the orbital facility. They then calculated that the piece of space debris will not come closer than 5 miles (8 kilometers) to the station. This also meant that they had no reason to order the crew of Expedition 24 to fire up the space lab's thrusters, in order to temporarily take the ISS of its low-Earth orbit. The situation was still rather tense yesterday, as the final message that the danger is gone came from Mission Control just one hour before the debris zoomed past the orbital facility.

“All three of our tracking passes show a consistent green miss distance, so at this time we think there is no probability of conjunction and we are not going to be sheltering in place,” experts from Mission Control radioed the astronauts. “Okay, we understand, Houston,” the reply came. The ISS generally flies at an altitude of 354 kilometers, or 220 miles, above the surface of the planet, but NASA prefers to have a half-a-mile-tall area around the station clear of any debris, both above and below. The safety perimeter extends for 25 kilometers (15 miles) on all sides, and the facility is moved off-course only if the chance of it being impacted goes lower than 1 in 10,000.

Over the past few years, space debris have been accumulating in Earth's orbit to such extent that even regular rocket launches are sometimes canceled due to the risks. Such concerns also plague space shuttle launches, as the orbiters have a huge surface to expose to wayward objects. Most debris are very small and very fast, which makes them incredibly dangerous. Others come from orbital collisions between satellites, or from former spacecrafts destroyed by Earth-based weapons.