SINGAPORE — The 25 radar and optical telescope centers around the world that help the U.S. Armed Forces track debris in space have become increasingly busy in the past couple of years as man-made junk orbiting Earth proliferates, posing a growing danger to both civilian and military use of space.

There is even talk now of extending mundane rubbish collection into space to remove the biggest and most dangerous junk — old spacecraft and parts of rockets that loft satellites into orbit. The main conclusion of an international conference on space debris held at the European Space Agency headquarters in Darmstadt, Germany, early last month was that active remediation measures must be devised and implemented to prevent further spread of junk.

At a separate conference held around the same time in the United States, Vice Adm. Carl Mauney, deputy commander of the U.S. Strategic Command, noted that 10 countries now had space-launch capabilities, compared to just three — the U.S., Russia and Europe — a decade or so ago. They include Japan, China, India and Israel, all of which have launch facilities that other countries pay to use in putting satellites into orbit.