Why is space debris such a problem? Why is NASA so concerned about India's recent anti-satellite test?

After India tested anti-satellite technology in space, NASA expressed concern, saying the debris puts the International Space Station at risk. Kurt Anderson, professor of mechanical, aerospace, and nuclear engineering at Rensselaer Polytechnic Institute, is an expert in space vehicle design and simulation, advanced algorithm development, and has a focus on space debris. Anderson has been studying the growing danger of space debris, what it could mean for integral satellites and the International Space Station, and how to potentially remove problematic debris. He is available to discuss these topics and emphasize the urgency with which this emerging crisis must be addressed.