1960s: Need to better understand space environmental threats to human spaceflight mission. Biggest concern is natural space debris specifically micrometeoroids.

1970s: Explosions begin creating more human-generated space debris. Kessler & Cour-Palais warn human-generated space debris may eventually become bigger threat than natural space debris.

1980s: More explosions, Space Station Freedom, and military ASAT testing create high-level awareness of space debris. Need to minimize creation of space debris from human activities in Space. Ronald Reagan – Minimize creation of space debris in tests, experiments, and systems. George HW Bush – Encourage other countries to adopt space debris minimization policies.

1990s: Need guidelines to minimize the creation of space debris through on-orbit activities. Adoption of national & international mitigation guidelines can slow growth. Bill Clinton – Develop design guidelines for space debris minimization, and take a leadership role in promoting international adoption.

2000s: Chinese ASAT test and Iridium-Cosmos collision undo progress from mitigation guidelines. Need to develop collision warning & avoidance measures. George W Bush – Follow national orbital debris mitigation standards, and incorporate into licensing of commercial satellites.

2010s: Post-mission disposal not enough, needs to be combined with remediation. Barack Obama – Preserve the space environment, foster development of space collision warning measures, and research debris removal technology.