Arecibo Observatory

Arecibo Observatory was located in Puerto Rico. Its best-known instrument was a 305-meter radio telescope built into a natural sinkhole. The National Science Foundation (NSF) has stewarded the observatory since the 1970s.

The observatory supported radio astronomy, planetary radar and atmospheric research. NSF credits Arecibo observations with demonstrating gravitational waves from a binary pulsar and enabling the first discovery of an extrasolar planet. Its planetary radar, supported by NASA's Near-Earth Object Observations Program, characterized the orbits, sizes and shapes of some near-Earth objects already detected by optical surveys.

In 2020, structural damage affected the telescope's support cables. After an assessment, NSF decided to decommission the 305-meter telescope, prioritizing safety. The telescope collapsed on December 1, 2020. NASA said the Arecibo facility and its STEM education and other assets would continue even as the large telescope was decommissioned.

The telescope's collapse did not end all activity at the site. NSF has described efforts to restore or continue other capabilities, preserve historically significant elements and develop the NSF Arecibo Center for Culturally Relevant and Inclusive Science Education, Computational Skills, and Community Engagement (Arecibo C3). The observatory's legacy includes both scientific research and education in Puerto Rico.