>Because they were tracked on Navy ship radar, Sonar, Space based radar, and jet fighter radar. But these systems weren't totally independent: https://news.yco

>Because they were tracked on Navy ship radar, Sonar, Space based radar, and jet fighter radar. But these systems weren't totally independent: https://news.ycombinator.com/item?id=19829428 https://news.ycombinator.com/item?id=19829428