Giotto’s 21.75-Second Silence

Transcript

On March 14, 1986, Giotto, a European Space Agency probe sent to encounter Halley’s Comet, made a remarkably close pass. It came within 596 kilometers and returned 2,000 images. But just before closest approach, the spacecraft’s telemetry stopped. Telemetry is the stream of information sent back to Earth. The book says a dense concentration of dust probably knocked Giotto’s high-gain antenna, which sends and receives signals, out of alignment with Earth. That explanation is probable, not certain. The interruption lasted 21.75 seconds before data transmission resumed. The antenna was properly oriented again after 32 minutes. The stakes were clear: Giotto had passed close to the comet, and the link with Earth had faltered amid dust impacts. The encounter’s historical value rests in what it delivered: a close look at Halley’s Comet and 2,000 images, despite a brief loss of contact.