NASA telescope teeters on Earth plunge after failed rescue mission

<p>An ageing NASA telescope is barely clinging to space after a failed rescue effort left it tottering lower and lower.</p> <p>The US Space Force predicts the Swift Observatory will come crashing down on or around Friday.</p> <p>Most of the 1.5-ton telescope is expected to burn up in the atmosphere. </p> <p>But a handful of pieces made of denser-than-lead tungsten and some mirror parts could survive re-entry, according to NASA's Brad Cenko, the mission’s chief scientist.</p> <p>Any surviving wreckage will most likely plunge into the ocean. But swaths of Africa, Australia, India, Southeast Asia, and Central and South America are within the re-entry zone. The Space Force is tracking the telescope’s dwindling path.</p> <p>Its cosmic cremation has the Swift team mourning yet full of gratitude for the observations the telescope made during its 22 years in orbit. </p> <h2>'We've known this day would come..