NASA’s Neil Gehrels Swift Observatory has returned to studying the universe after spending months in a low-endurance configuration while awaiting an orbital rescue mission that ultimately failed. Mission controllers restarted two of Swift’s three scientific instruments: its X-ray Telescope (XRT) and its Ultraviolet/Optical Telescope (UVOT), on August 26. Both instruments had been shut down in February as part of an effort to minimize atmospheric drag and keep the aging spacecraft in orbit long enough for another spacecraft to reach it and lift it to a higher altitude, according to an Aug. 28 NASA statement. Swift’s third instrument, the Burst Alert Telescope (BAT), remains offline. BAT operations were halted in April to conserve energy, allowing controllers to position Swift’s solar panels in a way that further reduced the drag of its interaction with Earth’s atmosphere. NASA says the mission team hopes to resume data collection with the instrument in the coming weeks. “For the past 21 years, Swift has been NASA’s multi-tool for studying the cosmos,” NASA officials said in the statement. “It observes a wide range of light, quickly signals short-duration bursts, and sends alerts to other facilities in space and on the ground to help coordinate follow-up observations.” The return to science follows NASA’s decision to abandon plans to boost Swift into orbit using LINK, a robotic service spacecraft built by Arizona company Katalyst Space. LINK launched on July 3 aboard a Northrop Grumman Pegasus XL rocket with the ambitious goal of rendezvousing with Swift, taking over the observatory and raising its orbit. You may like However, the rescue mission ran into trouble in late July when LINK developed attitude control problems that caused it to spin and disrupt communications. Two of the spacecraft’s three reaction wheels were found to be non-functional, while its cold gas propulsion system also experienced some loss of functionality. Although engineers managed to reduce LINK’s spin and regain attitude control, NASA and Katalyst announced on August 19 that the spacecraft would no longer attempt to capture and boost Swift. Instead, LINK is expected to rendezvous with Swift and conduct proximity operations, providing an opportunity to demonstrate technologies that could be used for future satellite servicing missions in space, leaving Swift without the orbital boost intended to extend its life and its future increasingly uncertain. Launched in 2004, Swift was originally designed for a two-year mission to study gamma-ray bursts, the most powerful explosions in the universe. More than two decades later, the observatory continues to detect and rapidly track fleeting cosmic events in gamma rays, X-rays, ultraviolet and visible light, while alerting other observatories so they can direct their attention to the same targets. Unlike some spacecraft in low Earth orbit, Swift does not have a propulsion system capable of counteracting atmospheric drag. Increased solar activity has heated and expanded Earth’s upper atmosphere, increasing drag on Swift and causing its orbit to decay more rapidly than expected. NASA’s low-drag operations were expected to keep Swift above an altitude of about 185 miles (300 kilometers) until October. Below that threshold, operating the observatory becomes increasingly difficult and its descent accelerates, NASA officials said in the statement. Now that science operations have resumed (and the planned orbital boost is off the table), NASA expects Swift to reach that critical altitude within a month or two. Without intervention, the observatory is likely to crash back to Earth later this year, mostly burning up as it re-enters the atmosphere, according to the space agency. For now, the veteran space telescope is making the most of its remaining time and exploring the universe once again.
