Swift thinking buys NASA observatory a little more time before re-entry

NASA’s decision to halt most science operations on its Swift observatory has paid off. Estimates now put the spacecraft’s descent past the point of no return to the end of summer rather than the start. The space agency presented the latest set of re-entry forecasts for the spacecraft, which now point to a descent below the critical altitude of 300 km (185 miles) in September rather than July. The figure is important, since the higher the spacecraft is, the better the chances of a successful rescue mission. Scientists continually update forecasts for the orbital decay of spacecraft. Once a mission is within two years of re-entry, those forecasts are updated more frequently. In November 2023, forecasts suggested Swift was entering that two-year window. Others estimated it would remain in orbit well into the 2030s. However, the outlook changed in 2024 as the Sun reached its solar maximum phase and Earth’s atmosphere expanded slightly, increasing drag on Swift. By 2025, the picture was less rosy, with most forecasts estimating the observatory would re-enter by summer 2026. NASA put out a call to industry for a solution, eventually awarding the contract to Katalyst. The forecasts eventually became weekly and were key to deciding when to halt most science operations aboard the spacecraft. They will be equally critical in predicting where Swift will be when the reboost mission is launched. Michael Shoemaker, deputy flight dynamics lead in Space Science Missions Operations at NASA’s Goddard Space Flight Center, said: “These predictions evolve, based on space weather forecasts and other factors like Swift’s current height and orientation. “It’s also an iterative process with members of Swift’s operations team. They determine new ways to point the spacecraft to reduce drag, and we do some new computations to see how much extra time that buys them.” Normally, Swift would slow to view targets such as gamma-ray bursts, but earlier this year, the team decided to put the spacecraft in an orientation to minimize atmospheric drag. The hope was that, by doing so, the team would eke out a little more time for the rescue mission, which is currently due for launch in June or July. The decision appears to have paid off. NASA wrote: “According to the most recent predictions, the Swift team’s actions will likely keep the spacecraft above the critical altitude into early fall.” That’s plenty of time for the reboost mission, which, if successful, could add years to the spacecraft’s operational lifetime. ®

المصدر: The Register