NASA's Neil Gehrels Swift Observatory is back to studying the universe with two of its three science instruments after plans to raise the spacecraft into a higher orbit were scaled back. The observatory's Ultraviolet/Optical Telescope and X-ray Telescope were switched back on Wednesday, Aug. 26. Both instruments had been shut down in February as part of an effort to reduce atmospheric drag and help Swift remain in orbit longer while NASA prepared for a possible orbital boost.
Swift's third instrument, the Burst Alert Telescope, has not yet resumed science operations. NASA stopped using it in April to lower the spacecraft's power needs, which allowed engineers to position Swift's solar panels in a way that further reduced drag. The team now expects to restore that instrument to data collection within the next few weeks.
For 21 years, Swift has served as one of NASA's most versatile observatories. It studies the universe across multiple wavelengths of light and is especially valuable for tracking sudden, short-lived cosmic events. When Swift detects an outburst, it can quickly turn toward the source and alert other observatories on the ground and in space.
That rapid response helps astronomers gather follow-up observations before fleeting events fade away. One of Swift's biggest challenges is its location in low Earth orbit. Even hundreds of miles above Earth, traces of the planet's atmosphere remain.
Those thin upper layers create drag on spacecraft, gradually slowing them and causing their orbits to drop. Swift does not have a propulsion system that can raise its orbit, so it cannot directly counter that effect. The problem became more urgent as recent solar activity caused Earth's upper atmosphere to expand.
When the Sun is more active, extra energy heats the atmosphere and makes its outer layers extend farther into space. That expansion increases atmospheric drag on satellites in low Earth orbit. For Swift, the result was a faster-than-expected loss of altitude.
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