How did Swift get its name?
Goddard Science Question of the Week
February 25, 2005
The names of most space missions are either acronyms (like MESSENGER) or recognition of famous scientists (like Hubble and Cassini). One recent NASA mission, however, is named for a bird. What mission is that, and why was that name picked?
The mission named for a bird is Swift, which was launched on November 20, 2004. Swifts are birds that are found around the world. Here in the eastern United States, we have the chimney swift, which migrates from South America. Swifts are among the fastest flying birds. They spend most of their lives on the fly, soaring in long sweeps and then quickly darting to catch insects out of the air. Unlike most birds, they cannot stand or perch. Swifts roost only on vertical surfaces (like chimneys).
The Swift satellite is not catching insects, but something much more exotic - gamma-ray bursts. First discovered by military satellites searching for clandestine nuclear explosions, gamma-ray bursts (GRBs) are short, powerful bursts of light that are brightest in the high-energy part of the spectrum known as gamma rays. They come randomly in time and can appear from any direction in the sky. The primary burst fades away in seconds; only a handful of GRBs have lasted for more than 2 minutes. After the initial burst, a faint afterglow can be seen for days or weeks, but only if the location of the burst is well enough known to point large telescopes in the right direction. These afterglows have revealed that at least some bursts come from cosmological distances, making them the brightest explosions in the Universe, far brighter even than a supernova. The mechanisms for these incredibly powerful bursts remains unknown but is probably related to the formation of a black hole.
The trick to measuring the properties of a GRB is to ascertain its location on the sky before it fades. If you have ever watched a meteor shower, you probably understand the frustration of trying to pinpoint the direction of a flash in the sky that disappears before you can turn your head to focus on it. That is where the Swift satellite acts like the bird of the same name. Swift scans the sky with a wide-field gamma-ray telescope (BAT, the Burst Alert Telescope). When BAT detects a GRB, it measures its arrival direction fairly accurately in seconds. Based on that information, the entire Swift satellite (which is over 5 meters long) re-points in just tens of seconds to aim two other telescopes - an X-ray telescope and an optical/ultraviolet telescope) - at the GRB before it fades away. These other telescopes measure additional characteristics of the GRB, including a more accurate location on the sky that is then quickly sent to the ground and distributed to astronomers around the world. By using a multiwavelength approach, astronomers learn more about these powerful flashes than they could using any one type of telescope.
Because Swift is an operating mission, you can watch its progress as it detects and learns more about gamma-ray bursts.
This question was answered by Dr. Dave Thompson. He helped build, test, and analyze data from EGRET on the Compton Gamma Ray Observatory, and he helped build part of the Fermi Gamma-ray Space Telescope, which launched in 2008. His particular scientific interest is gamma-ray pulsars.