Serendipity plays a large part in science.
A series of new NASA images highlight the hypotrochoid nature of orbiting bodies.
Fermi’s Motion Produces a Study in Spirograph
NASA’s Fermi Gamma-ray Space Telescope orbits our planet every 95 minutes, building up increasingly deeper views of the universe with every circuit. Its wide-eyed Large Area Telescope (LAT) sweeps across the entire sky every three hours, capturing the highest-energy form of light — gamma rays — from sources across the universe. These range from supermassive black holes billions of light-years away to intriguing objects in our own galaxy, such as X-ray binaries, supernova remnants and pulsars.
This image compresses eight individual frames, from a movie showing 51 months of position and exposure data by Fermi’s Large Area Telescope (LAT), into a single snapshot.
The pattern reflects numerous motions of the spacecraft, including its orbit around Earth, the precession of its orbital plane, the manner in which the LAT nods north and south on alternate orbits, and more.
The LAT’s sensitivity to gamma rays is greatest in the center of its wide field of view and decreases toward the edge. LAT scientists regard the effective limit of the instrument’s field of view to be 78.5 degrees (red circle) from its center.