Latest Orbits Stories
In August 1960, NASA launched its first communications satellite, Echo 1. Fifty years later, NASA has achieved another first by placing the ARTEMIS-P1 spacecraft into a unique orbit behind the moon, but not actually orbiting the moon itself. This type of orbit, called an Earth-Moon libration orbit, relies on a precise balancing of the Sun, Earth, and Moon gravity so that a spacecraft can orbit about a virtual location rather than about a planet or moon. The diagrams below show the full...
Near the end of the mission of Apollo 16, on April 24, 1972, just before returning back home to Earth, the three astronauts released one last scientific experiment: a small "subsatellite" called PFS-2 to orbit the Moon about every 2 hours. The intention? Joining an earlier subsatellite PFS-1, released by Apollo 15 astronauts eight months earlier, PFS-2 was to measure charged particles and magnetic fields all around the Moon as the Moon orbited Earth. The low orbits of both subsatellites were...
Retrograde Motion -- Retrograde motion is the orbital motion of a body in a direction opposite that which is normal to spatial bodies within a given system. 'Retrograde' derives from the Latin words retro, backwards, and gradus, step. In the Solar system, mostly everything rotates in the same sense: all major planets orbit the Sun counterclockwise as seen from the pole star (Polaris). Most planets spin in the same sense, including Earth. The same happens with the orbital motions of the...
- A murmuring sound; a rushing or whistling sound, like that of the wind; a deep sigh.
- A gentle breeze; a waft; a breath.
- Any rumor that engages general attention.
- To make a rushing, whistling, or sighing sound; emit a hollow murmur; murmur or sigh like the wind.
- To breathe in or as in sleep.
- To utter in a whining or monotonous tone.