Talk:PFS-1

Background on the fortuitous orbital inclination selection of 28 degrees

Adding a bit of background on PFS-1, that might be useful if an article is ever written about PFS-1 rather than the redirect used today:

Decades after PFS-1's subsatellite mission from Apollo 15, through a study of many Lunar orbiting satellites, scientists came to discover that most Low Lunar orbits are unstable. Fortunately, PFS-1 had been placed, unknown to mission planners at the time, very near to one of only four Lunar frozen orbits, where a Lunar satellite may remain indefinitely.<ref name=nasa20061106> {{cite web |title=Bizarre Lunar Orbits|url=http://science.nasa.gov/science-news/science-at-nasa/2006/06nov_loworbit/ |work=NASA Science: Science News |date=2006-11-06 |publisher=NASA |accessdate=2012-12-09 |quote=''Lunar mascons make most low lunar orbits unstable ... As a satellite passes 50 or 60 miles overhead, the mascons pull it forward, back, left, right, or down, the exact direction and magnitude of the tugging depends on the satellite's trajectory. Absent any periodic boosts from onboard rockets to correct the orbit, most satellites released into low lunar orbits (under about 60 miles or 100 km) will eventually crash into the Moon. ... [There are] a number of 'frozen orbits' where a spacecraft can stay in a low lunar orbit indefinitely. They occur at four inclinations: 27º, 50º, 76º, and 86º"—the last one being nearly over the lunar poles. The orbit of the relatively long-lived [[Apollo 15]] subsatellite [[PFS-1]] had an inclination of 28º, which turned out to be close to the inclination of one of the frozen orbits—but poor PFS-2 was cursed with an inclination of only 11º.''}}</ref>

Cheers. N2e (talk) 22:06, 9 December 2012 (UTC)