The period of 223 synodic month, equaling 6585.32 days or 18 years, 11.33 days, after which the Sun, Earth, and Moon return to approximately the same relative geometry. When two eclipses are separated
by a period of one Saros, they occur at the same node with the Moon at nearly the same distance from Earth and at the same time of year. Thus, the Saros is a useful tool for organizing eclipses into families or series. Each series typically lasts 12 or 13 centuries and contains 70 or more eclipses.
This system is a fundamental reference system for most spinning spacecraft since the S/C - Sun meridian can
easily be determined on board using a narrow-slit sun sensor. Thus a spacecraft-fixed instru
mental system
has only a longitudinal offset with respect to SAS linear in time.
+Z-axis: spacecraft spin axis vA, right-handed orientation.
+Y-axis: cross-product between +Z-axis and S/C - Sun vector vS.
Complex, fragile shapes of snow on top of sea ice that resemble sand dunes; they form parallel to the prevailing wind direction; sastrugi can also form on snow cover over land.
A series of long, frequently sharp, wave-like ridges of hard snow characteristic of windswept polar plains when the winds blow continually from one direction. Sastrugi are oriented perpendicular to th
e wind with a gentle slope to windward and a steep slope to leeward. syn. zastrugi
Sharp, irregular ridges formed on a snow surface by wind erosion and deposition. On drift ice the ridges are parallel to the direction of the prevailing wind at the time they were formed.