Lunar Trajectory in Heliocentric Coordinates

This plot shows the heliocentric motion of the center of the Moon, based upon M. Soma's calculations from the Yohkoh orbital ephemeris of Jan. 28, 1998. The scales are in arc sec with N up and W to the right. The points with asterisks show when Yohkoh is outside the Earth's shadow. The asterisks are two minute apart. The peculiar and complicated pattern (not like your usual Kansas eclipse!) is due to the rapid motion of Yohkoh in its low Earth orbit, with an altitude fluctuating between about 500 and 800 km and orbital period of about 96 minutes. The solid circle represents the solar disk, and the dotted circle has a radius equal to the sum of the lunar and solar apparent radii (at one particular time). Thus points within this larger circle show when an eclipse is underway. Because the eclipse track does not intersect the center of these circles, once again Yohkoh has missed having a total eclipse, even though it gets three partial ones.