PPT Slide
1. Earth orbits the sun at a mean distance of 1.5 X 108 km. It completes one orbit every year. Compute its orbital velocity in km.sec.
2. The Pathfinder required a greater velocity than Earth orbital velocity to achieve its transfer orbit (why?). Since additional velocity costs NASA money for fuel, can you explain why we launched the spacecraft eastward? (Hint: When viewed from celestial north, the Earth and planets orbit the sun counter-clockwise.)