A spacecraft that has been put into a circular orbit around the Sun (in the same plane as Earth's orbit) with a sidereal period of 2.25 years is unobservable behind the Sun once every:

Question

Quizplus · Accepted Answer

The spacecraft and Earth will align with the Sun once every synodic period, which can be calculated using the formula: 1/S = 1/P - 1/E, where P is the spacecraft's period (2.25 years) and E is Earth's period (1 year). Solving gives S = 1.80 years.

A Spacecraft That Has Been Put into a Circular Orbit