Before the Apollo missions, NASA and other space agencies determined the orbital positions of the Earth and Moon around the Sun using a combination of astronomical observations, mathematical calculations, and measurements.
Astronomical Observations: Observations of celestial objects, such as stars, planets, and the Moon, were made from Earth-based observatories. These observations involved tracking the positions of these objects over time and noting their apparent motions across the sky. This data provided valuable information about the Earth's orbit around the Sun and the Moon's orbit around the Earth.
Radar Measurements: Radar technology was utilized to measure the distances between Earth and the Moon accurately. By bouncing radar signals off the lunar surface and timing their return, scientists could calculate the Moon's distance from Earth at different times. This data helped refine our understanding of the Moon's orbit and its interactions with Earth.
Lunar Laser Ranging: After the Apollo missions began, retroreflectors were placed on the Moon's surface by the astronauts. These retroreflectors are devices that reflect incoming light back to its source, and they are still in use today. By precisely measuring the time it takes for laser beams to travel to the Moon and bounce back, scientists can calculate the Moon's distance from Earth with exceptional accuracy. This ongoing technique, known as lunar laser ranging, contributes to refining our knowledge of the Moon's orbit and its dynamics.
Mathematical Calculations: Scientists and mathematicians utilized the data obtained from observations and measurements to develop models and equations that describe the gravitational interactions between the Earth, Moon, and Sun. These models, such as those based on Isaac Newton's laws of motion and universal gravitation, allowed for the prediction and calculation of orbital positions.
It's important to note that the accurate determination of orbital positions was not solely dependent on NASA but involved collaborations with various international space agencies, observatories, and scientific institutions. Through continuous refinement and the accumulation of data over time, our understanding of the Earth-Moon-Sun system's orbital dynamics has improved, providing the necessary knowledge for planning and executing space missions like the Apollo program.