You cannot talk about the speed of light without defining your frame of reference. The measured speed of light in local inertial frames is 299792.458 km/sec. So if you want to make a comparison with "299792.458 km/sec" then you have to make it in a "local inertial frame".
Special Relativity requires the frame of reference to be inertial (travel in a straight line). Since Earth (our local frame of reference) is orbiting the sun then it is not traveling in a straight line, hence it is non-inertial. So when we compare the nominal speed of light with 12000 Lunar Orbits / Earth Day inside the gravitational field of the sun (non-inertial frame) we get 11% difference; however when the geocentric frame is inertial we get zero% difference.
As long as Earth is not traveling in a straight line then any geocentric frame is not inertial, hence NASA's measurement of the lunar orbit is made in a non-inertial frame. So we have to calculate the lunar orbit in an inertial frame starting from the measured one in this non-inertial frame. We need to calculate 12000 Lunar Orbits / Earth Day when the geocentric frame travels in a straight line, on the other hand we already know that outside sun's gravity it would travel in a straight line. But from the equivalence principle we know that these two experiments are equivalent, that is, whenever Earth is inertial you will get the same results as if Earth is outside sun's gravity. We chose to calculate the lunar orbit outside sun's gravity because it is easier to calculate however these two experiments are absolutely identical.
In a local frame non-rotating with respect to sun the moon speeds up when it heads towards the sun and then slows down by the same amount when it heads away from the sun. However in a local frame non-rotating with respect to stars the sectors where the moon speeds up and slows down are actually moving forward inside the orbit by the same angle Earth orbits the sun. In this frame there is a rotational force around Earth. This means that the lunar orbit is influenced by a torque-like force around Earth (twist, assist). As the distance to the sun increases to infinity the lunar orbit loses this twist. When we remove the energy gained from this twist we can calculate the total energy and hence the length of the lunar orbit outside gravitational fields. When the Earth-moon system exits the solar system the geocentric frame travels in a straight line (becomes inertial) and 12000 Lunar Orbits / Earth Day becomes equivalent to the speed of light. The difference in this local inertial frame is 0.01%. See: Orbital Mechanics.
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