How does an astronaut's mass while orbiting in the space shuttle compare with his mass while standing on the earth's surface?

An astronaut's mass remains unchanged whether they are in orbit aboard the space shuttle or standing on Earth's surface; mass is a measure of the amount of matter in an object and does not vary with location. However, the astronaut experiences weightlessness in orbit due to the microgravity environment, which is a result of the shuttle and astronaut being in free fall together around the Earth. This sensation of weightlessness can lead to the common misconception that mass decreases in space, but it does not; only the effects of gravity on the astronaut's body change.