Measurement apparatus, positioning apparatus, lithography apparatus, and article manufacturing method

A measurement apparatus that measures a position of a measurement target surface, comprising:

• a sensor including a facing portion which faces the measurement target surface, and configured to measure a position of the measurement target surface in a first state in which the facing portion is arranged at a predetermined spacing from the measurement target surface;
• and
• a moving unit configured to move at least the facing portion of the sensor,
• wherein the moving unit operates in a first mode for moving the facing portion in a direction away from the measurement target surface in accordance with reception of a first signal instructing to retract the facing portion when measurement by the sensor ends, and a second mode for moving the facing portion in the direction in accordance with reception of a second signal instructing to retract the facing portion in an emergency, and
• wherein a time from reception of the second signal to an end of retraction of the facing portion in the second mode is shorter than a time from reception of the first signal to an end of retraction of the facing portion in the first mode.