Asteroids striking the moon

[HarveyAlaric]

How large would an asteroid striking the moon have to be to actually disturb its orbit?

[neufer]

How large would an asteroid striking the moon have to be to actually disturb its orbit?

If TU24 had impacted the moon on either its leading or trailing end
it could changed its orbital speed (of ~ 1 km/s) by enough to have
changed its orbital major axis (of ~ 770,000 km) by about 1 centimeter.

This is sufficient to be measured by Apollo era lunar retro-reflectors:

• <<The McDonald Laser Ranging Station (MLRS) is a dedicated
  laser ranging station capable of measuring round trip light travel times
  to a constellation of artificial earth satellites and lunar retro-reflectors
  to a precision of about 1 centimeter.>>