Division 4.4

The required impact velocity, the angle of impact and the impactor mass must be determined in accordance with paragraphs 4.5 and 4.6. The tolerance on the impact velocity is ± 2 % and the tolerance on the impact direction is ± 2 °. The effect of gravity must be taken before the time of first contact. The impactor mass should be measured to an accuracy of better than ± 1 %, and if the measured value differs from the required value then the required velocity should be adjusted to compensate, in accordance with paragraph 4.7.1.