An Accounting of Contamination Control Requirements, Implementation, and Verification of the Sample Tubes for the Mars 2020 Mission and Future Return Sample Science.

The Sample Tubes on the Mars 2020 Perseverance rover were required to meet strict cleanliness standards for possible organic and inorganic contamination introduction to collected samples. There were also strict planetary protection cleanliness standards required to limit possible biological contamination. Together, these sets of standards also applied to associated hardware, like the Sample Tube hermetic seals.

Neutralization at infinity in streak retinoscopy.

A new principle of retinoscopy proposes that the endpoint of neutralization be placed at infinity rather than into the aperture of the retinoscope. The advantages of the method are (1) the pupillary reflex is sharply defined and enhanced at neutralization, (2) the pupillary reflex width is equal to the diameter of the smallest aperture of the observation system, (3) the relative speed of the pupillary reflex is equal to 1, that is, the speed of the reflex is that of the scanning speed, and (4) neutralization at infinity is independent of the observation distance. The lens used gives the "net" retinoscopy.