The following research proposes an approach for an on-orbit single axis focus control mechanism in optical telescopes on small satellites. This solution addresses the need in the aerospace industry for maintaining orbital optical performance, in various extreme environmental conditions, while adhering to the severe size, weight, and power constraints of small satellites. A heavy emphasis in this effort is on the Systems Engineering approach to design, build and test. Considerable time is spent identifying the key stakeholders, categorizing design constraints, developing system requirements, conducting design trades, and comparing potential solutions. The chosen design is an electro-mechanical mechanism that provides single axial displacement of the image sensor parallel to the principal optical axis, allowing for depth of focus adjustments and compensation. This design is fabricated and subjected to random vibration and thermal vacuum testing.