ISIR-AL

The final element of this project is the Risley Wedge assembly. It is shown to the right. A risley wedge assembly consists of at least one pair of wedged optics. The two elements of the pair can be rotated independently to steer a beam of light in a particular direction. The design shown to the right has two pairs of risley wedges. It is designed for use with the SLA laser which is mounted inside the same type of can as the ISIR instrument. This assembly allows ISIR-AL and SLA to be bore-sighted by adjusting the angle of the out-going laser beam. The outer ring (shown in brown) mates to the interface flange on the GAS cans and provides an airtight seal.

Challenges and lessons learned

The main challenge on this project was to keep costs at a minimum. Welch Mechanical Designs (WMD) took over the design from a competitor who ran significantly over budget and failed to produce a viable design. We created a design that met all of the requirements and even added an element that was not required. The extra element is a mechanism for adjusting the decenter (X-Y) of the optics at the top of the telescope tube. The extra mechanism was added to the design while still keeping the budget well below that used by my competitor.

This was also the first project where we had to perform rigorous safety analyses to qualify the design. The analyses are required to prove that the design is safe for use on the Space Shuttle and is not a safety threat to the human passengers.