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Alignment and Phasing System Achieves Major Milestone: Advancing to Final Design Phase

The Alignment and Phasing System (APS) team has progressed to the Final Design stage after successfully completing the Preliminary Design Review (PDR) for the APS Optical Bench and Instrument Control System (ICS). This review was held at the Thirty Meter Telescope (TMT) International Observatory LLC (TIO) Project Office in Pasadena on September 12–13, 2024. This accomplishment was the result of a collaborative effort between experts from Jet Propulsion Lab (JPL) and TIO.

This review represents a significant step forward in the development of the APS, reaffirming TIO's commitment to advancing its critical subsystems. The success of this review, combined with the previous reviews on the APS algorithm and the APS Procedure Executive and Analysis Software (PEAS) and System Engineering PDR last year, now ensures that the entire APS is moving into the Final Design Phase (FDP).

This important milestone was achieved with the active participation of both in-person and remote attendees, including external reviewers from the National Research Council Canada, the W. M. Keck Observatory (Keck), and the National Aeronautics and Space Administration.

The design team, reviewers and observers during the session of the APS Optical Bench and Instrument Control System Preliminary Design Review held at the TIO Pasadena office.

Dr. Gelys Trancho, TIO Project Systems Engineer, chaired the review which included participation from both TIO and JPL design teams. The Bench and ICS work was led by Patrick Morrisey at JPL, managed by John Rogers, TIO APS work package manager and technical oversight from the principal investigator, Mitchell Troy at JPL. 

TIO is very fortunate to have the same core team working on APS, who have provided the very successful alignment and phasing system used at Keck, known as the Phasing Camera System (PCS). Similar elements of the PCS design are employed within TIO’s APS.

Review slide highlighting the Keck Phasing Camera System experience

The APS is a Shack-Hartmann wavefront sensor responsible for the overall pre-adaptive-optics wavefront quality of TIO. To produce wavefronts of acceptable quality, APS will adjust the: Primary Mirror (M1) segment pistons and tip/tilts, M1 segment surface figure, Secondary Mirror (M2) piston and tip/tilt (or decenters), and Tertiary Mirror (M3) rotation and tilt. The purpose of the APS is not to verify that individual optics, such as M2 and M3, have met their respective surface requirements, but rather to align and phase the telescope.

This review was focused on the opto-mechanical design of APS, including all optical modules, detectors and motion stages, the associated motors, drivers, electronics and networking equipment, along with the software to monitor and control all these elements. During the review, the team presented on closure of action items from previous reviews, requirements and interface key drivers, the Bench optical and mechanical design, risks, the ICS hardware and software designs, requirements compliance and verification, and provided an updated cost and schedule for future work. The team presented a very mature design that was shown to meet or exceed their requirements.

The APS Bench is 3.4 meters (11.2 feet) long and 2.6 meters (8.5 feet) wide.

The review made clear how much specialized knowledge acquired during the alignment and phasing experiences at Keck has carried over to TIO. The continuity of the core team coupled with the ability to continually test and prototype at Keck has been of tremendous value, allowing the team to confidently scale the design for TIO.

We extend our gratitude to all participants and look forward to continued success as we advance towards the FDP of the APS development, guided by the valuable feedback from our reviewers.

 

This material is based upon work supported by the National Science Foundation under Cooperative Agreement No. 2331108. Any opinions, findings and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.