Dr. Blake Crowther, principal engineer for imaging optics in the Synopsys Optical Solutions Group, shares his insights about the objectives, challenges, and most satisfying aspects of designing the zoom camera aboard the Mars rover Perseverance. Synopsys optical engineers partnered with Malin Space Science Systems, Motiv Space Systems, and Arizona State University to design the Mastcam-Z zoom lens system using CODE V optical design software.
Can you tell us a little background about this project and the objectives?
Several missions to Mars over the last 10 to 20 years indicated that Mars once held liquid water, which may have provided an environment in which microbial life could have existed. For the Mars 2020 mission, its primary goal is to explore the past habitability of Mars and to prepare and cache a set of samples for potential return to Earth by a future mission.
Perseverance was created for this mission, and on February 18, 2021, the rover arrived on the surface of Mars at the Jezero crater with a suite of cameras and other scientific instrumentation. In terms of optical design, color stereo imaging at variable magnification was needed to accomplish the Mars 2020 primary objectives.
The two Mastcam-Z cameras, which are both mounted on the Remote Sensing Mast, deliver the desired imagery. The Mastcam-Z cameras each make use of the first zoom lenses in interplanetary or deep space applications, which is the reason for the “Z” in the name of the camera (Mast Camera Zoom). In addition to their zoom capability, the lenses can be focused over a broad range of object distances.
What was most challenging about designing the Mastcam-Z?
One of the challenges was the extensive modeling that needed to be done. We had to make sure that the as-fabricated lenses would deliver the necessary image quality over all operational conditions. We therefore modeled all the fabrication processes and the resulting tolerances. We also modeled the lens at the various environmental operating conditions. There are a lot of variables to keep in mind when performing all these analyses. That was challenging!
What did you find the most satisfying about this project?
One satisfying moment was when we were able to demonstrate to all the reviewers that the lens would produce excellent image quality over all the operating conditions, and then to see it accepted for fabrication.
Another very satisfying moment was when we received the first images from the engineering model of the camera. This model, though it did not fly, was used to demonstrate that the lens hardware would work.
The most satisfying moment was when we got the first Mastcam-Z image back from Mars. The image was very sharp and showed the geography and geology in incredible detail. We were kept in great suspense until we saw that image!
Any general advice for optical design engineers?
Optical design can be grueling, especially for something that has never been done before. It is important to keep at the design, changing it as needed when the inputs change. Keep agile and keep going on the design. You may have to prove and prove again that the design will deliver –but keep at it. The design and modeling tools in CODE V today are better than ever but they need an intelligent designer to create a design.
Also, be honest when representing the design. If there is a problem, admit it and work to find a solution.
Mars 2020 Perseverance rendering courtesy of NASA/JPL-Caltech
For more detailed information about the optical design of the Mastcam-Z lenses, download the team’s technical paper from our website.