Mars Rover Perseverance's First Zoom Lens in Space

On July 30, 2020, NASA launched the Mars 2020 Perseverance rover, which is scheduled to land today. Perseverance has been deployed to Mars with a new mission: to search for evidence of past life and collect samples that will eventually be brought back to Earth by future missions.

According to NASA, the Perseverance Mars mission “takes the next step by not only seeking signs of habitable conditions on Mars in the ancient past, but also searching for signs of past microbial life itself.” The Perseverance rover is similar in size and design to the Curiosity rover – about the size of a compact car –but features new camera systems to facilitate rock and soil sample collection.

One of these is the Mastcam-Z instrument, which functions as the rover’s mast-mounted scientific “eyes.” The “Z” in Mastcam-Z stands for “zoom.” It represents a milestone in the history of space exploration: it’s the first zoom lens system to be included on a deep space instrument.

Mastcam-Z: Powerful Zoom Capabilities

The Mastcam-Z instrument is an update of the Mastcam instrument on the Mars Curiosity rover. It will perform several key functions:

• Scanning the landscape on Mars to help scientists understand the terrain.
• Assessing atmospheric and astronomical conditions.
• Helping scientists identify and characterize materials for rock and soil sampling.

Mastcam-Z is capable of producing multispectral, stereoscopic images. With its powerful zoom, it will help scientists see small features on the Mars landscape from far away. To give an idea of its power, it is capable of resolving features as small as 3cm from a distance of 100m.

Synopsys optical engineers partnered with Malin Space Science Systems and Arizona State University to design the Mastcam-Z zoom lens system using Synopsys’ CODE V optical design software. There were many technical challenges to resolve. The lenses needed to be well corrected over an extended visible spectral range and needed to operate over at least a 3x zoom range while being able to focus from close to the rover out to infinity. The lenses also had to operate over a large temperature range, including extreme temperature gradients. This set of operating conditions required substantial design effort as well as extremely detailed analyses. Synopsys optical engineers needed to show that the lenses could be successfully fabricated and that they would function over all the operating conditions.

Illuminating Sample Collection

Another updated camera system on the Perseverance Mars rover is the CacheCam, one of several engineering cameras on board. The CacheCam is located underneath Perseverance and takes pictures of sampled materials as they are being prepared for sealing and caching. Synopsys optical engineers contributed to the design of illumination optics on the CacheCam.

The CacheCam includes a fixed illuminator (no moving parts) to provide close to uniform illumination of the materials throughout the collection process; at the beginning, the samples are far from the imaging optics and, at the end, the samples are much closer. In addition, the illuminator has to account for the presence of dust on the outer surface of the optics, as well as on the inner surfaces of the collection tube.

Simon Magarill, one of the engineers who worked on the CacheCam design, noted, “The  requirement to include the dust in the analysis and design process required a lot of calculations to account for different sizes and concentrations of scattering particles. We developed a systematic approach to design an illuminator that provides optimum performance in such challenging conditions.”