After the Moon, Mars is getting laser-reflecting mirror to help future landings on the Red Planet

Artists concept of the Mars Perseverance Rover on the Red PlanetNASA
  • The Mars Perseverance Rover is currently on its way to the Red Planet scheduled to land on February 21.
  • The rover is carrying laser-reflecting mirrors on board, similar to the ones already deployed on the Moon, in hopes of making future landings on Mars easier.
  • The retroreflector being placed by Perseverance is so small that it can fit in the palm of your hand whereas some of the array’s on the Moon are as big as the average computer monitor.
The National Aeronautics and Space Administration’s brand-new Mars Perseverance Rover is currently on its way to the Red Planet. And, the landing that’s to ensue will not be easy.

Perseverance will rely on the Terrain-Relative Navigation (TRN) system. It compares images taken during the descent to an onboard map to keep the rover away from obstacles.

Visible both in the inset photograph on the upper left and near the center of NASA's Perseverance Mars rover in this illustration is the palm-size dome called the Laser Retroreflector Array (LaRA)NASA

But NASA is hoping that things will be easier for future missions. Perseverance is carrying laser-reflecting mirrors — officially called the Laser Retroreflector Array (LaRA) — on board. Once deployed, they act as a series of reference points to a check on the performance of the TRN systems, maybe even make it more accurate.

After the palm-sized LaRA is placed on Mars, the InSight lander is also carrying the laser retroreflector for Insight (LaRRI), and another will be aboard the ExoMars rover rescheduled to launch in 2022 in a collaboration between NASA and the European Space Agency (ESA).

Laser Retroreflector for InSight (LaRRI) is the copper-colored half-dome on the deck of NASA's InSight landerNASA

"Laser retroreflectors are shiny, pointlike position markers," said Simone Dell'Agnello, who led development of all three retroreflectors. "Because they're simple and maintenance-free, they can work for decades," he added.


Mirrors on the Moon have already told us a lot
The Apollo astronauts already placed the first of these on the Moon. The first generation was mere retroreflectors made up of many tiny mirrors. Scientists beamed lasers up at the Moon, and the time it took for the light to reflect helped with precise measurements of the Moon’s orbit, its shape, and how it changed until the influence of the Earth’s gravitational pull.

The Laser Ranging Retro-Reflector (LR3), which the Apollo 14 astronauts deployed on the Moon during their lunar surface extravehicular activityNASA

With laser reflectors on Mars, scientists hope to continue these experiments on the Red Planet. “Laser ranging could open up new kinds of Mars exploration,” said Dell’Agnello.

However, LaRA is much smaller than the retroreflectors on the Moon. Those were around the same size as a typical computer monitor, while LaRA can fit in the palm of your hand. And the beams reflected from the Moon have been known to become faint as they travel through the Earth’s atmosphere.

Laser beams bounced off of LaRA would travel a much shorter distance. Rather than travelling the entire distance between Earth and the Moon, these beams would only have to reflect to the future Mars orbiter, which would come equipped with an appropriate laser.

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