In the upper left of this image is the Laser Retroflector, which will be located near the center of NASA's Mars Perseverance Rover in the larger image. Some time in the future, a Mars orbiter spacecraft will be able to use a laser to determine the exact location of Perseverance on the Martian surface.
(Image Sources: NASA, Jet Propulsion Laboratory of the California Institute of Technology)
By Glenn A. Walsh
Reporting for SpaceWatchtower
Astronauts on the lunar landing missions of Apollo 11, 14, and 15 installed Laser Retroreflectors on the Moon, so scientists could better determine the distance between Earth and the Moon. Now, NASA is sending a Laser Reflector to Mars, on the Perseverance Rover, for similar scientific experiments.
Laser Retroreflectors are small arrays of special mirrors which reflect a laser beam directly back to its source, as a bicycle reflector reflects traffic light back to the vehicle source. Scientists use Laser Retroreflectors for laser ranging experiments, such as distance between planets or the distance between an object in orbit and a planet. Such experiments can also be used to determine the shape of a planet, the orbit of a planet, and how the planet's orbit changes over time.
In the case of the Laser Retroreflectors left on the Moon, laser beams are directed from Earth to the Moon; scientists measure the time it takes the laser beam to reach the Moon and return to Earth. The result of this experiment has provided detailed data regarding how the Moon is slowly moving farther away from the Earth. At the present time, the Moon is moving 1.49 inches / 3.8 centimeters away from the Earth each year.
Laser ranging experiments, using Apollo-era Laser Retroreflectors, continues to this day.
In the case of Laser Retroreflectors on Mars (smaller than the Laser Retroreflectors left on the Moon), it is currently not possible to conduct laser ranging experiments directly from the Earth, due to the great distance between the two planets. A future Mars orbiter spacecraft will use a laser, not yet developed, to conduct laser ranging experiments from Martian orbit.
Scientists, then, will be able to determine the location of rovers on the surface of Mars. As NASA will know the precise orbit of the spacecraft originating the laser beam, scientists will then be able to derive the laser ranging data sought from the Laser Retroreflector on the Martian surface. This could also make future landings on Mars more precise.
These laser ranging experiments could also provide future proof of Albert Einstein's General Theory of Relativity. As Perseverance is mobile, scientists will be able to receive data from several points of reference on Mars. This will help determine the influence on Mars' orbit from curvature in space-time. This could help scientists understand how gravity shapes our Solar System, and possibly even understand the roles of Dark Matter and Dark Energy in our Universe.
Perseverance will be the first rover on Mars to be equipped with the palm-size Laser Retroreflector Array (LaRA). A smaller Laser Retroreflector was also installed on NASA's Mars InSight Lander, which does not independently move, which landed on Mars on 2018 November 26. A Laser Retroreflector will also be aboard the European Space Agency's (ESA) ExoMars Rover scheduled for launch in 2022.
Perseverance launched toward the Red Planet on July 30, at 7:50 a.m. Eastern Daylight Saving Time (EDT) / 11:50 Coordinated Universal Time (UTC), from the Cape Canaveral Air Force Station in Florida. It is expected to land next February 18, at 3:00 p.m. Eastern Standard Time (EST) / 20:00 UTC, in Mars' Jezero Crater.
Originally titled NASA's Mars 2020 mission, the Perseverance Rover was designed with the assistance of the Curiosity Rover engineering team, to create a more robust Mars rover. The Perseverance Rover will have a major astrobiology mission, as well as investigate the planet's geology. The project is managed for NASA by the Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, California.
During its travels on the planet, Perseverance will collect soil samples and store the samples in special containers. NASA expects to retrieve these sample containers and return them to Earth for scientific analysis, during a potential, future Mars sample-return mission.
Internet Links to Additional Information ---
NASA Mars 2020 Mission: Link >>> https://en.wikipedia.org/wiki/Mars_2020
NASA Perseverance Rover: Link >>> https://en.wikipedia.org/wiki/Perseverance_(rover)
Laser Retroreflector: Link >>> https://en.wikipedia.org/wiki/Retroreflector
Image: Laser RetroReflector on the top deck of the Mars InSight space
lander, for laser range-finding from Martian orbit and future node in a proposed Mars geophysical network:
Link >>> https://spacewatchtower.blogspot.com/2018/11/astronomical-calendar-2018-november.html
Planet Mars: Link >>> https://en.wikipedia.org/wiki/Mars
Related Blog-Posts ---
"Thur.-AM U.S. Joins China & U.A.E in Race to Mars; Watch Launch Live."
Mon., 2020 July 27.
"'InSight' Space Probe to Land on Mars Monday Afternoon." Mon. 2018 Nov. 26.
Glenn A. Walsh Reporting for SpaceWatchtower,
a project of Friends
of the Zeiss.
Wednesday, 2020 October 7.
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Formerly Astronomical Observatory Coordinator & Planetarium Lecturer, original Buhl Planetarium & Institute of Popular Science (a.k.a. Buhl Science Center), Pittsburgh's science & technology museum from 1939 to 1991.
Formerly Trustee, Andrew Carnegie Free Library and Music Hall, Pittsburgh suburb of Carnegie, Pennsylvania.
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