Sent to the moon israeli privateOn April 11, the Bereshit spacecraft should land in the crater Sea of Clarity, which is in the northern hemisphere of the visible side of our natural satellite. On board the spacecraft there is a small device, the successful verification of which will make it much more accurate (with an error of up to several centimeters) to calculate the landing sites for robotic as well as manned missions to the surface of the Earth satellite.
The spacecraft "Berishit", whose name withHebrew is translated as “at the beginning, was sent to the Earth satellite on February 21. The research boarding module is the brainchild of the private Israeli non-profit organization SpaceIL and Israel Aerospace Industries. As part of the flight, the device made several planned corrective maneuvers around the Earth, due to which it almost went into orbit around the satellite.
Together with the landing module "Bereshit" on the moonA small device, called a retroreflector, went. He was provided by the US aerospace agency NASA. The device is a system of quartz mirrors enclosed inside a domed aluminum frame.
If “Bereshit” successfully moons on April 11, thenThe NASA Lunar Reconnaissance Orbiter (LRO) spacecraft orbiting satellite uses its altimeter (a device for measuring altitude) and “fires” the retroreflector of the landing module with laser pulses. Thanks to this, the project team says, they will be able to determine the location of the vehicle on the lunar surface with an accuracy of up to 10 centimeters.
In the future, NASA plans to send to the moonmany similar retro reflectors. All of them will serve as fiducial markers. That is, the spacecraft that will be sent to the moon will be able to use these devices to make very precise landings in the planned areas.
Retro Reflector (LRA), which NASA providedfor Bereshita, it was developed by engineers and scientists from the Goddard Space Launch Center, as well as by experts from the Massachusetts Institute of Technology. It is located on the top of the landing module, so it is easily visible from orbit.
Retro Reflector itself does not perform any activefunctions. It will be paired with a lunar orbital laser altimeter (LOLA) of the LRO spacecraft. The rays of this altimeter strike and bounce off the lunar surface. After each pulse, LOLA calculates the time of movement of the beam to the surface and, based on this, calculates the distance to it.
While "Bereshit" will perform initiallythe tasks assigned to it, the retrorefletor installed on it will not be. This is explained by the fact that the altimeter laser beam can damage other sensitive equipment that is on board the landing module. To avoid this, the experiment with the device’s retroreflector will be conducted after the “Bereshit” has become “obsolete,” says David Smith, a LOLA project manager at MIT.
“This experiment aims to test the concept. It will continue as long as possible. Perhaps, until the LOLA tool on board the LRO is maintained. By the way, in June of this year there will be an anniversary - the time that the device is in satellite orbit will be 10 years, ”says Smith.
Smith notes that the lasers system was inventedand was developed by him and his colleague from the Goddard Space Flight Center about 15 years ago, even for the mission of the Phoenix spacecraft that operated on Mars.
"It was assumed that this retroreflector willwork in tandem with a laser altimeter mounted on a Mars Global Surveyor orbital spacecraft. Unfortunately, by the time the landing module landed on the Red Planet, the instrument on the orbital station was out of order, ”explains Smith.
According to the engineer, the main purpose of deploymentlaser systems on Mars and the Moon is to use these devices to determine the exact location of the landing apparatus from the orbital stations. However, the method has one drawback - its accuracy is associated with limiting the size of the surface area, which is illuminated by a laser pulse. According to Smith, a laser that creates a 5-meter “point” in diameter on the surface of a celestial body requires a very precise pointing system. In this case, of course, it would be easier and more convenient to use wider laser beams to determine the location of the reflector, but this will greatly reduce the accuracy of the data on the location of the device on the surface.
LRO orbiting device
Lonely laser on the moon
"Correctly adapted measurement systemdistance can solve this problem. Still, the LOLA tool was designed to measure height, not distance to a small system of reflectors. But for the near future, this is the only available laser on the satellite of our planet, ”says Smith.
With the help of surface shotsorbiter LRO, scientists in any case will be able to accurately determine the location of the Israeli module "Bereshit." Therefore, the emphasis in this experiment is to understand how difficult it will be for the LRO to determine the distance to the landing module.
"If you locate around the landing zone a fewsmall reflectors, then in future missions it will be possible to plant the apparatus directly at this point. This system does not require power, so it can work on the satellite for decades, perhaps even longer, ”adds Smith.
Lunar orbital laser altimeter (LunarOrbiter Laser Altimeter, LOLA), aboard a NASA Lunar Reconnaissance Orbiter spacecraft. With the help of it, as well as the retroreflector installed on the Israeli landing module "Bereshit"
According to Smith, similar compactRetro reflectors are planned to be installed on other celestial bodies, including small ones, for example, the same asteroids. Installing (or simply resetting) a certain number of such reflectors onto the surface of an object will allow probes working near this object to perform more accurate calculations of their characteristics, for example, to more accurately determine their rotational speed, location relative to the Earth, as well as their shape.
"Because reflectors can workFor decades, the object of interest can be explored simultaneously by several spacecraft in different missions. In addition, the presence of these reflectors on the surface will make it easier for the spacecraft to land on the celestial body of interest, ”adds Smith.
Of course, very compact reflectors havelimited range. According to Smith, the prototypes at the Goddard Space Launch Center are capable of picking up laser pulses from a distance of about 10,000 kilometers.
"The weight of compact reflectors is onlyabout 20 grams, but using larger ones will allow them to be determined from much larger distances. At the same time, “big” means heavier. And the advantage of the smaller ones is that they can be installed on almost any small landing gear, ”says Smith.
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