MOSCOW, Oct 18 , Tatyana PichuginaAfter the failure to land the Luna-25 spacecraft, proposals were made to speed up the implementation of the Russian lunar program, make more launches, and create duplicate missions. Scientists presented an updated flight plan to the Moon and Venus at the 14th international symposium on solar system research, held at the Space Research Institute of the Russian Academy of Sciences.
«Nine days of one year»
The Luna-25 automatic station was launched on August 11 from the Vostochny Cosmodrome. The launch was very successful, the device reached the lunar orbit, making two trajectory corrections. However, during the transition to the pre-landing orbit, an emergency situation occurred: the engines worked one and a half times longer than necessary, and the station crashed. The commission that studied the causes of the accident came to the conclusion that, most likely, an error arose in the software control of the accelerometer unit in the BIUS-L device.“We had nine happy days in August of this year,” — noted in the report Academician Lev Zeleny, professor, scientific director of the Institute of Space Research of the Russian Academy of Sciences and the first stage of the Russian lunar program. According to him, during the flight of Luna-25, all scientific instruments were tested and there were even some scientific results.
For example, a detailed analysis of a photograph of the Zeeman crater taken from lunar orbit and a comparison with a map constructed using data from the Lunar Reconnaissance Orbiter (LRO) made it possible to find areas of soil enriched with hydrogen, which most likely indicates water ice. Maya Dyachkova, an employee of the Department of Nuclear Planetology at the IKI RAS, spoke about this. Layers with water ice are located mainly on the southern slopes of the Zeeman crater, more precisely, in smaller craters that formed later than the main one. They contain approximately 0.2 percent hydrogen equivalent of water by mass, which is half the average at the south pole. Why the bottom of the Zeeman is dry, while in the younger parts of the crater there is water ice, remains to be seen.
Plasma physics experiments were also carried out during the flight. The crater left by the device during a hard landing was also studied. Its depth and dimensions coincided with calculations performed by scientists from the Geochemical Institute of the Russian Academy of Sciences.
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More “Moons”, good and different
Luna 26 will be launched next, in 2027. This vehicle will provide data for topographic maps needed when selecting landing sites for future missions. Equipment will be installed on board for full registration of radiation of different wavelengths, gamma rays, neutron fluxes, radio sounding to a depth of up to one hundred meters, and again for experiments in plasma physics. For future landing missions, the orbital station will become a relay station.
The Luna 27 landing module will be sent in 2028 or later. “During preparation, we will take into account all errors. The module will be equipped with tools for high-precision landing and avoiding dangers,” emphasizes Lev Zeleny.
Several landing scenarios are being developed in the area of the south pole — at an optimal point, clearly visible from the Earth, maximally illuminated by the Sun and promising for searching for water ice.
More scientific equipment will be installed on Luna-27 than in previous domestic lunar missions. It is necessary to study the regolith, heat flow at the landing site, seismicity and the exosphere — the dust shell of the Moon. Power supply is from solar panels, during a lunar night — from a radioisotope source. The device is designed for a year of operation.
“The main thing is that we decided to make a backup of Luna-27, a completely identical device, in order to insure ourselves in case of failure,” continues Academician Zeleny. The backup will be launched a few months after the main mission, landing is also planned in the polar regions.
Prospective landing sites have already been determined based on LRO data, the final choice will be after Luna-26 enters orbit.
The next one in the program is Luna-28, which will return with a soil sample without “defrosting” it. “This is a short mission: it takes samples and delivers them to Earth,” the scientists specify.
Plans for the next decade are already being discussed — the Luna-29 orbital station, landing with the Luna-30 lunar rover-geologist, a reusable landing platform «Luna-31». However, Lev Zeleny warns, it is difficult to plan for such a long period. Much depends on the results of the upcoming missions — Luna-27 and Luna-28.
What do we want from the Moon
«What are the main scientific goals of lunar missions? Research of regolith and dust, permafrost, volatile compounds, mineral resources,” the academician lists.
One of the important tasks is to establish the origin of water on our natural satellite. Now there are two hypotheses: endogenous and exogenous. The first says that water was formed chemically when the surface was bombarded by streams of particles — mainly protons from the solar wind. According to the second, comets brought water. If so, then you need to pay attention to organic molecules discovered, for example, by the Rosetta mission to comet 67P/Churyumov — Gerasimenko.
“Will we find these molecules in the polar regions along with water? If it is of cometary origin, then yes. Perhaps the polar regions are deposits of cometary material that is stored there forever,” the scientist says.
It is also important to examine dust, since it is very dangerous and toxic, consisting of jagged particles that constantly circle above the surface, get into the suit, and stick to equipment. American astronauts who visited the Moon spoke about this. Before installing instruments there, especially such as a telescope, you need to consider dust protection. For this purpose, the Dust experiment is provided on board Luna-27. The issue of conducting this experiment on the Chinese Chang'e-7 spacecraft, which is scheduled to launch in 2026, is currently being discussed.
Moon dust moves along with the terminator — the boundary between day and night — at a speed of four meters per second under the influence of static electricity. The electric field strength in this meter-long dust layer can reach 300 volts per meter, which is unsafe for instruments. To describe this phenomenon, Lev Zeleny suggests using a mathematical apparatus from plasma physics, developed by academician Roald Sagdeev.
“The Moon is a paradise for radio astronomy. There is no radio noise there, like on Earth. But not only that. It is also good for optical, submillimeter, X-ray and gamma-ray astronomy, and cosmic ray physics,” says Lev Zeleny. And the best place is the far side of the Moon. In 2019, the Chinese station Chang'e-4 landed there and installed a radio antenna. The polar region is also suitable for this kind of task, the academician believes.
The surface of the Moon can serve as a natural particle detector if instruments similar to detectors of atmospheric showers of elementary particles are placed there (since there is no atmosphere, they will register not secondary, but primary particles). This was previously proposed by the Russian physicist Mikhail Panasyuk, who at one time headed the space program of Moscow State University.
The moon is a potential source of minerals. Thus, according to data from the NASA Lunar Prospector orbital station, the regolith contains rare earth minerals. “Global exploration of geological resources will be continued by Luna-26,” clarifies Lev Zeleny.
In the future, when permanent bases appear on the Moon, it is possible to build a cosmodrome there for launch to Mars and other planets. The gravitational hole on the Moon is much smaller, than on Earth, which means it is easier to overcome gravity. And if water is found, then fuel will be made on the spot.
Twin planet, mystery planet
In addition, scientists have been hatching plans for a long time return to Venus. The Soviet Union was the first to launch a probe (in 1961) and a lander (in 1969) to this planet. In total, the USSR sent 16 successful missions there.
Venus is similar to Earth in size and mass. Most likely, they have a common origin, but something went wrong at an early stage of evolution, dramatically changing conditions on the surface, climate, atmosphere.
«We do not know why events on Venus took such a turn and its history developed otherwise. This is a mystery planet. It has been studied much worse than Mars,» says Dmitry Gorinov, a researcher at the Department of Planetary Physics at the Institute of Space Research of the Russian Academy of Sciences.
Here are the main questions that have not yet been answered: why is there a strong greenhouse effect on Venus, what is the mechanism of atmospheric superrotation and the nature of absorption of ultraviolet radiation by clouds, why is there no magnetic field, did it exist before, are its remains preserved somewhere, like on Mars? There is evidence that there was water on Venus. Where did she go? What does the surface consist of? What is the geological history of the planet? Many exoplanets similar to Venus have been discovered in our Galaxy. Then the Earth is an exception?
Who is flying to Venus
They are again showing interest in the second planet of the solar system — several missions are being prepared. The first after a long break will be the private American Rocket Lab to study habitability. The start is scheduled for 2025.
NASA has VERITAS (2031) and DAVINCI+ (2029) in its project, and the European Union is working on the EnVision device. India (the Shukrayan-1 orbiter) and China (VOICE, also orbital) announced plans to fly to Venus.
Russia is engaged in the Venera-D mission (D — “long-lived”). So far, it is the only one with a full-fledged landing module and tools for surface exploration. It consists of two blocks: the orbital and the descent module (which includes a landing module with a balloon).
The flight to Venus takes from 111 to 188 days, depending on the start date. Another 225 days will be spent on the gravity maneuver, during which the landing site will be determined. Next, the descent module will separate from the orbital station at an altitude of 125 kilometers and enter the atmosphere. At 75 kilometers the landing module with the balloon will begin braking and descending.
The orbiter will enter a 24-hour polar orbit centered on the south pole. “It can make in situ and remote measurements, determine all the necessary parameters of the planet, study the dynamics, structure, composition of the upper and lower atmosphere, the ionosphere and magnetosphere and its interaction with the solar wind,” lists Dmitry Gorinov.
Venus-D equipment
There are five phases in the preparation of the mission; next year they should begin the second — the preliminary design. Scientists have reduced the list of tools. Seven of the 12 proposed ones remain on the orbital station: a Fourier transform spectrometer along with a millimeter radiometer for measuring atmospheric temperature, UV mapping and an infrared spectrometer for composition analysis, and a high-resolution heterodyne spectrometer that will profile the atmosphere. And also a photometer for recording lightning activity, four cameras, like on the Venus Express, with IR and UV vision for tracking clouds, instruments for studying the magnetosphere. They will also conduct a radio sounding experiment on Venus to better understand its atmosphere.
The study of the atmosphere will begin during the descent, which will last 51 minutes. The device will measure the microphysical properties of clouds and their composition. Upon landing, he will immediately take panoramic photographs and microphotos of the surface to accurately understand its type. Using a drill, you will begin to extract samples. Chemical and mineral analysis will be carried out on the spot. This will help establish the age of the surface, its geological history, and the nature of its interaction with the atmosphere.
Currently, the scientific load of the lander includes nine instruments: four for descent (a set of sensors, a gas chromatograph and mass spectrometer, an IR laser tunable spectrometer, a nephelometer ), five — for ground-based research (several cameras and spectrometers — X-ray and fluorescence, laser mass spectrometer, Mössbauer, active gamma and neutron).
The lander will have three hours to do everything. You can’t stand it any longer due to the aggressive acidic environment, 500-degree heat and pressure of almost a hundred atmospheres, like at the bottom of the ocean. “There should be enough time,” says Lev Zeleny.
At an altitude of 53-57 kilometers, the balloon will separate from the landing module and begin exploring the cloud layer. Scientists are interested in everything: temperature, wind speed and direction, the composition of noble gases and aerosol microphysics, habitability. Four instruments are responsible for this: a set of sensors for determining key parameters of the atmosphere, an IR multichannel laser absorption spectrometer, a gas chromatograph and mass spectrometer for analyzing air samples, and a nephelometer for studying clouds. The weight of the scientific payload is 10.5 kilograms.
Scientists hope that, unlike the balloons in the Soviet Vega missions, which lasted only two days, the new device will operate for two weeks and collect much more information.
The preliminary design of the Venera-D mission should be ready by 2026, launch no earlier than 2031.