In this and in the next decade, several space agencies send missions to the moon, with plans to establish infrastructure that enable many returns. This includes the Lunar Gateway and the Artemis Base camp of NASA, the Chinese Roscosmos International Lunar Research Station (ILRS) and the Moondorf of the ESA. With so many space agencies and commercial companies that concentrate on moon research, there are also several plans for the determination of research institutions and scientific experiments.
In particular, NASA, China and the ESA have proposed to create radio astronomy experiments that would work on the other side of the moon. In a recently carried out work, an international team of European astronomers proposed a single ultra long wave length radio interferometer, which could examine the cosmological periods that are known as cosmic dark age and cosmic dawn. Known as The Dark Age Explorer (Dex), this telescope could provide new insights into one of the least understood periods in the history of the universe.
The study was headed by Christiaan Brinkerink, a scientific engineer of the Radio Radio Lab (RRL) at Radboud University Nijmegen. He was JOINED BY Researchers from the Netherlands Institute for Radio Astronomy (Astron), The Eindhoven University of Technology, The Delft University of Technology (TU Delft), The Laboratory for Instrumentation and Research in Astrophysics (Lira), The Kapteyn Astronomical Institute, The Cambrige Institute of Astronomy, The Kavli Institute for Cosmology, The European Research Infrastructure Consortium (ERIC) and the European Space Research and Technology Center of the ESA (ESTEC).
Consider cosmic dawn
According to current cosmological models, the early universe (approx. 380,000 to 1 billion years after the Big Bang) was penetrated by neutral hydrogen. During this era, known as the “cosmic dark age”, the only light sources in the universe were photons from the first electrons and protons that came together during the recombinations era (approx. 380,000 years after the Big Bang) and those who during the era of rice sionization (approx. 250 to 500 million years after Big Bang.),
While the former are now visible as a cosmic microwave background (CMB), today the latter are only visible as a “hydrogen line” (also known as 21 cm). This refers to photons that were released by neutral hydrogen because it was irritated by the ultraviolet radiation, which was released by the first stars and galaxies in the universe. This time is known to the astronomers as “cosmic dawn” (approx. 50 million to a billion years after the big bang) and is considered the final limit of astronomy and cosmology.
Due to the associated distances, the light becomes visible from this time to the point at which it is only visible in the UHF band of the microwave window in the Ultrahohoh Frequency (UHF) band (Ultrahohe frequency). So far, thanks to instruments such as the James Webb Space Telescope (JWST), astronomers have received a look at what is behind the veil of the cosmic dark age. As Brinkerink said today by e -mail, there are still many unanswered questions about this cosmological time:
“We have a trust model for how the structure formation has progressed from the time of the CMB to the formation of the first stars (whereby the lumps of dark matter was excavated by cooling by radiation from baryonic matter), but significant uncertainties remain over the rate in which this structural formation has made progress.
“The observation of the signal made of neutral hydrogen (the red-drawn 21 cm line) is basically the only way to examine this period directly. With the results of JWST, it is likely that we do not fully understand the phase of structural education that is present before the existence of the first stars.”
In particular, the early observations of WebB showed a surprising number of galaxies that were also brighter than expected. Astronomers also found that the “seeds” of the first super massive black holes (SMBHS) were larger than expected. These results were “tension” with earlier cosmological models and strengthened previous research such as the experiment to detect the global EOR signature (edges). This experiment showed an absorption feature in the global spectrum around 70 MHz (about twice as high as expected), which indicates that we do not fully understand the active processes during cosmic dawn.
The “tension” generated by these results has inspired new theories about early galaxy and the Smbh formation. It has also provided an additional incentive to create institutions of the next generation to examine the early universe deeper. The Dex aims to carry out these secrets by measuring the spectrum of the neutral hydrogen signal across an area of red shifts. This will first cover the cosmic dawn (red shifts from Z = 28 to 14) and finally the dark age (z = 50 to 28). As Brinkerink explained:
“The red shift area is divided, since these areas lay very different requirements for the size of the array size, the antenna size and placement. By measuring the spatial range of services as a function of red shift, we can make a film about how the early universe develops and create the role of darkness in the failure and acceleration of this process.
“Dex continuously creates Sky snapshots (pictures) In many frequencies in its observation bandwidth, which are integrated over time (~ minutes per integration) to manage the starting data rate. Back on earth, these Sky snapshots can be inserted into a processing pipeline that execute the spatial and spectral variations and the foreground.
The other side of the moon has long been considered the ideal place for observatories, including radio, optical and other telescopic species. These facilities would be shielded from radio frequency disorders (RFI) in front of the earth, and the atmospheric distortion would not be a factor. However, the technical challenges in building and maintaining such a observatory would be significant.
Enter Dex
Your study builds on earlier works by the ESA. In 2020, the ESA created the astrophysical moon observatory topical team (alo TT) to realize a cosmological radio array on the moon based on moon. This team comprises approximately 60 researchers, engineers and trading partners from universities, institutes and companies from Europe and beyond. This was followed by an ESA study on the simultaneous construction study (CDF) entitled “Assessment of an astrophysical lunar object on the other side of the moon”, which examined the feasibility of a lunar object using today's technologies with high technological standby level (TRL).
According to Brinkerkirk, the results confirmed that such an array with technology would be possible, which is available in the not too distant future:
“The CDF study carried out by ESA in 2021 showed that the scale, in which a moon array with existing technology can be realized, does not yet connect to what we have to bring for a new science: a 4×4 array was considered feasible, but for the science that we need at least 32×32 array. ~ 200×200 m and show us towards a relatively young surface (Less craters and boulders).
The study also focused on the southern polar region of the moon, since NASA plans to carry out regular missions through the Artemis program. Data relay services are also possible in this region because they will be most of the time in view of the Mondgateway. The temperature fluctuations are lower during the lunar cycles in the polar area and range from about 54 ° C (130 ° F) to low from -203 ° C (-334 ° f), compared to high highs of 121 ° C (250 ° f) and lows of -133 ° C (-208 ° f) near the equator. With Brinkerink and his colleagues, this creates greater technical challenges that medium-sized Latitudes cover a better sky and ultraviolet.
Your design study took many different strength scenarios into account. The classic method, he said, generated from a central facility and distributed with conductive cabling, would make up to 50% of the total mass of the system, which makes it very expensive for transport and use. Such a system would also affect the placement of antennas, since it would require electricity distribution centers near the antennas. Therefore, the team took into account alternatives, including the transmission of optical fibers and radio frequency data.
However, they also looked at distributed systems that were used near the antennas, but excluded this because it would create a source for locally generated RFI. In addition, the team identified several technological developments that are necessary to make Dex possible. In particular, they found that the mass budget for sending the necessary elements to the moon could be treated with a film-based structure for the radiant elements. As Brinkerkirk described:
“These make it possible to develop, handle or remove them as provision methods. The amplifiers with low recording must be temperature tolerant directly in the moon environment due to their exposed placement. Even with protective measures, the temperature range that they are exposed is still even greater than the survival span for more standard solutions.
“In addition, we need a reliable and efficient array deployment system that ensures that all antennas are placed in a predictable pattern, since all deviations from the nominal antenna positions lead to a reduction in the quality of the scientific edition (in the form of the spatial mix in the power spectra).”
Ultimately, the study found that the number of antennas that are required to achieve the primary scientific goals of the observatory is not yet possible. Nevertheless, Brinkenkirk and his colleagues emphasize how it also creates a way for the technological development, which could lead to a realistic and valuable experiment in the next or two. In the meantime, the development of these technologies will have spin-off applications here on Earth. To Brinkenkirk:
“[C]Omunication systems in small satellites benefit from the foil-based-based technology, and radio recipients who have to work over longer periods in rough thermal environments can use the implementations developed for Dex. In terms of science, the measurement of spatial power spectra from the dark age and cosmic dawn with the actual attitude of the structure of the lumps in these epochs (dark age/cosmic twilight omography), which can help us understand the development of super massive black holes and the role of early galactic feedback in galaxy growth. “
The paper that recently describes its concept appeared online and is checked for publication in the Experimental Astronomy Journal.
