Impenetrable Barrier: Earth\u2019s Ionosphere<\/strong> This ionization in Earth\u2019s upper atmosphere generates a huge amount of radio \u201cnoise\u201d at wavelengths longer than 3 meters. All that noise limits astronomers\u2019 capability to glean meaningful information about our galaxy, other galaxies, and the distant universe at those wavelengths.2<\/sup> Nevertheless, because of the importance of this wavelength range, astronomers have dedicated five instruments to making observations at wavelengths longer than 3 meters: (1) the Square Kilometer Array<\/a> (SKA), (2) the Low Frequency Array<\/a> (LOFAR), (3) Large Array Low-Frequency Sky Survey<\/a> (VLSS), (4) the Galactic and Extragalactic All-Sky MWA Survey<\/a> (GLEAM), and (5) the Eighth Cambridge (8C) Survey<\/a>. <\/p>\n\n\n\n The longest wavelength yet observed by the first four instruments has been 4.2 meters. Astronomers used the fifth instrument to observe radio sources at 7.9 meters; however, the quality of their data was marginal.3<\/sup><\/p>\n\n\n\n At wavelengths longer than 10 meters, Earth\u2019s ionosphere is almost entirely opaque. Consequently, ground-based telescopes have been unable to detect radio sources at those wavelengths coming from beyond the solar system. <\/p>\n\n\n\n Impenetrable Barrier: Radio Transmissions<\/strong> The number of radio, radar, and television transmitters has multiplied exponentially. At wavelengths longer than 3 meters, Earth\u2019s ionosphere reflects radio signals with an efficiency that is proportional to the wavelength. The radio noise just from AM radio stations is huge. For example, there are 220 AM radio stations broadcasting at 50,000 watts in the United States alone. For comparison, the extragalactic radio sources astronomers desire to detect at wavelengths longer than 10 meters are weaker than 10-26<\/sup> watts per square meter per hertz. Thus, nowhere on Earth can astronomers\u2019 instruments detect radio emissions from stars, galaxies, and nebulae at wavelengths longer than 10 meters. <\/p>\n\n\n\n Escaping the Barriers<\/strong> Another problem is that the longer the wavelength astronomers observe, the greater the uncertainty in determining the positions and sizes of the radio sources. To gain sufficient resolution to determine the sizes and positions of radiation emissions at such wavelengths, astronomers must construct interferometers. <\/p>\n\n\n\n In radio interferometry, astronomers combine the radiation signals they receive from multiple telescopes that are spatially separated from one another to create a high-resolution image of the astronomical source. However, for radio interferometry to deliver a reliable image, astronomers must continuously know the precise positions of each telescope in the array and the timing of incoming waves to each telescope. This requirement is attainable only when all the telescopes are mounted on a single fixed, solid body like Earth where the position of each telescope is accurately known and each telescope possesses a calibrated high-precision clock. An example of this arrangement is the Very Long Baseline Array<\/a>, a set of 10 radio telescopes, each equipped with a sophisticated hydrogen maser atomic clock, stretching from Hawaii to the US Virgin Islands. It is much more challenging, by far, when the radio telescopes are in separate orbits about Earth.<\/p>\n\n\n\n Moon\u2019s Far Side: The Last Refuge<\/strong> <\/p>\n\n\n\n Figure 1: Moon\u2019s Far Side<\/strong> The Moon\u2019s far side is also the only unspoiled haven for broadband astronomical observations in the 1-centimeter to 3-meter wavelength range. In that range, radio astronomy has been squeezed into a few protected narrow bands. This loss of detection sensitivity is not trivial. The Moon\u2019s far side is the one place where the detection sensitivity that broadband observations make possible can potentially be recovered. <\/p>\n\n\n\n Going Where No One Has Gone Before<\/strong> We\u2019re no longer so limited. Today, the technology does exist to place radio telescopes on the Moon\u2014even on its far side\u2014and at relatively low cost. NASA and the US Department of Energy have developed a robotic telescope that will attempt first-of-its-kind measurements.<\/p>\n\n\n\n LuSEE\u2013Night Instrument <\/strong> <\/p>\n\n\n\n Figure 2: LuSEE\u2013Night Instrument<\/strong> The LuSEE\u2013Night landing site is a 100-meter ellipse centered on the lunar far side near the antimeridian. The chosen site is near the antipode (the location most opposite to Earth) so as to minimize terrestrial radio frequency interference. There is not a total blockout of radio interference from Earth since at the lowest frequencies some noise will likely be refracted by the tenuous lunar ionosphere.5<\/sup> The landing site was also chosen for its relative flatness and low horizon.<\/p>\n\n\n\n LuSEE\u2013Night\u2019s four monopole antennae will observe the radio sky and feed a full-bandwidth spectrometer operating in the frequency range of 0.1 to 50 megahertz, corresponding to wavelengths ranging from 6 meters to 3,000 meters. If it works as planned, it will give astronomers their first-ever glimpse at objects beyond our solar system at wavelengths longer than 7.9 meters. <\/p>\n\n\n\n Observations will be conducted during the 14-day, or 340-hour, \u201clunar night\u201d when the Moon\u2019s far side is pointed away from the Sun so that any interference from solar radiation will be blocked out. The time researchers have chosen for observations will also minimize radio interference from Jupiter and Saturn. LuSEE\u2013Night will be powered up at the beginning of the lunar night and will be permanently powered down at the end of the lunar night. This timing will eliminate the risk of interference from electromagnetic emissions generated by the LuSee spacecraft, which could threaten the integrity of the observations.<\/p>\n\n\n\n LuSEE\u2013Night\u2019s antennae patterns and observations will be calibrated by known 10-second-duration signals from a CLPS lunar orbiter. This orbiter will send timed signals to LuSEE-Night throughout its observing run. <\/p>\n\n\n\n Discovering What the Heavens Reveal <\/strong> Radio waves at wavelengths longer than 10 meters represent the only signals astronomers can measure from the Dark Ages. Therefore, LuSEE provides an opportunity for astronomers to learn how some of the universe\u2019s first nonluminous matter condensed to form the universe\u2019s first stars.<\/p>\n\n\n\n Astronomers anticipate that their investigation of the Dark Ages will affirm which of several LCDM (lambda cold dark matter) inflationary big bang models most accurately describes the origin and history of the universe. LCDM models are those in which most of the universe is comprised of dark energy and most of the remainder of the universe is composed of cold dark matter. Part of exploring the Dark Ages includes the cosmic dawn, the appearance of the universe\u2019s first stars. As described in last week\u2019s article (\u201cCosmic Dawn Bolsters Case for Creation<\/a>\u201d), the James Webb Space Telescope will be exploring events that occurred from the cosmic dawn onward to the universe\u2019s first galaxies and first galaxy clusters. The LuSEE\u2013Night and, eventually, much larger radio arrays on the Moon\u2019s far side, could allow us to explore the events leading up to the cosmic dawn. Together these two observing programs have potential to penetrate astronomy\u2019s last frontier, taking us to previously hidden moments in cosmic history.<\/p>\n\n\n\n As An\u017ee Slosar, the Department of Energy science lead and LuSEE\u2013Night Collaboration spokesperson comments, \u201cEvery time we have opened a new frequency window in cosmology, we have unlocked new discoveries about the history of the universe and our place within it.\u201d6<\/sup> I expect the missions to reveal new cosmic design features and more insights into how the universe was purposefully and precisely prepared for the entry of humanity. We can all look forward to the revelation of even more of God\u2019s glory and goodness (Psalm 19:1\u20134<\/a>; Psalm 50:6<\/a>, Psalm 96:7<\/a>). <\/p>\n\n\n\n Endnotes<\/strong><\/p>\n\n\n\n Explore LuSEE\u2013Night: a groundbreaking robotic radio telescope on the Moon’s far side set to unveil cosmic Dark Ages beyond Earth’s interference.<\/p>\n","protected":false},"author":586,"featured_media":349856,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_person_authors":[],"_kad_blocks_custom_css":"","_kad_blocks_head_custom_js":"","_kad_blocks_body_custom_js":"","_kad_blocks_footer_custom_js":"","footnotes":"","_classifai_error":"","_classifai_text_to_speech_error":"","_classifai_text_to_speech_scheduled":false},"categories":[63966,63993],"tags":[70618,70573,70508],"discipline":[64073],"reading-level":[64149],"class_list":["post-349273","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-tools-tech","category-universe","tag-cosmic-conditions","tag-exploration","tag-observational-astronomy","discipline-astronomy","reading-level-advanced-deep-dive"],"acf":[],"yoast_head":"\n
One reason astronomers have been unable to explore the universe at wavelengths longer than 10 meters has to do with the effects of Earth\u2019s ionosphere<\/a>, the region where Earth\u2019s atmosphere meets interplanetary space. Earth\u2019s ionosphere extends from 48 to 965 kilometers (30\u2013600 miles) above sea level. It\u2019s where ultraviolet and x-ray radiation from the Sun ionizes (strips away the electrons of) atoms and molecules.<\/p>\n\n\n\n
At wavelengths longer than 3 meters, the electromagnetic spectrum is saturated by AM and FM radio station broadcasts, short-wave radio transmissions, ham radio transmissions, VHF television broadcasts, and military over-the-horizon radar.4<\/sup> Decades ago, there were a few locations on Earth where one could avoid such radio transmissions. Not anymore.<\/p>\n\n\n\n
With Earth\u2019s surface ruled out for very-long-wavelength radio astronomy, astronomers have considered Earth-orbiting telescopes. However, radio transmission that leaks through Earth\u2019s ionosphere creates a major interference. <\/p>\n\n\n\n
For long-wavelength radio astronomy, the far side of the Moon (see figure 1) is the only unspoiled detection location in the solar system. It\u2019s the only place where Earth\u2019s intense radio transmissions and noisy ionosphere are permanently blocked out. It\u2019s the only place where astronomical observation at wavelengths longer than 10 meters is even possible. For observations in the 3 to 10-meter range, it remains the only place where astronomers can detect faint signals from far distant galaxies and quasars.<\/p>\n\n\n\n![\"\"](\"https:\/\/reasons-prod.storage.googleapis.com\/wp-content\/uploads\/2023\/07\/Picture2-1-1024x1024.jpg\")
<\/figure>\n\n\n\n
Credit: NASA<\/em><\/p>\n\n\n\n
While twenty-first-century technology has seriously disrupted Earth-based radio astronomy, it also holds promise. I did my PhD research long ago, during the Apollo program<\/a>, and I remember talking to my professors back then about the benefits of putting radio telescopes on the back side of the Moon. They laughed. The technology didn\u2019t exist at that time to construct radio telescopes anywhere<\/em> on the Moon, much less on the back side.<\/p>\n\n\n\n
This new instrument, the Lunar Surface Electromagnetics Experiment\u2014Night (LuSEE\u2013Night) consists of four monopole antennae arranged in a cross-configuration and mounted on top of a rotating platform (see figure 2). The plan is to place it in the CS-13 region of the Moon\u2019s far side via a Commercial Lunar Payload Services<\/a> (CLPS) mission scheduled, as mentioned above, for late 2025 or early 2026. Since it will be fully robotic, the mission will include all the technology needed to deliver the LuSEE-Night instrument to the Moon\u2019s far side, set it up, and<\/em> make it fully operational. No astronauts will be needed.<\/p>\n\n\n\n![\"\"](\"https:\/\/reasons-prod.storage.googleapis.com\/wp-content\/uploads\/2023\/07\/Picture3-1.png\")
<\/figure>\n\n\n\n
Credit: NASA\/DOE<\/em><\/p>\n\n\n\n
LuSEE\u2013Night\u2019s scientific mission is to study the astronomical \u201cDark Ages.\u201d The Dark Ages is the one unexplored portion of cosmic history\u2014the era between the last scattering of the cosmic microwave background radiation (CMBR) and the formation of the universe\u2019s first stars. The last scattering of the CMBR occurred 380,000 years after the cosmic creation event, and the universe\u2019s first stars formed 200\u2013300 million years after that event. Only a cold, non-luminous mixture of hydrogen and helium gases existed during that era, as far as we know. <\/p>\n\n\n\n\n