Lunar Farside Radio Cosmology

Speculative If the cosmic Dark Ages 21-cm monopole is ever measured at the depth standard cosmology predicts — which no instrument has done, and section 7 says what would — the prize is a probe of a purely linear epoch carrying of order 10¹² independent Fourier modes, against about 10⁶ from Planck 2018 and about 10⁸ from Stage-IV large-scale-structure surveys. The condition comes first because nothing in that sentence has been observed. What has been observed is one contested feature at a different frequency, and a non-confirmation of it.

Established The target is a specific number, not a hope: an absorption trough of −44.09 ± 0.96 mK centred at 17.14 ± 0.03 MHz, derived from Planck constraints in standard cosmology with the HYREC-2 recombination code. That frequency is the whole argument for the Moon. The 21-cm line rests at 1.42 GHz and expansion drags it to roughly 7–50 MHz for redshifts around 200 to 30; Earth’s ionosphere absorbs and reflects that band before it reaches the ground, and terrestrial transmitters fill what gets through. Established The lunar farside is the only place in the inner solar system where the band is both transmitted and quiet: the Moon’s 3,400 km thickness shields its far surface by as much as 90 dB, and the −80 dB quiet zone stretches 4,366 km across the anti-Earth point.

Frontier What a measurement would buy, in the units the forecasts use: 1,000 hours of integration gives about 10% precision on the cosmological parameter combination the signal constrains, and 10,000 hours gives 3.2% plus a 9.9% constraint on the primordial helium fraction. Speculative A 5 mK measurement of the trough would bound dark-matter annihilation at roughly 10⁻²⁸ cm³ s⁻¹ GeV⁻¹ in the combination of cross-section, mass and abundance — an order of magnitude tighter than Planck 2018. These are forecasts, and the brief flags them as such.

Frontier The gain accrues to whoever can put mass on the farside, and today that is two state programmes. NASA buys delivery through a commercial contract vehicle with a combined maximum value of $2.6 billion through November 2028; China’s lunar research station programme schedules lunar-based astronomy for its post-2028 phase. Handwave Nothing in the arrangement makes the resulting data a commons, and nothing in it protects the quiet.

Speculative The condition on all of it is a number nobody has demonstrated: a spectral dynamic range near 10⁷, because the sky at 17 MHz is of order 10⁵ K and the signal is 44 mK. The bottleneck list in section 5 is where that number is unpacked, and it is worth reading before the forecasts above are believed.

Established The Dark Ages are the interval between the release of the microwave background, roughly 380,000 years after the Big Bang, and the ignition of the first stars. There is no starlight in them, which is the point: the only physics operating is expansion, gravitational growth of linear density perturbations, and atomic collisions in neutral hydrogen. An epoch with no astrophysics is an epoch with nothing to marginalise over.

Established The observable is the hyperfine transition of neutral hydrogen, rest frequency 1.42 GHz, seen in absorption against the microwave background. Cosmic expansion redshifts it: emission from redshift 85 arrives at about 17 MHz, and the useful Dark Ages window spans roughly 7 to 50 MHz for redshifts around 200 down to 30. Established Two measurements live in that band: the monopole, or global signal, the sky-averaged brightness measured by a single well-characterised antenna; and the power spectrum, the spatial fluctuation about that average, which requires an interferometer. They fail in different ways and this brief keeps them separate.

Established The coupling that makes the Dark Ages signal visible is collisional, and it switches off as the universe thins. Collisions drag the hydrogen spin temperature below the radiation temperature while the gas is dense, producing absorption; as expansion dilutes the gas the coupling weakens and the trough closes. That is why the predicted signal has a definite minimum rather than an arbitrary one, and why its depth depends on the expansion rate and the matter and baryon densities: a faster expansion makes collisional coupling inefficient sooner and the trough shallower.

Frontier The band is unobservable from the ground because the ionosphere does not pass it. Below the ionospheric plasma frequency, radio waves are reflected rather than transmitted, and in the partially transmitting region above it they are refracted and absorbed in a way that varies with the hour and the solar cycle. This brief could not source a single defensible cutoff frequency — the honest statement is the qualitative one, that the Dark Ages band cannot be measured from Earth because the atmosphere absorbs and reflects it, and the quantitative one is left out rather than guessed.

Established Even where the ionosphere passes signal, the band is occupied. The FM broadcast band at 88–110 MHz is bright enough that its reflection off the Moon is itself a measured contaminant: the lunar disc returns about 7% of incident radiation, and array measurements of the Moon’s apparent brightness temperature come in at 184.4 ± 2.6 K and 173.8 ± 2.5 K by two methods. Established A body that reflects Earth’s transmitters back at Earth’s telescopes is also a body whose far hemisphere never sees them.

Established The farside is a geometric instrument, not a preference. The Moon is tidally locked, so its far hemisphere is permanently shielded from direct emission generated on or near Earth; a site survey using Lunar Reconnaissance Orbiter laser altimetry at 200 m resolution states that the 3,400 km thickness and tidal locking of the Moon shield the farside surface from interference by as much as 90 dB, and that the −80 dB radio-quiet zone begins at ±108° of longitude and stretches 4,366 km across the anti-Earth point. Established That survey assessed eight farside craters — Apollo, Daedalus, Hertzsprung, Korolev, Mare Ingenii, Mare Moscoviense, Mendeleev and Tsiolkovsky — and favoured Mare Moscoviense, whose roughly 280 km floor holds slopes under 20° over most of its area.

Established International regulation already names this place. The Radio Regulations define a Shielded Zone of the Moon in Article 22, Section V, as the area of the lunar surface and adjacent space shielded from emissions originating within 100,000 km of Earth’s centre. Frontier The protection is real on paper and thin in practice, which section 10 takes up.

Frontier One distinction does more work in this subject than any other: the Dark Ages are not cosmic dawn. Cosmic dawn is the period when the first stars begin to couple the spin temperature radiatively, near redshift 17, which lands the 21-cm feature near 78 MHz. It is brighter, reachable from the ground, and entangled with the astrophysics of the first galaxies, and every claimed global 21-cm measurement to date is one. Speculative The Dark Ages signal has never been the subject of a detection claim by anyone, and treating the two as one story is the error section 15 opens with.

Established On 1 March 2018 the EDGES collaboration reported a flattened absorption profile centred at 78 MHz, 19 MHz wide at half maximum and about 0.5 K deep. The paper stated plainly that the best-fitting amplitude was more than a factor of two greater than the largest predictions available. A 2025 re-analysis quotes the profile as 500 mK with a 99% confidence range of 500 ⁺⁵⁰⁰₋₂₀₀ mK and a width of 19 ⁺⁴₋₃ MHz, against a standard expectation near 250 mK where the radio background is the microwave background alone.

Frontier The depth, not the detection, is what made it famous. A companion paper published the same day proposed that baryons were scattering off cold dark matter, cooling the gas below the adiabatic floor, and concluded that such a particle would be no heavier than several proton masses — far below the mass range of the weakly interacting candidates then being searched for. Speculative The alternative family of explanations keeps the gas temperature standard and adds a radio background hotter than the microwave background at cosmic dawn.

Frontier Within ten weeks, an independent group argued the fit was not physical. Refitting the released EDGES data, they found that the unconstrained solution required a negative optical depth for the ionosphere and a negative electron temperature, and in the linearised version an ionospheric emission brightness above 10⁴ K together with a negative astronomical foreground brightness. Established When physically admissible priors were imposed — ionospheric optical depth greater than 0.005 at 75 MHz and electron temperature between 200 and 2,000 K — the recovered absorption depth grew to roughly 2 K, four times the published value. Frontier The same analysis showed the nine-parameter fit is not unique: sine waves and Gaussian features reproduce the data comparably well. Their conclusion was carefully worded and has not been withdrawn — the evidence falls well short of the level required to invoke new physics for its explanation.

Frontier The EDGES reply, published 19 December 2018, defended the unconstrained fit and conceded little, reframing the objection as a statement about parameter degeneracy rather than about the physicality of the recovered values. Speculative That exchange ended unresolved; what moved the question came four years later and from a different instrument.

Established On 28 February 2022 the SARAS 3 experiment reported that the EDGES best-fitting profile is rejected with 95.3% confidence, and EDGES-like signals more generally at 90.4% significance. SARAS 3 observed 55–85 MHz — overlapping the claimed feature — from southern India, with the antenna floating on water to give a uniform, well-characterised ground plane, a design choice aimed squarely at the ground-plane systematic the EDGES critics had raised. Established The collaboration’s own statement of the result is that the profile found by EDGES is not of astrophysical origin.

Frontier A non-detection is still a measurement, and SARAS 3’s constrains cosmic dawn astrophysics on its own. A Bayesian analysis of the same data disfavours, at 68% confidence, radio-luminous galaxies in dark-matter haloes of mass between about 4.4 × 10⁵ and 1.1 × 10⁷ solar masses at redshift 20; galaxies converting more than 5% of their gas into stars; a radio luminosity per unit star-formation rate above 1.549 × 10²⁵ W Hz⁻¹ per solar mass per year at 150 MHz; and synchrotron backgrounds exceeding the microwave background by more than 6% at 1.42 GHz. Established As of the analysis that produced them, these were described as the only upper limits strong enough to constrain cosmic dawn astrophysics.

Frontier Two 2025–2026 results push the same way without closing the file. A 2025 study that forward-models the EDGES data with physical rather than phenomenological signal models finds a cosmic 21-cm signal of non-standard depth decisively disfavoured, and reads the data as evidence against an excess radio background at cosmic dawn. Frontier A 2026 re-analysis using SARAS 3 to constrain Coulomb-like interacting dark matter rules out signals stronger than −277.6 mK at redshift 23.6, about 57.7 MHz, at the 3-sigma level, and returns a Bayes factor near 1.7 in favour of interacting dark matter over cold dark matter — which its authors describe as inconclusive, with no statistically significant preference. Established That paper lists the live explanations for the disagreement as foreground modelling, ground-plane systematics and calibration systematics, and names a third ground experiment, REACH, as the one that could resolve it.

Established The state of the anchor, stated plainly: the EDGES measurement exists, its cosmological interpretation does not survive contact with the only comparable instrument built since, and eight years after publication nobody has confirmed it. Frontier The one nuance worth adding is that 95.3% is not an extinction-level number — it is a two-sigma-class result, which is why the field is still arguing rather than moving on.

Established The Dark Ages target is a different and much better-specified object: standard cosmology with Planck constraints and the HYREC-2 recombination code puts the trough at a central frequency of 17.14 ± 0.03 MHz and a depth of −44.09 ± 0.96 mK. Established Its depth is set by the Hubble parameter, the matter density and the baryon density, all of which are measured independently, so the prediction is a genuine prediction rather than a fit. Frontier An independent 2025 treatment quotes approximately −42 mK for the same feature and sets a detection threshold at −38 mK once 5 mK of observational and 6 mK of theoretical uncertainty are allowed — the two agree to within their stated errors, and the brief reports both rather than an average.

Established The obstacle is a ratio. The low-frequency sky is dominated by Galactic synchrotron emission that is conventionally modelled as 60 × (wavelength in metres)^2.55 kelvin; at 17.14 MHz that gives roughly 8.9 × 10⁴ K. Established Against a 44.09 mK signal, that is one part in about 2 × 10⁶ — arithmetic on two sourced numbers, and consistent with the figure a filled-aperture farside concept gives for the spectral dynamic range it must calibrate across, approximately 10⁷. Established For comparison, a beamforming study of the easier cosmic dawn problem measures a sky between 2,703 K at 50 MHz in the quietest beam and 39,650 K at Galactic plane transit against a target near 200 mK — about 200,000 to one, with EDGES itself working at an antenna temperature of 5,607 K — and a separate treatment puts the foreground at 10⁴ to 10⁵ times the signal in the ground-accessible band. The Dark Ages problem is the harder version of the one the field has so far failed to settle.

Frontier What has actually flown to the Moon for this science is one 4 kg instrument, and it went to the near side. ROLSES — four wire antennas — launched on Intuitive Machines’ Odysseus lander on 15 February 2024 for a 22 February landing at Malapert A near the south pole, explicitly as a pathfinder. Established Its results were published in 2026 as a study of terrestrial technosignatures and the low-frequency Galactic background; this brief cites that paper by name because it could not be retrieved, and claims nothing about its contents beyond its title.

Established LuSEE-Night is the first farside radio instrument that exists as hardware. It is a NASA and Department of Energy collaboration led by the Space Sciences Laboratory at Berkeley, with the spectrometer built at Brookhaven and antenna work at Lawrence Berkeley. Established The instrument digitises four channels at the Nyquist rate of a 50 MHz baseband and computes auto- and cross-correlation spectra on an FPGA software-defined radio; the collaboration’s own descriptions variously give the band as 0.1–50 MHz, 0.5–50 MHz and 1–50 MHz with primary interest in 4–40 MHz, and the antenna as four monopoles in a cross on a rotating platform or two orthogonal dipoles about 6 m tip to tip. Frontier The brief records that spread rather than picking one.

Established The mass budget is the design. The payload allocation is 128 kg; the battery that carries the instrument through a 14-day lunar night without sunlight is about 50 kg of it, which is 39% of the total by arithmetic. Established The Brookhaven contribution came in at 76 kg against an 85 kg allocation. Established It must survive surface temperatures quoted between about −173 °C and +173 °C, managed with heat pipes, radiators and thermal switches. Established The data budget is roughly 6 GB per 28-day lunar cycle through a relay — the binding constraint on how much raw diagnostic information ever reaches the ground.

Frontier The schedule record is the most honest single indicator of where this field is. The collaboration’s own pages have given delivery as late 2025, late 2025 or early 2026, 2026, July 2026 and late 2026 at various points; the lander vendor’s own mission page for Blue Ghost Mission 2, which carries LuSEE-Night to Nassau crater on the farside, says the mission is set to launch no earlier than 2027. Established Environmental testing was scheduled for summer 2025 at Utah State and lander integration for early autumn 2025. Frontier A payload that is built and a delivery that keeps moving right is the normal condition of this market, not a LuSEE-Night anomaly.

Established The collaboration does not claim it will detect the Dark Ages. Its science spokesperson has said in a public interview: “I don’t think we’ll be able to see dark age signal unless something really surprising happens.” Established The stated primary objective is a technology demonstration — that a radio telescope can operate through the lunar night on the farside at all — with the first low-resolution sky maps ever made at these frequencies as the concrete deliverable. Handwave Any brief that presents LuSEE-Night as a Dark Ages detector is overriding the people who built it.

Frontier Everything beyond LuSEE-Night is a concept with a mass problem. The FARSIDE study proposes 128 dual-polarisation antennas with 20 m dipole elements across a 10 km diameter, covering 200 kHz to 40 MHz in 1,400 channels of 28.5 kHz, deployed by a 420 kg rover unreeling eight tethers into four petals over about four months, with a 590 kg base station inside a roughly 3,000 kg lander, at $1.08 billion current best estimate and $1.33 billion with reserves in FY2019 dollars.

Frontier A European concurrent-design study put numbers on the scaling, and they are the most useful numbers in this brief. The Dark Ages Explorer is a filled aperture of crossed dipoles 5 m tip to tip on a 4 m grid, 18–45 MHz for the Dark Ages and 45–80 MHz for cosmic dawn, 12 kHz channels, targeting about 10 mK per spatial frequency shell with 10,000 hours of integration. Established A 4 × 4 array masses about 0.98 tonnes and fits one launch; the 32 × 32 array of 1,024 antennas that reaches the science goal masses about 10.5 tonnes and needs about seven; a 128 × 128 array masses about 157.8 tonnes and needs about ninety. Established Only the 4 × 4 system is achievable with high-readiness technology today, on the study’s own conclusion.

Frontier The monopole-only route has a matching number from the other direction. A 2023 forecast for precision cosmology from the Dark Ages finds 10% precision at 1,000 hours and 3.2% at 10,000 hours with a 9.9% helium-fraction constraint, and states that a 10 km² collecting area would require about 400,000 stations. Speculative A 2026 treatment assumes 1,000 hours for a single-antenna spectrometer and 10,000 hours for a compact 25 km² farside interferometer. Established Ten thousand hours is 417 days of continuous observing; restricted to lunar night it is about thirty lunar nights, or two and a half years of elapsed mission time, by arithmetic.

Frontier The quiet itself is being measured, and it is degrading on a published schedule. A 2026 modelling study of interference at a farside site at 23.789°S, 182.137°E across 0.1–2,700 MHz for 2025–2030 puts the most contaminated frequency at 410.9 MHz and the intended emissions at 2.4–2.6 GHz. Frontier Its operational conclusion is a requirement, stated in its own words: a uniform shielding effectiveness of 31.40 dB is required to place the maximum unintended emission below the instrument sensitivity threshold at every analysed frequency. Frontier Its schedule conclusion is sharper — from 2025 to 2027 the mean daily number of visible satellites stays low, typically one to two, while by 2030 the increase is not confined to a few bad locations but affects a broad range of azimuths and elevations, reducing the availability of consistently quiet skies for exactly the broad-beam low-frequency antennas this science needs. Established This brief quotes no absolute interference power from that study: the figures a first retrieval returned did not reproduce on a second, narrower fetch, so they are left out rather than repeated.

The questions below are ordered by how much a resolution would move the rest of the brief.

Frontier First: is the EDGES feature astrophysical at all, or is it an artefact of a nine-parameter fit to an imperfectly characterised instrument? For artefact: the unconstrained fit returns unphysical ionospheric and foreground parameters, physical priors quadruple the recovered depth, alternative functional forms fit comparably, and an independent instrument rejects the profile at 95.3%. Speculative For astrophysical: the feature sits where cosmic dawn is expected and the EDGES team has defended its calibration in print. Frontier Nobody has done the obvious thing — a blind third-party re-analysis of the raw data with the pipeline registered before unblinding.

Frontier Second: can any single antenna reach a spectral dynamic range of 10⁶ to 10⁷ with a smooth-spectrum foreground assumption? The entire global-signal method rests on the foreground being spectrally smooth enough that a low-order function absorbs it while leaving a 44 mK feature behind. Speculative Nothing guarantees that at 17 MHz, where free-free absorption, the Galactic plane and the antenna beam all vary with frequency. Handwave The field’s standard answer — that better calibration and better sky models will get there — is an assertion about future work, not a measurement, and this brief flags it accordingly.

Frontier Third: what does the lunar surface do to an antenna at these wavelengths? At 17 MHz the free-space wavelength is about 17.5 m, comparable to or larger than the regolith structures underneath a lander, so the ground plane is neither uniform nor known. Speculative Regolith dielectric properties at decametric wavelengths, layer depth and buried structure all enter the antenna response, and no farside measurement of them exists. Frontier The near-side ROLSES pathfinder was flown in part to learn how cosmic radio waves scatter in porous regolith.

Speculative Fourth: does the Moon have an ionosphere that matters? Solar ultraviolet liberates photoelectrons from the dayside surface and the resulting plasma sheath has a characteristic frequency; whether it is high enough to distort observations in the 1–50 MHz band, and whether it persists into the lunar night at the terminator, is listed by the LuSEE-Night team as one of the unknown challenges the mission exists to find. Handwave Any forecast that treats the farside surface as free space is assuming this question away.

Frontier Fifth: will the farside still be quiet when an instrument capable of using it exists? The modelling puts one to two visible satellites a day from 2025 to 2027 and a broad azimuth-and-elevation spread by 2030, while the array concepts that could actually measure the power spectrum are decade-scale. Frontier The stated fix is a uniform 31.40 dB of shielding effectiveness on every satellite, which is an engineering requirement placed on parties who have no obligation to meet it.

Speculative Sixth: what would a Dark Ages measurement actually discriminate? The forecasts name expansion history, baryon and matter densities, the primordial helium fraction, the running of the spectral index at sigma of 0.034, dark-matter annihilation, early dark energy, neutrino mass and cosmic strings. Handwave Most assume a measurement quality nobody has demonstrated in any band: the discriminating power is real in principle and unpriced in practice.

Frontier Seventh, and the one the field talks about least: what does a null result mean? Speculative Section 15 answers it, because the answer is a correction to a claim already in circulation.

Established The binding bottleneck is spectral dynamic range, and it is quantified: approximately 10⁷ for a Dark Ages power-spectrum instrument, and about one part in 2 × 10⁶ for the monopole by arithmetic on the sky model and the predicted depth. Frontier Nothing in the radio-astronomy record demonstrates bandpass calibration at that level across a decade of frequency.

Frontier Receiver calibration is the sub-bottleneck with the most active literature and the least reassuring results. Bayesian noise-wave calibration methods published in 2024 achieve solutions accurate to within 5% of the noise floor on laboratory datasets, with fractional errors within 25% of expected noise on simulations. Frontier The same work observes that the EDGES approach of downweighting open and short calibration cables is not self-consistent, which is a technical criticism aimed at exactly the measurement the field is arguing about. Speculative Five percent of a noise floor is a long way from one part in a million of a foreground.

Frontier Beam chromaticity is the second sub-bottleneck: an antenna whose pattern changes with frequency converts a spatially structured sky into a spectrally structured measurement, which is indistinguishable from signal. Frontier Beamforming mitigates it, as section 15 sets out, but does not remove the requirement for a sky model — and below 30 MHz no sky model of useful resolution exists, because no instrument has ever mapped there.

Established Power and thermal survival consume the mass budget before science does. Fifty kilograms of battery in a 128 kg payload is 39% of the allocation spent on surviving 14 days without sunlight, and the instrument must ride a temperature swing quoted from about −173 °C to +173 °C using heat pipes, radiators and thermal switches. Frontier Every kilogram of battery is a kilogram not spent on antenna length, and antenna length is what sets sensitivity at decametric wavelengths.

Established Telemetry is a hard ceiling: about 6 GB per 28-day lunar cycle. Frontier That forces on-board averaging, which is precisely the step that destroys the diagnostic information needed to identify a systematic after the fact. Speculative A contested detection with no raw data to re-analyse would reproduce the EDGES situation on the Moon, where nobody can build a second instrument for a decade.

Established Mass to the farside is the bottleneck that scales worst. A 4 × 4 demonstrator is about 0.98 tonnes and one launch; the 32 × 32 array that reaches the science goal is about 10.5 tonnes and roughly seven launches; a 128 × 128 array is about 157.8 tonnes and roughly ninety. Speculative Neither figure is the constraint by itself; the constraint is that the delivery market that would carry them is priced and scheduled for payloads two orders of magnitude smaller.

Frontier Deployment on the surface is unsolved at scale. The FARSIDE concept has a rover unreeling eight tethers of antenna nodes into four petals over about four months; the filled-aperture concept uses tubular boom antennas chosen for compactness and flight heritage. Speculative Nobody has deployed a kilometre-scale structure on any planetary surface, and a tether that snags at antenna 40 of 128 has no demonstrated recovery.

Frontier Integration time collides with the duty cycle. Ten thousand hours is 417 days of continuous observing; observing only during lunar night makes it about thirty lunar nights, which is two and a half years of elapsed time before any allowance for commissioning, downtime or a failed night. Established LuSEE-Night’s stated goal of up to two years on the surface is therefore roughly the minimum credible mission length for this science, not a generous one.

Frontier The quiet is a consumable. Keeping the modelled interference below an instrument threshold requires a uniform 31.40 dB of shielding effectiveness on satellites, applied before the 2030 environment the same study projects. Handwave There is no mechanism that applies it, which makes this the one bottleneck on the list that no amount of engineering budget removes.

Established The first dependency is a sky model that does not exist. Foreground separation at the 10⁶ level requires knowing the sky’s spatial and spectral structure well enough to predict what a chromatic beam will do to it, and below about 30 MHz there is no survey to build that model from. Established LuSEE-Night’s concrete deliverable is the first low-resolution sky maps ever made at these frequencies, which is a dependency being discharged rather than a bonus.

Frontier The second is the recombination and thermal history calculation the prediction rests on. The −44.09 ± 0.96 mK figure is derived with the HYREC-2 recombination code under Planck constraints; a second group quotes about −42 mK with different assumptions. Frontier The agreement is good at the few-mK level, which is the same level as the entire proposed observational error budget, so theory accuracy is not a free parameter.

Speculative The third is measured regolith electromagnetics at decametric wavelengths. Antenna impedance, ground-plane behaviour and scattering all depend on it, and the pathfinder flown to learn about it went to the near side.

Speculative The fourth is the lunar plasma environment, including the photoelectron sheath and its behaviour through the night. Handwave This brief found no quantitative farside measurement of it in the sources it could retrieve, and treats every forecast that ignores it as provisional.

Established The fifth is a relay, because the farside cannot see Earth by construction. Blue Ghost Mission 2 carries the European Space Agency’s Lunar Pathfinder communications satellite alongside LuSEE-Night, and a JPL user terminal, with the orbital element planned to operate for five years. Frontier A relay is also a transmitter in lunar orbit, which makes the communications dependency and the interference problem one object seen from two sides.

Established The sixth is delivery capacity, and it is contractual rather than technical. NASA’s commercial lunar delivery vehicle covers 17 lunar deliveries to five vendors with a combined maximum value of $2.6 billion through November 2028 and more than 60 instruments planned by that date. Frontier Nothing in that structure is sized for a ten-tonne, seven-launch astronomy array.

Frontier The seventh is regulatory and it binds hardest. Protection for the Shielded Zone rests on Article 22, Section V of the Radio Regulations and on a recommendation reserving 300 MHz to 2 GHz for radio astronomy there, with frequencies below 30 MHz also requiring protection and an extension to 100 MHz recommended; 2,000–3,000 MHz is permitted for communication. Established The global navigation satellite bands at 1,164–1,300 MHz and 1,559–1,610 MHz are incompatible with those rules and there is no enforcement mechanism, no mandatory compliance verification for lunar missions, and a non-interference provision that operators invoke to claim compliance they have not demonstrated.

Speculative The eighth is a second instrument, and no programme has funded one. Every lesson of the EDGES episode is that a single unreplicated measurement of a faint spectral feature is not a result; the farside architecture currently on the books produces exactly one.

Frontier The tests below are ranked by what a result would settle, and the top item is the only one with hardware built.

Frontier The decisive experiment for this brief is LuSEE-Night returning a calibrated spectrum at its systematic floor across a full lunar night. Established It is decisive not because it would detect the Dark Ages signal — the collaboration says it will not — but because it is the only measurement that converts the central assumption of this entire field from an assertion into a number. Frontier The assumption is that the farside is quiet enough and an antenna on regolith is well-enough behaved that a sky-noise-limited spectrometer can integrate down toward a millikelvin floor. Speculative If the achieved floor is within an order of magnitude of sky-noise-limited, every array concept in section 9 becomes a funding question; if it is three orders worse because of regolith coupling, a photoelectron sheath or thermal drift, the programme needs a new architecture rather than a bigger budget.

Frontier The horizon is near and the window is short. The instrument is built, environmental testing was scheduled for summer 2025 and lander integration for early autumn 2025; the delivery has been quoted at various times as late 2025, July 2026 and late 2026 by the collaboration, while the lander vendor says no earlier than 2027. Established The first night of data arrives within weeks of landing, and the team plans an early transfer during that first night as a contingency against later failure.

Frontier Second: a blind third-party re-analysis of the raw EDGES data with the pipeline registered before unblinding. Established The data exist, the objections are specific and published — unphysical ionospheric parameters, a fourfold change in depth under physical priors, non-unique nine-parameter fits — and no new hardware is required. Handwave The obstacle is entirely that no institution can compel it.

Frontier Third: a third ground-based global 21-cm instrument reporting on the 55–85 MHz band. Established The 2026 SARAS 3 re-analysis names REACH as the experiment that could resolve the disagreement, and PRATUSH and SEAMS are in the same family. Frontier A third independent non-detection would close the cosmic dawn argument; a third independent detection at the EDGES depth would reopen the case for non-standard cooling that the 2025 forward-modelling study decisively disfavoured.

Speculative Fourth: an in-situ measurement of the farside interference environment across 0.1–2,700 MHz, taken rather than modelled. Established The 2026 study that produces the 31.40 dB shielding requirement is a simulation built from a mission catalogue, and its authors present it as such. Frontier LuSEE-Night would produce that measurement as a by-product, which is a second reason the first test on this list dominates the others.

Speculative Fifth: a 4 × 4 filled-aperture demonstrator, the only array configuration the design study calls achievable today at about 0.98 tonnes and one launch. Frontier It cannot reach the power-spectrum goal — that needs 1,024 antennas, 10.5 tonnes and about seven launches — but it would measure deployment, calibration and correlation on the surface at a scale where a failure is affordable. Handwave Nobody has funded it.

Speculative Sixth: a laboratory demonstration of bandpass calibration at one part in 10⁶ across a decade of frequency. Frontier This requires no spacecraft and would be the cheapest result on the list, and its absence is why the dynamic-range claim in section 5 is flagged rather than assumed. Established The best published calibration work reaches within 5% of a noise floor, which is a different and much weaker statement.

Speculative Seventh: a measurement of regolith dielectric response and any photoelectron sheath at 1–50 MHz from the farside surface. Handwave The brief could not source a farside measurement of either, and lists this as a test rather than a dependency because it is separable from the main spectrum and could be done by a much smaller payload.

Frontier What would not settle anything: another forecast. Handwave The literature between 2021 and 2026 contains many sensitivity projections for arrays that do not exist, and their spread is not evidence about the sky.

Established The vehicle-level requirement is delivery of a 128 kg payload to a farside site with a relay overhead, and it is being met commercially. Blue Ghost Mission 2 targets Nassau crater on the farside with about a 44-day transit and at least 10 days of surface operations for the lander, carrying LuSEE-Night, the European Lunar Pathfinder relay, a JPL user terminal, a seismic instrument, a rover and a wireless power receiver, with an orbital element planned for five years. Frontier Sharing a lander with five other payloads is an electromagnetic compatibility problem, and the design answer is to observe during the lunar night, when the lander systems are not operating.

Established Thermal engineering is the discriminating requirement for night operation. Surviving a swing from about −173 °C to +173 °C without a radioisotope heat source needs heat pipes, radiators and thermal switches acting as thermostats, and a 50 kg battery charged during the 14-day day. Frontier Lunar Energy Infrastructure owns this problem at settlement scale; the astronomy case is the strictest version, because a heater is a noise source and a radioisotope unit is a regulatory complication.

Frontier The receiver requirement is stated as sky-noise-limited performance across 1–50 MHz, with four channels digitised at the Nyquist rate of a 50 MHz baseband and auto- and cross-correlation spectra computed on an FPGA. Established Listening to the whole band all the time, rather than sampling a fraction of it, is what makes an internal calibration and interference-rejection loop possible at all. Speculative Whether that loop holds calibration across a 300-kelvin excursion is the unmeasured part.

Established Antenna engineering is where the wavelength bites. Six metres tip to tip against a 17.5 m wavelength is a short antenna, and the array concepts respond with 5 m crossed dipoles on a 4 m grid or 20 m dipole elements across a 10 km baseline. Frontier Deployment mechanisms are tubular booms for the filled aperture and rover-unreeled tethers for the sparse array, the latter over about four months of surface operations.

Frontier Communications are a designed scarcity, not an oversight. Roughly 6 GB per 28-day cycle through a relay sets the entire on-board processing architecture, and the relay itself is a payload on the same lander. Frontier Deep Space Communications owns the link budget; this page owns the consequence, which is that the raw data a future sceptic would want will mostly never leave the Moon.

Speculative The scaling requirement is industrial rather than instrumental. Seven launches for a 10.5-tonne array, or ninety for a 157.8-tonne one, is a cargo problem that Lunar Industry and Moon-Based Manufacturing own; the astronomy case is one of the few payload classes where in-situ fabrication of simple aluminium dipoles would change the economics rather than merely the rhetoric. Handwave No programme has costed farside antenna manufacture from local material.

Frontier Navigation and timing are a quiet requirement with a loud consequence. An interferometer needs phase coherence across kilometres, which needs a common clock, and Cislunar Navigation and Lunar Time owns the standard being built for it. Established The same infrastructure that makes an array possible is a constellation of transmitters over the site, which is the interference problem again.

Frontier The optical analogy is instructive because the cost scaling is not the same. Mega-Telescopes records construction cost scaling as roughly the 2.7 power of aperture, which is why the largest ground telescope under construction is 39 m rather than 100 m. Speculative A low-frequency array scales by antenna count and delivered mass instead, so its ceiling is set by launch cadence rather than by optics fabrication — which is why 400,000 stations can be written down as a requirement without anyone laughing, and why it is nonetheless not happening.

Established The nearest neighbours are the ground-based global 21-cm experiments, because they are the ones producing data. EDGES and SARAS 3 are the two that have reported; REACH, PRATUSH and SEAMS are the named successors, and PRATUSH has been studied for lunar orbit. Frontier Their collective record — one contested claim and one rejection — is the empirical base this whole subject stands on.

Established The farside array concepts form a recognisable family with recognisable ancestry. The Dark Ages Lunar Interferometer, the Cosmic-dawn Dark-ages EXplorer, the Large-scale Array for Radio Astronomy, FARSIDE and FarView, the Astronomical Lunar Observatory, and the Dark Ages Explorer all describe surface arrays of dipoles below about 50 MHz. Speculative None has been funded to build, and the differences between them are mostly in deployment strategy rather than in physics.

Frontier The orbital route is the main alternative architecture, and it is being pursued outside the United States. The Hongmeng or Discovering the Sky at the Longest Wavelengths concept places an interferometer in lunar orbit rather than on the surface, trading the regolith and thermal problems for a duty cycle limited to the fraction of each orbit spent behind the Moon. Speculative The lunar research station roadmap schedules lunar-based astronomical observation and very-long-baseline interferometry for its post-2028 phase.

Established Ground arrays already observe the lunar disc to measure Earth’s own leakage reflected off it — the source of the 7% reflectivity figure, and a direct measurement of the thing farside astronomy is hiding from.

Frontier Cosmology’s open problems are the customer. Cosmological Tensions owns the expansion-rate disagreement that a Dark Ages measurement would attack from a completely different direction, since the trough depth depends directly on the Hubble parameter and the matter density. Speculative Dark Matter Alternatives owns the interacting-dark-matter models that the EDGES depth was used to motivate and that SARAS 3 now constrains.

Speculative Other messengers reach the same epoch by other routes. Multi-Messenger Astronomy and Neutrino Astronomy own the non-electromagnetic channels; Hidden-Sector Searches owns the laboratory route to the same particle physics the trough depth would bound. Frontier The Dark Ages monopole is unusual among them in being a prediction of standard physics that nobody disputes and nobody can measure.

Frontier The interference neighbourhood is shared with a much larger constituency. Megaconstellation Externalities owns the terrestrial version of the same fight, where the affected parties are numerous and organised and the protections are still losing; Orbital Debris and Space Traffic owns the physical-congestion analogue. Speculative The lunar case is the same problem with two differences that cut opposite ways: far fewer emitters, and a protected party consisting of about four instruments that do not yet exist.

Established Delivery runs through a commercial contract vehicle whose ceiling is public: a combined maximum value of $2.6 billion through November 2028, covering 17 lunar deliveries to five vendors from a pool of 13 eligible companies, with more than 60 instruments planned by that date. Frontier The structure buys rides, not observatories, and a farside astronomy array of the size the science requires has no procurement home in it.

Established The instrument itself is an unusual inter-agency arrangement and worth naming as one. LuSEE-Night is led by a NASA-funded university laboratory with the spectrometer built by a Department of Energy national laboratory and antenna work at a second one. Frontier That pairing exists because the instrument is closer to a particle-physics detector than to a spacecraft camera, and it is the template a larger programme would reuse.

Established Protection of the farside is written into the Radio Regulations and is not enforced. The Shielded Zone is defined in Article 22, Section V; a recommendation reserves 300 MHz to 2 GHz for radio astronomy within it, asks protection below 30 MHz, and recommends extension to 100 MHz, while permitting 2,000–3,000 MHz for communication. Established The navigation bands at 1,164–1,300 MHz and 1,559–1,610 MHz sit inside the protected range and are incompatible with it; there is no compliance verification requirement for lunar missions, spectrum monitoring is encouraged rather than mandated, and operators invoke a non-interference provision to claim compliance that nobody checks.

Frontier The quantitative version of the governance gap is a single number: 31.40 dB. That is the uniform shielding effectiveness the 2026 modelling study says satellites would need for a farside instrument to reach its sensitivity threshold at every analysed frequency, and it has to be applied before the 2030 environment the same study projects. Handwave No body has the authority to require it of a commercial lunar operator, and the proposal on the table is a new international agreement negotiated by consensus — a process any single state can stall.

Established There is a second programme with a published roadmap and it schedules lunar astronomy explicitly. China’s International Lunar Research Station runs a basic-model phase from 2024 to 2028 — a farside sample return in May 2024, a south-polar mission in 2026, a resource-utilisation mission in 2028 — with an improved-model phase after 2028 that names lunar-based astronomical observation and very-long-baseline interferometry among its activities, and a transition to a multifunctional base after 2040. Established Its cooperation organisation was constituted with initial memoranda in October 2023 and inter-governmental agreements in December 2024, headquartered in Hefei.

Frontier Two programmes with lunar astronomy on their books and no shared spectrum discipline is the institutional situation. Space Law and Governance owns the treaty layer and Standards as Governance owns the mechanism by which a technical recommendation becomes a constraint on behaviour. Speculative The relevant precedent is terrestrial radio-quiet zones, which work because a national regulator can revoke a licence inside a defined geography; nothing analogous exists for the far side of the Moon.

Frontier Roughly two dozen lunar missions may be operating within a few years, each with communications, navigation and operational transmitters, against a scientific user community whose entire hardware presence is one 128 kg payload awaiting a ride. Handwave Protection regimes are won by organised incumbents, and this one has no incumbent.

Frontier The core ethical structure is a commons with one-way damage: any single non-compliant emitter degrades the resource for every user, and the cost falls on parties with no standing to object. Established The regulatory instruments that exist — a definition in Article 22, Section V and a recommendation about protected bands — distribute no liability and create no remedy.

Speculative The distributional question is who gets the data. The measurement is expensive, singular and produced by two state programmes; the knowledge it produces is non-rival and, in the Western case, conventionally published. Frontier Nothing in the contractual structure guarantees that, and a commercial delivery market with instrument-hosting arrangements is a plausible route to proprietary farside data that no existing rule forbids.

Frontier There is a real conflict between astronomy and every other lunar activity, and pretending otherwise weakens the astronomy case. Resource extraction, navigation, human presence and communications all require transmitters; the quiet the science needs is quiet for everyone. Speculative A defensible position is a bounded reservation — a defined farside area with enforced emission limits, in exchange for no claim on the rest — rather than a general assertion that the far hemisphere belongs to astronomy.

Speculative Site selection has a consent dimension with no obvious rights-holder, which is itself the problem. Mega-Telescopes records what happens when a large observatory is sited without settled consent on Earth; the Moon inverts the situation by having no community to consult and no process for deciding what the surface is for. Handwave Whether that absence is an ethical simplification or an ethical vacuum is a judgement this brief does not make for the reader.

Frontier Opportunity cost deserves stating in the brief’s own units. A 32 × 32 array is about 10.5 tonnes and roughly seven launches; the sparse alternative is $1.08–1.33 billion in FY2019 dollars. Speculative Those are resources that would otherwise deliver power, habitat or other instruments, and the Dark Ages case has to be argued against that baseline rather than against zero.

Frontier A funded, flight-ready instrument whose own spokesperson says it will probably not see the target signal is easy to describe either as a triumph or as a boondoggle, and both are wrong. Established It is a pathfinder, its deliverable is a first sky map and a demonstrated systematic floor, and the field’s public communication has not consistently said so.

Speculative The largest claim available here is an information-theoretic one: the Dark Ages contain of order 10¹² independent Fourier modes, against about 10⁸ for Stage-IV large-scale-structure surveys and about 10⁶ for Planck 2018. Frontier If even a small fraction of those modes became measurable, cosmology’s statistical limit moves by orders of magnitude, and the discipline stops being sample-variance-limited for the first time in its history. Handwave The gap between the mode count and any achievable measurement is enormous: the nearest concrete forecast asks for about 30,000 probed modes to reach a running-of-the-spectral-index constraint merely competitive with Planck.

Frontier The civilizational asset is a place, and places can be spent. The radio-quiet farside is a band 4,366 km across whose value depends entirely on an absence, and the modelling puts the erosion of that absence between 2027 and 2030 under current mission plans. Speculative That makes it structurally like an atmosphere or a groundwater basin: cheap to degrade, expensive to restore, and with the benefit stream accruing to people who cannot bid for it now.

Speculative It is also a governance test case with unusually clean boundaries. The protected resource is defined geometrically, the harmful activity is measurable, the required remedy is a number — a uniform 31.40 dB of shielding effectiveness — and the affected parties are few. Frontier If a commons this tractable cannot be protected, that is informative about the harder cases; if it can, the mechanism generalises.

Speculative The epoch has no other messenger: no stars to look at, and the 21-cm line the only signal it emits. Handwave Claims about what a civilization does with a 3.2% expansion-history constraint are not claims this brief can support; the value is epistemic rather than economic.

Frontier The realistic long-run shape is that the astronomy rides on an industrial presence it does not justify. Seven launches for a 10.5-tonne array is not a science budget; it is a rounding error on a lunar logistics economy. Speculative Every credible path to Dark Ages cosmology runs through Lunar Industry existing for other reasons, which means the science is a beneficiary of lunar development and simultaneously its most exacting critic on emission discipline.

These horizons track three clocks that run independently: the delivery manifest, the calibration problem, and the interference environment. The third is the only one with a published deadline.

• 10 yr: Frontier Expect LuSEE-Night to land and return a first farside spectrum on a schedule the collaboration has quoted as late 2025 through late 2026 and the lander vendor quotes as no earlier than 2027, with the first low-resolution sky maps below 50 MHz as the concrete product. Frontier Expect REACH, PRATUSH or a successor to report on the 55–85 MHz band and either close or reopen the EDGES argument. Established Expect the interference environment to degrade on the modelled schedule: one to two visible satellites a day from 2025 to 2027, and by 2030 a broad spread across azimuth and elevation that reduces the availability of consistently quiet skies. Speculative Expect no Dark Ages detection, on the collaboration’s own assessment. Frontier A 4 × 4 demonstrator at about 0.98 tonnes is the only array step technically available in this window, and it is unfunded.
• 25 yr: Speculative This is the window in which a 32 × 32 filled aperture at about 10.5 tonnes over roughly seven launches, or a FARSIDE-class sparse array at $1.08–1.33 billion in FY2019 dollars, either enters a real programme or joins the concept archive alongside the Dark Ages Lunar Interferometer and the several proposals that preceded it. Speculative It is also the window in which the 10,000-hour integration required for a 3.2% constraint becomes schedulable, at about two and a half years of elapsed time under lunar-night duty. Handwave Whether the farside is still usable by then is a governance outcome, and the mechanism that would decide it does not exist today. Lunar Industry and Cislunar Navigation and Lunar Time set the boundary conditions.
• 50 yr: Speculative A power-spectrum measurement across several redshift shells, the thing that would deliver the mode count, needs antenna numbers in the 10⁵ range — the 2023 forecast puts 10 km² of collecting area at about 400,000 stations — which is an in-situ manufacturing problem rather than a launch problem. Handwave That makes the 50-year outlook a claim about Moon-Based Manufacturing rather than about radio astronomy, and this brief flags the inference as such.
• 100 / 250+ yr: Handwave At this horizon the question is whether a permanently protected, permanently instrumented radio reserve on the lunar far side exists as an institution, in the way that a handful of terrestrial radio-quiet zones do. Handwave Nothing in the present record — a definition without enforcement, a delivery market without an astronomy line item, and two state programmes with no shared spectrum discipline — makes that outcome more likely than its opposite, and a brief that projected one anyway would be writing fiction.

• Depends on This brief waits on results other briefs own. Cosmological Tensions supplies the parameters the −44.09 ± 0.96 mK prediction is derived from, and the prediction is only as good as the expansion rate and matter density that go into it — a subject with an unresolved 8–9% disagreement at its centre. Dark Matter Alternatives owns the non-standard cooling models whose observational status is the entire reason the EDGES depth mattered. Cislunar Navigation and Lunar Time owns the timing standard an interferometer needs for phase coherence, and Deep Space Communications owns the relay link that is the only route data takes off the far side. Mega-Telescopes owns the general lesson that instrument scale is set by appropriations and consent rather than by engineering, which this subject reproduces with different nouns.
• Requires (not on this map) Five things nothing on this map produces. A sky survey below 30 MHz at degree-scale resolution, because foreground separation at one part in 10⁶ needs a model of the sky a chromatic beam is looking at and no instrument has ever mapped there — LuSEE-Night’s first low-resolution maps are the opening instalment. A laboratory demonstration of bandpass calibration at one part in 10⁶ across a decade of frequency, because the published state of the art reaches within 5% of a noise floor. Routine multi-tonne cargo delivery to the farside, because the array that reaches the science goal is about 10.5 tonnes across roughly seven launches while the delivery vehicle that exists carries 128 kg payloads under a $2.6 billion ceiling to November 2028. Low-noise receivers qualified to hold calibration from about −173 °C to +173 °C, which is a supply-chain fact rather than a research question and does not exist as a catalogue part. And an enforceable emission limit inside the Shielded Zone — the modelling names 31.40 dB of satellite attenuation before 2028, Article 22, Section V defines the zone, and no body can require the number of anyone.
• Enables A measured Dark Ages monopole would give Cosmological Tensions a constraint on the expansion rate derived from pre-stellar physics with systematics unrelated to either the distance ladder or the sound horizon, and would give Dark Matter Alternatives and Hidden-Sector Searches an annihilation bound roughly an order of magnitude tighter than Planck 2018 from a 5 mK measurement. No typed enabling edge is claimed for the hardware, because a farside array enables a science programme rather than another brief’s technology.
• Adjacent Megaconstellation Externalities owns the terrestrial version of the interference fight and is the closest available analogue for how this one goes. Multi-Messenger Astronomy and Neutrino Astronomy own the other channels to early-universe physics. Lunar Energy Infrastructure owns surviving the night, Lunar Industry and Moon-Based Manufacturing own the mass problem, Space Law and Governance and Standards as Governance own the protection mechanism, and Deep Space Infrastructure owns the relay and network contention. Outside this map: ionospheric physics, antenna metrology, Bayesian model selection, and the Radio Regulations.

Handwave Claim in circulation: the Dark Ages signal was detected in 2018. Established It was not. The EDGES feature is centred at 78 MHz, which corresponds to redshift about 17 — cosmic dawn, when the first stars are already coupling the spin temperature radiatively. The Dark Ages trough is predicted at 17.14 MHz, a factor of four and a half lower in frequency and a different physical regime. Established No detection claim has ever been made for the Dark Ages monopole by anyone.

Handwave Claim: the EDGES result is evidence for dark-matter–baryon interaction. Frontier It was presented that way in a companion paper the same day, which concluded the particle would be no heavier than several proton masses. Established Since then: an independent instrument rejects the best-fit profile at 95.3% confidence; a re-analysis shows the fit returns a negative ionospheric optical depth, a negative electron temperature and a negative foreground brightness, and that imposing physical priors quadruples the depth to about 2 K; and a 2025 forward-modelling study finds a non-standard depth decisively disfavoured. Speculative The interaction hypothesis is not excluded, but the measurement that motivated it no longer supports it.

Handwave Claim: SARAS 3 disproved EDGES. Established SARAS 3 rejected the best-fitting profile at 95.3% confidence and EDGES-like signals at 90.4% significance. Frontier Those are roughly two-sigma and 1.7-sigma statements, which is why a 2026 paper still lists foreground modelling, ground-plane systematics and calibration systematics as live explanations and names a third experiment as the one that could settle it. Established Reporting the number and reporting “disproved” are different acts.

Handwave Claim: LuSEE-Night will detect the Dark Ages signal. Established The collaboration’s science spokesperson has said publicly that he does not think they will be able to see the dark age signal unless something really surprising happens, and the mission’s stated primary objective is a technology demonstration. Frontier Its real product is a measured systematic floor and the first sky maps below 50 MHz — the thing every array concept needs and none of them has.

Handwave Claim: the lunar far side is radio quiet. Established It is shielded from Earth by as much as 90 dB, and that part is true. Frontier It is not shielded from anything in lunar orbit or on the lunar surface, and a 2026 model of a farside site puts the most contaminated frequency at 410.9 MHz and requires a uniform 31.40 dB of satellite shielding to hold the worst unintended emission below an instrument threshold, while projecting that by 2030 the growth in visible satellites affects a broad range of azimuths and elevations rather than a few bad patches of sky.

Handwave Claim: the Moon has no ionosphere, so the band is clean. Speculative Solar ultraviolet liberates photoelectrons from the surface, producing a plasma sheath whose effect on 1–50 MHz observations is listed by the LuSEE-Night team among the unknowns the mission exists to find. Handwave This brief could not source a quantitative farside measurement of it and declines to assert either that it matters or that it does not.

Handwave Claim: an interferometer sidesteps the foreground problem. Established Beamforming genuinely helps: it drops the antenna temperature from 5,607 K to 2,703 K by steering off the Galactic plane, allows simultaneous calibrator observation, and permits in-situ beam measurement. Established It does not remove the dynamic-range requirement — the filled-aperture farside design study still states approximately 10⁷.

Handwave Claim: it is just a matter of building a bigger array. Established The design study’s own mass table is the answer: 4 × 4 at about 0.98 tonnes and one launch, 32 × 32 at about 10.5 tonnes and roughly seven, 128 × 128 at about 157.8 tonnes and roughly ninety — and its conclusion is that only the smallest is achievable with high-readiness technology today.

Handwave Claim: the farside is protected by international law. Established The Shielded Zone of the Moon is defined in Article 22, Section V of the Radio Regulations, and a recommendation reserves 300 MHz to 2 GHz within it for radio astronomy. Established The navigation bands at 1,164–1,300 MHz and 1,559–1,610 MHz are incompatible with those rules, there is no mandatory compliance verification for lunar missions, and spectrum monitoring is encouraged rather than required. Frontier A definition without a remedy is a description, not a protection.

Handwave Claim: a null result would refute standard cosmology. Speculative A farside spectrometer that integrates for 10,000 hours and sees nothing at 17 MHz has three candidate explanations in order of prior probability: the instrument, the foreground model, and cosmology. Handwave Separating them needs a second independent instrument, which nobody has funded, and any brief that skips that step is selling the third explanation on the strength of the first two being unexamined.