{"id":"9fb85411-dfd8-4f25-9d84-fd6d1b97baa2","arxiv_id":"2507.04382","paper_version":3,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":4.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":6,"one_line_summary":"HERON is a proposed hybrid radio array combining 24 phased stations and 360 standalone antennas to detect ultra-high-energy neutrinos above 10^16 eV with a threshold below 100 PeV and sub-degree angular resolution.","lead":"This paper describes HERON, a proposed radio telescope array in Argentina for detecting ultra-high-energy neutrinos by combining two existing radio detection techniques. It claims that fewer than 1,000 antennas could outperform much larger planned detectors at energies below 100 PeV, making it a potential discovery instrument for neutrino astrophysics.","discovery_kind":"new_method","skeptic_critique":{"model":"deepseek-v4-flash","headline":"Sub-100 PeV sensitivity rests on a phased-array trigger model in the 30–80 MHz band that this paper does not simulate; only the 50–200 MHz standalone component is explicitly tested, so the central comparison to GRAND10k is not yet supported.","rationale":"I read the paper as an instrument proposal, not a measurement. The central claim is a projected sensitivity and design performance. For that claim to hold, the simulations in the companion paper [9] must faithfully describe radio emission from Earth-emergent tau showers in the 30–80 MHz band, noise at the San Juan site, coherence across phased-array baselines, and the trigger efficiency of the BEACON-style noise-riding trigger. The strongest point in the paper's favor is that it builds on two prototyping programs with published hardware and simulation work, and the design choices (elevation, hybrid triggers, RFI survey) are physically motivated. The weakest point is that the quantitative curves in Figs. 2, 4, and 6 are not reproducible from this text: no code, data, or simulation parameters are given, and the only explicitly described simulation in Sec. 2.1 covers the standalone, 50–200 MHz component, not the phased 30–80 MHz component that is responsible for the sub-100 PeV reach. That gap is load-bearing because if the phased-array trigger model is wrong, the central comparison to GRAND10k and the 'below 100 PeV' threshold fail even if all 936 antennas are built exactly as planned. I do not see fraud or overclaim beyond what is typical for a proceedings proposal; the paper is honest that the design is preliminary and optimization is ongoing. The most useful single check is to expose the companion simulation's phased-array assumptions to a 30–80 MHz noise and coherence test, as described above. This is exactly the kind of validation the reader's CONDITIONAL verdict asks for, so I do not change the verdict.","tokens_in":11667,"tokens_out":5921,"duration_ms":65624,"concrete_test":"Take the companion DANTON setup [9] and compute Fig. 2's effective area twice: once with the standalone-only 50–200 MHz noise and trigger model, and once with a phased-array trigger model at 30–80 MHz using the measured San Juan power spectrum (Fig. 3, right) as an additive noise term and checking coherence of the simulated pulses across 100–200 m baselines. If the sub-100 PeV effective area drops by more than a factor of 2, or if the 30–80 MHz noise exceeds the assumed sigma = 22 μV/m equivalent by that margin, the GRAND10k comparison and threshold claim need to be revised.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The paper's headline quantitative claim—that HERON's 936 antennas beat GRAND10k and reach below 100 PeV—hangs on the phased-station trigger path. The only simulation shown in §2.1 is for the standalone array: about 1,000 tau-decay events, 65 antennas, 50–200 MHz, galactic noise sigma = 22 μV/m, and a spherical-wavefront beamforming model. The phased stations, by contrast, are specified in §1.1 to operate at 30–80 MHz with 24 dual-polarized antennas over 100–200 m baselines. Nothing in the presented text demonstrates that 30–80 MHz pulses from Earth-emergent showers remain coherent across those baselines, nor that the noise at the San Juan site in this band is low enough for the BEACON-style noise-riding trigger to reach sub-100 PeV energies. If the 30–80 MHz phased-array efficiency is lower than the companion simulation [9] assumes—for example, because galactic or anthropogenic RFI is higher than the 50–200 MHz sigma = 22 μV/m value, or because the point-source coherence assumption overestimates the beamforming gain—the low-energy threshold shifts above 100 PeV and the headline comparison in Fig. 2 loses its basis. This is a correctness risk, not an internal contradiction: the paper is transparent that full details are in [9], but the central claim is not independently derivable from the material presented here.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper presents the preliminary design of HERON, a hybrid radio array for detecting ultra-high-energy (UHE) tau neutrinos through coherent radio emission from Earth-emergent air showers. The proposed instrument combines 24 phased antenna stations (576 dual-polarized antennas, 30--80 MHz) with 360 standalone antennas (50--200 MHz), deployed along a 72 km mountain ridge overlooking a valley in San Juan, Argentina. The authors claim that this arrangement, with 936 antennas total, reaches an energy threshold below 100 PeV, achieves sub-degree angular resolution, and provides better instantaneous sensitivity to UHE neutrinos than GRAND10k and BEACON-24, making HERON a potential discovery instrument for transient neutrino sources. Quantitative support is drawn from DANTON simulations of roughly 1,000 tau-decay events for the standalone array, site RFI measurements, and sensitivity curves whose derivation is deferred to a companion paper.","tokens_in":11939,"tokens_out":4678,"duration_ms":51392,"significance":"If the projected sensitivity is realized, HERON would be a compelling and cost-effective hybrid design that extends UHE neutrino searches to lower energies while retaining the reconstruction power of a sparse array. The paper is transparent about its preliminary status, provides concrete hardware and site details, and makes an honest attempt to connect the design to multimessenger transient science. However, the central quantitative claims are not independently supported within this manuscript: the phased-array trigger path that sets the sub-100 PeV threshold is not simulated or validated here, the sensitivity comparisons in Fig. 2 are deferred to an external companion paper, and the projected event rates carry no error bars or background treatment. These gaps currently exceed what the presented evidence can justify.","major_comments":[{"comment":"The core claim that HERON's 936 antennas outperform GRAND10k and BEACON-24 and reach below 100 PeV is not supported by the simulations shown in this paper. Section 2.1 describes only the standalone-array simulation (65 antennas, 50--200 MHz, galactic noise sigma = 22 μV/m), while the phased stations specified in §1.1 operate at 30--80 MHz over 100--200 m baselines. No simulated trigger efficiency, beamforming gain, or coherence model for the phased stations is presented, so the low-energy threshold and the Fig. 2 comparison rest entirely on the companion paper [9]. Please include the phased-array simulation results, or at least the trigger-efficiency curves and their underlying assumptions, so that the central claim can be assessed without reference to an external document.","section":"§2.1 / Fig. 2"},{"comment":"The projected discovery rates, such as the statement that HERON could detect '~300 (3000) PeV neutrinos from a realistic sample of 200 short-duration (long) GRBs in 5--10 years,' are presented without error bars, systematic uncertainties, or an exposure and background calculation. The estimate folds in a GRB sample scaled by a 6%-sky instantaneous field of view, but no trigger duty cycle, background rejection efficiency, or uncertainty propagation is given. Please present the underlying calculation and label these numbers as illustrative forecasts, or temper the 'discovery instrument' language accordingly.","section":"§2.2 / Fig. 6"},{"comment":"The 30--80 MHz noise assumption at the San Juan site is not quantitatively validated. The site RFI spectra in Fig. 3 are shown in arbitrary units, and the sensitivity model assumes galactic noise sigma = 22 μV/m, a value stated for the 50--200 MHz band, while the phased stations operate at 30--80 MHz where anthropogenic RFI is typically more prominent. Please provide the measured noise level in the 30--80 MHz band and assess how a higher noise floor would shift the energy threshold and the comparison in Fig. 2.","section":"§1.4 / Fig. 3"},{"comment":"The quoted angular-resolution performance of 0.4 degrees on average from the beamforming scan is reported without a spread, event-to-event variation, or systematic uncertainty. Since the same section states that results improve when phased-array data are added, the manuscript should present the standalone-only result with its statistical uncertainty so that the sub-degree angular-resolution claim can be properly evaluated.","section":"§2.1 / Fig. 5"}],"minor_comments":[{"comment":"The text 'synchronized to then s level accuracy' appears to contain a typo; it should likely read 'ns level accuracy.'","section":"§1.3"},{"comment":"The description of HERON-200 as a scaled-up version with 200 stations and '2 facing mountain ridges instrumented with 50 antennas each' is internally inconsistent; presumably this should refer to 50 stations per ridge, and the text should be corrected.","section":"§2.2 / Fig. 4"},{"comment":"References [25] and [29] are incomplete: they lack titles, years, and venues, which prevents readers from locating the cited work.","section":"References"},{"comment":"The terrain color scale in the right panel of Fig. 4 is difficult to read in grayscale; consider using labeled contours or a grayscale-friendly colormap.","section":"Fig. 4"},{"comment":"The terms '6%-sky instantaneous field of view' and '70%-sky daily field of view' are used without derivation or definition; please specify how these numbers are computed from the array geometry and trigger strategy.","section":"§2.2"}],"recommendation":"major_revision","confidential_remarks":"The manuscript reads as a proceedings-style design study. Most of the quantitative support for the headline sensitivity is deferred to the companion paper [9], which makes the present paper's standalone value mainly conceptual. For a journal submission, the authors should either reproduce the key simulations or summarize them in enough detail for the claims to be independently checked. The central idea is promising, but the current evidence does not yet support the stated performance comparisons or the discovery-instrument framing."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Quick take: this is a clean, honest instrument proposal from the BEACON/GRAND people, and the hybrid concept is plausible. But the headline sensitivity claim—beating GRAND10k and reaching below 100 PeV—is not established in this paper. It rests on the phased-array trigger path at 30–80 MHz, and the only simulation shown in the text is for the standalone array at 50–200 MHz. The authors admit this; the full simulation is in the companion paper. Read this as a system design and roadmap, not as demonstrated performance.\n\nWhat is actually new is the concrete integration: the San Juan site with measured RFI spectra, the trigger architecture (noise-riding phased trigger, second-level polarization cuts, WiFi distribution), the DAQ block diagram, and the argument that valley topography roughly doubles effective area. That last point is backed by the standalone-array simulation in Fig. 4, a real if preliminary result. The paper is also explicit about what remains under optimization—the 30–80 MHz band, antenna gains, and trigger thresholds are flagged as open. That honesty deserves credit.\n\nThe soft spots are the ones the reader flagged. Fig. 2 is a projection, not a measurement. Effective area and fluence curves are deferred to [9], and the sub-100 PeV threshold depends on the phased stations performing in a band this text does not simulate. There are no error bars, no uncertainty estimates on the simulation inputs, and no code or parameters to reproduce the curves. The language also overshoots: calling HERON a 'discovery instrument' and stating it 'will achieve greater sensitivity than GRAND10k' is stronger than the evidence here. If the phased-array efficiency is lower than assumed—worse RFI at 30–80 MHz, or spherical-wavefront beamforming overestimating coherence over 100–200 m baselines—the threshold could shift above 100 PeV.\n\nNone of that breaks the concept. It is a design study, coherent and well-grounded in the prototype programs. It is a legitimate companion to the concept paper and points to the real simulation paper for the numbers.\n\nRecommendation: send it to peer review. It deserves a referee; the referee should ask that the phased-array simulation results be included or Fig. 2 be clearly marked as an extrapolation, and that systematic uncertainties in the trigger model be quantified.","headline":"A well-structured, honest design study whose headline sensitivity claim is a projection—the phased-array trigger path that would deliver sub-100 PeV sensitivity is not simulated in this paper.","tokens_in":12614,"tokens_out":3160,"would_cite":true,"duration_ms":31407,"reading_group":"yes","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"deepseek-v4-flash","headline":"With 936 antennas, HERON aims to beat 10,000-antenna rivals","keywords":["ultra-high-energy neutrinos","radio detection","tau air showers","phased antenna array","sparse array","transient neutrino sources","multi-messenger astronomy","San Juan site"],"falsifier":"Deploy one full HERON-style phased station with its 24 antennas and the surrounding 15 standalone antennas at the chosen San Juan site for a year, and compare the measured rate and signal-to-noise of impulsive radio events to the DANTON-based prediction. If the measured events are absent or their signal-to-noise falls short of the simulated distribution to a degree that no trigger threshold setting recovers the predicted 100 PeV sensitivity, the central claim is contradicted.","tokens_in":11422,"feed_emoji":"📡","tokens_out":6820,"duration_ms":68531,"temperature":0.7,"pith_summary":"HERON is a proposed radio observatory for ultra-high-energy neutrinos, designed as a hybrid of two existing techniques: 24 dense phased-array stations that trigger on faint radio pulses, and 360 sparse standalone antennas that reconstruct the arriving shower. The paper claims that with fewer than 1,000 antennas, this layout reaches an instantaneous sensitivity above that of GRAND10k and BEACON-24, extends the energy threshold below 100 PeV, and achieves sub-degree angular resolution. That combination would let a single instrument act as a discovery instrument for transient neutrino sources such as gamma-ray bursts and magnetars, rather than waiting for a much larger array. The quantitative case rests on end-to-end simulations of tau neutrinos emerging from the ground in the San Juan valley, with the standalone antennas beamformed to a spherical wavefront.","feed_headline":"With 936 antennas, HERON aims to beat 10,000-antenna rivals","feed_subtitle":"The hybrid array pairs phased triggers with sparse antennas to reach the sub-100 PeV range where neutrino flux rises.","key_machinery":"The load-bearing mechanism is the two-tier trigger-and-reconstruction architecture. Each phased station digitally delays and sums 24 antenna signals to form beams aimed at the horizon, lowering the energy threshold below 100 PeV; when a phased station triggers, it alerts the 30-45 nearby standalone antennas, which buffer a few milliseconds of waveform and then send the event to the central DAQ. The standalone antennas self-trigger as well, and their long baselines allow beamforming scans that map the shower's coherence peak and recover the trajectory. The site's topography, a 30-60 km wide valley flanked by 2,000 m ridges, is itself part of the machinery: the valley provides a large target volume for tau neutrinos to interact and emerge, and the paper's simulations show topography roughly doubles the effective area relative to a flat spherical Earth. The quantitative performance figures come from DANTON simulations of about 1,000 tau-decay events at neutrino energies $2\\times10^{7}$ to $10^{9}$ GeV, with galactic noise $\\sigma = 22\\,\\mu\\mathrm{V/m}$ and spherical-wavefront beamforming in the 50-200 MHz band.","core_discovery":"The central claim is that a hybrid array in which BEACON-style phased stations provide the low-energy trigger and GRAND-style sparse antennas provide the reconstruction can outperform both parent concepts. HERON's design uses 24 phased stations, each with 24 dual-polarized antennas, spaced 3 km apart along a 72 km mountain ridge, plus 15 standalone antennas between stations, 360 total. According to the simulated effective area and fluence sensitivity, this 936-antenna instrument is more sensitive instantaneously than GRAND10k (10,000 antennas) and BEACON-24, reaches neutrino energies below 100 PeV where the flux is higher, and reconstructs arrival directions to about $0.4^\\circ$ on average with standalone data alone. The paper further claims that in 5-10 years HERON could detect neutrinos around 300 PeV from a realistic sample of short gamma-ray bursts linked to binary neutron star mergers, and around 3000 PeV from long bursts, making it a discovery instrument for transient astrophysical sources.","pith_inferences":["If the sub-100 PeV threshold is realised, the same phased-array trigger logic could be adapted to search for downward air showers from cosmic rays, giving the instrument a dual use as an air-shower radio detector.","The 30-80 MHz band choice is the main untested risk; a prototype that quantifies anthropogenic radio interference at the San Juan site and measures signal coherence would discriminate between the optimistic and pessimistic sensitivity predictions.","HERON's narrow instantaneous field of view could be paired with IceCube's all-sky alerts so that a coincident 100 PeV to 1 EeV burst tests hadronic emission models for gamma-ray bursts and magnetars.","Extending the paper's fluence-sensitivity calculation to other transient classes, such as tidal disruption events or supernova shock breakouts, would map where the instrument's discovery space actually lies."],"forward_implications":["With fewer than 1,000 antennas, HERON would reach instantaneous sensitivity comparable to or better than GRAND10k and BEACON-24, lowering the cost barrier for large-aperture neutrino astronomy.","The sub-100 PeV threshold lets HERON connect to the IceCube energy range, extending multi-messenger neutrino observations upward by about an order of magnitude.","Sub-degree angular resolution on neutrino-induced showers would allow point-source identification and rapid target-of-opportunity follow-up inside a multi-messenger network.","In 5-10 years, HERON could detect roughly 300 PeV neutrinos from short GRBs and 3000 PeV from long GRBs, using source lists from Fermi GBM and SVOM folded with its sky coverage.","A scaled HERON-200 over two or four mountain ridges would shrink the time needed to accumulate triggered GRB events in proportion to the number of sites."],"supporting_citations":[{"why":"Supplies the BEACON prototype phased-array design that HERON's 24-station trigger system evolves from.","marker":"[4]"},{"why":"Define the GRAND sparse-array concept and its contributions, the basis for HERON's standalone reconstruction antennas.","marker":"[5, 6]"},{"why":"Companion simulation paper giving the DANTON event set, topography, and array layout behind the effective-area and sensitivity figures.","marker":"[9]"},{"why":"Motivate the 30-80 MHz band choice and antenna designs that set HERON's low-energy threshold.","marker":"[10, 11]"},{"why":"GRAND Proto300 commissioning results justify HERON's standalone antenna and DAQ reference design in 50-200 MHz.","marker":"[12]"},{"why":"Provides the beacon-based synchronization method used to align phased stations and standalone antennas to nanosecond accuracy.","marker":"[14]"},{"why":"Simulation result that spaced arrays can achieve better than 0.1 degree angular resolution, supporting HERON's reconstruction claim.","marker":"[19]"},{"why":"DANTON shower simulation tool that generates the tau-decay events used in HERON's performance studies.","marker":"[25]"}],"fun_headline_variants":["HERON: 936 antennas, sub-100 PeV neutrino hunter","Hybrid radio array aims to beat 10,000-antenna neutrinos","Mountain-ridge neutrino detector punches above its antenna count","HERON's hybrid design targets neutrinos below 100 PeV","Radio array on mountain ridge seeks ultra-high-energy neutrinos"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"Everything below 100 PeV hinges on the unvalidated assumption that radio pulses from Earth-emergent tau air showers are as strong and coherent in the 30-200 MHz band at the San Juan site as DANTON models them to be, with anthropogenic noise low enough not to mask the trigger.","fun_headline_variants_meta":{"raw":{"variants":["HERON: 936 antennas, sub-100 PeV neutrino hunter","Hybrid radio array aims to beat 10,000-antenna neutrinos","Mountain-ridge neutrino detector punches above its antenna count","HERON's hybrid design targets neutrinos below 100 PeV","Radio array on mountain ridge seeks ultra-high-energy neutrinos"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000205,"raw_usage":{"total_tokens":1434,"prompt_tokens":1025,"completion_tokens":409,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":641,"completion_tokens_details":{"reasoning_tokens":318}},"tokens_in":641,"tokens_out":409,"duration_ms":4646,"temperature":1.0,"reasoning_tokens":318,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-06T19:48:38.032894+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Deploy one full HERON-style phased station with its 24 antennas and the surrounding 15 standalone antennas at the chosen San Juan site for a year, and compare the measured rate and signal-to-noise of impulsive radio events to the DANTON-based prediction. If the measured events are absent or their signal-to-noise falls short of the simulated distribution to a degree that no trigger threshold setting recovers the predicted 100 PeV sensitivity, the central claim is contradicted.","supporting_citations":[{"cited_title":"Wisselet al","cited_arxiv_id":null,"evidence_quote":"Supplies the BEACON prototype phased-array design that HERON's 24-station trigger system evolves from."},{"cited_title":"ZeollaPoSICRC2025(2025)","cited_arxiv_id":null,"evidence_quote":"Companion simulation paper giving the DANTON event set, topography, and array layout behind the effective-area and sensitivity figures."},{"cited_title":"Zhang, P","cited_arxiv_id":null,"evidence_quote":"GRAND Proto300 commissioning results justify HERON's standalone antenna and DAQ reference design in 50-200 MHz."},{"cited_title":"Aabet al","cited_arxiv_id":null,"evidence_quote":"Provides the beacon-based synchronization method used to align phased stations and standalone antennas to nanosecond accuracy."},{"cited_title":"Guelfand, V","cited_arxiv_id":null,"evidence_quote":"Simulation result that spaced arrays can achieve better than 0.1 degree angular resolution, supporting HERON's reconstruction claim."},{"cited_title":"Niess and O","cited_arxiv_id":null,"evidence_quote":"DANTON shower simulation tool that generates the tau-decay events used in HERON's performance studies."}],"review_version":1}