Abstract
<title>Abstract</title> <p>The interstellar object 3I/ATLAS has been the subject of intensive multi-instrument monitoring since its discovery, yielding published production rates for H2O, CO2, CO, and several minor species from numerous ground- and space-based facilities. Several studies have noted that individual production-rate measurements disagree between instruments, and multiple recent papers have explicitly identified the absence of a formal cross-instrument calibration — accounting for differing physical apertures, fluorescence excitation models, and unquantified systematic uncertainties — as an open gap in the literature. We address this gap directly, compiling and calibrating 125 published production-rate measurements of H2O, CO2, CO, Ni, and Fe from 12 distinct instruments, extending the literature compilation of Frincke & Seligman (2026). Aperture standardization is applied to H2O using the two-component nucleus-plus-extended-source model of Li et al. (2026); CO2, CO, Ni, and Fe measurements are found not to require an aperture correction, since their published production rates already derive from standard Haser modeling that is aperture-independent in the absence of a confirmed extended source. Fluorescence-model harmonization is applied to Ni and Fe measurements following Hutsemékers et al. (2026a,b). Measurement, aperture, and fluorescence uncertainties — including systematics correlated within individual source papers — are propagated via a Monte Carlo approach (N = 10,000). At the reference epoch used by Cordiner et al. (2025), our independently calibrated CO2/H2O production-rate ratio is 7.24 + 0.55 − 0.52, in agreement with their published value of 7.6 ± 0.3 within 0.58σ. This result provides independent, multi-instrument confirmation that 3I/ATLAS's anomalously high CO2/H2O ratio is not an artifact of any single instrument's aperture or analysis methodology. We further present calibrated heliocentric production-rate trends for all five species and use a leave-one-out analysis to identify which trends are statistically robust to the exclusion of any single contributing literature source, finding H2O pre-perihelion and Ni pre-perihelion trends to be comparatively sensitive to individual data sources despite meeting standard sample-size thresholds.</p>