The NASA Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) mission, launched 8 February 2024, carries the Ocean Color Instrument (OCI), a hyperspectral scanning radiometer providing continuous spectral coverage from 315 to 895 nm at 2.5 nm sampling. This study presents a post-launch validation and requirements verification of the OCI-derived remote-sensing reflectance Rᵣₛ(λ) (Reprocessing Version 3.2, V3.2) using 932 quality-controlled satellite-to-in situ matchups drawn from three complementary sources: AERONET-OC fixed-platform radiometers (N = 743), SeaBASS hyperspectral field campaigns (N = 119), and SeaBASS multispectral campaigns (N = 70), spanning March 2024 to May 2026. The OCI water-leaving reflectance ρw(λ) [unitless] = π × Rᵣₛ(λ) is examined against the threshold and baseline requirements specified in the PACE Science Requirements Document (SRD) Table 2 in terms of the 50th-percentile absolute error |Δρw| over deep ocean (depth > 1000 m). We found that ρw(λ) at every assessed wavelength (350–710 nm) satisfies the absolute baseline criterion in deep water; bootstrap resampling confirms these assessments are statistically robust at all but the 443 and 490 nm bands, where the small deep-water sample (N ≈ 52) limits precision. Across all matchups, reduced-major-axis slopes within approximately ±3% of unity are achieved through 490–620 nm (Pearson r = 0.95–0.98), where OCI exhibits a small negative bias: the median signed difference Δₘ ranges from -2.1 to -0.5 × 10⁻⁴ sr⁻¹ and the median signed percent difference ψₘ from -3 to -8% across the green. Relative agreement in the violet-blue spectral range (412–443 nm; median absolute percentage difference |ψ|ₘ = 17–23% across all matchups including coastal, and 6.6–6.8% for deep waters) and red (665 nm; 29%) remains the principal gap, driven by residual atmospheric-correction and calibration uncertainty where the ocean signal is small; the negative sign of ψₘ throughout the visible indicates a systematic low bias rather than random scatter. Spectral-shape fidelity, assessed through the second derivative of Rᵣₛ, is high across the visible (Pearson r = 0.95–0.96 at 443–665 nm) and degrades only in the UV. Within the available deep-water matchup sample, OCI V3.2 Rᵣₛ is consistent with the SRD absolute baseline at all evaluated wavelengths.
原文链接
分享
引用
