The brightness temperatures are intercalibrated with the RSS Radiative Transfer Model (RTM). We obtain instrument data from NASA Goddard Earth Sciences Data and Information Services Center, back process the data to raw counts and apply our own on-orbit calibration to convert counts to brightness temperatures. The thirteen instrument channels are summarized in the following table. Some details of the GMI instrument are listed here: GMI paper listed in the reference section below. More information about GMI is available in the paper by D. These features allow us to be very confident of the quality and accuracy of the GMI data we provide here. Several features of GMI provide the higher calibration accuracy, including protection of the hot load from sun intrusion, noise diodes on the low-frequency channels for a dual calibration system, and a reflective antenna coating. The GMI instrument was designed with a strict calibration accuracy requirement to a greater precision than any previous microwave satellite sensor, thereby enabling the instrument to serve as a microwave radiometric standard. GMI is a dual-polarization, multi-channel, conical-scanning, passive microwave radiometer with frequent revisit times. The GPM platform undergoes yaw maneuvers approximately every 40 days to compensate for the sun's changing position and prevent the side of the spacecraft facing the sun from overheating. One of the primary differences between GPM and other satellites with microwave radiometers is the orbit, which is inclined 65 degrees, allowing a full sampling of all local Earth times repeated approximately every 2 weeks. The GPM satellite was launched on February 27th, 2014 with the GMI instrument started a few days later. The calibration approach of the mixed EARTHTIME 235U- 233U- 205Pb(- 202Pb) tracers, in addition to updated values for reference materials (e.g., mixed gravimetric reference solutions), and parameters (e.g., Pb reference material assay), can be applied to other laboratory-specific U-Pb tracers and will facilitate the generation of accurate and directly inter-comparable U-Pb data.The Global Precipitation Measurement (GPM) satellite has a microwave radiometer onboard called GMI (GPM Microwave Imager). For suitable terrestrial materials such as zircon, when other sources of uncertainty have been minimised (e.g., open-system behaviour, 238U/ 235U variation, intermediate daughter product disequilibrium, common Pb, etc.) the U-Pb tracer calibration uncertainty is a limiting factor in the accuracy of U-Pb geochronology - but less so than the uncertainty in the 238U and 235U decay constants (☐.11 and 0.14% 2σ). The parameters used in calculating U/Pb ratios (and inferentially U-Pb dates) have correlated uncertainties that result in a total uncertainty contribution to 206Pb/ 238U dates of ± < 0.03% (95% confidence). The accuracy of the EARTHTIME U-Pb tracer isotopic composition can be traced back to SI units via a series of assay and isotopic composition reference materials combined with the experiments described herein. The methods and results for the preparation and calibration of the U/Pb ratio and isotopic abundances are given, and the various sources of uncertainty are discussed and quantified. Mixed 235U- 233U- 205Pb(- 202Pb) tracers for U-Pb isotope-dilution isotope ratio mass spectrometry have been prepared under the auspices of the EARTHTIME Initiative.
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