Calibration and postlaunch performance of the Meteor 3/TOMS instrument

Abstract

Prelaunch and postlaunch calibration results for the Meteor 3/TOMS instrument are presented here. The instrument, launched aboard a Russian spacecraft in 1991, is the second in a series of total ozone mapping spectrometer (TOMS) instruments designed to provide daily global mapping of ozone overburden. Ozone amounts are retrieved from measurements of Earth albedo in the 312‐ to 380‐nm range. The accuracy of albedo measurements is primarily tied to knowledge of the reflective properties of diffusers used in the calibrations and to the instrument's wavelength selection. These and other important prelaunch calibrations are presented. Their estimated accuracies are within the bounds necessary to determine column ozone to better than 1%. However, postlaunch validation results indicate some prelaunch calibration uncertainties may be larger than originally estimated. Instrument calibrations have been maintained postlaunch to within a corresponding 1% error in retrieved ozone. Onboard calibrations, including wavelength monitoring and a three‐diffuser solar measurement system, are described and specific results are presented. Other issues, such as the effects of orbital precession on calibration and recent chopper wheel malfunctions, are also discussed.

Postlaunch performance of the Suomi National Polar‐orbiting Partnership Ozone Mapping and Profiler Suite (OMPS) nadir sensors

“…The integral of the curve above the thresholds is the fraction of macropixels impacted at greater than 1% of the signal: 0.59% 331 nm, 0.62% 317 nm, 1.8% 378 nm, and 15% 306 nm (NM); 18.6% 306 nm, 83% 292 nm, 100% 270 nm and 252 nm (NP). Following the successful approach of heritage instruments [Jaross et al, 1995], working and reference diffusers are used to monitor longterm diffuser change. To measure over the full 110°of the OMPS telescope, the diffuser is rotated to a series of seven positions; each position overlaps with the position before and after it, and measurements from the seven positions are "stitched" into a single plane of solar irradiance.…”

An assessment of the world ground‐based total ozone network performance from the comparison with satellite data

“…The Nimbus 7 satellite was operated in a near-noon sun synchronous polar orbit such that the time of the overpasses was always close to the local noon (except at very high latitudes). While Nimbus 7 was in a stable, nearnoon orbit, the orbital plane of the Meteor 3 spacecraft precessed relative to the Sun-Earth vector with a period of approximately 212 days, and the overpass observation time varied [Jaross et al, 1995]. The most recent versions of satellite data (Version 7 of TOMS data and Version 6 of SBUV data) were used for the analysis.…”

The Meteor 3/total ozone mapping spectrometer version 7 data set: Calibration and analysis

“…As reported previously [Jaross et al, 1995], the M3/TOMS instrument began to experience chopper wheel synchronization problems in mid May 1993. By the beginning of June, the loss of synchronization, as measured by a detector on the chopper wheel, had reached 100%.…”

“…Details of the calibration and algorithm used to generate the previous M3/TOMS data set (using the version 6 algorithm) as well as some of the results have been reported in the literature [Jaross et al, 1995;Herman et al, 1995a]. These reports contain two key conclusions: (1) the long-term M3/TOMS instrument calibration was maintained to within a corresponding ozone error of 1% over the life of the instrument, and (2) the agreement between total column ozone data from Meteor 3 and N7/TOMS, when both satellites viewed scenes under similar conditions, was generally within 1%.…”