Michael Alan Gibson

Solar Irradiance Measurements: Minimum through Maximum Solar Activity

The Earth Radiation Budget Satellite (ERBS) and the NOAA-9 spacecraft solar monitors were used to measure the total solar irradiance during the period October 1984 to December 1989. Decreasing trends in the irradiance measurements were observed as sunspot activity decreased to minimum levels in 1986; after 1986, increasing trends were observed as sunspot activity increased. The magnitude of the irradiance variability was found to be approximately 0,1% between sunspot minimum and maximum (late 1989). When compared with the 1984 to 1989 indices of solar magnetic activity, the irradiance trends appear to be in phase with the 11-year sunspot cycle. Both irradiance series yielded 1 365 Wm-2 as the mean value of the solar irradiance, normalized to the mean Earth/Sun distance. The monitors are electrical substitution, active-cavity radiometers with estimated measurement precisions and accuracies of less than 0,02% and 0,2%, respectively.

Earth Radiation Budget Satellite extraterrestrial solar constant measurements - 1986-1987 increasing trend

Abstract From June 1986 through Nov 1987, the Earth Radiation Budget Satellite (ERBS) pyrheliometric measurements indicated that the solar constant was increasing approximately +0.02% per year. Earlier ERBS measurements indicated that the solar constant was declining approximately −0.03% per year during the 1984 through mid-1986 period. Since mid-1986 represents the beginning of solar cycle 22, it is believed that the reversal in the long-term solar constant trend may be linked to increased solar activity which is associated with the beginning of the 11-year sunspot cycle. The typical value of the solar constant was found to be 1365 Wm-2.

In-flight Evaluations of Tungsten Calibration Lamps Using Shortwave Thermistor Bolometers and Active-cavity Radiometers

The stabilities of type 715, T-1, tungsten calibration lamps were evaluated aboard three spacecraft platforms during the period 1984 to 1989. In the 0,2 μm to <5,0 μm broadband spectral region, the emitted radiant power from each lamp was measured using shortwave thermistor bolometers and active-cavity radiometers. The radiant power was found to be constant to ±1%. The responses of filter and silicon photodiode monitoring systems used to evaluate the lamps were found to degrade as much as 6% during the first two years in orbit.

Ground and in-flight calibrations of the Earth Radiation Budget Experiment nonscanning radiometers

This paper describes the algorithms and procedures used for in-flight calibration of the nonscanning radiometers used in the Earth Radiation Budget Experiment (ERBE) instruments. The computation of the count conversion coefficients used in the basic ERBE radiometric equations is described, as well as the determination of the offsets and time-dependent coefficients used to account for the in-flight changes in the radiometers. The calibration results for more than 5 years of ERBE data are summarized for all nonscanning radiometers. Discontinuities in the observed data, and the effects of these discontinuities are discussed. Applications of ERBE type calibration algorithms to the EOS/CERES platforms are suggested.

In-flight calibration of shortwave active cavity radiometers: approach and results

Beginning in 1984, three Earth Radiation Budget Experiment (ERBE) spacecraft were launched to measure the Earths radiation budget components: Solar-incident, Earth-emitted, and Earth-reflected radiation. The National Aeronautics and Space Administrations Earth Radiation Budget Satellite was launched in 1984 in a low-inclination orbit, and the National Oceanic and Atmospheric Administrations NOAA-9 and NOAA-10 satellites were launched in Sun-synchronous polar orbits in 1984 and 1986, respectively. This paper describes the method used for correcting for changes in the gains and offsets used for determining the final count conversion coefficients used in processing the in-flight calibration data. We also describe a technique for the determination of WFOV shortwave offsets which proxies for nighttime offsets during months of continuous daytime only orbits near sunrise and sunset when no nighttime measurements are available. The final result covering the period of 1984 through 1991 are discussed in this paper.

Evaluation of the Earth Radiation Budget Experiment (ERBE) shortwave channel's stability using in-flight calibration sources

The Earth Radiation Budget Experiment (ERBE) radiometers were designed to make absolute measurements of the incoming solar, earth-reflected solar, and earth-emitted fluxes for investigations of the earths climate system. Thermistor bolometers were the sensors used for the ERBE scanning radiometric package. Each thermistor bolometer package consisted of three narrow field of view broadband radiometric channels measuring shortwave, longwave, and total (0.2 micron to 50 microns) radiation. The in-flight calibration facilities include Mirror Attenuator Mosaics, shortwave internal calibration source, and internal blackbody sources to monitor the long-term responsivity of the radiometers. This paper describes the in-flight calibration facilities, the calibration data reduction techniques, and the results from the in-flight shortwave channel calibrations. The results indicate that the ERBE shortwave detectors were stable to within +/- 1 percent for up to five years of flight operation.

In-flight shortwave calibrations of the active cavity radiometers using tungsten lamps

The Earth Radiation Budget Experiment (ERBE) active cavity radiometers are used to measure the incoming solar, reflected shortwave solar, and emitted longwave radiations from the Earth and atmosphere. The radiometers are located on the NASAs Earth Radiation Budget Satellite (ERBS) and the NOAA-9 and NOAA-10 spacecraft platforms. Two of the radiometers, one wide field of view (WFOV) and one medium field of view (MFOV), measure the total radiation in the spectral region of 0.2 to 50 microns and the other two radiometers (WFOV and MFOV) measure the shortwave radiation in the spectral region of 0.2 to 5.0 microns. For the in-flight calibrations, tungsten lamp and the sun are used as calibration sources for shortwave radiometers. Descriptions of the tungsten lamp and solar calibration procedures and mechanisms are presented. The tungsten lamp calibration measurements are compared with the measurements of solar calibration for ERBS and NOAA-9 instruments.