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Geist, J.

Publications and source records attributed to Geist, J..

8 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Direct measurement of solar luminosity variation

Two rocket flights of an absolute pyrheliometer, separated by 30 months, indicate an increase in solar luminosity (solar constant) of 0.4 percent. The significance of this result is considered in light of the instrument performance during the rocket flights and of pre- and postflight intercomparisons with independently maintained pyrheliometers. There is a high probability that the measured difference is real. Additional observations are required to determine whether the difference results from random fluctuations in solar luminosity, a nonrandom change of short duration, or a sustained change that has climatological significance.

Willson, R. C.↗
NASA NTRS1979

Solar cell spectral response characterization

The absolute spectral response of solar cells is reported in the 400-1000-nm spectral region. Measurements were performed using two different types of monochromatic sources: amplitude-stabilized CW laser lines and interference filters with an incandescent lamp. Both types of calibration procedures use electrical substitution radiometry as the basis of traceability to absolute SI units. The accuracy of the calibration is shown to be limited by the nonideal characteristics of the solar cells themselves, specifically spatial nonuniformities and nonlinearities induced by high light levels.

Zalewski, E. F.↗
NASA NTRS1976

A laser based characterization facility for silicon photocell studies

A computer controlled laser based characterization facility used for detailed studies of silicon photodetectors and spectral response measurement on silicon solar cell is described. The power in the laser beam is measured with respect to electrical standards using an electrically calibrated pyroelectric radiometer.

Geist, J.↗
NASA NTRS1972

Fundamental principles of absolute radiometry and the philosophy of this NBS program (1968 to 1971)

A description is given work performed on a program to develop an electrically calibrated detector (also called absolute radiometer, absolute detector, and electrically calibrated radiometer) that could be used to realize, maintain, and transfer a scale of total irradiance. The program includes a comprehensive investigation of the theoretical basis of absolute detector radiometry, as well as the design and construction of a number of detectors. A theoretical analysis of the sources of error is also included.

Geist, J.↗
NASA NTRS1972

Circumsolar radiation and the International Pyrheliometric Scale.

Issue is taken with the ascription of the 2% discrepancy in values of solar irradiance at the surface of the earth, found between the measurements performed by the absolute radiometers of Kendall and Wilson and those obtained by Eppley-Angstrom pyrheliometers, to the possibility that the two types of instruments might collect different amounts of circumsolar radiation. It is shown that this explanation is very unlikely.

Geist, J.↗