Linear-array apertures for in-flight dynamic solar calibration of radiometric channels for Earth radiation-budget applications

The zero-frequency gain of nonimaging radiometers used in Earth radiation-budge applications is usually verified by a procedure that allows the instrument to view the Sun through an appropriate attenuating aperture and then equates its response to the known attenuated solar constant. However, channel intercomparison often requires that data from a low-resolution, relatively slow instrument such as an active-cavity radiometer be compared with data from a high-resolution, fast instrument such as a scanning thermistor-bolometer radiometer. In such a case, consideration of the difference in the dynamic responses of the two channels may be important. A novel technique for in-flight measurement of the radiometric transfer function of such instruments is described and then demonstrated through the use of a high-order dynamic model o the total, wide-field-of-view, nonscanning channel of NASA's Earth Radiation Budget Experiment (ERBE).