NSSDCA ID: 1969-037A-01
Mission Name: Nimbus 3The Nimbus 3 Monitor of Ultraviolet Solar Energy (MUSE) experiment was designed (1) to look for temporal variations in the solar UV flux in five broad bands in the interval 1150 to 3000 A, (2) to measure the solar flux in these regions, and (3) to measure the atmospheric attenuation at these wavelengths as the sensors on board viewed the setting sun after the spacecraft had crossed the terminator in the Northern Hemisphere. The sensors had their maximum response at 1216 A, 1600 A, 1800 A, 2000 A, and 2600 A. The MUSE instrumentation, which consisted of five vacuum photodiodes housed in an electronics package and a sensor package, was mounted in the rear of the Nimbus spacecraft. All sensors except the 1216-A sensor had semi-transparent photocathodes that were deposited on the windows. The 1800-, 2000-, and 2600-A sensors had aluminum oxide windows, while the 1216-A and 1600-A sensors had MgF2 and CaF2 windows, respectively. The five spectral regions were determined by the transmittance of the filter or window materials on the short wavelength side, while the long wavelength cutoffs were produced by the varying degrees of opacity of the different photocathode materials. The appropriate bands of UV flux entered the photodiodes and produced a current that was measured by an electrometer and digitized by the Nimbus pulse code modulation (PCM) system. Simultaneously, the solar aspect system measured the angle of incidence of the solar rays and transmitted its digital information to the PCM system. The PCM data were stored on magnetic tape and transmitted on playback to the data acquisition facility. The instrument had a basic 48-s cycle and a one sample per second data rate. The field of view of the sensors was about 90 deg. Solar acquisition began, therefore, at 45 deg prior to the earth day/night terminator and ceased completely at the satellite day/night transition. The instrument had only an inflight electrical calibration sequence because there were no known suitable UV sources that could provide an inflight optical calibration. A similar experiment was flown on Nimbus 4. For a more detailed description, see Section 7 of "The Nimbus III User's Guide" (TRF B03409). The detector response degraded in a known and correctable manner. This experiment was turned off when the spacecraft operations were terminated in January 1972. No archival data have been produced due to lack of funding.
Questions and comments about this experiment can be directed to: Coordinated Request and User Support Office
Name | Role | Original Affiliation | |
---|---|---|---|
Dr. Donald F. Heath | Principal Investigator | NASA Goddard Space Flight Center |