[Previous] | [Session 4] | [Next]
A. R. Hendrix (JPL)
We present results from an ongoing program to perform UV measurements (215.0 and 237.0 nm) of the Moon at varying solar phase angles. The Student Nitric Oxide Explorer (SNOE) is a student-built satellite operated at the University of Colorado. The SNOE spacecraft was launched in February of 1998 and is in a low altitude, polar Earth orbit. The ultraviolet spectrometer (UVS) on the spinning spacecraft is in a configuration such that it serendipitously observes the Earth’s moon once per month. The spacecraft is offset from the orbital plane by ~10 deg. so that the lunar measurements generally occur 1-2 days before full moon. The offset angle can be adjusted, thereby varying the solar phase angle at which the moon is observed. The UVS slit is 0.75x0.071 deg., so as the slit scans over the moon, 7-9 samples are obtained. The UVS has made measurements of stellar sources, and calibration of both channels is well understood.
The phase angle range of the current data set is 5-20 deg. We use the lunar phase curve to extrapolate to 0 deg. phase to determine the geometric albedo at these two UV wavelengths. These results are compared with measurements from other instruments such as HUT, Cassini UVIS and Galileo UVS. The current SNOE phase angle range is somewhat limited and may not allow for unique determination of Hapke photometric parameters; however, this analysis is underway and results will be compared with those determined at visible wavelengths to investigate wavelength-related variations that may result from surface scattering-volume scattering differences. Furthermore, the SNOE data set may be combined with the Galileo UVS set of lunar observations to increase the phase angle range for better determination of photometric parameters. Such a lunar phase curve can potentially be used by ultraviolet investigations that use the global Moon as a calibration source.