Measurement Results of the Antenna Phase Patterns Onboard Flying Spin Satellites

This paper reports measurement results of the antenna phase patterns onboard flying spin satellites during the SELENE (KAGUYA) mission period, and shows monthly variations clearly for the first time. When an antenna is loaded on a spin satellite, due to the effects of the antenna phase patterns, periodical components with the spin frequency f(s) and higher order harmonics occur and influence Doppler measurements. Because Rstar and Vstar, two subsatellites of SELENE, have octagonal prismatic bodies, the 8th, 16th, and 24th harmonics are relatively stronger than the other ones in the 2-way and 4-way Doppler data. These three harmonics' amplitudes over the entire mission longer than one year clearly varied with a period of 27.32 days (one sidereal month). The antenna phase patterns were estimated using 1-26th harmonics, whose rms variations were also with a period of 27.32 days. From the 24th harmonic and the antenna phase patterns, the spin frequency variations of Rstar and Vstar over the entire mission were estimated with an accuracy of 10(-5) Hz