AMF phasing—A precise control of the ignition timing of AKM for reduction of the injection error

This paper deals with a new concept, named “AMF Phasing”, which intends to minimize the effect of injection error that would result during apogee motor firing (AMF) of the spinning spacecraft. The characteristic of velocity increment error is derived analytically, based on the disturbed spinning motion during AMF. In order to precisely estimate the amount of fuel required for post-AMF orbital correction maneuvers, a probability model is proposed which estimates the total injection error probability combining the dominant error factors, i.e. pre-AMF attitude determination error and velocity increment error during AMF.It is shown that a substantial saving in fuel normally consumed for post-AMF can be expected, when the resultant velocity increment error contribution, which otherwise would be randomly directed in inertial space, is controlled so that it appears in the direction of local right ascension by igniting AKM at the proper instant (AMF Phasing). The procedure for AMF phasing, using a Sun pulse as a reference signal for the ignition timing is described in this paper. It was actually applied for GMS-2, Japan's second Geostationary Meteorological Satellite (HIMAWARI-II). The HIMAWARI-II post-AMF orbit determination shows that AMF Phasing worked successfully and it is concluded that a substantial fuel saving was achieved.     

Solar cycle dependence of global distribution of solar wind speed

A review is given of observational results concerning the solar cycle dependence of the global structure of solar wind speed distribution during the years from 1973 to 1987. Since observations of solar wind speed in 3-dimensional space can only be made by the interplanetary scintillation method which has been carried out over one sunspot activity cycle since the early 1970's, the review is based on IPS observations. The low-speed regions tend to be distributed along neutral lines which are derived on the source surface, so comparisons between speed distribution and the neutral line are discussed.