Figure 10.2.12 Shading of the Rectenna The beam will be controlled by a simplified retrodirective phase control system as explained in the section on beam control. The range of steerability of the beam will be dependent on the orbit position limitations and thus on the shadowing problem as described in the previous section. It is supposed to be in the range of +/- 30 degrees measured from the maximum antenna gain direction. Command and Data Handling A functional block diagram of the microwave experiment, showing also the power and data flows, is illustrated in Figure 10.2.13 The data handling system has the following main functions: • overall command and control of the mission equipment • data acquisition from the phased array antenna controller • acquisition of power readings from rectenna elements • acquisition of measurement data from scientific sensors • adaptation to Mir and Progress data handling subsystem in terms of electrical connections and data protocols All science data from the scientific experiments as well as all power readings from the rectenna side are acquired by a computer residing in the Progress spacecraft, and transmitted to the Mir station via a telecommunication link. This data will be received by a computer inside the Mir and stored temporarily. The computer inside Mir also acquires data from the phased array controller and combines it with the data received from the Progress. All stored data are then transmitted to Earth via a communication channel allocated to the mission. Now let us consider the data budget of our mission in order to predict its net impact on Mir operations. We can have a very rough order of magnitude estimate of the total data rate by assuming a 1 Hz sampling frequency for all acquisitions. Table 10.2.2 summarizes the estimated data budget for the mission. The total data rate is considered to be relatively low and therefore would be easily adapted to the existing Mir data handling subsystem.
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