Even so, an on-off switch on the pilot signal transmitter is needed to avoid unnecessary power consumption. It is thus desirable to use optical fibre for the tether wire since optical fiber is suitable for data/command communications even in the strong electric fields of the microwaves. If this is not adopted, a simple command receiver is necessary, and a programmable timer is used as a back-up system for on-off control. One other interesting idea—now under study—is to use the high power microwave beam itself as a switch. In such a case, the microwaves would be radiated without the pilot signal before the transmission test. 3. Diagnostic Package (DGP) Ohmic heating and excitation of the plasma through scattering are expected to be the dominant nonlinear interactions. As mentioned in the introductory section, this will be investigated by producing a hot spot in the plasma. The microwave beam will be focused at one point to produce a very strong electric field. Sensors are extended upwards to approach the microwave focal point from the PLU with two rigid extension booms as shown in Fig. 13. Only key data measurements will be transmitted to the ground because of limitations on the transmission speed of the telemeter. All data, however, will be stored in the PLU’s data recorder and later recovered. The diagnostic package consists of six scientific instruments to observe plasma phenomena excited by high power microwaves. Parameters of the plasma and the neutral atmosphere (electron density, electron temperature and pressure) will be measured, as well as plasma waves over a wide frequency range from ELF to HF. The six sensors are a Langmuir probe (LP), an impedance probe (IMP), a density fluctuation detector (DFD), a vacuum meter (VAM), receivers from ELF to HF (VLF and HF) and a microwave detector (MWR). A block diagram of all the sensors is shown in Fig. 14.
RkJQdWJsaXNoZXIy MTU5NjU0Mg==