Preliminary design of a space system operating a ground-penetrating radar

Ground Penetrating Radars (GPR) are currently used only in ground campaigns or in few airborne installations. A feasibility analysis of a space mission operating a GPR for archaelogical applications is presented in this work with cemphasis on spacecraft critical aspects: antenna dimension and power required for achieving adequate depth and accuracy. Sensor parametric design is performedconsidering two operating altitudes (250 and 500 km) and user requiremts, such as minimum skin depth, vertical and horizontal resolution. A 500-km altitude 6 a.m.-6 p.m. sun-synchronous orbit is an adequate compromise between atmospheric drag and payload transmitted average power (12 kW) to achieve 3 m penetration depth. The satellite bus preliminary design is then performed, with focus on critical subsystems and technologies. The payload average power requirement can be kept within feasible limits (1 kW) by using NiH2 batteries to supply the radar transmitter, and with a strong reduction of the mission duty cycle (40 km x 1100 km are observed per orbit). As for the electric power subsystem, a dual-voltage strategy is adopted, with the battery charge regulator supplied at 126 V and thye bus loads at 50 V. The overall average power (1.9 kW), accounting for both payload and bus needs, can be supplied by a 20 m2 GaAs solar panel for a three-year lifetime. Finally, the satellite mass is kept within reasonable limits (1.6 tons) using inflatable-rigidisable structure for both the payload antenna and the solar panels.