A system to determine a size, extent, and orientation of a hydraulic fracture of a reservoir, the system comprising: a plurality of transponders, each of the plurality of transponders configured to be carried by a fluid into a hydraulic fracture of a reservoir, and each of the plurality of transponders adapted to be deployed within a hydraulic fracture in the reservoir being power assisted transponders and comprising a substrate carrying: a radiofrequency receiver comprising an RF antenna, the RF receiver being configured to receive, through the RF antenna, command RF signals transmitted from an RF antenna of a reader, an acoustic transmitter configured to transmit an acoustic return signal to the reader, a power source operably coupled to the acoustic transmitter and configured to store energy to provide a power assist to the acoustic transmitter responsive to a command RF signal received from the reader, and a control circuit being adapted to be coupled to the RF antenna and to the acoustic transmitter and configured to: receive the command RF signal from the reader through the RF antenna of the respective transponder, determine a power level of a received command RF signal, and selectively control a state of the acoustic transmitter of the respective transponder in response to the power level of the command RF signal determined, the selective controlling comprising: causing the acoustic transmitter to enter an active state when the power level of the received command RF signal is at or above a predetermined power level, the active state comprising causing the acoustic transmitter to transmit an acoustic return signal; and causing the acoustic transmitter to enter a quiescent state when the power level of the received command RF signal is below the predetermined power level. a radiofrequency receiver comprising an RF antenna, the RF receiver being configured to receive, through the RF antenna, command RF signals transmitted from an RF antenna of a reader, an acoustic transmitter configured to transmit an acoustic return signal to the reader, a power source operably coupled to the acoustic transmitter and configured to store energy to provide a power assist to the acoustic transmitter responsive to a command RF signal received from the reader, and a control circuit being adapted to be coupled to the RF antenna and to the acoustic transmitter and configured to: receive the command RF signal from the reader through the RF antenna of the respective transponder, determine a power level of a received command RF signal, and selectively control a state of the acoustic transmitter of the respective transponder in response to the power level of the command RF signal determined, the selective controlling comprising: causing the acoustic transmitter to enter an active state when the power level of the received command RF signal is at or above a predetermined power level, the active state comprising causing the acoustic transmitter to transmit an acoustic return signal; and causing the acoustic transmitter to enter a quiescent state when the power level of the received command RF signal is below the predetermined power level. receive the command RF signal from the reader through the RF antenna of the respective transponder, determine a power level of a received command RF signal, and selectively control a state of the acoustic transmitter of the respective transponder in response to the power level of the command RF signal determined, the selective controlling comprising: causing the acoustic transmitter to enter an active state when the power level of the received command RF signal is at or above a predetermined power level, the active state comprising causing the acoustic transmitter to transmit an acoustic return signal; and causing the acoustic transmitter to enter a quiescent state when the power level of the received command RF signal is below the predetermined power level. causing the acoustic transmitter to enter an active state when the power level of the received command RF signal is at or above a predetermined power level, the active state comprising causing the acoustic transmitter to transmit an acoustic return signal; and causing the acoustic transmitter to enter a quiescent state when the power level of the received command RF signal is below the predetermined power level.