An apparatus comprises switches, a measurement unit, and a telemetry subsystem. The switches connect the current sources to a power bus when in a first position and to the measurement unit when the switches are in a second position. The measurement unit generates a ramp signal to control the solar strings from an open circuit state to a short circuit state linearly in a short duration and provides continuous current and voltage telemetry data at the output while the set of switches is in the second position. The telemetry subsystem is pre-set to a dwell mode and samples a large amount of voltage and current telemetry data. The telemetry subsystem transmits this data to ground directly to eliminate the need for processing and storage resources in the spacecraft. The telemetry data is used to plot I-V curve for health monitoring.