To know the health of a satellite it is importent to receive the telemetry the satellite transmits. Telemetry is the only way to know if everything is operating in the right way and working as expected, so on the satellite systems collect data and transmit them to groundstations for further analyses.
Below are a couple examples
E1P (Explorer-1 Prime)
FUNcube-1, 2, 3, etc
MCubed, MCubed-2, GRIFEX MXL (Michigan University)