This paper compares the performance of Mass Memory Unit(MMU) between Science and Technology Satellite 1(STSAT-1) and STSAT-2 from developed Proto Flight Model(PFM) for Miniaturization, lightweight and low power consumption. MMU receives the payload data at 200Kbps and transmits them to XTX at 10Mbps in the STSAT-2. The performance of PFM MMU in the Functional and space environments test satisfies the requirements of STSAT-2.