Complex sentence: Alternatively, Mars Global Surveyor could be used as a relay using the UHF antenna at multiple times each Martian day; however the Deep Space Network could only receive data from and not send commands to the lander using this method.
Split into simpler sentences: Alternatively, Mars Global Surveyor could be used as a relay using the UHF antenna at multiple times each Martian day. However the Deep Space Network could only receive data from, and not send commands to, the lander using this method.