What do the letters in a satellite’s mode designator specify?

The letters in a satellite's mode designator are shorthand codes for specific amateur radio frequency bands. The format typically presents the uplink band first, followed by a slash, and then the downlink band (e.g., V/U or U/V). In this system, 'V' stands for VHF (usually 144 MHz), 'U' stands for UHF (usually 435 MHz), 'L' stands for L-band (1.2 GHz), and 'S' stands for S-band (2.4 GHz). These letters do not specify power limits, ground station locations, or polarization. They solely dictate which frequency ranges you must transmit on to reach the satellite and which you must tune your receiver to in order to hear the downlink.