Why Modern satellite mode designators are written as two letters separated by a slash, uplink first and downlink second, with each letter naming a band: H for HF (21 MHz), A for 29 MHz, V for 2 m (145 MHz), U for 70 cm (435 MHz), L for 23 cm, S for 13 cm, and so on. So a U/V satellite takes your transmission on 435 MHz and returns it on 145 MHz. Knowing the mode tells you instantly which radios, antennas and frequency ranges you need to work that bird.
Watch out Polarization is a real satellite concern (many use circular polarization to fight spin fading), but it is never encoded in the mode letters; power levels and control station location are not part of the designation either.
Mode = Up letter / Down letter. U/V means Up on UHF, down on VHF.