Why A satellite beacon is a low duty telemetry transmission the spacecraft sends on a known frequency, carrying housekeeping data such as battery voltage, temperature, transponder mode and callsign ID. Operators use it to confirm the satellite is in range and working, to check which mode the transponder is in, and to measure Doppler shift before transmitting. Beacons are often sent in CW or a digital telemetry format so they can be decoded with simple equipment.
Watch out The antenna and reflective surface choices describe hardware, not a signal; a beacon is the transmission itself, and the word appears in the same sense for terrestrial propagation beacons on HF and VHF.
Beacon = broadcast of status. It tells you the satellite's health, not where to aim.