Communication - Specifications (page 1 of 11)
The dish antenna on the lander unit is an L-band (1.5 GHz) High Gain Antenna (HGA) with a diameter of 0.8m (four times the wavelength of transmission). With an efficiency of 80%, the gain of this antenna is 19.16dB and the Half Power Beam Width (HPBW) is 5.89 degrees. Given that the satellite is travelling at a speed of 52.42 degrees/second, it would remain within the 3-dB beam width of the Lander’s HGA for 308 seconds. The Transmission bandwidth is chosen such that the Lander can complete the transmission well within this time slot. The transmitted power is 3W giving an effective isotropic radiated power (EIRP) of about 24dBW.
Additionally, a 10cm dipole antenna mounted on the
side of the dish will be used in helping the Orbiter unit locate the Lander unit
after initial deployment. The dipole antenna has a gain of 2.5dB with a HPBW of
78 degrees. With a slightly increased transmitted power, this antenna could be
used as a back-up antenna for the HGA.