Dual Frequency Radio Science experiment onboard Chandrayaan-2: a radio occultation technique to study temporal and spatial variations in the surface-bound ionosphere of the Moon

The Dual Frequency Radio Science experiment aboard Chandrayaan-2 uses the communication channel between orbiter and ground in radio occultation mode to study the temporal evolution of electron density in the lunar ionosphere. It consists of a highly stable 20 MHz evacuated miniaturized crystal oscillator source, having a stability of the order of 10-11, which generates two coherent signals at the X (8496 MHz) and S (2240 MHz) bands of radio frequencies. The coherent radio signals, transmitted simultaneously from the satellite and received at the ground-based deep station network receivers would be used to study temporal and spatial variations in the lunar ionosphere. The major science objectives of the experiments include: (i) to study variations in the ionosphere/atmosphere of the Moon; (ii) to explore if the ionosphere of the Moon is omnipresent or has episodic appearances, and (iii) to confirm the source of ions in the lunar ionosphere - whether dusty or molecular.