RAMBHA LP aboard Chandrayaan-3

The Radio Anatomy of Moon Bound Hypersensitive Ionosphere and Atmosphere-Langmuir Probe (RAMBHA-LP) payload on Chandrayaan 3 lander was designed with objective of carrying out the first ever in-situ measurements of electron density and electron temperature in the near surface lunar plasma environment close to poles.

It was located on the top deck of the Chandrayaan 3 lander.

The instrument consisted of a spherical Langmuir Probe of 5 cm diameter, with a CFRP boom of ~1 m length so that the probe was exposed to the ambient plasma outside the lander sheath. The probe was protected from dust by a dust protection box and kept in stowed condition by the hold and release system prior to torsion spring-based deployment after landing. The RAMBHA Onboard Controller (ROC) system is a DSP based controller and spacecraft interface system for the Langmuir Probe. The primary functions of the ROC were sensor probe control, data acquisition and spacecraft interface for Telecommand (TC), Telemetry (TM) and Baseband Data Handling (BDH). The Onboard controller handled the data Telecommand reception and execution, acquired the analog signals from the LP probe and converted it into digital domain using an onboard bipolar ADC. The necessary control signals for biasing the probe was also provided by the onboard controller. In the default mode, the RAMBHA-LP was provided with a sweep potential of ±12V at 0.1 V step with dwell time of 60 ms at each step. The RAMBHA-LP probe operated successfully during the entire duration of the Chandayaan 3 mission and provided excellent data on the near surface plasma environment. The photograph of the RAMBHA-LP payload is shown in figure.

Figure: Functions of deployment and penetration mechanism of ChaSTE probe.