Chandrayaan-3: The Vikram lander's Radio Anatomy of Moon Bound Hypersensitive ionosphere and Atmosphere-Langmuir Probe (RAMBHA-LP) payload has discovered that the plasma (ionised gas) above the lunar surface on the Moon's south pole is sparse compared to other regions. These represent the first-ever measurements of the lunar plasma environment above the Moon's south pole.
RAMBHA-LP's primary objectives are to measure different parameters of the plasma above the surface of the Moon. The instrument is conducting experiments to measure the density of the different constituent particles of plasma, and how it changes with time.
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Due to lunar plasma, radio wave communication between the Moon and the Earth is often disrupted. Therefore, such quantitative measurements can help develop equipment to mitigate the noise generated by lunar plasma. Also, scientists can create instruments with enhanced designs for future Moon missions.
The Indian Space Research Organisation (ISRO) has named the Langmuir Probe after Irving Langmuir, an American chemist who was awarded the 1932 Nobel Prize in Chemistry. The function of LP is to characterise plasma. There is a five-centimetre metallic spherical probe atop a one-metre boom attached to the upper deck of Vikram.
A hold-release mechanism deploys the probe. The function of the boom is to ensure that the spherical probe operates within an undisturbed lunar plasma environment. This environment is isolated from Vikram's body.
There are about five to 30 million electrons per cubic metre in the plasma environment above the lunar south pole. According to ISRO, these measurements were made during the early hours of a lunar day.
The RAMBHA-LP probe is continuously working and investigating the changes occurring in the near-surface plasma environment throughout the lunar day.
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The plasma above the lunar near-surface region is subject to charging and ionisation due to fluctuations in solar space weather conditions. Therefore, measurements by the probe will help scientists obtain more insights into the mechanism of charging in the lunar near-surface region.
ISRO has released a graph which shows the variation between current and bias voltage, which is the amount of voltage required by an electronic device to be powered and to function. RAMBHA-LP made these measurements.
RAMBHA-LP measures the amount of return current, or the electric current that returns to the instrument through the ground. By measuring the return current, the RAMBHA-LP payload determines ionic and electronic densities.