Pragyan roves 100 metres on lunar surface
The Indian Space Research Organisation (ISRO) announced on September 2, 2023, that Chandrayaan-3’s rover Pragyan had completed traversing more than 100 metres on the lunar surface and its instruments were continuing to send data. This is a significant achievement for the rover, which has a mission life of one lunar day (14 Earth days) and carries scientific payloads to carry out experiments on the lunar south pole region.
Pragyan, which means ‘wisdom’ in Sanskrit, was deployed from the lander Vikram on August 23, 2023, after a successful soft landing on the Moon. The rover has six wheels and can travel up to 500 metres at a speed of one centimetre per second. It is equipped with two cameras, an alpha particle X-ray spectrometer (APXS) and a laser-induced breakdown spectroscope (LIBS) to analyse the chemical composition of the lunar soil.
Challenges and achievements of rover operations
Rover operations are not fully autonomous and require commands to be sent from Earth. Pragyan’s movement is riddled with multiple challenges, each of which need to be overcome every time the rover moves. For every path planning, onboard navigation camera data must be downloaded to ground for generation of a digital elevation model (DEM), then the ground and mechanisms team will decide which path to take and uplink the command for the rover to follow.
The maximum DEM that can be generated is only for 5 metres each time the navigation camera sends images, which means every time the rover is commanded to move, it can at best cover 5 metres. Even there, there are challenges of obstacles. For instance, Pragyan has so far safely negotiated a small crater whose depth was 10cm (100mm) and avoided a bigger crater whose diameter was 4 metres to choose a safer path.
ISRO has already done multiple rover movements as of September 2, 2023. The rover has traversed over 100 metres from the lander and is still continuing its journey. The rover has also performed in-situ measurements using its APXS and LIBS payloads and transmitted the data to Earth via the lander. The data will help scientists understand the origin and evolution of the Moon as well as its potential for future exploration.
Preparing for long lunar night
ISRO chief S. Somnath said that they are likely to start the process of putting the rover to sleep in the coming days because it has to withstand the long lunar night, which lasts for about two weeks on Earth. During this period, the temperature on the Moon can plunge below minus 200°C, posing a threat to the survival of the battery and electronics of the rover.
“The lander and the rover will stay on the Moon for 14 days until they get sunlight. When there is no sunlight, a small solar panel, which is on the rover, will generate power to charge the battery for the next 14 days until they get sunlight,” Mr. Somnath said.
He added that ISRO did some tests and they get the feeling that they will survive even in such harsh conditions. “The battery is fully charged and the solar panel is oriented to receive the light at the next sunrise expected on September 22, 2023. The receiver is kept on. Hoping for a successful awakening for another set of assignments! Else, it will forever stay there as India’s lunar ambassador,” he said.
Chandrayaan-3 is India’s third lunar mission and the first one to attempt a soft landing on the Moon’s south pole region, which is believed to have traces of water ice and other resources. The mission aims to expand India’s footprint in space and demonstrate its technological capabilities.