Why Vikram lander, Pragyan rover remain dormant despite best efforts to reactivate them?

The recent endeavours by the Indian Space Research Organisation (ISRO) to reactivate the Vikram lander and Pragyan rover of Chandrayaan-3 mission have encountered formidable challenges. Both the lander and the rover entered a state of dormancy for two weeks during the lunar night. The lunar surface, particularly the south polar region where Vikram and Pragyan are stationed, experiences extreme temperature variations. During lunar nights, temperatures can plummet to a bone-chilling -200 degrees Celsius. Such frigid conditions pose a significant threat to the survival of materials, electronic components, and power systems. These circumstances necessitate advanced thermal management solutions to safeguard the spacecraft.

Both the lander and the rover were originally engineered for a 14-day lunar mission. Their systems were optimized to operate seamlessly within this limited time-frame. Extending their operational duration in the harsh lunar environment requires innovative strategies and the ability to adapt to extreme conditions.

“For a spacecraft to awaken after a prolonged dormancy, maintaining an operational battery is paramount. ISRO has carefully managed the power systems to ensure the battery remains charged during the lunar nights, while vital instruments have been placed in sleep mode to conserve energy. The reactivation process hinges on the successful utilization of this stored energy. Despite these challenges, there remains a glimmer of hope. ISRO may have implemented cutting-edge thermal insulation and power management techniques. If successful, these efforts could result in a miraculous revival of Vikram and Pragyan, defying the harshest lunar conditions,” said Srimathy Kesan, founder and CEO of Space Kidz India, which is into design, fabrication and launch of small satellites, spacecraft and ground systems.

The Chandrayaan-3 mission's primary objective is to detect the presence of water on the moon's surface. Previous experiments have hinted at water through remote sensing, but conclusive physical evidence is still needed. The ability to identify hydrogen, a fundamental component of water, would provide irrefutable proof of lunar water, unlocking new possibilities for lunar science and exploration.

“The challenges faced in reviving Vikram and Pragyan underscore the audacious nature of space exploration. Success in this endeavour would not only extend the mission's scientific contributions but also set a precedent for future lunar missions. The lessons learned from this mission will shape the trajectory of India's lunar exploration efforts. The ongoing efforts to awaken the Vikram lander and Pragyan rover are a testament to ISRO's unwavering commitment to lunar exploration. While the technical hurdles are substantial, the potential rewards in terms of scientific discovery and future missions make this endeavour both noble and visionary,” added Kesan.

The mission’s original plan was for it to operate for a single lunar day, which equates to approximately 14 earth days. “The concept behind this design was that the lander and rover could potentially reawaken once they received sufficient sunlight as the sun ascended near their location at the lunar south pole. ISRO’s scientists expressed confidence that the spacecraft could endure the harsh conditions and reawaken on September 22. This date marked the point when the rover and lander’s location would have been bathed in sunlight, providing them with the chance to replenish their batteries. However, the space agency has been unsuccessful in establishing communication with the mission and there is a diminishing sense of optimism. ISRO has stated their commitment to persist in contact attempts with the spacecraft until September 30, coinciding with the coming lunar sunset,” remarked space expert Girish Linganna.

Before placing the lander and rover in sleep mode, scientists at ISRO emphasised that the Chandrayaan-3 mission had achieved its primary objectives and considered it a significant success. Even if Vikram and Pragyan did not awaken, they would remain on the moon as India’s lunar ambassadors. Chandrayaan-3 established India as the first country to reach the lunar south pole and the fourth to land on the moon, bolstering its status as a global space exploration leader.

During its week-long lunar surface exploration, the Pragyan rover was assigned the mission of uncovering ‘lunar secrets’, covering a distance of 100 metres and relaying images and data to Earth. It successfully confirmed the existence of such elements as sulphur, iron, oxygen and others on the moon.

Experts point out that there could be multiple causes for the unsuccessful revival attempts. “A lunar night, lasting approximately 14 earth days, exposes spacecraft to temperatures as low as -253°C. To combat this extreme cold, many moon missions rely on radioisotope heater units (RHUs) to maintain operational temperatures. These RHUs produce both heat and electricity through the controlled radioactive decay of specific elements. For instance, the Soviet Lunokhod 1 rover, active on the moon for 10 months during the 1970s, employed polonium-210 as a heat source. The Chinese Chang'e 3 lander and its Yutu rovers, which successfully landed on the moon in 2013 and 2019, too, employed similar technology to endure the lunar night. ISRO has not disclosed the reasons for the absence of radioisotope heater units (RHUs) aboard Chandrayaan-3,” explained Linganna.

Linganna said there was optimism that as sunlight once more illuminated the solar panels, the spacecraft would re-energize and come back to life. However, this optimism proved unfounded. “Both Vikram and Pragyan were not engineered to endure an extended, harsh lunar night where temperatures plummet to more than a 100°C below zero, far surpassing the tolerance level of their electronic components. While it was technically feasible for the spacecraft designers to incorporate heaters or utilize more resilient components, such choices would have entailed additional expenses, increased weight and heightened complexity,” added Linganna.

He pointed out that many additional factors need to be considered which may be posing a challenge to reviving the lander and rover. “How effectively both the lander and the rover can endure the temperature fluctuations on the moon and the resulting thermal stress and mechanical shock; to what extent can they shield their delicate components from the lunar cold and radiation, ensuring their protection in these challenging conditions; and how effectively can they close off their openings to safeguard against lunar dust and the vacuum of space, addressing this crucial aspect of lunar conditions. Considering lunar conditions, it is crucial to assess the strength of both the lander and the rover's signal transmissions and the alignment of their antennas when communicating with the Indian space agency. Additionally, the clarity of their frequencies and available bandwidths becomes a vital consideration. Moreover, evaluating the compatibility of their communication protocols and data formats in the lunar environment is of utmost importance,” Linganna told THE WEEK.