India’s lunar lander misses wake-up call after successful mission

As the sun rose Friday over the lunar plateau where India's Vikram Lander and Pragyan Rover sit, the robotic explorers were silent.

Indian Space Research Organization, India's equivalent of NASA, said on Friday that mission controllers sent a wake-up message to Vikram on the ground.

The landing party, as expected, did not respond. The effort will continue for the next few days, but it could be Chandrayaan-3, India's first successful space mission to the surface of another world.

India is only the fourth country to complete an intact lunar landing, after the United States, the Soviet Union, and China. Vikram, which arrived a month ago, was also the first spacecraft to land on the moon's south polar region, which has become an area of ​​intense scientific curiosity in recent years.

Shortly after landing, the small rover, Pragyan, rolled off the ramp and began moving. Over the next week and a half, as the Sun moved across the sky, the two solar-powered spacecraft studied their environment, measuring subsurface temperatures, identifying elements in the lunar soil, and listening for lunar earthquakes.

As the sun set, ISRO officials sent orders for Vikram and Pragyan to sleep. Their batteries were fully charged and Pragyan's solar panels were pointed where the sun was still rising.

The hope was that when sunlight warmed the solar panels again, the spacecraft would be recharged and revived. But it was optional. Neither Vikram nor Pragyan was designed to survive a long, cold moonlit night when the temperature dropped to over a hundred degrees below zero, much colder than the electronic components were designed for. Spacecraft designers could have added heaters or used more flexible components, but that would have added cost, weight, and complexity.

Even if the spacecraft is not resurrected, the mission, named Chandrayaan-3, was a success for ISRO, easing the disappointment of four years ago when the first attempt to land on the moon ended in a crash during the Chandrayaan-2 mission.

ISRO built a replica of the failed lander – fixed the flaws in the original design – and tried again. This time, on August 23, the landing went off without a hitch. With Prime Minister Narendra Modi watching via video link, the control room erupted in cheers when Vikram's safe arrival was confirmed.

“The triumph of Chandrayaan-3 reflects the aspirations and capabilities of 1.4 billion Indians,” Mr. Modi said afterward, describing the event as “a moment for a new, emerging India.”

The mission's scientific observations included a temperature probe deployed from Vikram that penetrated the lunar soil. The probe recorded a sharp drop, from about 120 degrees Fahrenheit at the surface to 10 degrees just three inches below. Lunar soil is a poor conductor of heat.

Poor heat conduction could be a boon for future astronauts; An underground outpost would be well insulated from the huge surface temperature fluctuations.

Another of Vikram's instruments, the seismometer, detected what appeared to be a lunar earthquake on August 26.

Pragyan walked a total of over 300 feet. As it moved, it fired laser pulses into the rocks and soil, allowing it to identify elements based on the colors of light emitted from the vaporized material. The instrument confirmed the presence of elements such as aluminum, calcium, iron and titanium. It was a little surprising that he also discovered sulfur.

Trace amounts of sulfur have been measured in lunar soil and rock samples brought back to Earth by NASA's Apollo astronauts and Soviet robotic spacecraft decades ago. Pragya measurements suggest that sulfur concentrations may be higher in polar regions. Sulfur is a useful element in technologies such as solar cells and batteries, as well as fertilizer and concrete.

Before going to sleep earlier this month, Vikram made a small final move, firing its engines about 16 inches above the surface before gently landing again. The hop changed Vikram's position by 12 to 16 inches, ISRO said.

“Hope for a successful awakening for another set of tasks!” ISRO published on XThe social network formerly known as Twitter, on September 2. “Otherwise he will stay there forever as India's moon ambassador.”