India’s Chandrayaan-3 lunar lander Vikram, which crashed on its attempted moon landing in 2019, has come back to life as a locator beacon thanks to NASA’s Lunar Reconnaissance Orbiter (LRO) spacecraft. The LRO recently pinged Vikram using its laser altimeter instrument, marking the first successful laser communication from lunar orbit to the lunar surface.
Background on Chandrayaan Missions and Vikram Lander
The Chandrayaan missions are a series of lunar exploration missions conducted by the Indian Space Research Organisation (ISRO). Chandrayaan-1, launched in 2008, orbited the moon and ejected an impactor that detected water ice on the lunar surface for the first time.
Chandrayaan-2 was launched in 2019 with the goal of soft-landing a rover on the lunar south pole to analyze the water ice in more detail. The mission consisted of an orbiter, lander (Vikram), and rover (Pragyan). However, shortly before touchdown, mission control lost contact with Vikram. The suspected crash landing dashed India’s hopes of becoming the fourth nation to accomplish a soft lunar landing.
NASA Finds Vikram Impact Site
In the years since, NASA’s LRO, which has crisscrossed the lunar surface since 2009, took detailed images clearly showing the impact site of Vikram near the lunar south pole. The images showed that Vikram had made a hard landing, with debris scattered across several hundred meters.
While the lost lander could still serve a scientific purpose as a geology study target, its onboard instruments were likely damaged beyond repair. But in a surprising new development this month, NASA engineers used a new laser communication technique to revive Vikram into active service as a locator beacon.
Experimental Laser Pings Success
On January 18th, 2024, NASA announced that an experimental laser altimeter aboard the LRO, called LOLA, had successfully pinged Vikram’s laser retroreflector. By measuring the time it took for the laser pulse to return to LOLA, engineers obtained an extremely precise distance measurement placing Vikram within 100 meters of its known impact site.
|Lunar Orbiter Laser Altimeter (LOLA) Specs
|5 laser beams
|1064 nm wavelength
|28 Hz pulse rate per beam
|Centimeter-scale vertical resolution
This success opens up the possibility that Vikram could serve as a locating beacon for future lunar landers headed to the south pole region, which is of great interest due to the water ice deposits located there.
Image credit: NASA's Goddard Space Flight Center
Door Opens to New Lunar Targeting Technique
Up until now, pinpoint landing on the moon has relied on onboard navigation systems to autonomously calculate descent and targeting in real time during the lander’s final approach. This requires carrying additional weight in backup computing and sensor hardware.
With the laser ping success, NASA has proven the viability of using a lunar orbiter to actively locate and range ground targets for approaching landers. By installing additional small retroreflector targets, future landing zones could be precisely mapped relative to each other, creating an inflight calibration reference for navigation computers.
Next Steps for Orbiter Laser Communications
While the proof-of-concept test only utilized LOLA’s 1064nm laser wavelength, NASA’s LRO project scientist Noah Petro indicated that follow-on demonstrations will test laser communications using LOLA’s two other wavelengths at 532nm and 355nm. The ultraviolet 355nm beam would enable significantly faster data rates compared to infrared wavelengths.
If the multi-wavelength tests succeed, NASA hopes to upgrade LOLA with a dedicated high-speed lasercomm terminal that could relay data, command sequences, and even live telemetry between mission control and assets on the lunar surface.
This orbiter-to-surface lasercomm infrastructure would greatly simplify logistics for future lunar base modules, rovers, and astronauts exploring the moon by removing onboard high-gain antennas and keeping communication equipment centralized on the long-lived orbiter.
Outlook for Chandrayaan-3 Relaunch
While India’s space agency successfully placed the Chandrayaan-2 orbiter around the moon to map lunar minerals, water deposits, and perform other science, ISRO still aims to demonstrate an independent soft lunar landing capability.
Current reports indicate that ISRO is targeting a relaunch of the Chandrayaan-3 lander and rover mission in mid-2024. With NASA’s orbiter laser technique proving the ability to precisely locate Vikram’s crash site, the door is open for Chandrayaan-3 to utilize LRO targeting support on its next landing attempt. This could greatly improve odds of success without carrying redundant onboard hardware solely for backup navigation.
Only time will tell, but Vikram’s silent instrument deck sparking back to life as a tiny locator beacon may have just paved the way for India to stick its next landing in humanity’s return to the moon.
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