Mapping the Moon—NASA Announces LiDAR-based Lunar Backpack
The focus is back on the moon, with NASA, backed by Aeva's LiDAR technology, creating a backpack to help map the moon.
Space exploration is a field that has catalyzed many revolutionary technologies throughout history. Technological staples in our daily lives, such as LEDs and portable computers, exist today only due to investment in space travel and exploration.
As NASA sets its sights on returning humans to the moon, the historical trend of invention and innovation is continuing. Recently, NASA announced that, in collaboration with Aeva, it has successfully designed a LiDAR-based "lunar backpack" to be used to map the surface of the moon.
NASA's prototype backpack is being tested out. Image used courtesy of NASA and Michael Zanetti
This article will discuss some of the unique technology that Aeva's LiDAR offers and how NASA's new lunar backpack works.
3D LiDAR and Challenges for Space
In most cases, when people talk about LiDAR, they are likely referring to 3D LiDAR, which is used in applications like autonomous vehicles (AVs) and robotics.
Most 3D LiDAR systems work using a time-of-flight (ToF) principle where the sensor can interpret the distance of objects from the source from the total time it takes for incident photons to reflect and return after being transmitted.
The resulting data from 3D LiDAR is an environmental map in only three dimensions (i.e., X, Y, and Z).
Working principle of ToF LiDAR. Image used courtesy of Analog Devices
While powerful, 3D LiDAR has certain shortcomings that can hinder its use in space applications.
One such challenge is that, to enable 3D LiDAR systems to create a 3D map of their environment, systems must rely on external sensors such as inertial measurement units (IMUs) and GPS to locate themselves within that map. This requirement may not be a problem in terrestrial applications such as vehicles, but in GNSS-restricted environments, like the moon, this can be severely limiting.
4D LiDAR With FMCW
To address the shortcomings of 3D LiDAR, many are turning to frequency modulated continuous wave (FMCW) LiDAR as the solution. FMCW LiDAR ditches the traditional ToF approach and instead measures distance by transmitting a continuous laser pulse and chirping it repeatedly in frequency.
The concept follows that the rise time of the chirp is longer than the time it takes for the light to reach the incident object. Thus, when the reflected signal returns, engineers can then tell how much the frequency changed while the reflected light made its round trip to the object.
Multiplying that interval by the chirp speeds yields the distance.
The working principle of 4D LiDAR. Image used courtesy of Laser Focus World
Even more importantly, engineers can further process the data to extract the Doppler shift of the object. From this, the measured object's velocity relative to the LiDAR can be determined.
This ability leads to increased accuracy and resolution as compared to ToF approaches. Because of this fourth dimension, FMCW is also known as 4D LiDAR.
Notably, the addition of velocity data allows 4D LiDAR to provide better, more accurate maps of an environment and for the LiDAR to locate itself within a 3D map without the need for IMUs or GPS.
NASA’s Lunar Backpack—the KNaCK
As mentioned, NASA recently announced that it had developed a new lunar backpack system to perform mapping and location of vehicles and astronauts on the moon.
The central challenge with creating a device to map and locate an astronaut on the moon is that there is no GPS or GNSS service available on the lunar surface. Instead, NASA needed a different technology to do the job. The solution yielded its newest device, the Kinematic Navigation and Cartography Knapsack (KNaCK).
NASA's KNaCK technology is used alongside a drone. Image used courtesy of NASA and Michael Zanetti
Naturally, the fundamental underlying technology of KNaCK is Aeva's FMCW 4D LiDAR technology. The resulting sensor is a backpack surveying tool for navigation and science mapping with the ability to generate high-resolution 3D maps combined with information about the velocity of objects in the map relative to the KNaCK.
In this way, KNaCK can allow rovers and astronauts to understand their relative location within a map, which is necessary for ensuring safety on the lunar surface.
Currently, the prototype weighs about 40 pounds, but NASA's future plans for the project include miniaturization to make it cheaper and easier to wear. If all goes well, NASA hopes the KNaCK will be usable for future space missions in the near future.