October 17, 2023
Above: South pole of the moon. NASA/Goddard Space Flight Center Scientific Visualization Studio
Sandeep Singh, assistant professor of mechanical, aerospace and nuclear engineering, answers questions about the significance of landing on the moon’s south pole and how his lab is tackling some of the challenges associated with traveling between the Earth and moon.
What is significant about the recent Indian and Russian lunar missions to the south pole of the moon?
The first thing to know is that the south pole of the moon has never been explored. During the space race of the 1960s and 1970s, lunar missions focused on areas near the moon’s equator. But now we know that the south pole of the moon could hold an important key for future lunar exploration and deep space missions. This is because the moon’s poles contain ice deposits. This ice could allow people to stay longer on the moon and allow the moon to become a crucial steppingstone for missions to Mars. These ice deposits were discovered by NASA's Moon Mineralogy Mapper (M3) aboard Chandrayaan 1, one of India’s lunar probes. Last month, India’s Chandrayaan 3 mission put the un-manned Vikram lander on the south pole of the moon. This represents the first landing on the lunar south pole. Around that same time, Russia tried to land its Luna-25 space craft on the south pole, but it crashed into the lunar surface.
India launched Chandrayaan 3 on July 14 and the lander only arrived on the moon on August 23. Why did it take so long to get there?
Landing a spacecraft on the moon is like trying hit a moving target in the dark with only one opportunity to succeed. So precision is paramount! To make sure everything is aligned for a smooth landing, the Indian Space Research Organization first orbited the spacecraft several times around the Earth. During this time, ground-based mission control can adjust the spacecraft’s trajectory as needed and make sure everything on the craft is working correctly and that communication links are intact. Ensuring uninterrupted communication is not only a matter of data transfer, but also a lifeline for the mission's success.
Why is soft landing so important and so difficult?
In the case of Chandrayaan 3, the spacecraft was carrying a lunar rover outfitted with an array of sensors that are inherently fragile. These rovers have the capacity to unravel a multitude of captivating scientific insights — but only if they arrive with these sensors intact. A soft landing ensures these delicate instruments are operable. But soft landings are difficult on the moon for a few reasons. The moon has no atmosphere, so there is nothing to slow down the spacecraft as it nears the lunar surface. This means that even the slightest deviations in navigation data or the timing of maneuvers can lead to disastrous repercussions. In addition, unlike the Earth, the moon's gravitational pull is uneven, with some areas containing extreme mass concentrations called mascons that can lead to inaccuracies ultimately resulting in a crash.
What information do we expect to get from the mission?
Chandrayaan 3 mission duration is set at one lunar day, which is equivalent to approximately 14 Earth days. It features both a lander and a rover, each with its scientific equipment. The lander is equipped with the Chandra’s Surface Thermophysical Experiment (ChaSTE), which will characterize the thermal properties of the dust-like top layer of the lunar surface, called lunar regolith, in the landing area. It also has a probe to measure the density of plasma — electromagnetically charged particles — near the lunar surface. It is also equipped with the Instrument for Lunar Seismic Activity (ILSA) for recording local seismic activity around the landing site. Additionally, a NASA payload called the Laser Retroreflector Array (LRA) will map the distance between the Earth and moon in high detail over the 14 Earth day period. On the other hand, the rover will quantify the elemental composition in the vicinity of the landing site.
Our own G. Reid Wiseman will be leading the Artemis II mission next year, which is also our bicentennial year. What makes that mission special?
It is indeed an extremely proud moment for the entire Rensselaer family that one of our own is leading such a landmark mission. The Artemis II mission is a follow-on from the Artemis I mission and is the second scheduled mission of NASA’s Artemis Program. It will be the first scheduled crewed mission of the Orion Spacecraft and is an intermediate step to take humans back to the moon via Artemis III. Artemis II will perform a flyby of the moon and return to Earth. The Artemis II mission is special because it marks mankind’s return to the moon since the Space Race era after more than 50 years!
You worked at ISRO and NASA before joining RPI. What are you working on in your lab? How does your work connect to these exciting present and future missions?
At the Advanced Space Concepts Lab (ASCLab) here at RPI, I collaborate alongside a dedicated group of graduate students to tackle pressing challenges related to space mission design and implementation and strive to find innovative and ingenious solutions.
For instance, Kevin Alvarado, PhD Student at the ASCLab has developed a novel approach for finding “special” destination orbits that are geometrically similar to traditional periodic orbits, as well as a strategy for quantifying accurate maintenance costs for the discovered orbits in the context of representative missions between the Earth and moon.
Abigail Rolen, another Ph.D. student, is studying how to apply deep learning AI to the problem of spacecraft autonomous guidance, which is of huge significance for both deep-space and entry, descent and landing missions.
Lastly, Ph.D. student Ickbum Kim is working on advancing the development of 3D scene reconstructions using data-fusion from hybrid sensors which is an important technological capability for future planetary landing, in-orbit docking and estimation of previously unexplored space-object physical properties and composition.
Anything else we should know?
The renewed interest in crewed missions to the Moon and beyond presents an exciting array of research opportunities aimed at achieving the necessary technological readiness for the entire space community. Personally, space has always been a captivating subject and often demands innovative thinking and multi-disciplinary research endeavors to enable ambitious missions. As someone deeply passionate about astrodynamics, I understand the intricacies involved in planning and executing space missions. It's incredibly exhilarating to contemplate the future advancements in science and engineering that might ultimately lead to a better understanding of the universe's origins and our place within it.