Artemis missions may convey probably the most highly effective imaging telescope to the Moon

Ground-based interferometry on Earth has proven to be a successful method for scientific purposes by combining the light from multiple telescopes, making it function like a single large telescope. But how can an ultraviolet (UV)/optical interferometer telescope on the Moon provide better science, and can the Artemis missions help make this a reality? This is what a recent paper submitted to the SPIE Astronomical Telescopes + Instrumentation 2024 conference hopes to explore, in which a team of researchers proposes the Artemis-enabled Stellar Imager (AeSI), which, as the name suggests, could potentially be launched onto the lunar surface with NASA's upcoming Artemis missions. This proposal was recently accepted as a Phase 1 study under NASA's Innovative Advanced Concepts (NIAC) program, and holds the potential to develop a revolutionary extremely high angular resolution method for scientific research on other planetary bodies while also contributing to other missions.

Here, Universe Today discusses this incredible research with Dr. Gioia Rau, astrophysicist at NASA's Goddard Space Flight Center and program director at NSF, about the motivation behind this study, key takeaways from this work, next steps should this move beyond Phase 1, long-term goals regarding lunar surface locations, and how AeSI can improve our understanding of exoplanet habitability. So what was the motivation behind this study?

Dr Rau tells Universe Today: “The motivation behind this study is to assess whether we can build and operate a large, low-aperture observatory (interferometer) on the lunar surface in collaboration with the manned Artemis program and whether it can compete with a previously developed free-flyer option. The ultimate goal is to enable the study of our Universe in Ultra High Definition at ultraviolet and optical wavelengths with an angular resolution of about 200 times that of HST! Ultraviolet observations are not possible from the Earth's surface due to the overlying atmosphere and even in the visible, the Earth's atmosphere limits the ultimate resolution achievable with ground-based interferometers.”

For the study, the researchers are drawing on long-standing proposals to launch UV/optical interferometers into space. However, due to the lack of infrastructure on the lunar surface, scientists have favored using satellites and orbiters, which the researchers call “free-flyers.” For AeSI, the researchers propose building a lunar interferometer using infrastructure launched to the Moon via NASA's Artemis program, with the goal of providing advanced scientific insights into exoplanet systems, including the surfaces of stars, their interiors, magnetic fields, space weather, and the habitability of exoplanets.

Artist's impression of six interferometers on the lunar surface combined to simulate a single, giant interferometer. (Source: Figure 3/Rua et al. (2024))

To achieve this, AeSI will consist of a 1-kilometer UV/optical imaging interferometer near the Moon's south pole, the landing region for the Artemis program, specifically Artemis III. In addition to improved science, the team also touts the scalability of the project, noting that it can potentially include up to 30 or more elements to serve as a single interferometer. In addition, the team is addressing several issues that could arise in this endeavor, including lunar dust, seismic activity, and the use of robotic assistants to assist with construction. So what are the key takeaways from this study?

Dr. Rau tells Universe Today: “The key findings from this study are that the project is feasible and that the visionary idea of ​​our PI, Dr. Kenneth Carpenter (NASA/Goddard Space Flight Center), can realistically be implemented. The study provides important recommendations for further research and technology development that will be critical to advancing the project and overcoming any technical challenges and further technology development required.”

As mentioned above, AeSI was approved for a Phase 1 trial (less than 4% success rate!) under NASA's Innovative Advanced Concepts (NIAC) program. The NIAC has successfully contributed to the advancement of technology in the aerospace industry since 1998. It was originally called the NASA Institute for Advanced Concepts until its closure in 2007. Just two years later, Congress asked the National Academy of Sciences to review the reasons for the closure, which made recommendations for the future that led to the current NIAC program in 2011.

Since then, NIAC has made technological advances in nanosatellites, planetary exploration, exoplanet spectroscopy, astrophysics, cosmology, solar science, human space exploration, and many other areas. These proposals move through three phases, with each phase allowing increased funding and time for the project. Given that AeSI is a Phase 1 study, what are the next steps if it is approved to move forward?

Dr. Rau tells Universe Today: “The next steps would be to request support for Phase 2 from NIAC and explore additional funding opportunities and resources. Phase 2 would focus on further developing and refining the initial 9-month study we are conducting in Phase 1. We believe our visionary concept has the potential to revolutionize scientific research and provide a significant opportunity for demonstrating technologies on the lunar surface, so we really hope to receive further support from NIAC and/or other supporting sources!”

Regarding AeSI's long-term goals, Dr. Rau tells Universe Today: “There are numerous limitations to placing interferometers on the lunar surface, especially optical and UV interferometers! We describe this in more detail in the final report of the NIAC Phase 1 study, which will be publicly available and released early next year. Our project is currently planned to start with a Phase 1 consisting of 15 rovers in an elliptical array with a 1 km major axis. The observatory will evolve in later phases to an array of about 30 rovers with an improved hub to combine the beams from the larger number of rovers (mirror stations) and provide extremely high angular resolution of celestial objects such as distant Sun-like stars, active galactic nuclei (AGN), exoplanets, cool evolved stars and more!”

As mentioned above, in addition to expanding research on stars, one of AeSI's scientific goals will be to determine the habitability of exoplanets. To this end, NASA has confirmed the existence of over 5,700 exoplanets in our Milky Way galaxy. Of these, nearly 70 are currently considered to be in the “habitable zone” of their parent star, with 29 of them potentially being terrestrial (rocky) worlds and the remaining 41 potentially being “water worlds” or mini-Neptunes. These potentially habitable worlds have been found to orbit inside and outside the habitable zone, with some lying both inside and outside the habitable zone during one orbit. So how might AeSI improve our understanding of exoplanet habitability?

Dr Rau tells Universe Today: “AeSI will give us a deeper insight into the properties of the host stars in distant exoplanet systems. By analyzing these stars in more detail, we can better understand the conditions that affect the habitability of the planets orbiting them. This includes studying the interactions between planets and their stars, which can significantly affect the potential for life on these exoplanets.”

As NASA prepares to send humans back to the Moon for the first time since 1972 as part of the Artemis program, it is important to note the incredible science that can be achieved with the infrastructure created by Artemis. Because ground-based interferometry from Earth is a long-established and successful scientific field that has contributed to a better understanding of radio astronomy, solar physics, nebulae, galaxies, and exoplanets, AeSI offers a unique opportunity to conduct revolutionary science and create images of distant stars with the highest angular resolution ever seen on other planets, while also testing new technologies.

Dr. Rau concludes to Universe Today: “AeSI will provide the first-ever ultra-high angular resolution images of the Universe in the ultraviolet (UV) range. This is a huge advance for many aspects of astrophysics, from understanding magnetic activity in stars and its effects on surrounding planets to detailed studies of exoplanets, space weather, AGN, stellar astrophysics and more! AeSI's high-resolution ultraviolet and optical observations will open new horizons in astrophysics, providing a more comprehensive and detailed picture of the most energetic and enigmatic components of the Universe.”

How will AeSI help improve UV/optical interferometry in the coming years and decades? Only time will tell, and that's why we do science!

And as always, keep doing science and keep looking up!

Further links:

Astronomical telescopes and instrumentation of SPIE 2024

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