NASA’s Commercial Lunar Payload Services to Study the Stars from the Moon with MoonLITE

Optical interferometry is a long-standing scientific technique that uses multiple telescopes to act as one large telescope, obtaining more accurate data than each telescope operating individually. But Earth’s chaotic atmosphere often makes it difficult to achieve scientific research on the ground, but what if you could do it on the Moon?

This is what a recent study presented at SPIE Astronomical Telescopes + Instrumentation 2024 and available on the arXiv preprint server aims to address in its proposed MoonLITE (Lunar Interferometric Explorer) as part of the NASA Astrophysics Pioneers program.

This comes after the same research team recently proposed the Big Fringe Telescope (BFT), a 2.2-kilometer diameter interferometer telescope to be built on Earth with the aim of observing bright stars.

Here, Universe Today speaks with Dr. Gerald Van Belle, an astronomer at Lowell Observatory in Flagstaff, Arizona, about his motivation for proposing MoonLITE, the science he hopes to accomplish, his preferred location on the lunar surface, the cost of MoonLITE, and the next steps to make MoonLITE a reality.So what’s the motivation for proposing MoonLITE?

“The real obstacle to making ultra-sensitive, high-resolution optical interferometry measurements is Earth’s atmosphere,” says Dr. van Belle. “The atmosphere is a boiling, turbulent medium, which ultimately limits telescope exposure times to less than a millisecond.”

“Telescopes with longer exposures would be more sensitive but would sacrifice angular resolution and result in blurring. With its 2-inch (50mm) aperture, MoonLITE can observe for many minutes at a time, making it more than 1,000 times more sensitive than a ground-based 8-meter collecting aperture.”

Compared to exposure times of just a few milliseconds on Earth, the amount of light captured by these tiny dime-store-sized telescopes exceeds that captured by gigantic industrial telescopes within the first second of opening their shutters.”

Like the recently proposed BFT, MoonLITE has a number of scientific goals it wants to achieve, and the study lists three science cases including studying the radii of low-mass stars (M dwarfs) and brown dwarfs, young stars (YSOs), and active galactic nuclei (AGNs). For M dwarfs and brown dwarfs, which have proven difficult to observe with ground-based telescopes, the team aims to obtain long-sought data on their size and temperature.

For YSOs, MoonLITE will also enable the researchers to see the inner regions of these stars and their sizes, so they hope to better understand the formation and evolution of habitable exoplanets in the protoplanetary disks of pre-main-sequence stars.

As for AGN, researchers want to learn more about supermassive black holes, especially the jets that shoot out from them, and MoonLITE will be able to observe these objects at visible wavelengths for the first time.But what else can we learn from these three science cases?

“We actually have many more scientific cases than this – so many cases, in fact – that we realized MoonLITE’s new features would be beyond our imagination to cover every aspect,” says Dr. van Belle. “So we built 20% of the total observing time into the program and put it up for competitive selection by the community – crowdsourcing some really creative ideas.”

“The three we wrote highlighted what can be done with greater sensitivity from the Earth’s surface. For example, the smallest stars (10% the size of the Sun) are also the faintest stars. And measuring their size is not possible with ground-based interferometers.”

“The same goes for YSOs and AGNs. We can observe some from Earth, but for a more general sample – one that represents more typical objects rather than super-luminous foreign objects – we need very high sensitivity.”

One thing that’s unique about MoonLITE is that it can be brought to the lunar surface through NASA’s Commercial Lunar Payload Services (CLPS), a collaboration with the private sector to send science and technology payloads to the Moon to test technologies that will benefit both human missions as part of the Artemis program and science missions like MoonLITE that deepen our understanding of the universe.

Companies taking part in the upcoming CLPS mission include Intuitive Machines, Astrobiotic, Firefly Aerospace and Draper, all of whom are delivering payloads to different locations on the lunar surface. But are there specific locations where MoonLITE would work best?

“We designed MoonLITE to be completely location independent,” Dr. van Belle said, “for small experiments like this, it will fly aboard the NASA CLPS lander as a minor guest. By imposing minimum requirements on boarding, we increase the chances of getting a boarding assignment, so it will work at both polar and equatorial latitudes, and near and far.”

As mentioned above, this same research team has recently proposed the Big Fringe Telescope, which would be a 2.2-kilometer interferometric telescope made up of 16 small telescopes with a diameter of 0.5 meters. Along with conducting cutting-edge scientific research, such as observing binary star systems and taking transit “movies” of exoplanets, one of the most notable features of the BFT is its extremely low cost compared to current optical interferometers around the world, costing approximately $28,496,000.

By contrast, the European Southern Observatory’s Very Large Telescope Interferometer (VLTI), consisting of four 8.2-meter telescopes and four movable 1.8-meter telescopes, is estimated to cost hundreds of millions of dollars. So how does MoonLITE’s potential cost compare to other Earth-based interferometers?

“MoonLITE was designed to work within the cost envelope of the NASA Pioneer Call for Proposals,” says Dr. Van Belle. “The CfP (Call for Projects) stipulated several things, including a cost ceiling of $20 million with a 25% unfunded reserve, so the actual activities and hardware budget level was $15 million.”

There are a few things you can request in CfP. First, your flight onto CLPS must be within the 50kg mass limit of CLPS. CfP’s hypothetical CLPS lander will also provide other capabilities such as power, communications, and rover locomotion. So your flight onto CLPS actually includes quite a bit of in-kind support.”

Submitting a proposal to NASA is a very thorough process involving multiple steps, also called phases, with a very low acceptance rate and often multiple rejections and improvements before being accepted. These proposals range from cubesats to full-scale multi-billion dollar space missions, and most of them, even if selected, take years to become actual missions.

For example, of the four proposals selected for further development in the Astrophysics Pioneers program in January 2021 (Aspera, Pandora, StarBurst, and PUEO), only two have clear launch dates (StarBurst in 2027 and PUEO in 2025).

So even if MoonLITE is selected for development, it could be years, or even decades, before we officially land on the moon’s surface to conduct scientific research.Unfortunately, Dr. Van Vels says the 2024 Pioneer proposal period has been canceled due to federal budget issues, so what are the next steps to make MoonLITE a reality?

“We applied for the NASA Pioneer 2023 call for proposals but were rejected,” Dr. Van Belle said, “but received positive feedback and were encouraged to improve, address identified issues and reapply. We are conducting laboratory and ground-based testing to mitigate risks.”

“That’s another great element of MoonLITE: We can build a representative system on the ground and test it directly here. You won’t get the excellent sensitivity that you would on the moon, but other than that it will work just as well. You just need to look at bright things here from Earth. So we hope to address some of those issues from the review panel and resubmit in 2025.”

As NASA prepares to send humans to the Moon for the first time since 1972 with its Artemis program, the level of science that could be achieved on the lunar surface would be unprecedented. This is especially evident considering that the Moon has no atmosphere, which could provide more precise data and give scientists a deeper understanding of the universe and our place in it.

Scientists hope that MoonLITE will enable them to gain insights into low-mass stars, brown dwarfs, young stars and active galactic nuclei from anywhere on the lunar surface, increasing the variety of observing locations and objects that can be observed.

Dr van Belle concluded by telling Universe Today: “MoonLITE is incredibly exciting not only because it’s a very affordable and highly impactful experiment, but also because it shows that the holistic approach works and can go even further.”

“For example, high-precision astronomical measurements from lunar interferometers will enable us to characterize the masses of Earth-sized exoplanets. We need to perform mass measurements ahead of the Habitable World Observatory in the 2040s to understand the spectra of HWOs and decipher those spectra to look for signs of life.”