The project assembles a team of experts from across the country to prove technology that will help search for life outside our solar system

The first space mission led by the University of Michigan Department of Astronomy is scheduled to launch in 2029 with the support of a NASA grant worth $10 million.

The mission is called STARI—STarlight Acquisition and Reflection toward Interferometry—and will showcase the viability of a new technique for studying exoplanets, or planets outside of our solar system.

The technique could be used in the future to better understand whether any of the exoplanets we know about are capable of supporting life as we know it.

“We’ve detected thousands of these planets and most by indirect means—in other words, not directly through the light they emit,” said John Monnier, U-M professor of astronomy and leader of the project. “It’s time to change that.”

The grant was awarded by the Astrophysics Research and Analysis program of NASA’s Astrophysics Division.

Proof of technology

STARI itself isn’t designed to show us new things about those planets. Rather, it will demonstrate a crucial technology for a powerful technique called interferometry to prove that larger, more expensive future missions can use this approach to look for signs of life on other planets.

Interferometry requires multiple satellites, separated by hundreds of yards, maneuvering in precise coordination to bounce starlight between each other. The satellites need to transmit light to each other with pinpoint accuracy while moving and being separated by roughly the length of a football field.

It’s this level of control and stability that STARI intends to demonstrate using two small satellites called CubeSats. Both of STARI’s satellites—named STARI-1 and STARI-2—are about the size of a briefcase.

“The most challenging aspect of the STARI mission will be achieving the precise coordination and control required for formation flying on a CubeSat platform,” said Gautam Vasisht, a collaborator on the project and a research scientist at NASA’s Jet Propulsion Laboratory, or JPL.

The advantage of using CubeSats is that they cost a small fraction of what it would take to get a larger mission off the ground. Although they can’t completely match the performance of bigger, more sophisticated satellites, CubeSats offer a lower cost way to prove components of the technology needed for those larger missions.

“By testing formation flying technologies on a CubeSat platform, STARI paves the way for future missions that could revolutionize our ability to study distant Earth-like planets,” Visisht said. “It’s a demonstration of how innovative engineering and a strong collaboration can push the boundaries of what’s possible in astronomy.”

In addition to Vasisht of JPL, the team is joined by experts from across the country, led by Simone D’Amico at Stanford University, E. Glenn Lightsey at the Georgia Institute of Technology and Leonid Pogorelyuk at Rensselaer Polytechnic Institute, or RPI.

James Cutler, a professor of aerospace engineering who also spearheads the CubeSats Working Group in the U-M Space Institute, is also a co-investigator.

An all-STARI team

Collaboration is a critical and intentional component of the project.

“The team combines the key required expertise and experience in several major areas, including formation-flying, optical interferometry, propulsion and system engineering,” said D’Amico, an associate professor of aeronautics and astronautics who leads the Space Rendezvous Laboratory at the Stanford School of Engineering.

D’Amico, for instance, has helped design and operate several previous small satellite formation-flying missions with a focus on their guidance, navigation and control systems. He and his colleagues have experience in different key areas that STARI will combine in a unique way with a very high level of precision.

“This has never been accomplished before,” D’Amico said. “So the STARI technology demonstration has huge value per se and not only as a precursor of flagship missions for larger interferometers.”

Lightsey, a collaborator and professor at Georgia Tech, sees STARI as part of a larger shift happening in space missions.

Rather than packing all the technology a mission needs into a single spacecraft, missions are working to accomplish more than was previously possible by dividing the load between multiple vessels and even ground-based instruments.

“I believe this is a much more powerful concept,” said Lightsey, a veteran of many small satellite missions whose team is responsible for STARI’s maneuvering system.

“It’s going to lead to incredible scientific discoveries and improvements in human life on Earth because of the capabilities it provides,” he said. “I’m excited to be involved with a significant project like this that could really advance the state of the art.”

Although this is the first mission led by Michigan’s astronomy department, U-M has a long history of working in space. In fact, Cutler leads the Michigan Exploration Laboratory, or MXL, that has already launched nine satellites.

“We have pioneered the use of CubeSats for space weather studies and exploration with missions near Earth, past Mars and to the moon,” Cutler said. “We’re excited to help astronomers explore even further with STARI.”

MXL will integrate and optimize the STARI satellites.

“Although many of our faculty have played leading roles in previous NASA astrophysics missions, having STARI led by U-M Astronomy is a major milestone,” said Michael Meyer, chair of the Department of Astronomy. “We look forward to a bright future, in collaboration with partners such as the University of Michigan Space Institute.”

STARI, STARI flight

Scientists have already shown they can get clues about the composition of an exoplanet’s atmosphere by analyzing the light that passes through it, which is known as transmission spectroscopy.

But astronomers are working to develop better tools, developed specifically to detect the infrared light emitted by cooler planets against the glare of their much brighter and hotter host stars. Scientists could then probe the light from the planets for signatures of life as we know it.

One way researchers are doing that is by building increasingly large telescopes on Earth to collect as much light as possible. That’s the goal of the Extremely Large Telescope, currently being built by the European Southern Observatory in Chile. With its 128-foot diameter primary mirror, it will be the world’s largest telescope for capturing visible and near- to mid-infrared light when it’s finished in 2028.

U-M astronomers are helping develop the first instruments for the Extremely Large Telescope, but they’re also interested in the complementary approach of interferometry.

This approach would use multiple satellites that observe light from a distant source and reflect it to another spacecraft that combines the beams. Here, the reflected light overlaps, creating interference patterns that help remove starlight and reveal clues about an exoplanet’s atmosphere.

Increasing the distance between the satellites improves the resolution of the technique, but also heightens the degree of difficulty, said Pogorelyuk, an assistant professor and collaborator at RPI.

Although STARI won’t be doing interferometry, it will be testing the ability of its satellites to gather light into a hair-like optical fiber and beam light to its partner, up to 100 meters away.

The satellites will need to maintain their position and orientation relative to each other to within millimeters—roughly the thickness of a dime—while zipping around in a low-Earth orbit.

“The way you do things in space is very different from how you do things on Earth. Nothing’s bolted to the ground—everything’s moving like it’s sliding on an ice rink and can’t stop,” Pogorelyuk said. “From an engineering perspective, it’s a very cool problem.”

The team is excited to tackle the challenges and bolster the outlook for future projects like the Large Interferometer For Exoplanets, or LIFE, led by the Swiss university ETH Zürich. LIFE is proposed as part of the European Space Agency’s long-range science planning, dubbed Voyage 2050.

“While we feel that the worldwide scientific community strongly supports our ambition, we also know that we still have some scientific and technological challenges to overcome before we have LIFE on the launch pad,” said Sascha Quanz, the principal investigator for LIFE and professor at ETH Zürich.

“Projects like STARI are excellent examples of how smaller, faster missions with a clear focus can help us develop and test relevant technologies for LIFE in a very efficient way.”

LIFE would use larger satellites and more of them to probe distant atmospheres for signs of life, but STARI’s small CubeSats could go a long way toward showing it could be done, Monnier said.

“We hope the technology developed by STARI will lead to a future space interferometer capable of imaging Earth-like planets around nearby stars, with enough capability to search for signs of life,” he said.