Laser-driven artificial star will provide telescope test bed

A micro-sized, laser-equipped satellite – an artificial star – will soon shine in Earth’s sky.

A veritable who’s who of the biggest names in observational astronomy are backing the effort to boost the clarity of their ground-based telescopes’ vision by eliminating atmospheric interference. Researchers at George Mason University said on June 10, 2024, they will lead the Landolt NASA Space Mission to put the mock sun into space. The mission is planned for launch to a geosynchronous orbit in 2029.

David Ciardi, chief scientist for NASA Exoplanet Science Institute (NExScI) at Caltech/IPAC, described the mission’s important impact:

Landolt is an exciting opportunity to enable absolute calibration in astronomy at an unprecedented level. For as long as people have looked up at the night sky, a fundamental question has always been: ‘What is the true brightness of that star?’ Landolt has the opportunity to change astronomy for the relatively minimal cost of a NASA Astrophysics Pioneer program.

The entire mission budget for Landolt – which includes a set of eight high-precision lasers to mimic a star – is $19.5 million.

Landolt NASA Space Mission’s star will not be visible to the unaided eye. However, it will be visible in small telescopes.

Accurate stellar brightness means accurate science

The brightness of far off stars is key to much of our understanding of processes taking place many light years from Earth. How accurately we know stars’ magnitudes limits the quality of data we can gather. We know, for instance, the universe is expanding, and that knowledge is based on knowing the brightness of distant stars. But for a better understanding of this phenomenon – and many others – scientists need more accurate measurements.

Knowing how bright stars are is also critical for finding exoplanets and learning about their nature, Ciardi said:

Even with today’s modern instruments, true brightness calibration has only been good to a few percent, and Landolt will enable an improvement by more than a factor of 10. Understanding the true brightness of stars allows us to understand the stars better, and, perhaps more importantly, understand the planets that orbit the stars better.

Tiny satellite bears big name in stellar photometry

The Landolt NASA Space Mission’s name honors late American astronomer Arlo Landolt. Known primarily for a series of papers that established the Landolt Photometric Standard Star Catalog, his three decades of work improved measurements of stellar brightness and color. Physicists and astronomers worldwide still use the standard stars he recorded as calibration metrics.

Members of the American Astronomical Society are expecting big results from the Landolt star. They need the improved Landolt data to help shed light on some of the greatest mysteries the universe has yet to fully reveal.

The Landolt mission will allow us to re-calibrate the brightnesses of millions of stars. Such measurements can only be achieved by a space-based orbiting artificial star, where the physical photon flux is accurately known. Consequently, Landolt will enable the refinement of dark energy parameters, improve our ability to assess the habitability of terrestrial worlds, and advance fundamental constraints on stellar evolution.

And it will be a small package carrying such big hopes. The eight high-precision National Institute of Standards and Technology (NIST) laser beacons that make up the artificial star will all fit in a satellite no bigger than a bread box. Landolt’s artificial star will be housed in a tiny 12U Platform CubeSat. It will weigh no more than 24 kg (53 pounds) in a space around 8,700 cubic centimeters (530 cubic inches).

Artificial star will share a ride to orbit

While a firm date for the 2029 Landolt launch hasn’t been fixed, the mission will fly to a geosynchronous orbit aboard a SpaceX rocket. The company’s SmallSat Rideshare Program carries dozens of CubeSats into orbit with each trip to space.

From a height of 22,236 miles (35,785 km) above Earth, the Landolt will appear as another star on the celestial sphere. But it will be a star with a known magnitude. For the first time, ground-based astronomers will know exactly what kind and how much light their telescopes are showing them. Piotr Pachowicz, associate professor in GMU’s Department of Electrical and Computer Engineering, explained why that’s important:

This calibration under known laser wavelength and power will remove effects of atmosphere filtration of light and allow scientists to significantly improve measurements.

Peter Plavchan, a George Mason associate professor of physics and astronomy and the Landolt Mission primary investigator, elaborated:

When we look at a star with a telescope, no one can tell you today the rate of photons or brightness coming from it with the desired level of accuracy. We will now know exactly how many photons-per-second come out of this source to 0.25% accuracy.

And that has researchers – like Eliad Peretz, NASA Goddard mission and instrument scientist and Landolt’s deputy principal investigator – excited:

This mission is focused on measuring fundamental properties that are used daily in astronomical observations. It might impact and change the way we measure or understand the properties of stars, surface temperatures and the habitability of exoplanets.

Bottom line: The Landolt Space Mission will orbit an artificial star to aid with telescope calibration. Better data will lead to new insights on a range of cosmic mysteries.