The Role of Interferometry in Space-Based Telescopes

By Ibtisam AbbasiReviewed by Lexie CornerApr 28 2025

Interferometry is a technique that combines light waves to produce interference patterns, which can be analyzed to measure distances, shapes, and surface features with extreme precision.¹

Thanks to its ability to deliver high resolution and detect very small changes, interferometry has become essential for advancing astronomy.

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It plays a critical role in studying distant and complex regions of space, such as areas where young stars form or where black holes exist, both of which demand exceptional spatial resolution.²

Today, interferometry is key to producing the sharp, high-quality images needed for space exploration and future astronomical discoveries.

What Is Interferometry?

Interferometry involves superimposing waves to create interference. An interferometer consists of a light source, a beam splitter, and a reference surface. The light beam from the source is split into different light waves. Upon recombination, the amplitude and phase difference of the waves can lead to a variation in the intensity of the light.

Comparable intensity and in-phase light waves lead to constructive interference, resulting in a 4-times increase in light intensity. Out-of-phase light waves cause destructive interference.

The interference pattern consists of light and dark bands due to the constructive and destructive interference phenomena. The analysis of the interference patterns allows the experts to accurately estimate the path length differences.³

Types of Interferometers

Different types of interferometers are used depending on the application and setup. The Mach-Zehnder interferometer uses two beam splitters to split and then recombine beams, producing two outputs. It also allows the path length difference to be adjusted so that all the light can be directed into a single output if needed.

The Michelson interferometer, invented by Albert A. Michelson, uses just one beam splitter. Michelson’s early experiments with broadband light sources led to the development of an interferometer with almost zero arm length difference.⁴

Another widely used design is the Fabry-Pérot interferometer, where two parallel mirrors are positioned to face each other. This setup allows light waves to make multiple round trips between the mirrors. Transmission through this optical cavity creates sharp resonances, making it useful for improving the precision and accuracy of high-resolution optical spectroscopy.⁵

Why is Interferometry So Valuable for Space Telescopes?

Overcoming Resolution Limits

Shorter wavelengths generally offer better angular resolution in space observations. However, we can’t freely choose any wavelength to study distant objects—many targets are simply too faint or emit at specific wavelengths.

This limitation meant that traditional imaging techniques, like those used in conventional telescopes, had a hard cap on how much detail they could resolve.

In the 1960s, Very Long Baseline Interferometry (VLBI) revolutionized astronomy. By linking multiple antennas across vast distances, astronomers could dramatically boost angular resolution, creating sharper and more detailed images than ever before.

VLBI also enhanced sensitivity by increasing the total collection area, making interferometry one of the most effective methods for imaging distant astronomical objects.⁶

Importance for Space Exploration

In space-based astronomy, the resolution of a telescope is directly tied to the diameter of its aperture. Larger mirrors offer better resolution, but building ever-bigger telescopes comes with major challenges. Gravity causes optical distortions, and scaling up mirror size becomes technically difficult and prohibitively expensive.

Interferometry offers a way around these limits. By linking multiple smaller telescopes to act together as one large "virtual" telescope, scientists can achieve high resolution without the need for physically massive structures.

In these arrays, it’s the distance between the telescopes, known as the baseline, that determines the effective resolution, not the size of each individual unit.

During astronomical observations, interferometers combine light from multiple telescopes to create interference patterns. By analyzing the amplitude and phase of these patterns, astronomers can extract detailed information about the size, brightness, and structure of distant stars, exoplanets, and galaxies.⁷

This approach makes high-resolution imaging more practical, scalable, and cost-effective for the next generation of space missions.

Key Examples of Space Interferometry Missions

Early Interferometry Missions

Space-based interferometry became a huge focus for both NASA and the European Space Agency (ESA) in the late 1990s. NASA’s first Space Interferometry Mission (SIM) was a major milestone. Designed around a 10-meter Michelson stellar interferometer, it aimed to achieve astrometric precision at the 4-micrometer level.⁸

Around the same time, ESA launched the Darwin project, which explored the use of nulling interferometry to detect exoplanets directly. Nulling techniques suppressed light from central stars, making it easier to measure the temperature and surface properties of nearby planets.

In far-infrared interferometry, NASA developed the concept for the Space Infrared Interferometric Telescope (SPIRIT), a 36-meter structurally connected instrument selected for study as a potential Origins Probe mission in 2004.

In 2006, the European Space Agency’s Concurrent Design Facility (CDF) began studying the Far-InfraRed Interferometer (FIRI) concept. Around the same time, ESA also explored ESPIRIT, a related idea involving a heterodyne far-infrared interferometer with large free-flying collector satellites.⁹

Gaia: Mapping the Milky Way

ESA’s Gaia spacecraft, which has been operational since 2014, is another key example.

While not a classical interferometer, Gaia uses precise optical measurements with interferometric techniques to survey over two billion stars, building the most detailed 3D map of our galaxy ever created. Its data is helping to answer major questions about the formation and evolution of the Milky Way.¹⁰

LISA: The Future of Space-Based Laser Interferometry

The Laser Interferometer Space Antenna (LISA) project represents a bold step forward for space interferometry—it will be the first-ever gravitational-wave observatory in space.

Scheduled for launch in the 2030s, LISA will consist of three spacecraft flying in a triangular formation with 2.5 million kilometers long arms. Using laser interferometry, LISA will detect and measure gravitational waves from sources such as merging black holes and neutron stars, providing new insights into the "invisible" universe.

LISA’s highly sensitive detectors will cover low-frequency gravitational waves in the range of 0.1 millihertz to 0.1 hertz—a part of the spectrum unreachable by ground-based observatories like LIGO.¹¹

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Challenges of Space-Based Interferometry

Despite steady progress, space-based interferometry still faces significant technical challenges. Achieving ultra-high resolution and precision requires overcoming issues related to optical control, data processing, and environmental conditions.

One key difficulty is developing highly tunable, coherent light sources that can operate reliably across wide frequency ranges. Many designs also depend on cryogenic amplifiers, which consume large amounts of power and add further complexity to spacecraft operations.

Data processing poses another major hurdle. Combining signals from multiple telescopes requires calculating coherence and time delays with extreme precision, demanding powerful onboard processors. Safely storing large volumes of data for long periods is equally challenging, as radiation events like solar flares can threaten sensitive equipment.¹²

These factors mean space interferometry missions must be carefully planned and engineered to handle demanding operational environments.

Still, there is strong momentum in the field. Recent advances in far-infrared interferometry, such as the successful development of the SHARP-IR small interferometer, have encouraged optimism.

System-level demonstrations are helping researchers solve key challenges, with the goal of building more reliable and capable space-based interferometry missions in the coming years.

Interested in learning more about the latest advances in space optics and astronomy? Explore these related articles:

• What is Deep Space Optical Communication?
• James Webb Space Telescope Captures Key Evidence of Gas Giant Formation in Nearby Star System
• Keeping up to Speed with Space Using Robotic Telescopes
• Exploring Ultra-Lightweight Space Cameras for Space Missions
• Using Telescopes for Deep Space Imaging

References and Further Reading

1. Laser Interferometer Gravitational-Wave Observatory (2025). What is an Interferometer? By Caltech and MIT. [Online]. Available at: https://www.ligo.caltech.edu/page/what-is-interferometer [Accessed on: April 10, 2025].
2. Kouveliotou, C. et. al. (2014). Enduring quests-daring visions (NASA astrophysics in the next three decades). arXiv preprint arXiv:1401.3741. Available at: https://doi.org/10.48550/arXiv.1401.3741
3. Photonics Spectra. (2025). Interferometry: Measuring with Light. Zygo Corporation. [Online]. Available at: https://www.photonics.com/Articles/Interferometry_Measuring_with_Light/a25128 [Accessed on: April 11, 2025].
4. Dr. Paschotta, R. (2025). Interferometers. RP Photonics Encyclopedia. Available at: https://doi.org/10.61835/kva
5. Dr. Paschotta, R. (2025). Fabry–Pérot Interferometers. RP Photonics Encyclopedia. Available at: https://doi.org/10.61835/qrw
6. The European Space Agency. (2025). Observations: Very Long Baseline Interferometry (VLBI). Science & Exploration. [Online]. Available at: https://www.esa.int/Science_Exploration/Space_Science/Observations_Very_Long_Baseline_Interferometry_VLBI [Accessed on: April 13, 2025].
7. Center for High Angular Resolution Astronomy, Georgia State University. (2025).  Basics of Interferometry. [Online]. Available at: https://www.chara.gsu.edu/public/basics-of-interferometry [Accessed on: April 14, 2025].
8. Marr, J. et. al. (1999). Space interferometry mission: measuring the universe. In IMTC/99. Proceedings of the 16th IEEE Instrumentation and Measurement Technology Conference (Cat. No. 99CH36309) (Vol. 2, pp. 1117-1122). IEEE. Available at: https://doi.org/10.1109/IMTC.1999.777031
9. Rinehart, S. et. al. (2016). The path to interferometry in space. In Optical and Infrared Interferometry and Imaging V (Vol. 9907, pp. 187-201). SPIE. Available at: https://doi.org/10.1117/12.2231754
10. The European Space Agency. (2025). GAIA: ESA's billion star surveyor. [Online]. Available at: https://www.esa.int/Science_Exploration/Space_Science/Gaia [Accessed on: April 15, 2025].
11. Max Planck Institute for Gravitational Physics (Albert Einstein Institute) (2025). Interferometry in Space: LISA.  Laser Interferometry and Gravitational Wave Astronomy. [Online]. Available at: https://www.aei.mpg.de/lisa [Accessed on: April 16, 2025].
12. Gurvits, L. et. al. (2022). The science case and challenges of space-borne sub-millimeter interferometry. Acta astronautica, 196, 314-333. Available at: https://doi.org/10.1016/j.actaastro.2022.04.020

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