Advancements and Challenges in Time-Delay Interferometry for Space-Based Gravitational Wave Detection

Time-Delay Interferometry (TDI) is a cornerstone technique for space-based gravitational wave detection, primarily designed to suppress laser frequency noise that would otherwise mask the extremely weak signals of gravitational waves. Since no local strain reference has yet achieved the precision required for direct detection, interferometry remains the most viable measurement approach.

In space-based detectors, light must propagate over millions of kilometers, requiring the combination of long-baseline interferometry and weak-light phase-locking amplification. The intrinsic laser frequency noise imposes stringent constraints: the optical path lengths of the interferometer arms must be matched to a precision comparable to the laser coherence length, or inversely proportional to the noise level.
TDI with weak-light phase-locking has emerged as a critical technique for gravitational wave detection in both the low-frequency (millihertz to microhertz) and mid-frequency (decihertz) bands. It enables the effective cancellation of laser frequency noise in unequal-arm interferometers.

This Research Topic aims to address the technical and theoretical challenges that remain in time-delay interferometry for space-based gravitational wave detection. These issues are crucial to enhancing the precision and robustness of TDI, thereby enabling future space-based gravitational wave observatories to reach their full scientific potential.

To gather further insights in the application and development of TDI technologies, we welcome articles addressing, but not limited to, the following themes:

• Integration of TDI with other advanced techniques, such as arm locking, optical frequency combs, ultra-stable reference cavities, etc.
• Novel designs or approaches to improve interferometric accuracy, including clock synchronization, precision ranging techniques, etc.
• Reduction or compensation of other limiting noises within the TDI framework, such as clock noise, tilt-to-length coupling, pointing jitter, drag-free noise, etc.
• Investigation of new or previously underappreciated physical effects that may impact TDI performance and data interpretation
• Evaluation of TDI performance under realistic detector dynamics, including orbital motion, and the development of optimized TDI configurations and data pipelines to ensure robustness in operational missions
• Exploration of alternative TDI architectures or hybrid schemes tailored to specific mission profiles or detection goals
• Emerging technologies, novel concepts, and innovative approaches related to TDI that are not explicitly covered by the above categories.

We invite a range of article types, including Original Research, Review and Perspective, as part of the published collection of works on this topic to advance the theoretical understanding, algorithmic development, experimental validation, and mission-level integration of TDI and related technologies.

Article types and fees

This Research Topic accepts the following article types, unless otherwise specified in the Research Topic description:

• Brief Research Report
• Data Report
• Editorial
• FAIR² Data
• FAIR² DATA Direct Submission
• General Commentary
• Hypothesis and Theory
• Methods
• Mini Review
• ... View all formats

Articles that are accepted for publication by our external editors following rigorous peer review incur a publishing fee charged to Authors, institutions, or funders.

Article types

This Research Topic accepts the following article types, unless otherwise specified in the Research Topic description:

• Brief Research Report
• Data Report
• Editorial
• FAIR² Data
• FAIR² DATA Direct Submission
• General Commentary
• Hypothesis and Theory
• Methods
• Mini Review
• Opinion
• Original Research
• Perspective
• Review
• Study Protocol
• Technology and Code

Keywords: Time-Delay Interferometry, Gravitational Waves, space GW Detection, Extended Michelson Interferometry

Important note: All contributions to this Research Topic must be within the scope of the section and journal to which they are submitted, as defined in their mission statements. Frontiers reserves the right to guide an out-of-scope manuscript to a more suitable section or journal at any stage of peer review.