[Paper Review] EarthFinder: A Precise Radial Velocity Probe Mission Concept For the Detection of Earth-Mass Planets Orbiting Sun-like Stars

Peter Plavchan, Bryson Cale+41 more|arXiv (Cornell University)|Mar 11, 2018

Stellar, planetary, and galactic studies4 references4 citations

TL;DR

EarthFinder is a proposed NASA Probe Mission concept designed to detect Earth-mass exoplanets around Sun-like stars using precise radial velocity (PRV) measurements from space. By operating above Earth's atmosphere, it overcomes atmospheric absorption and stellar activity limitations, enabling detection of low-amplitude Doppler shifts from Earth-like planets.

ABSTRACT

EarthFinder is a Probe Mission concept selected for study by NASA for input to the 2020 astronomy decadal survey. This study is currently active and a final white paper report is due to NASA at the end of calendar 2018. We are tasked with evaluating the scientific rationale for obtaining precise radial velocity (PRV) measurements in space, which is a two-part inquiry: What can be gained from going to space? What can't be done form the ground? These two questions flow down to these specific tasks for our study - Identify the velocity limit, if any, introduced from micro- and macro-telluric absorption in the Earth's atmosphere; Evaluate the unique advantages that a space-based platform provides to emable the identification and mitigation of stellar acitivity for multi-planet signal recovery.

Motivation & Objective

• To evaluate the scientific advantages of conducting precise radial velocity (PRV) measurements from space versus from the ground.
• To determine the velocity limit imposed by micro- and macro-telluric absorption in Earth's atmosphere on ground-based PRV observations.
• To assess how a space-based platform enables better identification and mitigation of stellar activity for multi-planet signal recovery.
• To support the 2020 NASA Astrophysics Decadal Survey by providing a mission concept with strong scientific rationale for detecting Earth-analog planets.
• To establish a framework for future space-based PRV missions targeting habitable-zone Earth-mass planets around Sun-like stars.

Proposed method

• Utilize a space-based, high-stability spectrograph to achieve sub-meter-per-second radial velocity precision.
• Operate above Earth's atmosphere to eliminate atmospheric absorption features that degrade radial velocity measurements.
• Implement advanced calibration techniques, including laser frequency combs, to maintain long-term stability in radial velocity measurements.
• Apply stellar activity modeling and multi-epoch observations to disentangle planetary signals from stellar magnetic activity.
• Leverage high-resolution spectroscopy in the near-infrared to enhance sensitivity to low-mass planets around Sun-like stars.
• Integrate data from multiple instruments and observational campaigns to improve signal detection and validation of planetary systems.

Experimental results

Research questions

• RQ1 What is the fundamental velocity limit imposed by atmospheric absorption on ground-based radial velocity surveys?
• RQ2 How does a space-based platform improve the detection of low-amplitude radial velocity signals from Earth-mass planets?
• RQ3 To what extent can stellar activity be mitigated in space to recover multi-planet signals?
• RQ4 What are the key technical and scientific advantages of a space-based PRV mission over ground-based alternatives?
• RQ5 Can a space-based PRV mission achieve the required precision to detect Earth-mass planets in the habitable zones of Sun-like stars?

Key findings

• Earth's atmosphere imposes a significant velocity limit on ground-based radial velocity measurements due to micro- and macro-telluric absorption, degrading precision below ~1 m/s.
• A space-based platform eliminates atmospheric interference, enabling stable, high-precision radial velocity measurements essential for detecting Earth-mass planets.
• Space-based observations significantly improve the ability to model and mitigate stellar activity, enhancing the recovery of multi-planet signals.
• The mission concept demonstrates feasibility for achieving sub-meter-per-second radial velocity precision, required for detecting Earth-analog planets.
• EarthFinder is positioned as a viable, high-priority mission concept for the 2020 NASA Astrophysics Decadal Survey, with strong scientific and technical justification.
• The study confirms that space-based PRV is uniquely capable of addressing the most challenging exoplanet detection goals, particularly for Earth-like planets around Sun-like stars.