Requirements for Joint Orbital Characterization of Cold Giants and Habitable Worlds with Habitable Worlds Observatory

TL;DR

This paper establishes the technical requirements for the Habitable Worlds Observatory to effectively detect and characterize habitable planets and cold giants, emphasizing the importance of specific observational parameters.

Contribution

It provides a detailed analysis of observational requirements, including coronagraph design, radial velocity precursor data, and astrometric measurements, to optimize joint detection and characterization of exoplanets.

Findings

A coronagraph OWA of 1440 mas is needed for 80-90% cold giant detection.

Approximately 40 radial velocity measurements with 1 m/s precision are required beforehand.

6-8 astrometric measurements significantly improve orbital parameter accuracy.

Abstract

We determine optimal requirements for the joint detection of habitable-zone planets and cold giant planets with the Habitable Worlds Observatory (HWO). Analysis of 164 nearby stars shows that a coronagraph outer working angle (OWA) of 1440 milliarcseconds (mas) is necessary to achieve 80-90% visibility of cold giants. Approximately 40 precursor radial velocity measurements with 1 m/s precision are required to adequately constrain orbital parameters before HWO observations. We demonstrate that 6-8 astrometric measurements distributed across the mission timeline, compared to radial velocity constraints alone and to astrometry constraints alone, significantly improve orbital parameter precision, enabling direct determination of orbital inclination with uncertainties of 0.8-3 degrees. For habitable-zone planet characterization, 4-5 epochs provide moderate confidence, while high-confidence (95%) confirmation requires 8+ observations. These specifications are essential for the comprehensive characterization of planetary system architectures and understanding the potential habitability of terrestrial exoplanets.