The Habitable-zone Planet Finder Calibration System

TL;DR

This paper describes the design of a highly stable wavelength calibration system for the Habitable-zone Planet Finder, aiming to enable precise radial velocity measurements for detecting Earth-like planets around M-dwarfs in the near-infrared.

Contribution

It introduces a novel calibration system combining laser frequency combs, Fabry-Perot interferometers, and other technologies to achieve unprecedented precision in NIR spectrograph calibration.

Findings

Demonstrated performance gains over previous calibration systems

Successfully tested components in laboratory settings

Achieved stability suitable for 1 m/s RV measurement precision

Abstract

We present the design concept of the wavelength calibration system for the Habitable-zone Planet Finder instrument (HPF), a precision radial velocity (RV) spectrograph designed to detect terrestrial-mass planets around M-dwarfs. HPF is a stabilized, fiber-fed, R$\sim$50,000 spectrograph operating in the near-infrared (NIR) z/Y/J bands from 0.84 to 1.3 microns. For HPF to achieve 1 m s$^{-1}$ or better measurement precision, a unique calibration system, stable to several times better precision, will be needed to accurately remove instrumental effects at an unprecedented level in the NIR. The primary wavelength calibration source is a laser frequency comb (LFC), currently in development at NIST Boulder, discussed separately in these proceedings. The LFC will be supplemented by a stabilized single-mode fiber Fabry-Perot interferometer reference source and Uranium-Neon lamp. The HPF calibration system will combine several other new technologies developed by the Penn State Optical-Infrared instrumentation group to improve RV measurement precision including a dynamic optical coupling system that significantly reduces modal noise effects. Each component has been thoroughly tested in the laboratory and has demonstrated significant performance gains over previous NIR calibration systems.