A Versatile Technique to Enable Sub-Milli-Kelvin Instrument Stability for Precise Radial Velocity Measurements: Tests with the Habitable-Zone Planet Finder

Published

December 16, 2016

Author(s)

Ryan C. Terrien, Guomundur K. Stefansson, Fred Hearty, Paul Robertson, Suvrath Mahadevan, Tyler Anderson, Chad Bender, Matthew Nelson, Andrew Monson, Basil Blank, Samuel Halverson, Chuck Henderson, Lawrence Ramsey, Arpita Roy, Christian Schwab

Abstract

Insufficient instrument thermo-mechanical stability is one of the fundamental roadblocks for achieving 10 cm s⁻¹ Doppler radial velocity (RV) precision, the precision needed to detect Earth-twins orbiting Solar-type stars. Exquisite temperature and pressure stabilization is required for such measurements, as variations in temperature and pressure inside the spectrograph can easily induce systematic Doppler drifts orders of magnitude larger than the RV signals produced by such planets. Highly stabilized spectrographs allow us to better calibrate out instrumental drifts, thereby helping in distinguishing stellar activity from bona-fide planets. We present the design and performance of the Environmental Control System (ECS) for the Habitable-zone Planet Finder (HPF), a high-resolution (R=50,000) fiber-fed near infrared (NIR) spectrograph for the 10 m Hobby Eberly Telescope at McDonald Observatory. HPF will operate at 180 K, driven by the choice of an H2RG NIR detector array with a 1.7 υm cutoff. This ECS has demonstrated 0.6 mK RMS stability over 15 days at both 180 K and 300 K, and maintained high quality vacuum (−7 Torr) over months, during long-term stability tests conducted without a planned passive thermal enclosure surrounding the vacuum chamber. This control scheme is versatile and can be applied as a blueprint to stabilize future NIR and optical high precision Doppler instruments over a wide temperature range from ∼77 K to elevated room temperatures. For this reason, a similar ECS is being implemented to stabilize NEID, the NASA/NSF NN-EXPLORE spectrograph for the 3.5 m WIYN telescope at Kitt Peak, operating at 300 K. A full SolidWorks 3D-CAD model and a comprehensive parts list of the HPF ECS are included with this manuscript to facilitate the adaptation of this versatile environmental control scheme in the broader astronomical community.

Citation

The Astrophysical Journal

Pub Type

Journals

Keywords

spectrographs, techniques: radial velocities, techniques: spectroscopic

Citation

Terrien, R. , Stefansson, G. , Hearty, F. , Robertson, P. , Mahadevan, S. , Anderson, T. , Bender, C. , Nelson, M. , Monson, A. , Blank, B. , Halverson, S. , Henderson, C. , Ramsey, L. , Roy, A. and Schwab, C. (2016), A Versatile Technique to Enable Sub-Milli-Kelvin Instrument Stability for Precise Radial Velocity Measurements: Tests with the Habitable-Zone Planet Finder, The Astrophysical Journal (Accessed October 3, 2025)