Ultra-stable temperature and pressure control for the Habitable-zone Planet Finder spectrograph

We present recent long-term stability test results of the cryogenic Environmental Control System (ECS) for the Habitable zone Planet Finder (HPF), a near infrared ultra-stable spectrograph operating at 180 Kelvin. Exquisite temperature and pressure stability is required for high precision radial velocity ( -7 Torr over months.