Terra Hunting Experiment

The HARPS3 instrument is a fibre-fed, high resolution, high stability, echelle spectrograph. It will be installed on the 2.5m Isaac Newton Telescope in La Palma in the Canary Islands. The design is a close-copy of the very successful High Accuracy Radial-velocity Planet Searcher - HARPS and also the more recent HARPS-North; with some additional design heritage from ESPRESSO. HARPS3, like its predecessors, will be high resolution (R = 115,000) and via two optical fibres will provide simultaneous measurement of the science source and a spectral calibration source allowing accurate RV measurements to be made. The wavelength range is 380-690 nm; the blue limit allows the measurement of the Calcium H and K lines which are one of the indicators used to monitor the stellar activity cycle. HARPS3 will also have an integrated polarimeter enabling spectro-polarimetry studies.

During the design and build phase of the project we have also refurbished and upgraded the Isaac Newton Telecope (INT) to a robotic facility (completed in 2025). The Terra Hunting Experiment requires nightly sampling of our targets and the optimised flexible scheduling enabled by a robotic operation allows this to be efficiently executed. This new mode of operation also opens up a new domain for other community programmes that have may have time sensitive studies or require time-series measurements which require a specific sampling rate and any other programme that would benefit from a flexible or non-traditional allocation of observing time.

HARPS3 was delivered to the Isaac Newton Telescope on 23rd October 2025. There will be a phased programme of installation and commissioning that continues into 2026 before full operations commence.