The third version of the High Accuracy Radial velocity Planet Searcher (HARPS3) instrument is built for a ten-year programme aimed at achieving 10 cm/sec radial velocity precision on nearby stars to search for Earth-like planets. HARPS3 will be commissioned on the to-be-roboticized 2.54-m Isaac Newton Telescope at La Palma in 2021. One of the main changes compared to its predecessors is the novel dual-beam Cassegrain focus, featuring a stabilised beam feed into the HARPS3 spectrograph and an insertable polarimetric sub-unit. This polarimetric sub-unit enables HARPS3 to directly measure stellar activity signatures, which can be useful for correcting activity-induced radial velocity jitter in the search for Earth-like planets. The sub-unit consists of superachromatic polymer quarter- and half-wave retarders for circular and linear polarizations respectively, designed to suppress polarized fringing, and a novel polarimetric beam splitter based on a wire-grid design, separating the two polarimetric beams by 30 mm and feeding two separate science fibers. The dual-beam exchange implementation in combination with the extreme stability of the HARPS3 spectrograph enables a polarimetric sensitivity of 10−5 on bright stars. One of the main challenges of such a system is in the characterization of instrumental polarization effects which limit the polarimetric accuracy of the polarimetric observing mode. By design and characterization of this subsystem and by pre-emptively mitigating possible noise sources, we can minimize the noise characteristics of the polarization sub-unit to allow for precise observations. In this paper we report on the design, realization, assembly, alignment, and testing of the polarimetric unit to be installed in the Cassegrain Adaptor Unit of the HARPS3 spectrograph
Over the last two decades, Optical Search for Extra-Terrestrial Intelligence experiments have been conducted to search for either continuous or pulsed visible-light laser beacons that could be used for interstellar communication or energy transmission. Near-infrared offers a compelling window for signal transmission since there is a decrease in interstellar extinction and Galactic background compared to optical wavelengths. An innovative Near-InfraRed and Optical SETI (NIROSETI) instrument has been designed and constructed to take advantage of a new generation of fast (> 1 Ghz) low-noise near-infrared avalanche photodiodes to search for nanosecond pulsed near-infrared (850 - 1650 nm) pulses. The instrument was successfully installed and commissioned at the Nickel (1m) telescope at Lick Observatory in March 2015. We will describe the overall design of the instrument with a focus on methods developed for data acquisition and reduction for near-infrared SETI. Time and height analyses of the pulses produced by the detectors are performed to search for periodicity and coincidences in the signals. We will further discuss our NIROSETI survey plans.
We are designing and constructing a new SETI (Search for Extraterrestrial Intelligence) instrument to search for direct
evidence of interstellar communications via pulsed laser signals at near-infrared wavelengths. The new instrument
design builds upon our past optical SETI experiences, and is the first step toward a new, more versatile and sophisticated
generation of very fast optical and near-infrared pulse search devices. We present our instrumental design by giving an
overview of the opto-mechanical design, detector selection and characterization, signal processing, and integration
procedure. This project makes use of near-infrared (950 - 1650 nm) discrete amplification Avalanche Photodiodes
(APD) that have > 1 GHz bandwidths with low noise characteristics and moderate gain (~104). We have investigated the
use of single versus multiple detectors in our instrument (see Maire et al., this conference), and have optimized the
system to have both high sensitivity and low false coincidence rates. Our design is optimized for use behind a 1m
telescope and includes an optical camera for acquisition and guiding. A goal is to make our instrument relatively
economical and easy to duplicate. We describe our observational setup and our initial search strategies for SETI targets,
and for potential interesting compact astrophysical objects.