The NIROSETI project is based on the assumption that hypothetical communicative extraterrestrials may send out pulsed laser signals in the optical, as well as infrared spectrum. Near-infrared offers a possible way for signal transmission since there is a decrease in both interstellar extinction and Galactic background compared to optical wavelengths.[4][5] The near-infrared bands remain largely unexplored because instruments capable of capturing short pulses of infrared light have only recently become available.[5][6]
The NIROSETI instrument makes use of the 1-meter optical Nickel telescope located at the Lick Observatory in California to search for near-infrared (laser) transmissions from extraterrestrial communication or technosignatures. This project was funded by the Bill and Susan Bloomfield Foundation and is based upon a predecessor called Lick Optical SETI instrument, conducted between 2001 and 2006.[4][5] Professor Shelley Wright leads the team that built and operates the NIROSETI program.[7]
The NIROSETI instrument employs a new generation of near-infrared (900 to 1700 nm) detectors, cooled at -25 °C, that have a high speed response (>1 GHz) and gain comparable to photomultiplier tubes, while also producing very low noise,[2][5] and significantly reducing false positives.[4] Its field-of-view is 2.5"x2.5" each,[8] and focuses
on detecting short (nanosecond) pulsed laser emissions. The NIROSETI instrument is also being used to study variability of very short natural near-infrared transient stars.[2][6]
Targets
The NIROSETI survey has been designed for observing several thousand objects over a few years, and commenced full operations on 28 January 2016. During a clear night of observations, about 20 to 30 objects are observed.[4] Because infrared light penetrates farther through gas and dust than visible light, this search will extend to stars thousands of light-years away.[6] The initial target sample is mostly main-sequence and giant stars located within 50 parsecs from Earth, drawn from the Breakthrough Listen program target list.[4][9][10]
The sample of targets also includes 82 galaxies for being the nearest representatives of the five major morphological classes of galaxies (20 spirals, 36 ellipticals, 15 dwarf spheroidals, 9 irregulars, and 2 lenticular galaxies),[4] as well as stars that triggered alarms on other targeted SETI surveys.[4]
A significant drawback is that the extraterrestrial laser signals would need to be transmitted in the direction of the Solar System in order to be detected.[6]