PROGRESS IN TWO RADIO SETI EXPERIMENTS: THE SEARCH FOR EXTRATERRESTRIAL RADIO EMISSION FROM NEARBY DEVELOPED INTELLIGENT POPULATIONS (SERENDIP) AT ARECIBO OBSERVATORY AND SETI IN THE KEPLER FIELD WITH THE GREEN BANK TELESCOPE

摘要

While the basic methodology of most electromagnetic searches for extraterrestrial intelligence have remained thesame during the last half century, the speed and sensitivity of current searches are many orders of magnitude greaterthan their predecessors. Modern digital electronics and effcient algorithms allow sub-Hz spectroscopy across GHzof bandwidth, with the ability to search the entire terrestrial microwave window for cosmic narrow band signals lessthan a decade away. The supporting astrophysics and biology underpinning the search for extraterrestrial life has alsomade great strides, as we are now in an era where we can say with scientific certainty that planets are the rule, ratherthan the exception, that the galaxy is teeming with biomolecules and water and that life can exist in extraordinarilyextreme environments.Here we present two experiments, currently underway, aimed at detecting intelligent extraterrestrial life via sensingradio emission from their advanced technology, the SERENDIP Sky Survey and Kepler SETI at the Green BankTelescope. The Search for Extraterrestrial Intelligence from Nearby Developed Intelligent Populations (SERENDIP)is being conducted in sky survey mode at Arecibo Observatory using the 21cm feed array "ALFA." The SERENDIPdigital instrumentation performs a 128 million point Fourier transform over a 200 MHz band between 1.3 and 1.5GHz in real time, and reports individual 1.67 Hz channels with an instantaneous power exceeding a user-set threshold.These data are analyzed offine for signals that are isolated and stationary on the celestial sphere. The Kepler SETIat the Green Bank Telescope experiment consists of a 24 hour survey of the 105 sq deg. Kepler spacecraft field,including both a raster scan of the full field and targeted observations of stars hosting potentially habitable planetcandidates. In this experiment we have recorded nearly 50TB of baseband voltage data between 1.1 and 1.9 GHz, andwe are currently conducting searches for a wide variety of signal types, including narrow-band signals and dispersedpulses.