Strategies for Maximizing Detection Rate in Radio SETI

Abstract

The Search for Extraterrestrial intelligence (SETI) is a scientific and cultural effort seeking evidence of intelligent life beyond earth. Radio SETI observes the radio spectrum for "technosignatures" that could be produced by an advanced ET society. This work models radio SETI as an end-to-end system, and focuses on narrow-band intentional transmissions. We look at strategies to maximize the expected number of detections per year (DPY) of search. Assuming that ET civilizations will be associated with star systems, we want to maximize the number of stars that may be observed at one time. Assuming a representative star density, this requires maximizing the search volume in a cone defined by the detection range and field of view (FOV). The parameter trades are modified from the case where one simply maximizes signal-to-noise ratio. Instead, a joint optimization between FOV and sensitivity is needed. Some implications: 1) Instead of focusing on the terrestrial microwave window of 1 − 10 GHz, frequencies below 1 GHz may be optimal for detection rate due to the larger field of view; 2) Arrays of smaller dishes should be favored compared to a single dish of equivalent area; 3) Aperture arrays are desirable due to their large potential FOV. Many radio telescopes under development will provide both high sensitivity and large FOV, and should offer much improved SETI detection rates. Still higher DPY is needed, however, to achieve results in reasonable time horizons, which should be possible by greatly expanding computation capability to the next-generation wide-FOV antenna arrays.

A search for technosignatures toward the Galactic Centre at 150 MHz

“…Overall, there is growing support for broadening the frequency range searched for technosignatures to lower frequencies. For example, Houston et al (2021) find that, according to several detection optimisation metrics, SETI surveys should be undertaken down into the hundreds of megahertz frequency range.…”

“…These searches of ∼400-600 square degrees, are some of the largest published surveys, although no candidate technosignature signals were detected above the detection limits. Both Garrett, Siemion, & van Cappellen (2017) and more recently Houston, Siemion, & Croft (2021) have discussed the benefits of using aperture arrays like MWA for efficiently completing an all-sky SETI survey. Houston et al (2021)…”

“…Both Garrett, Siemion, & van Cappellen (2017) and more recently Houston, Siemion, & Croft (2021) have discussed the benefits of using aperture arrays like MWA for efficiently completing an all-sky SETI survey. Houston et al (2021)…”

A Search for Technosignatures toward the Galactic Centre at 150 MHz

“…These searches of ∼400-600 square degrees, are some of the largest published surveys, although no candidate technosignature signals were detected above the detection limits. Both Garrett et al (2017) and more recently Houston et al (2021) have discussed the benefits of using aperture arrays like MWA for efficiently completing an all-sky SETI survey. Houston et al (2021) outlines strategies of SETI searches from past, present, and future and suggests that if a receiver and transmitter are aligned in "...space, time and frequency, with adequate receive power, a detection can occur."…”

“…Both Garrett et al (2017) and more recently Houston et al (2021) have discussed the benefits of using aperture arrays like MWA for efficiently completing an all-sky SETI survey. Houston et al (2021) outlines strategies of SETI searches from past, present, and future and suggests that if a receiver and transmitter are aligned in "...space, time and frequency, with adequate receive power, a detection can occur." They suggest that unless there is a compelling reason to only search stellar regions, wide-field searches of any signal of unknown origin are required.…”