Laser SETI

Terrestrial Microwave Window

LaserSETI is an optical instrument designed to observe "all of the sky, all of the time" in search for laser pulses originating outside of our solar system. LaserSETI could give evidence of intelligent life beyond Earth as it searches for techno-signatures in the form of these laser pulses or high intensity monochromatic light sources. While the LaserSETI network of observatories is still in construction as of 2024, strategic placement of the current and future observatories will lend the network its capability for all-sky monitoring once it is complete. The technology, which consists of a robust assembly of straightforward optical and mechanical components, was prototyped and subjected to rigorous preliminary tests before the first light.

Slit-less spectroscopy is used by LaserSETI instruments to detect monochromatic light and is especially effective to distinguish monochromatic signals from other bright objects in the sky such as sunlight or airplane strobes. Much like a prism receives white light and splits it into a rainbow spectrum of light (because different colors of light bend at different angles), the gratings on the instrument smear the light spectrally, allowing the lens to then focus the light, and a camera to measure the result.  Monochromatic light only bends at one angle, remaining a single beam as it passes through the grating, resulting in a much more compact visual signature. In this way, LaserSETI instruments are capable of distinguishing man-made optical signals from those originating as techno-signatures, as there are no currently known natural sources which create monochromatic optical signals.

With consistent all-sky monitoring, even relatively rare events could be found via LaserSETI monitoring. LaserSETI can discover pulses over a wide range of pulse durations, and is especially sensitive to millisecond singleton pulses which may have been overlooked in previous astronomical surveys.

History

LaserSETI started in 2015 as a program of the SETI Institute, though the official name was not made public until 2016. Founded by Eliot Gillum, the project began with a small team dedicated to the design, math and science of initial prototypes. In August 2017, the crowdfunding goal of $100k was reached, which the team used to initially deploy one camera to measure the statistics of the sky. By October of the same year, the team had spent approximately $50k with 21 components in hand, 5 on order or in transit, 3 ready to order, and 7 waiting on test results or TBD.

In 2018, the first two cameras were manufactured. This same year, the SETI Institute announced that they were going to be able to deploy 8 cameras instead of four, meaning that they could fully monitor two independent fields-of-view.

In 2019, the entity announced that the final logistics were being worked out for the placement of LaserSETI's first observatory at RFO's (Robert Ferguson Observatory) idyllic facility, in Sonoma County. By August 6th of 2019, the installation at RFO was complete and LaserSETI had its first light.

The LaserSETI observatory at Robert Ferguson Observatory in California. Credit: Eliot Gillum

In August 2021, a second LaserSETI station was installed at the Haleakalā High Altitude Observatory Site in Hawai'i, which is owned and operated by Institute for Astronomy of the University of Hawai’i. This second LaserSETI observatory was operational by Dec 2021.

As of 2024, two new LaserSETI stations are slated for installation in Sedona, Arizona. Nine more observatories are currently under construction.

Note that cameras are installed in pairs with their diffraction gratings at 90 degrees to each other. Images are read out more than a thousand times a second.

LaserSETI Instruments

Each LaserSETI instrument is made up of two wide-field, highly sensitive large format CCD cameras fitted with 24mm SLR lenses, attached to an optical transmission grating, and set within a sturdy 3D printed weather-durable frame with Pyrex windows. Residing at the base of the instrument is a PC to implement data reduction from the high-speed data from the cameras, and a hard drive to store the raw data. A second computer at the top of the instrument supplies GPS capabilities for precise clocking as well as a gyrometer and accelerometer to measure any vibration in the system to help avoid error, and an internal camera providing monitoring capabilities of the instrument itself. The components are cost effective for this level of “all sky, all the time” technology since most are COTS (commercial-off-the-shelf), with only the transmission grating and stainless steel enclosure being custom made.