From Newsgroup: rec.aviation.military

Here are ways to detect exoplanets. https://www.space.com/astronomy/exoplanets/nasa-just-found-a-planet-hiding-in-tess-spacecraft-data-all-thanks-to-einstein

And this is how to analyze their atmospheres. https://science.nasa.gov/mission/webb/science-overview/science-explainers/how-will-webb-study-exoplanets/

Gases that are transparent to visible light have identifiable "color" in the infrared light the Webb detects, that's why CO2 interacts with heat
radiation. to give the greenhouse effect. I received an NSF summer research grant to study infrared absorption as an undergrad in college.

Our upper atmosphere blocks what may be the most likely radio frequencies
for alien communication, below 30 megahertz, the frequencies we used
earliest and which can travel around the Earth to reach any other listener. They do that because they reflect off instead of passing through the ionosphere. Likewise the ionosphere reflects away radio signals from deep space.

I got my amateur radio license from a retired British radar wizard who had studied this reflection in detail at the Mitre Corporation. In return we students performed antenna maintenance at his well equipped home laboratory. https://en.wikipedia.org/wiki/Maximum_usable_frequency

This is a proposal to circumvent the practical difficulty of orbiting a huge parabolic dish antenna to accurately locate the sources of low frequency natural or alien transmissions, and reject radio noise from Earth that could conceal or be mistaken for them. https://www.nasa.gov/general/great-observatory-for-long-wavelengths-go-low/

"Humankind has never before seen the low frequency radio sky. ItrCOs hidden from ground-based telescopes by the Earths ionosphere and challenging to access from space with traditional missions because the long wavelengths involved (meter- to kilometer-scale) require infeasibly massive telescopes
to see clearly."

The small magnetic field antennas that make AM radio practical aren't sufficiently directional individually, but an array of them can be combined
by computer to simulate a single very large and highly directional antenna, the same way the brain uses two ears to locate the direction of sounds.

A Lagrange point is where the interaction of Earth's and the Sun's gravity combine to form a region where a spacecraft can follow the Earth's orbit around the sun at a reasonably accessible distance, like a dog on a long leash. The Webb telescope is at the one where the two gravities add to make the solar orbital period identical to the Earth's, though Webb is further
out. A spacecraft at or near one can maintain its position with minimal fuel expenditure for a long service life.

--- Synchronet 3.22a-Linux NewsLink 1.2