The PLANETS Telescope


The PLANETS Telescope is a pathfinder project for even more sophisticated instruments that will find life and civilizations on nearby exoplanets. The PLANETS telescope will be the world’s largest off-axis telescope (1.85 m) for night-time astrophysics and planetary science. The name is an acronym for,  Polarized Light from Atmospheres of Nearby ExtraTerrestrial Systems.

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The ExoLife Finder (ELF)

elf-telescopeThe ExoLife Finder, or ELF for short, will be the world’s first telescope to create surface maps of the nearby exoplanets, including Proxima b.

ELF is a “Colossus-lite” formed from a circular array of sixteen 5 meter mirrors. ELF uses the thin “printed-mirror” technology the Colossus telescope depends on, and image-domain phasing of each off-axis parabolic segment to create a single diffraction-limited image. ELF has a total diameter of about 40m and is large enough to begin a dedicated program of Rotational ExoPlanet Imaging.

The Colossus

colossus-telescopeThe Colossus Telescope will be the world-largest optical and infrared telescope optimized for detecting extrasolar life and extraterrestrial civilizations. It consists of 58 independent off-axis 8m telescopes which effectively merge telescope-interferometry concepts, yielding 74m diameter effective resolution.

The primary consists of 58x8m off-axis parabolic primaries. The secondary structure is less than 5m in diameter with 60 independent 0.5m optics. Thus, every primary is served by its own secondary which bring light into one Gregorian focus.

Each secondary mirror is illuminated by one primary mirror segment and becomes its steering and phasing element. In this way each beam is combined coherently at the Gregorian focus of the larger, two-axis tracking, primary parent optics without interferometer delay-lines.

This optical system achieves the full angular resolution of the parent while efficiently matching the “softness” of the mechanical structure to the atmospheric piston phase fluctuations.

The Colossus Array

colossus-arrayThe Colossus weighs so little and is scalable in size, making it possible to combine 10’s or 100’s of these building blocks into an optical system that can be 1 km or more across — ready for laser-propelling interstellar nano-craft to the nearest stars, over times shorter than a human lifetime.



coronagraph thumbnailAnother technique for suppressing scattered light from nearby bright sources is coronography. This image shows a simulation of a coronagraph mounted on a Keck-like segmented mirror telescope compared to a GMT-like telescope with a combination of 6 unobstructed off-axis mirrors.

The top row of the image shows the simulated wavefronts phase incident on the mirrors under normal atmospheric conditions. The coronagraph is efficient at suppressing the light from the central star, producing a “hole” in the middle of each image. However, the speckles formed at large angular separation are comparable to the intensity of the planet in the Keck-like design. The diffraction and scattering off the hexagonal segmented mirror edges produces a large scattered light background.

Adaptive Optics

Advanced adaptive optics technologyAdaptive optics can be used to suppress atmospheric distortion and scattering. The Planets group has experience with several types of adaptive optics in design, construction and use. By combining adaptive optics with other techniques, greater contrast enhancement and dynamic range are possible.

Off-Axis Design

Cutting edge off-axis telescope design

Off-axis systems are not asymmetric systems, they are decentered systems. They provide an inherently low scattered light design because there are no obstructions in the beam. There are a minimal number of scattered light sources. All mirrors can be robustly supported and articulated because of the easy access allowed by this design.

There are several myths about off-axis telescopes. They are more difficult to align, but are not inherently more “aberrated”. The telescope can be thought of as a section of a larger system where the full aperture is not illuminated. The blur in this system is only weakly dependent on the off-axis angle and the telescope will be entirely seeing limited.