Instrumentation

I have been involved in three major instrumentation projects at NRC Herzberg: SPIDERS (the Subaru Pathfinder Instrument for Detecting Exoplanets and Retrieving Spectra), the Gemini Planet Imager 2.0 / CAL2 upgrade, and NRC's optical aperture synthesis project.

SPIDERS has now been deployed at the Subaru Telescope.

SPIDERS is pictured in the image below, during final assembly and testing at NRC HAA's integration facility:

Photo credit: Olivier Lardière.

Focal Plane Wavefront Sensing

Focal plane wavefront sensing refers to any technique that measures the electric field of light at the science focal plane. This kind of approach is critically important for the next generation of direct imaging instruments, because it allows us to measure and suppress stellar glare, also known as "speckles".

In SPIDERS, we will demonstrate the Fast Atmospheric Self-Coherent Camera Technique (Gerard et al 2019). With the FAST SCC, we turn the science camera into an interferometer. Instead of simply blocking starlight with a coronagraph, we redirect it, filter it, and interfere it back with itself.

The upshot is that our science images become fringed anywhere light leaks past the coronagraph. Planets and disks, being incoherent with the star, remain unfringed, allowing us to instantly discriminate between planet light and starlight.

Using a deformable mirror and techniques from adaptive optics, we can use this information to perform an active correction and create a region around the star where the starlight has been dramatically suppressed—a.k.a. "digging a dark hole":

Coherent Differential Imaging

In addition to active correction, we can use the self-coherent camera to post-process our data and reveal even fainter planets. This software step can be combined with the hardware loop described above to further suppress stubborn speckles.

Fourier Transform Spectroscopy

Using spectral information to help discriminate planet light from starlight has a long history. Unfortunately, it has often not lived up to expectations. Real data from instruments like GPI, SPHERE, and SCExAO reveals that low-resolution integral field units give datacubes in which speckles evolve considerably with wavelength.

To better understand chromaticity in high contrast instruments, to try to improve on current performance, and to combine spectroscopy with the self-coherent camera, I proposed and helped to build an Imaging Fourier Transform Spectrograph (IFTS) for the SPIDERS instrument.

The SPIDERS IFTS will be capable of imaging exoplanets with a spectral resolution of over R = 15,000. Preliminary results show a factor of 40-50 starlight suppression may be possible using spectral differential imaging with this instrument. A collapsed cube is visible in the image below:

What's next: GPI 2.0 and the Habitable Worlds Observatory

SPIDERS is a pathfinder. The same focal-plane wavefront sensing approach is being built into CAL2, NRC's contribution to the GPI 2.0 upgrade of the Gemini Planet Imager at Gemini North. GPI 2.0 will be a powerful tool for imaging planets found by Gaia.

Looking further ahead, techniques like the self-coherent camera and coherent differential imaging are relevant to NASA's Habitable Worlds Observatory, which aims to image Earth-like planets around nearby stars. Through NRC's NEW-EARTH Lab, we are developing wavefront sensing and control methods with that goal in mind.

The real-time software behind SPIDERS is open source and written in Julia; see the Software page.

Last updated October 2026

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