Speckle Space-Time Covariance in High-Contrast Imaging

We introduce a new framework for point-spread function (PSF) subtraction based on the spatio-temporal variation of speckle noise in high-contrast imaging data where the sampling timescale is faster than the speckle evolution timescale. One way that space-time covariance arises in the pupil is as atmospheric layers translate across the telescope aperture and create small, time-varying perturbations in the phase of the incoming wavefront. The propagation of this field to the focal plane preserves some of that space-time covariance. To utilize this covariance, our new approach uses a Karhunen-Lo\'eve transform on an image sequence, as opposed to a set of single reference images as in previous applications of Karhunen-Lo\'eve Image Processing (KLIP) for high-contrast imaging. With the recent development of photon-counting detectors, such as microwave kinetic inductance detectors (MKIDs), this technique now has the potential to improve contrast when used as a post-processing step. Preliminary testing on simulated data shows this technique can improve contrast by at least 10-20% from the original image, with significant potential for further improvement. For certain choices of parameters, this algorithm may provide larger contrast gains than spatial-only KLIP.Comment: Accepted to A

The MKID Exoplanet Camera for Subaru SCExAO

We present the MKID Exoplanet Camera (MEC), a z through J band (800 - 1400 nm) integral field spectrograph located behind The Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) at the Subaru Telescope on Maunakea that utilizes Microwave Kinetic Inductance Detectors (MKIDs) as the enabling technology for high contrast imaging. MEC is the first permanently deployed near-infrared MKID instrument and is designed to operate both as an IFU, and as a focal plane wavefront sensor in a multi-kHz feedback loop with SCExAO. The read noise free, fast time domain information attainable by MKIDs allows for the direct probing of fast speckle fluctuations that currently limit the performance of most high contrast imaging systems on the ground and will help MEC achieve its ultimate goal of reaching contrasts of $10^{-7}$ at 2$\lambda / D$. Here we outline the instrument details of MEC including the hardware, firmware, and data reduction and analysis pipeline. We then discuss MEC's current on-sky performance and end with future upgrades and plans.Comment: To be published in Publications of the Astronomical Society of the Pacifi

Optical and Near-IR Microwave Kinetic Inductance Detectors (MKIDs) in the 2020s

Optical and near-IR Microwave Kinetic Inductance Detectors, or MKIDs, are superconducting photon counting detectors capable of measuring the energy and arrival time of individual OIR photons without read noise or dark current. In this whitepaper we will discuss the current status of OIR MKIDs and MKID-based instruments.Comment: Astro2020 APC Whitepaper. 16 pages, 10 figure

MKID Exoplanet Camera for Subaru SCExAO

We present the MKID Exoplanet Camera (MEC), a z through J band (800–1400 nm) integral field spectrograph located behind The Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) at the Subaru Telescope on Maunakea that utilizes Microwave Kinetic Inductance Detectors (MKIDs) as the enabling technology for high contrast imaging. MEC is the first permanently deployed near-infrared MKID instrument and is designed to operate both as an IFU, and as a focal plane wavefront sensor in a multi-kHz feedback loop with SCExAO. The read noise free, fast time domain information attainable by MKIDs allows for the direct probing of fast speckle fluctuations that currently limit the performance of most high contrast imaging systems on the ground and will help MEC achieve its ultimate goal of reaching contrasts of 10⁻⁷ at 2 λ/D. Here we outline the instrument details of MEC including the hardware, firmware, and data reduction and analysis pipeline. We then discuss MEC's current on-sky performance and end with future upgrades and plans

DARKNESS: A Microwave Kinetic Inductance Detector Integral Field Spectrograph for High-Contrast Astronomy

We present DARKNESS (the DARK-speckle Near-infrared Energy-resolving Superconducting Spectrophotometer), the first of several planned integral field spectrographs to use optical/near-infrared Microwave Kinetic Inductance Detectors (MKIDs) for high-contrast imaging. The photon counting and simultaneous low-resolution spectroscopy provided by MKIDs will enable real-time speckle control techniques and post-processing speckle suppression at framerates capable of resolving the atmospheric speckles that currently limit high-contrast imaging from the ground. DARKNESS is now operational behind the PALM-3000 extreme adaptive optics system and the Stellar Double Coronagraph at Palomar Observatory. Here we describe the motivation, design, and characterization of the instrument, early on-sky results, and future prospects.Comment: 17 pages, 17 figures. PASP Publishe

DARKNESS: A Microwave Kinetic Inductance Detector Integral Field Spectrograph for High-contrast Astronomy

We present DARKNESS (the DARK-speckle Near-infrared Energy-resolving Superconducting Spectrophotometer), the first of several planned integral field spectrographs to use optical/near-infrared Microwave Kinetic Inductance Detectors (MKIDs) for high-contrast imaging. The photon counting and simultaneous low-resolution spectroscopy provided by MKIDs will enable real-time speckle control techniques and post-processing speckle suppression at frame rates capable of resolving the atmospheric speckles that currently limit high-contrast imaging from the ground. DARKNESS is now operational behind the PALM-3000 extreme adaptive optics system and the Stellar Double Coronagraph at Palomar Observatory. Here, we describe the motivation, design, and characterization of the instrument, early on-sky results, and future prospects

Development of MKID Instrumentation for exoplanet direct imaging

Microwave Kinetic Inductance Detectors (MKIDs) are a highly sensitive cryogenic photodetector. These devices operate by measuring the increase in the surface impedance of a superconducting film when Cooper Pairs are broken by incident photons. This technique allows MKIDs inherent spectral resolution and instantaneous read out with essentially no false counts. In contrast to other cryogenic detectors, the intrinsic multiplexing of the pixels in frequency domain means that arrays of several tens of thousand of pixels can be readout with just a few feed-lines using room temperature radio electronics. These unique properties make MKIDs potentially transformative for exoplanet direct imaging, where residual speckle noise currently limits the minimum mass of the discernible exoplanets to several Jupiter masses. In this thesis I describe some of the developments of MKID instruments required for exoplanet imaging, and I investigate the potential of MKIDs to provide new discoveries in this field. One of the required developments was the automation of the tuning of pixel biasing prior to taking a set of observations. Previously this required inspecting the transmission profile of each pixel by eye and then selecting the optimal power. For the large format arrays necessary for exoplanet direct imaging (on the order of tens of thousand pixels) this process can take approximately 24 human hours to complete. I show that a machine learning-based algorithm can replicate this process in a matter of minutes with equivalent accuracy to that of humans when compared to a control dataset. I then discuss an extension to this algorithm that should enhance the phase measurement performance of MKIDs, ultimately improving the limiting mass of detected exoplanets. Simulation software was developed to make pragmatic predictions on the capabilities of MKIDs for exoplanet direct imaging. This software demonstrates the utility of Dark-Speckle Imaging discrimination technique for a realistic MKID device with appropriate limitations such as maximum count and reduced pixel yield. Possible extensions to this technique that exploit the wavelength dependence of speckles are also explored, which are found to yield superior performance to standard differential imaging methods. I also make predictions on the performance of a next generation MKID-based instrument systems. Preliminary results show that this system can achieve the contrast performance necessary for Neptune sized exoplanets and below. Finally, I present on-sky results of planetary nebula NGC 6751 taken with the ARCONS MKID instrument at Palomar. The inherent spectral resolution of the device meant that a low resolution spectrum of the central star could be created that provided further evidence to clarify its spectral type. The central star was also explored in the time domain at the fine resolution of MKIDs. No periodic feature was found on the time scale of the observation