Uploaded April 2025 | Updated September 2026, 3 weeks ago
Jayke Nguyen is part of the 2025 NASA ExoExplorers cohort, a program that aims to enable the professional development of graduate students and/or postdocs in exoplanet research (“ExoExplorers”).
The ExoExplorers program, sponsored by NASA’s Exoplanet Exploration Program Office and the ExoPAG Executive Committee, will focus on the professional development of ~10 graduate student and/or postdoc researchers (“ExoExplorers”) at US and international institutions. Each member of the cohort will be featured in a webinar that will be live-streamed to the exoplanet community, helping to increase their visibility within the field and build internal and external research networks. The cohort will also learn from the experiences of established exoplanet researchers and engineers in the field (“ExoGuides”) via a combination of tailored presentations and small group discussions.
Talk title: Improving Direct Imaging of Exoplanets in Ground-based Mid-IR Observations
Abstract: Mid-IR wavelengths are of particular interest to exoplanet science due to the fact they access the strongly-absorbing and well-understood CO ro-vibronic mode at ~4.6 microns. However, a significant source of uncertainty at mid-IR wavelengths is the thermal background present in ground-based observations. This background comes from blackbody radiation in the atmosphere and telescope and is therefore dependent on instrument design and atmospheric conditions. When performing imaging observations, this background manifests as a slowly varying inhomogeneous signal throughout the image, underlying our data. Using an M-band direct imaging observing sequence on NIRC2, we evaluate the thermal background of the Keck II telescope. The usage of 10-m class ground-based telescopes such as Keck are necessary since we typically require high angular resolution to image close-in exoplanets. Photometry at mid-IR can greatly constrain atmospheric models but existing data is usually scarce or has significant error bars due to the difficulty of subtracting the background. This work largely aims to improve photometric error in mid-IR data by reducing systematics. We present results that improve thermal background subtraction by factoring in the systematic background component of the de-rotator. We typically are able to image exoplanets ~12.5 magnitudes fainter than the host star at M-band, and by factoring in the thermal contribution of the de-rotator, we improve our contrast and sensitivity by a factor of ~2-4. Future on-sky and engineering observations using NIRC2 will test new strategies that minimize the telescope contribution to the thermal background and we will further evaluate the thermal background environment of the telescope. Beyond NIRC2, these results also have important implications for the impact of telescope design and how to treat systematics when performing data reduction and analysis.
Jayke Nguyen is part of the 2025 NASA ExoExplorers cohort, a program that aims to enable the professional development of graduate students and/or postdocs in exoplanet research (“ExoExplorers”).
The ExoExplorers program, sponsored by NASA’s Exoplanet Exploration Program Office and the ExoPAG Executive Committee, will focus on the professional development of ~10 graduate student and/or postdoc researchers (“ExoExplorers”) at US and international institutions. Each member of the cohort will be featured in a webinar that will be live-streamed to the exoplanet community, helping to increase their visibility within the field and build internal and external research networks. The cohort will also learn from the experiences of established exoplanet researchers and engineers in the field (“ExoGuides”) via a combination of tailored presentations and small group discussions.
Talk title: Improving Direct Imaging of Exoplanets in Ground-based Mid-IR Observations
Abstract: Mid-IR wavelengths are of particular interest to exoplanet science due to the fact they access the strongly-absorbing and well-understood CO ro-vibronic mode at ~4.6 microns. However, a significant source of uncertainty at mid-IR wavelengths is the thermal background present in ground-based observations. This background comes from blackbody radiation in the atmosphere and telescope and is therefore dependent on instrument design and atmospheric conditions. When performing imaging observations, this background manifests as a slowly varying inhomogeneous signal throughout the image, underlying our data. Using an M-band direct imaging observing sequence on NIRC2, we evaluate the thermal background of the Keck II telescope. The usage of 10-m class ground-based telescopes such as Keck are necessary since we typically require high angular resolution to image close-in exoplanets. Photometry at mid-IR can greatly constrain atmospheric models but existing data is usually scarce or has significant error bars due to the difficulty of subtracting the background. This work largely aims to improve photometric error in mid-IR data by reducing systematics. We present results that improve thermal background subtraction by factoring in the systematic background component of the de-rotator. We typically are able to image exoplanets ~12.5 magnitudes fainter than the host star at M-band, and by factoring in the thermal contribution of the de-rotator, we improve our contrast and sensitivity by a factor of ~2-4. Future on-sky and engineering observations using NIRC2 will test new strategies that minimize the telescope contribution to the thermal background and we will further evaluate the thermal background environment of the telescope. Beyond NIRC2, these results also have important implications for the impact of telescope design and how to treat systematics when performing data reduction and analysis.
