JWST: A Midnight Sun for Planetary Astronomers?

We present preliminary results from an ongoing project to assess whether or not the sun shield on JWST may serve as a practical solar calibrator source for ground-based spectroscopic observations of solar system objects. Although this idea may seem wild at first, various aspects of JWST's construction, orbit, and operation conspire to provide an always-visible, high-fidelity solar spectrum at roughly 16th magnitude, which is readily accessible to spectrographs on larger telescopes. We have conducted a multi-epoch observing campaign with SpeX (Rayner et al. 2003) at the NASA Infrared Telescope Facility to obtain low-resolution 0.7-2.5 micron spectra of JWST for direct comparison to contemporary spectra of solar twin calibrator stars (e.g. Ramírez et al. 2014) and main belt asteroids with well characterised reflectance spectra in the SMASS/MITHNEOS catalog (Binzel et al. 2001; Burbine & Binzel 2002). By analysing detections of JWST in survey data from the Asteroid Terrestrial-impact Last Alert System (ATLAS; Tonry et al. 2018), and by imaging it with IO:O at the Liverpool Telescope (Steele et al. 2004; Barnsley et al. 2016), we also place constraints on the variation of its visible brightness. Alongside our up-to-date analysis of JWST’s brightness variation we present a preliminary assessment of our attempts to use its reflectance spectrum to obtain an accurate and useful solar calibration spectrum. Finally, we outline our future plans for this project.

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