PEAS: the PLANET AS EXOPLANET ANALOG SPECTROGRAPH. E. C. Martin1 and A

Exoplanets in our Backyard 2020 (LPI Contrib. No. 2195) 3006.pdf

PEAS: THE PLANET AS EXOPLANET ANALOG SPECTROGRAPH. E. C. Martin1 and A. J. Skemer1, 1Department of Astronomy & Astrophysics, University of California, Santa Cruz, CA ([email protected])

Introduction: Exoplanets are abundant in our galaxy • Produce 2D surface maps of Venus, Mars, Jupi- and yet characterizing them remains a technical chal- ter, Saturn, Uranus, Neptune lenge. Solar System planets provide an opportunity to • Produce fiducial measurements that will be used test the practical limitations of exoplanet observations to plan instruments for future exoplanet mis- with high signal-to-noise data, and ancillary data (such sions, such as HabEx/LUVOIR and TMT. as 2D maps and in situ measurements) that we cannot Long term: access for exoplanets. However, data on Solar System • Time-series observations of Solar System plan- planets differ from exoplanets in that Solar System ets to explore variability and weather patterns planets are spatially resolved while exoplanets are all on planets unresolved point-sources. • Comparison to historical data (e.g. [4]) There have been several recent efforts to validate techniques for interpreting exoplanet observations by • Study planetary seismology (oscillation modes) binning images of Solar System planets to a single of Solar System planets pixel: For example, Cowan et al. [1] used images from the EPOXI mission to study Earth’s globally averaged PEAS Instrument Design Planetary light collect- properties as it rotated; Mayorga et al. [2] used data ed by the telescope will be split into a spectrograph from the Cassini spacecraft’s fly-by of Jupiter to ob- system and an imaging system for simultaneous obser- serve globally averaged reflected light phase curves; vations. Our innovative approach uses an integrating and Karalidi et al. [3] imaged Jupiter with the Hubble sphere to turn the spatially-resolved planet light into Space Telescope in the UV and red-optical as a test of disk-integrated light before it is dispersed inside a fi- their methods for determining spot size and location on ber-fed spectrograph. The modular design allows for exoplanet atmospheres. However, there is a dearth of easy changes to the spectrograph and imaging systems disk-integrated spectra of Solar System planets from as we iterate on the observational and analysis tech- modern equipment. niques. For example, we can swap out the beam split- We present a novel instrument designed to ob- ter, fiber optic cable, spectrograph, and imaging cam- serve Solar System planets as though they are exoplan- era, to optimize observations in different wavelength ets, the Planet as Exoplanet Analog Spectrograph ranges and resolving powers. We will continuously (PEAS). PEAS consists of a dedicated 0.5-m modify the instrument to perform new experiments as PlaneWave Telescope and off-the-shelf optics, which we work to achieve a comprehensive understanding of will be located at Lick Observatory. PEAS uses an the optimal observational and analysis combinations. integrating sphere to disk-integrate light from the Solar Continuous feedback between the instrument configu- System planets before it is dispersed in a fiber-fed rations, observations, and theoretical interpretations spectrograph, producing spatially mixed light more will be critical for determining which combination of similar to the spectra we can obtain from exoplanets. observations and theoretical interpretations produce PEAS will obtain optical and infrared spectra and imaging of Solar System planets, which will then be ana- accurate depictions of our Solar System planets. lyzed using exoplanet modeling tools, in order to validate and test those tools. Here we describe the science goals and general system design of the PEAS instrument.

Science Goals: Short term: • Produce an atlas of Solar System planet spectra and images observed by PEAS to serve as comparison to ground-truth observations from space missions • Measure atmospheric compositions and trace el- emental abundances, compared to in situ or fly- by measurements of Solar System planets

Figure 1. PEAS instrument layout Exoplanets in our Backyard 2020 (LPI Contrib. No. 2195) 3006.pdf

References: [1] N. B. Cowan, et al. (2009) ApJ, 700, 915–923. [2] L. C. Mayorga, et al. (2016) AJ, 152, 209–220. [3] T. Karalidi, et al. (2015) ApJ, 814, 65–82. [4] F. C. Gillett et al. (1969) ApJ, 157, 925– 934.