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Explore Alliance Ambassadors - Robert Zellem

Explore Alliance Ambassador - Dr. Robert Zellem
NASA Jet Propulsion Laboratory - USA
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Dr. Robert Zellem is a distinguished exoplanet astronomer, dedicated to exploring the atmospheres of planets beyond our Solar System. He is affiliated with NASA's Jet Propulsion Laboratory, where he engages in both ground- and space-based observations of exoplanets. His work revolves around gaining insights into these alien worlds, and he plays a pivotal role in several significant projects.

One of his notable roles is as a member of the Nancy Grace Roman Space Telescope's Coronagraph Instrument (CGI) Project Science Team. The CGI instrument is designed for direct imaging of exoplanets, and Dr. Zellem leads the development of its Science Calibration Plan. Furthermore, he serves as the JPL Commissioning Lead for NESSI, a cutting-edge multi-object spectrograph located at Palomar Observatory. NESSI is designed to study numerous exoplanets, making it a crucial component of Dr. Zellem's research endeavors.

Dr. Zellem has a strong background in benchmarking mission performance through simulations, contributing to missions like CASE, the NASA contribution to ESA's ARIEL mission, and the Astro2020 missions Origins Space Telescope and HabEx. Additionally, he heads the Exoplanet Watch project, a citizen science initiative aimed at aiding the characterization of exoplanets.

Dr. Zellem's academic journey started near Philadelphia but took him around the world. He pursued his Bachelor of Science in Astronomy and Astrophysics at Villanova University, with minors in Physics, Mathematics, and Classics, earning an Honors Concentration. Driven by his love for travel and interest in diverse cultures, he continued his education at University College London in England, where he obtained his MSc in Space Science. He later earned his PhD in Planetary Sciences from the University of Arizona's Lunar and Planetary Laboratory before joining NASA's Jet Propulsion Laboratory as a staff member.

Beyond his scientific pursuits, Dr. Zellem enjoys a range of hobbies and interests, including jazz piano, cooking, tending to his plants, brewing beer, playing ice hockey, and daydreaming about eventually working at Disney.


  • PhD in Planetary Science – Lunar & Planetary Laboratory – University of Arizona
  • MSc with Distinction in Space Science – University College London
  • BS in Astronomy & Astrophysics – Villanova University

Professional Experience:

  • Proficient in data reduction and analysis (Python3) with experience in MATLAB, IDL, Fortran, and C/C++
  • Expertise in design reference mission and instrument commissioning
  • Extensive involvement in ground-based observing and leadership in various projects

Community Service:

  • Actively engages in public talks to share research insights
  • Volunteering for Pasadena Heritage

Research Interests:

  • Focused on measuring atmospheric molecular abundances and thermal structures of exoplanets using transit and direct imaging methods
  • Passionate about mission design and development

Selected Awards:

  • NASA Group Achievement Award to Astrophysics Large Mission Study Team 2019
  • JPL Team Award for contributions to the CASE Step 2 Core Proposal Team 2019
  • JPL Team Award in recognition for NESSI instrument modification and scientific observations at Mt. Palomar 2019
  • JPL Team Award for contributing to the development of the EXCALIBUR science pipeline 2018
  • JPL Astronomy & Physics Directorate Special Thanks & Recognition (STAR) Award 2017

Selected Publications:

  • Zellem, R.; et al. (2020), Using Small Telescopes Operated by Citizen Scientists for Transiting Exoplanet Follow-up, PASP, 132, 054401
  • Zellem, R.; et al. (2019), Constraining Exoplanet Metallicities and Aerosols with ARIEL: An Independent Study by the Contribution to ARIEL Spectroscopy of Exoplanets (CASE) Team, PASP, 131, 094401
  • Zellem, R.; et al. (2019), Engaging Citizen Scientists to Keep Transit Times Fresh and Ensure the Efficient Use of Transiting Exoplanet Characterization Missions, submitted as an Astro2020 Science White Paper
  • Zellem, R.; et al. (2018) Additional Exoplanet Science Enabled by FINESSE, submitted as National Academy White Paper
  • Zellem, R.; et al. (2017) Forecasting the Impact of Stellar Activity on Transiting Exoplanet Spectra, ApJ, 844, 27
  • Zellem, R.; et al. (2015) XO-2b: A Hot Jupiter with a Variable Host Star That Potentially Affects Its Measured Transit Depth, ApJ, 810, 11


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