Sciences and Exploration Directorate

Rob Zellem


Rob Zellem's Contact Card & Information.
Org Code: 667
Mail Code 667
Greenbelt, MD 20771

Brief Bio

Dr. Rob Zellem is an astrophysicist at NASA’s Goddard Space Flight Center. His research focuses on the characterization of the atmospheres of exoplanets using both the transit and direct imaging methods. Rob is the Deputy Project Scientist for Communications for NASA’s Nancy Grace Roman Space Telescope where he is the primary liaison between the Roman Project Science team and Goddard's Office of Communications. He is also a member of the Roman Coronagraph Project Science team where he led the development of the science calibration plan. He is the Project Scientist and Lead for Exoplanet Watch, a citizen science project to observe transiting exoplanets to update their ephemerides to ensure the efficiency use of large telescope time. He is the Ground-Based Sub-working Group co-lead for Pandora, whereby he is coordinating ground-based observations to support both the operations and scientific interpretation of Pandora data. He is also a co-lead for NASA’s Nexus for Exoplanet System Science (NExSS) and a science team member for the NASA’s CASE contribution to ESA’s Ariel mission.

Research Interests

exoplanet atmospheric characterization

Astrophysics: Extrasolar planets

transiting exoplanet ephemeris maintenance

Astrophysics: Extrasolar planets

Current Projects

Roman Space Telescope

Technology & Missions

Deputy Project Scientist for Communications

Exoplanet Watch

Extrasolar planets

Project Scientist and Lead


Extrasolar planets

Ground-based Sub-working Group Lead


Research Astrophysicist

NASA Goddard Space Flight Center - Greenbelt, MD

May 2024 - Present


Jet Propulsion Laboratory - Pasadena, CA

March 2023 - May 2024


Jet Propulsion Laboratory - Pasadena, CA

December 2019 - March 2023

Temporary Scientist

Jet Propulsion Laboratory - Pasadena, CA

October 2017 - May 2019

Teaching Experience

Exoplanet Watch students – leading development of EXOTIC multi-object photometric data reduction, website content, and instructionals

  • Heather Hewitt, PhD candidate ASU (October 2022—present)
  • Olga Privman, Astrophysics Masters student CUNY (August 2023—present)
  • Bradley Hutson, undergrad ASU (October 2024—present)
  • Suber Corley, undergrad ASU (January 2023—present)
  • Fred Noguer, undergrad ASU (January 2023—present)
  • Isabela Huckabee, MSP undergrad ASU (Summer 2022—present)
  • Tamim Fatahi, MSP undergrad SLO Cal Poly (Summer 2020—present)
  • Leah Albrow, MSP undergrad U Canturbry (NZ) (Summer 2023)
  • Kiah May, MSP undergrad U Colorado – Boulder (Summer 2022—Spring 2023)
  • Jonah Rolfness, SURF undergrad Caltech (Summer 2021—June 2022)
  • Tiana James, MSP undergrad Howard (Fall 2020—Summer 2021)
  • Marlee Smith, undergrad Columbia (Summer 2020—Spring 2021)
  • Aaron Tran, SURF undergrad Caltech (Summer 2020)
  • Alexandra Iturralde, undergrad University of New Mexico (Summer 2019)
  • Ethan Blaser, undergrad University of Virginia (Summers 2018, 2019)

Roman Coronagraph Interns

  • Lindsey Payne, undergrad Stanford (Summer 2021—June 2022)
  • Ramzi Saber, undergrad Caltech (Summer 2022)
  • Erin Mayer, graduate University of Arizona (Summer 2020—January 2022)
  • Rebecca White, undergrad UCLA (Summer 2021)

Kyle Pearson, University of Arizona Planetary Science Graduate Student (Fall 2013 – May 2020)

  • Developing on-chip guiding capability for Palomar/NESSI
  • Making high-precision exoplanetary radii measurements with Gemini/GMOS, the University of Arizona’s 61” Telescope, and Vatican Observatory’s VATT Telescope
  • Focus on developing reduction pipeline for ground-based photometric and spectroscopic data
  • Currently an Early Career Hire at JPL (398K)

Teagan King, Whitson University (Summer 2018)

  • Co-advised on the development of a radiative transfer code to model the Earth’s transmission spectrum
  • Could be used to remove telluric signals from ground-based transiting exoplanet observations

John Chapman, CSU Long Beach Graduate Student (Fall 2015 – Fall 2017)

  • Advised on the construction of simulations to test the performance of FINESSE, a dedicated exoplanet telescope proposed to NASA in December 2016
  • Advised on the construction of simulations to test the performance of the CASE instrument, a NASA mission of opportunity contribution to ESA’s ARIEL, a dedicated exoplanet telescope currently in Step 2 for NASA’s Medium Explorers Program
  • Culminated in Chapman, Zellem, et al. 2017, PASP, 129, 980

Megan Hein, New Mexico Institute of Mining and Technology (Fall 2017 – present)

  • Serving on PhD thesis committee

Aishwarya Iyer, CSU Northridge Graduate Student (Spring 2015 – Summer 2017)

  • Analyzed Hubble/WFC3 data to find that a majority of transiting exoplanets have a H2O spectral feature and clouds that, on average, block half of their atmospheric column
  • Culminated in Iyer, Swain, Zellem, et al. 2016, ApJ, 823, 109

Arizona Ground-based Observing of Exoplanets (AzGOE) (Fall 2014 – Spring 2015)

  • Extracurricular independent study teaching 27 University of Arizona undergraduates how to prepare, conduct, reduce, and analyze their own transiting exoplanet observations with the University of Arizona’s 61” Telescope

Ryleigh Fitzpatrick, University of Arizona Astronomy Undergraduate (Fall 2014 – Spring 2015)

  • Making high-precision exoplanetary radii measurements with the University of Arizona’s 61” Telescope and Vatican Observatory’s VATT Telescope
  • Focus on how to conduct observations to minimize systematic errors and data analysis

Jake Turner, University of Arizona Astronomy Undergraduate (Fall 2011 – Spring 2013)

  • Constraining exoplanet magnetic field strengths (Turner et al. 2013; Turner et al. 2016)
  • Five conference poster presentations 



Caltech Post-doctoral Scholar at JPL


Planetary Science, Ph.D.


Space Science, Master of Science with Distinction


MAJOR : Astronomy and Astrophysics, Bachelor of Science

MINORS: Physics, Mathematics, and Classics


Professional Service

Nexus for Exoplanet System Science Co-lead (July 2023 – present)

Co-lead for NExSS. Will be organizing monthly virtual lectures for the community.

Exoplanet Explorer Organizing Committee Member (June 2020 – present)

Leading the curation of the website and helping with organizational tasks for the Exoplanet Explorers Science Series, sponsored by the ExoPAG Executive Committee and the NASA’s Exoplanet Exploration Program, that aims to enable the professional development of a cohort of graduate students and/or postdocs in exoplanet research.

Virtual Exoplanet Lecture Series (March 2020 – April 2024)

Managing Section 326’s weekly Virtual Exoplanet Lecture Series including inviting speakers and hosting talks. These lectures were one of the few that continued to operate throughout all of COVID.

JPL Ombuds Team Member (March 2022 – June 2023)

Part of the grassroots team of JPLers who successfully advocated to Lab leadership for the reinstitution of JPL’s Ombuds Program. Helped organize and coordinate visit from NASA Ombuds representatives and served on the JPL Ombuds Hiring Panel.

NASA Keck Telescope Allocation Committee Member (2018A – 2019B)

NOIRLab (formerly NOAO) NNExplore Telescope Allocation Committee Member (2018B – 2021B)

Referee for multiple peer-reviewed journals (e.g., the Astrophysical Journal and the Astronomical Journal) and NASA ROSES


  • NASA Exceptional Public Achievement Medal for leading the creation of Exoplanet Watch, allowing citizen scientists to undertake exoplanet science and enhance NASA missions (2024)
  • JPL Team Award for work on Roman Coronagraph Full Functional Testing (2024)
  • JPL Team Award for work on the telescopes at JPL’s Table Mountain for Exoplanet Watch (2024)
  • NASA Award for contributing to the Exoplanet Explorers Program (2023)
  • JPL Team Award for the successful launch of Exoplanet Watch (AAS Press Release) (2023)
  • JPL Voyager Award for contribution to the Roman Coronagraph Science Community Engagement and support of the Alignment and Calibration Functional Description Document (2022)
  • JPL Team Award for contributing to the Exoplanet Explorers Program (2022)
  • JPL Team Award for contributing to Roman Coronagraph CDR (2021)
  • JPL Team Award for organization and leadership of scientific journal clubs for Section 326 (2020)
  • JPL Team Award for developing 2 creative posters combining art and science for our Galaxy of Horrors, Halloween celebrations featuring sinister exoplanets (2020)
  • NASA Group Achievement Award to Astrophysics Large Mission Study Team (Origins) (2019)
  • JPL Team Award for contributions to the CASE Step 2 Core Proposal Team (2019)
  • JPL Team Award in recognition for modification and demonstration of the NESSI instrument for use at Mt. Palomar, and the resulting scientific observations (2019)
  • JPL Team Award for helping develop the EXCALIBUR science pipeline (2018)
  • JPL Astronomy & Physics Directorate Special Thanks & Recognition (STAR) Award (2017)
  • Galileo Circle Award for Excellence in the Sciences (2012, 2015)
  • U. of Arizona Lunar and Planetary Laboratory Outreach Excellence Award (Spring 2013)
  • University of Arizona Lunar and Planetary Laboratory Graduate Teaching Excellence Award (Spring 2012)