Exo-S: Starshade Probe-Class Exoplanet Direct Imaging Mission Concept Interim Report April 28, 2014 CL#14-1548 National Aeronautics and Space Administration Exo-S: Starshade Probe-Class Jet Propulsion Laboratory California Institute of Technology Pasadena, California Exoplanet Direct Imaging Mission Concept Interim Report ExoPlanet Exploration Program Astronomy, Physics and Space Technology Directorate Jet Propulsion Laboratory for Astrophysics Division Science Mission Directorate NASA April 28, 2014 Science and Technology Definition Team Sara Seager, Chair (MIT) JPL Design Team: M. Turnbull (GCI) D. Lisman, Lead W. Sparks (STSci) D. Webb S. Shaklan and M. Thomson (NASA-JPL) R. Trabert N.J. Kasdin (Princeton U.) D. Scharf S. Goldman, M. Kuchner, and A. Roberge (NASA-GSFC) S. Martin W. Cash (U. Colorado) J. Henrikson E. Cady The cost information contained in this document is of a budgetary and planning nature and is intended for informational purposes only. It does not constitute a commitment on the part of JPL and Caltech. © 2014. All rights reserved. Exo-S STDT Interim Report Table of Contents Table of Contents Executive Summary ....................................................................................................................................................... 1 1 Introduction .......................................................................................................................................................... 1-1 1.1 Scientific Introduction ............................................................................................................................... 1-1 1.1.1 The Diversity of Exoplanets ......................................................................................................... 1-1 1.1.2 Exoplanet Atmospheres ............................................................................................................... 1-3 1.1.3 An Anticipated Diversity for Planet Habitability and Biosignature Gases ..................................... 1-4 1.1.4 Why Space-Based Direct Imaging? ............................................................................................. 1-5 1.1.5 Summary ..................................................................................................................................... 1-5 1.2 Technical Introduction .............................................................................................................................. 1-5 1.2.1 Starshade Conceptual Introduction ............................................................................................. 1-5 1.2.2 History ......................................................................................................................................... 1-5 1.2.3 Starshade Strengths .................................................................................................................... 1-6 1.2.4 Programmatic Challenges ........................................................................................................... 1-8 1.2.5 Technical Challenges .................................................................................................................. 1-8 1.2.6 Summary ..................................................................................................................................... 1-9 1.3 The Exoplanet Science Landscape in 2024 ............................................................................................. 1-9 1.3.1 Indirect Detections Using Stellar Reflex Motion ........................................................................... 1-9 1.3.2 Transits ...................................................................................................................................... 1-10 1.3.3 Exoplanet Imaging Detections ................................................................................................... 1-10 1.3.4 Disk Imaging .............................................................................................................................. 1-11 1.3.5 Summary ................................................................................................................................... 1-12 2 Science Goals and Objectives ............................................................................................................................. 2-1 2.1 Science Goals .......................................................................................................................................... 2-1 2.2 Detailed Description of Science Objectives .............................................................................................. 2-1 2.2.1 Identifying Exoplanets .................................................................................................................. 2-1 2.2.2 Characterizing Exoplanets via Spectroscopy ............................................................................... 2-2 2.2.3 Known Giant Planets ................................................................................................................... 2-5 2.2.4 Circumstellar Disk Science .......................................................................................................... 2-6 2.3 Astrophysical Contaminants ..................................................................................................................... 2-8 2.3.1 Exozodiacal Clumps and Background Objects ............................................................................ 2-8 2.3.2 Scattered Light from Companion Stars ........................................................................................ 2-9 2.3.3 Background Stars ...................................................................................................................... 2-10 2.3.4 Extragalactic Sources ................................................................................................................ 2-10 2.3.5 Summary of Observing Protocols .............................................................................................. 2-11 2.3.6 Summary of Preparatory Science Recommendations ............................................................... 2-12 3 Design Reference Mission ................................................................................................................................... 3-1 3.1 Key System Performance Parameters ..................................................................................................... 3-1 3.2 Integration Times ..................................................................................................................................... 3-3 3.3 Target Lists .............................................................................................................................................. 3-4 3.3.1 Candidate Earth Twins ................................................................................................................ 3-4 3.3.2 Known RV Planets ....................................................................................................................... 3-5 3.3.3 Jupiter Twin Survey ..................................................................................................................... 3-5 3.4 Observing Sequence ................................................................................................................................ 3-6 3.5 Summary .................................................................................................................................................. 3-7 i Exo-S STDT Interim Report Table of Contents 4 Baseline Design ................................................................................................................................................... 4-1 4.1 Mission Design ......................................................................................................................................... 4-1 4.2 Telescope Spacecraft .............................................................................................................................. 4-3 4.2.1 Telescope .................................................................................................................................... 4-3 4.2.2 Instrument .................................................................................................................................... 4-3 4.2.3 Formation Sensing and Control ................................................................................................... 4-5 4.2.4 Telescope Bus ............................................................................................................................. 4-6 4.3 Starshade Spacecraft Design................................................................................................................... 4-7 4.3.1 Starshade Optical Design ............................................................................................................ 4-7 4.3.2 Starshade Beacon ....................................................................................................................... 4-8 4.3.3 Starshade Mechanical Design ..................................................................................................... 4-8 4.3.4 Starshade Bus ........................................................................................................................... 4-13 5 Baseline Implementation .....................................................................................................................................