SCIENCE AND ENABLING TECHNOLOGIES FOR THE EXPLORATION OF THE INTERSTELLAR MEDIUM Image Credit: Charles Carter / Keck Institute for Space Studies Study report prepared for the Keck Institute for Space Studies Opening workshop: September 8–11, 2014 Web-link: http://www.kiss.caltech.edu/study/science/index.html Closing workshop: January 13–15, 2015 Web-link: http://www.kiss.caltech.edu/study/scienceII/index.html Study Co-leads: Edward Stone (Caltech), Leon Alkalai (JPL), Louis Friedman (The Planetary Society) Study Members: Nitin Arora (JPL), Manan Arya (Caltech), Nathan Barnes (L. Garde Inc.), Travis Brashears (UC Santa Barbara), Mike Brown (Caltech), Paul Wilson Cauley (Wesleyan University), Robert J. Cesarone (JPL), Freeman Dyson (Institute for Advanced Study), Darren Garber (NXTRAC), Paul Goldsmith (JPL), Mae Jemison (100 Year Starship), Les Johnson (NASA-MSFC), Paulett Liewer (JPL), Philip Lubin (UC Santa Barbara), Claudio Maccone (IAA), Jared Males (University of Arizona), Kyle McDonough (UC Santa Barbara), Ralph L. McNutt, Jr. (JHU/APL), Richard Mewaldt (Caltech), Adam Michael (Boston University), Edward Montgomery (Space and Missile Defense Command), Merav Opher (Boston University), Elena Provornikova (Catholic University of America), Jamie Rankin (Caltech), Seth Redfield (Wesleyan University), Michael Shao (JPL), Robert Shotwell (JPL), Nathan Strange (JPL), Thomas Svitek (Stellar Exploration, Inc.), Mark Swain (JPL), Slava Turyshev (JPL), Michael Werner (JPL), Gary Zank (University of Alabama) i Participants in the 2nd KISS Workshop on “The Science and Enabling Technologies for the Exploration of the Interstellar Medium (ISM)” at the KISS facilities, California Institute of Technology, January 13-15, 2015. Workshop participants (some of the named participants below are not in the photo): Nitin Arora (JPL), Manan Arya (Caltech), Nathan Barnes (L. Garde Inc.), Travis Brashears (UC Santa Barbara), Mike Brown (Caltech), Paul Wilson Cauley (Wesleyan University), Robert J. Cesarone (JPL), Freeman Dyson (Institute for Advanced Study), Darren Garber (NXTRAC), Paul Goldsmith (JPL), Mae Jemison (100 Year Starship), Les Johnson (NASA-MSFC), Paulett Liewer (JPL), Philip Lubin (UC Santa Barbara), Claudio Maccone (IAA), Jared Males (University of Arizona), Kyle McDonough (UC Santa Barbara), Ralph L. McNutt, Jr. (JHU/APL), Richard Mewaldt (Caltech), Adam Michael (Boston University), Edward Montgomery (Space and Missile Defense Command), Merav Opher (Boston University), Elena Provornikova (Catholic University of America), Jamie Rankin (Caltech), Seth Redfield (Wesleyan University), Michael Shao (JPL), Robert Shotwell (JPL), Nathan Strange (JPL), Thomas Svitek (Stellar Exploration, Inc.), Mark Swain (JPL), Slava Turyshev (JPL), Michael Werner (JPL), Gary Zank (University of Alabama). ii TABLE OF CONTENTS Part A: Executive Summary ............................................................................ 1 Introduction ...................................................................................................................................... 1 Science Rationale ............................................................................................................................ 2 Part B: Overview of Previous Studies ......................................................... 7 Part C: Interstellar Medium Science and Instrumentation .............. 15 Chapter C.1: Science of the Outer Heliosphere and Nearby ISM ............................. 17 Chapter C.2: Science of the Pristine ISM ............................................................................ 30 Chapter C.3: Science of the Outer Solar System: Zodiacal Background, Dust, and Kuiper Belt Object Science ....................................................................................................... 34 Chapter C.4: Cosmic Background, Solar Wind and Perihelion Science ................ 38 Chapter C.5: Astrophysics Science ....................................................................................... 41 Chapter C.6: Science Instrumentation for Exploration of the ISM ......................... 48 Part D: Reaching the Local Interstellar Medium .................................. 51 Chapter D.1: A Mission to the Local ISM ............................................................................ 51 Chapter D.2: On-Board Probe-Propulsion Trades for a Near Term Missions to the ISM ........................................................................................................................................ 60 Part E: Journey Towards Another Star .................................................... 67 Chapter E.1: Enabling New Technologies ......................................................................... 67 Chapter E.2: Near-Term Technology Demonstration Missions............................... 73 Part F: The Path Forward ............................................................................. 75 References ......................................................................................................... 77 iii iv PART A: EXECUTIVE SUMMARY Introduction ...................................................................................................................................... 1 Science Rationale ............................................................................................................................ 2 A. Heliophysics Measurements: Breakthrough In-situ Science ............................................ 2 B. Astrophysics Measurements ......................................................................................................... 4 1. Zodiacal Dust...................................................................................................................................................... 4 2. Fundamental Physics ..................................................................................................................................... 4 3. Astrometry .......................................................................................................................................................... 5 C. Kuiper Belt Object Science: Visiting a Dwarf Planet ............................................................ 5 D. What Is a Reasonable First Step Towards Another Star? .................................................. 5 INTRODUCTION This report summarizes two very exciting and illuminating KISS workshops held on September 8, 2014 and January 12, 2015 entitled, “Science and Enabling Technologies for the Exploration of the Interstellar Medium (ISM),” led by Edward Stone (Caltech), Leon Alkalai (JPL), and Louis Friedman (The Planetary Society, Co-Founder and Executive Director Emeritus). The timing for these workshops aligned with two recent events related to the exploration of the ISM: in September 2013, Caltech professor and Voyager Project Scientist Edward Stone announced that the Voyager 1 spacecraft had detected the Heliopause a year earlier, in August 2012 [1]. Unrelated to this, the Kepler Space Telescope’s search for exoplanets (planets around other stars) has yielded spectacular results, including the detection of Earth-like planets. Thus, the vast space between our star and those with potentially habitable planets is slowly emerging into focus. This raises the question, “When and how will humanity bridge this divide and reach toward such destinations?” Even more compelling is the question, “What is a reasonable first step in that direction?” knowing full well that reaching another star is far beyond our current technical capability. The workshops brought together over thirty scientists and engineers to address the following key questions: • Is there compelling science to be achieved on the way to, at, and in the ISM? • What is a reasonable first step in the long road ahead? • What are some of the enabling technologies required to reach beyond our solar system? The answers to these questions were formulated in terms of 1) Astrophysics and Planetary science on the way to the ISM at 5–100 AU, which would include the zodiacal background and dust measurements and flyby of one or more Kuiper Belt Objects (KBOs); 2) Heliophysics measurements to obtain a better understanding of the complex environments inside and outside the protective bubble created by our Sun as it travels through the ISM; 3) and Astrophysics from the vantage point of being in the ISM at 100–700 AU, including parallax science, gravitational measurements, and the imaging of exoplanets using gravitational lensing. A major technological breakthrough endorsed by the team was the ability to reach the ISM in a much shorter timeframe than Voyager—approximately 10 years, compared to Voyager’s 36. Equipped with the study results produced by the JPL Blue Sky (Think Tank, December 2013) and Team-X (Mission Design, December 2014), the workshop team was presented with a Design Reference Mission (DRM 1.0) that would: (a) launch on NASA’s Space Launch System (SLS) in the mid-2020s; (b) perform a Jupiter gravity assist; (c) have a perihelion burn at 3–4 solar radii; (d) reach the Local ISM (LISM) within 10 years; and (e) achieve solar system escape velocities of >13 AU/year, reaching deep into the pristine ISM (>200 AU) in 20–30 years. Adding a KBO flyby could be considered in future studies. 1 The team also recognized that the proposed near-term capability to reach the ISM quickly (10–15 years) and leave the Heliopause at high velocities (>13 AU/year) does not scale well for missions to reach other stars.