Asteroids-For-All

ASTEROIDS-FOR-ALL: BUILDING AN OPEN-SOURCE ASTEROID DETECTION LINKING SOFTWARE by Nicole Tan Jieyi Submitted to Wellesley College in Partial Fulfillment of the Prerequisite for Honors in Astrophysics under the advisement of Carrie Nugent and Kim McLeod May 2020 © Copyright by NICOLE TAN JIEYI, 2020 ACKNOWLEDGMENTS I’d like to acknowledge that this work was partially written during the 2019-2020 coronavirus pandemic. My gratitude to everyone that I will mention below is infinitely greater because of it; despite the challenging conditions of countless back and forth emails, Zoom calls, scheduling conflicts with respect to a 12 hour time difference and the general state of the world, everyone has been immensely accommodating and kind in pushing me through the final stages of the thesis process. I’d like to express my deepest gratitude to my off-campus advisor, Professor Carrie Nu- gent at Olin College, for first taking me on as a summer student and then taking on the huge responsibility of becoming my thesis advisor over the academic year. Thank you for introducing me to the world (no pun intended) of asteroids and Solar System objects. I cannot begin to thank you enough for everything you’ve done for me, and I will miss our weekly thesis meetings. Thank you to my on-campus advisor, Professor Kim McLeod, for being incredibly sup- portive throughout the entire thesis process. Thank you for all your comments and advice through the different thesis drafts, and your continued faith in my abilities—not just during this thesis process, but throughout my four years at Wellesley. Many thanks to the rest of my thesis committee for not just their time in reviewing my thesis, but also for their individual contributions to my time here at Wellesley. Professor James Battat, for his role as my major advisor and a source of continued guidance; Professor Wes Watters, for his help in crafting my KNAC presentation on my initial summer work for this project; and Professor Lisa Rodensky, who deserves credit for any semblance of good writing I’ve done (and I am sorry for all the passive voice constructions). ii Thanks also to my friends and family. The Astro Squad, Maura Shea and Karisa Zdanky, for all the laughs (and tears) during our shared struggles through the astrophysics major. Laurel Stickney, my roommate of four years, for all the interesting conversations, both pro- found and nonsensical, that have acted as a sounding board for most of my ideas. My family for supporting me through this journey, and for leaving me (mostly) alone to write this. This work would not have been possible without Bill Gray’s wonderful software, Find_Orb. Thank you for putting it out there for all to use, and for your continuous updates, meticulous documentation and extremely helpful answers to all my questions, from software installation to orbital mechanics. This research has made use of data and services provided by the International Astronom- ical Union’s Minor Planet Center, and has made use of the NASA/IPAC Infrared Science Archive, which is funded by the National Aeronautics and Space Administration and oper- ated by the California Institute of Technology. The Pan-STARRS1 Surveys (PS1) and the PS1 public science archive have been made possible through contributions by the Institute for Astronomy, the University of Hawaii, the Pan-STARRS Project Office, the Max-Planck Society and its participating institutes, the Max Planck Institute for Astronomy, Heidelberg and the Max Planck Institute for Extraterrestrial Physics, Garching, The Johns Hopkins University, Durham University, the University of Edinburgh, the Queen’s University Belfast, the Harvard-Smithsonian Center for Astrophysics, the Las Cumbres Observatory Global Telescope Network Incorporated, the National Central University of Taiwan, the Space Tele- scope Science Institute, the National Aeronautics and Space Administration under Grant No. NNX08AR22G issued through the Planetary Science Division of the NASA Science Mission Directorate, the National Science Foundation Grant No. AST-1238877, the University of Maryland, Eotvos Lorand University (ELTE), the Los Alamos National Laboratory, and the Gordon and Betty Moore Foundation. iii ASTEROIDS-FOR-ALL: BUILDING AN OPEN-SOURCE ASTEROID DETECTION LINKING SOFTWARE by Nicole Tan Jieyi, B.A. Wellesley College May 2020 ABSTRACT We developed the first free and open-source asteroid detection linking software for use with time-series sky survey data. It takes cleaned Source Extractor outputs of non-stationary detections from the images and finds tracklets representing asteroid motion within them. The linking software is a Python-based program that incorporates Find_Orb, an orbit determi- nation program by Bill Gray. The bulk of the program identifies candidate tracklets based on exposure-to-exposure object movement. The program runs through all possible combi- nations of observation linkages, feeds possible tracklets through Find_Orb, and identifies candidate tracklets based on user-defined criteria including angular speed, angle between detections and mean residuals from Find_Orb. We tested the software with data from the Near-Earth Asteroid Tracking (NEAT) survey and from the Palomar Transient Factory (PTF). For NEAT tests with artificial noise added, we found that the code performed ideally for noise levels up to 80%. In the PTF tests, we discovered a previously unreported asteroid position. Subsequently, we have submitted this tracklet to the Minor Planet Center. Our trials show that under ideal conditions, the linking software is able to perform on par with the linking capabilities of the NEAT and PTF systems, which have a more complex design. iv TABLE OF CONTENTS Page ACKNOWLEDGMENTS ............................... ii ABSTRACT ....................................... iv LIST OF TABLES .................................... ix LIST OF FIGURES ................................... xi CHAPTER 1 Introduction .................................... 1 1.1 Project overview................................ 1 1.2 Overview of asteroids............................. 1 1.2.1 Small body taxonomy......................... 1 1.3 Asteroid significance ............................. 4 1.3.1 Clues to the past ........................... 4 1.3.2 Keys to further space exploration .................. 5 1.3.3 A potential hazard........................... 5 1.4 Detection method............................... 7 1.4.1 Introduction to asteroid surveys................... 7 1.4.2 Detection linking ........................... 9 1.5 Scope of work................................. 10 1.5.1 Expected inputs and outputs..................... 10 1.5.2 Purpose ................................ 11 CHAPTER 2 Methods ...................................... 13 2.1 Software overview............................... 13 v 2.2 Find_Orb................................... 13 2.2.1 Purpose ................................ 13 2.2.2 Find_Orb method........................... 14 2.2.3 Find_Orb limitations......................... 15 2.3 Tracklet Screening............................... 16 2.3.1 Data handling............................. 16 2.3.2 Software parameters.......................... 18 2.3.3 Recursion................................ 20 2.3.4 Screening passes............................ 22 CHAPTER 3 Code testing with NEAT ............................ 23 3.1 NEAT overview................................ 23 3.2 NEAT data .................................. 23 3.3 Code modifications for NEAT ........................ 24 3.4 Noise addition................................. 25 3.5 Findings.................................... 26 CHAPTER 4 Applications to PTF data ........................... 29 4.1 PTF overview................................. 29 4.2 Accessing PTF data.............................. 29 4.3 Star removal.................................. 30 4.3.1 Accessing Pan-STARRS data..................... 30 4.3.2 Code for star removal......................... 31 4.4 Trials...................................... 31 4.4.1 Testing on 20’ PTF data ....................... 32 CHAPTER 5 Conclusions .................................... 35 APPENDIX A ............................................ 41 A.1 Code...................................... 41 A.1.1 linking_library.py........................... 41 vi A.1.2 add_library.py............................. 55 A.1.3 FindPOTATOs.py........................... 66 vii LIST OF TABLES 1.1 Types of objects at hypothetical distances and their calculated orbital and angular speed, rounded to two significant figures. ............... 4 1.2 Specifications for the Near-Earth Asteroid Tracking (NEAT), Palomar Tran- sient Factory (PTF), and Outer Solar System Origins Survey (OSSOS) surveys, taken from Pravdo et al.(1999), Law et al.(2009) and Bannister et al. (2016). The streak limits for NEAT and PTF are calculated based on pixel size and exposure. For seeing-limited OSSOS, the streak limit is based on exposure and an assumed 2" seeing........................ 8 ix LIST OF FIGURES 1.1 MOID is a measure of the distance between the closest point of two orbits. This diagram shows the Earth MOID for a hypothetical NEO......... 6 1.2 An example of a tracklet found by the Catalina Sky Survey. These three images of asteroid 2010RX30 are of the same field of the sky. From exposure to exposure, most sources are stationary, except for detections of the asteroid (circled). This series of three detections is a tracklet. ............. 9 2.1 θ measurement in relation to the three detections ............... 19 2.2 Overview of the main

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