Cosmic RAy Telescope for the Effects of Radiation. (CRaTER): Science Overview

Transcription

1 Cosmic Ray Telescope for the Effects of Radiation (CRaTER): Science Overview Harlan E. Spence, Principal Investigator Boston University Department of Astronomy and Center for Space Physics

2 My Background PhD, Earth and Space Science, UCLA, 1989 Sr. Mem. of the Tech. Staff, The Aerospace Corp., ( casual status now) Professor of Astronomy, Boston University, 1994-present Lead instrument scientist of Imaging Proton Spectrometer on NASA/POLAR s/c (led design, development, testing, and calibration) Co-I on CEPPAD and CAMMICE energetic particle instruments on POLAR Co-investigator on energetic particle instrument suite on recently-selected SMART consortium for NASA/MMS Mission NASA POLAR IPS instrument and analog board POLAR CEPPAD Science Overview 2

3 CRaTER Science Team and Key Personnel Name Harlan E. Spence Larry Kepko Justin Kasper Bernie Blake Joe Mazur Larry Townsend Michael Golightly Terry Onsager Rick Foster Bob Goeke Brian Klatt Chris Sweeney Institution BU MIT Aerospace UT Knoxville AFRL NOAA/SEC MIT BU Role PI Co-I (E/PO, Cal, IODA lead) Co-I (Project Scientist) Co-I (Detector lead) Co-I (GCR/SCR lead) Co-I (Modeling lead) Collaborator (Biological effects) Collaborator (CR measurements) Project Manager Systems Engineer Q&A Instrument Test Lead Science Overview 3

4 Science/Measurement Overview CRaTER Objectives: To characterize the global lunar radiation environment and its biological impacts. to address the prime LRO objective and to answer key questions required for enabling the next phase of human exploration in our solar system. Science Overview 4

5 So What? Powerful Solar Variability. January 15, Image credit: J. Koeman Near solar minimum Few sunspots Few flares Quiet corona Giant sunspot 720 Sudden appearance Strong magnetic field Very large On west limb by January 20 Science Overview 5

6 Who Cares? Astronauts, s/c Operators dt < 30 minutes Science Overview 6

7 Magnitude and Scope of Effects? ISS: 1 REM (Roentgen Equivalent Man, 1 REM ~ 1 CAT Scan) Scintillations Hardened shelter Spacesuit on moon 50 REM (Radiation sickness) Vomiting Fatigue Low blood cell counts 300 REM+ suddenly Fatal for 50% within 60 days Also Two communication satellites lost Airplanes diverted from polar regions Satellite tracking problems, degradation in solar panels Science Overview 7

8 How Big is Big? Potentially Fatal. Big Bear Solar Observatory Apollo 16 in April 1972 Flare on August 7, 1972 Apollo 17 that December Derived dosage 400 REM Michener s Space is based on this event Science Overview 8

9 Why Characterize Radiation Sources? To understand risks to: Astronauts Radiation Poisoning from sudden events Heightened long-term risk Cancer Cataracts Spacecraft examples Single event upsets Attitude (Sun pulse & star tracker) Radiation damage Science Overview 9

10 Galactic Cosmic Rays: Another Source Advanced Composition Explorer Crab Nebula (ESO) Science Overview 10

11 When Is It Safe? Almost never. GCR flux is low-level but continuous and has weak solar cycle dependence Intense SEPs (>10 MeV p+) are episodic and approximately follow the solar cycle SEP event occurrence varies with the solar cycle in anti-phase with weaker galactic cosmic ray fluxes SEP events (plot courtesy R. Mewaldt, Cal Tech) At solar minimum: Min SEP occurrence Max GCR flux Solar Minimum Science Overview 11

12 Science Overview 12

13 CRaTER As-Proposed Traceability Matrix Science Overview 13

14 Science Measurement Concept Science Overview 14

15 Rationale for LET Spectra GCR/SCR parent spectra will be measured by other spacecraft during LRO mission Biological assessment requires not the incident CR spectrum, but the LET spectra behind tissue-equivalent material LET spectra are a missing link, currently derived largely by models; we require experimental measurements to provide critical ground truth CRaTER will provide information needed for this essential quantity Science Overview 15

16 Science Trades As-proposed design has evolved in response to selection debrief and as a result of detailed knowledge of s/c configuration and instrument accommodation Science trade studies ongoing to refine telescope configuration basic design is unchanged; internal configuration modified in response to simulation studies Other science/engineering trade studies are underway CRaTER science requirements essentially unchanged flowdown to be presented by J. Kasper Science Overview 16

17 Example Science Trade Study Modification from As-proposed D6 D5 Moon A2 Cylindrical telescope rather than conical D4 D3 Five-element detector stack with 3 volumes of TEP sandwiched between A1 Six-element detector stack with 2 volumes of TEP sandwiched between D2 D1 Space Science Overview 17

18 Science Overview 18