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C osmic Ra y T elescope for the E ffects of R adiation ( CRaTER ): Science Overview

C osmic Ra y T elescope for the E ffects of R adiation ( CRaTER ): Science Overview. Harlan E. Spence, Principal Investigator Boston University Department of Astronomy and Center for Space Physics. My Background. PhD, Earth and Space Science, UCLA, 1989

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C osmic Ra y T elescope for the E ffects of R adiation ( CRaTER ): Science Overview

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  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., 89-94 (“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

  3. CRaTER Science Team and Key Personnel

  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. ”

  5. So What? Powerful Solar Variability. January 15, 2005 • 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 Image credit: J. Koeman

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

  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

  8. How Big is Big? Potentially Fatal. • 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 Big Bear Solar Observatory

  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

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

  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 (plot courtesy R. Mewaldt, Cal Tech) SEP events • At solar minimum: • Min SEP occurrence • Max GCR flux Solar Minimum

  12. CRaTER As-Proposed Traceability Matrix

  13. Science Measurement Concept

  14. 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

  15. 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

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

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