C osmic Ra y T elescope for the E ffects of R adiation ( CRaTER ) Michael J. Golightly

1. Cosmic Ray Telescope for the Effects of Radiation (CRaTER) Michael J. Golightly CRaTER Deputy Project Scientist Boston University, Center for Space Physics 2008 Space Weather Workshop

2. One of 6 scientific instruments selected for the Lunar Reconnaissance Orbiter (LRO) • Galactic and solar cosmic ray radiation measured behind human “tissue-equivalent plastic” • Launch: Fall 2008 • Global maps of lunar radiation environment constructed from data collected over >1 year in low altitude lunar orbit • NASA will use real-time CRaTER data to assess deep space radiation dose rates and risks to astronauts

3. CRaTER co-Investigators/Science Team • Harlan SpenceBoston University (Principal Investigator) • Justin KasperHarvard Smithsonian (Project Scientist) • Michael GolightlyBU (Deputy Project Scientist, SOC lead) • J. Bernard BlakeAerospace Corp. (co-I, radiation physics) • Joseph MazurAerospace Corp. (co-I, SEP/GCR physics) • Larry TownsendUT Knoxville (co-I, radiation transport • modeling lead) • Terrence OnsagerNOAA/SWPC (co-I, space weather effects) • Tony CaseBU (Graduate student, CRaTER science) • Elly Huang BU (Research Associate, GCR/SEP modeling) • Eddie SemonesSpace Radiation Analysis Group • NASA/JSC, (Collaborator, astronaut safety) • Timothy StubbsNASA/GSFC (LRO Participating Scientist, dust) • Cary ZeitlinLBL/UC Berkeley (LRO Participating Scientist, radiation modeling)

4. CRaTER ESMD Measurement Goal • To characterize the global lunar radiation environment and its biological impacts • Six-element, solid-state detector and tissue-equivalent plastic (TEP) telescope • Sensitive to cosmic ray particles with energies greater than ~10 MeV, primarily protons, but also heavy ions, electrons, and neutrons • Galactic cosmic rays – GCRs • Solar energetic protons – SEPs • Measure spectrum of Linear Energy Transfer (LET = energy per unit path length deposited by cosmic rays as they pass through or stop in matter) • Accurate LET spectrum is missing link needed to constrain radiation transport models and radiation biology

5. CRaTER Primary SMD Science Goals • Map spatial variation of LET spectra to explore possible role(s) of lunar phase, LRO orbital phase, and lunar location on modulating cosmic rays • Resolve recently discovered, short-term temporal variation (minutes to hours) of GCRs to identify possible interplanetary modulation sources • Measure onset of SEPs at high temporal resolution to investigate particle acceleration mechanisms and structure

6. CRaTER Secondary SMD Science Goals • Search for spallated CRs off Moon whose properties vary with impacted surface material (i.e., rock vs. ice) • Search for microphonic signatures of largest dust impacts to constrain (upper limits of) grain properties

7. CRaTER Performance Specifications • CRaTER’s energy spectral range: • 200 keV to 100 MeV (3 “low LET” detector chains) • 2 MeV to >300 MeV (3 “high LET” detector chains) • Energy resolution <0.5% (at max energy); GF ~ 0.1 cm2-sr • This corresponds to: • LET from 0.2 keV/μ to 2 MeV/ μ • Excellent spectral overlap in the 100 kev/μ range (key range for RBEs) • 100 kbps data rate – able to telemeter every pulse height (energy) measured in all six detectors whenever any one detector passes detection threshold (i.e., no in-flight coincidence logic required) • Calibration at proton, heavy ion, and neutron beam facilities over the full incident particle energy range and measured LET range

8. LRO/CRaTER Flight Hardware Status • Two identical flight-quality models built and tested • Both units went through the full suite of environmental testing and calibration • Analog gain calibration using external precision charge pulser and alpha sources • End-to-end calibration using particle beam facilities • Vibration, thermal/vacuum, EMI/EMC, thermal balance • Science team selected one unit as flight model delivered in early January 08; the other reserved as flight spare • Both units meet or exceed design specifications • Integrated on spacecraft in April 08 • Environmental testing this summer; launch late ‘08

9. Massachusetts General Hospital (MGH) Proton Therapy Beam Facility Performance Testing • MGH Cyclotron delivers a proton beam of well-controlled energy to target room • Incident energy range <200 MeV • Final calibration runs conducted over several months before delivery

10. MGH Calibration Results Observation (Units of ADU) Simulation (Units of MeV)

11. Brookhaven National Laboratory/NASA Space Radiation Lab Performance Testing/Calibration • BNL/NSRL accelerator facility delivers >10 MeV/nucleon to ~1 GeV/nucleon ions from light ions (e.g., protons) to heavy ions (e.g., iron) • EM used to characterize CRaTER performance to high-E/high-Z primaries • BNL simulates both galactic cosmic ray (GCR) and solar energetic proton (SEP) populations we’ll see at Moon. (Note: True source of SEPs discovered by CRaTER team while on Long Island)

12. NSRL Results – Pre-fragmentation Response • Example of beam run on April 17, 2007 of 1 GeV/n incident iron ions • Iron ions fragment in air between beam pipe exit and CRaTER’s first two detectors (D1 and D2) • LET charge spectrum of secondaries observed • D1 optimized to measure higher LET deposits (in this case primary iron ions down to silicon) • D2 optimized to measure lower LET deposits (silicon down to protons) • Thick/thin detector design validated to provide range of required LET

13. NSRL Results – Internal Fragmentation Response • Another example showing evolution of radiation through CRaTER telescope as primary ions fragment while traversing “tissue equivalent plastic” (TEP) • A shower of secondaries is created as the primary particles enter the telescope • Subsequent detections in coincidence used to create a charge spectrum • Model comparisons validate CRaTER design and experiments validate required performance to meet science goals Iron nuclei enter D3 Breakup of iron into fragments after passing through TEP measured at BNL with EM Iron breaks up within first section of TEP Iron nuclei enter D1

14. CRaTER Data Products • L0 to L4 data products related to primary measurement: LET in six silicon detectors embedded within TEP telescope • Additional user-motivated data products to include: • “Surface” Dose Rate • “Tissue” Dose Rate • “Deep Tissue” Dose Rate • NASA/JSC’s Space Radiation Analysis Group and NOAA’s Space Weather Prediction Center - tailored data products to support astronaut operations and space weather customers

15. CRaTER Science Operations Center: Data Portal for Eventual CRaTER Data

16. The CRaTER team is ready for the final surge to launch and Phase E in Late 2008! • To learn more about CRaTER, please visit our web page at: • http://crater.bu.edu/