Cosmic RAy Telescope for the Effects of Radiation
Cosmic Ray Telescope for the Effects of Radiation
(CRaTER): Science Overview
Harlan E. Spence, Principal InvestigatorHarlan E. Spence, Principal InvestigatorBoston University
Department of Astronomy and Center for Space Physics
Cosmic RAy Telescope for the Effects of Radiation
• 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
My BackgroundMy Background
NASA POLAR IPS instrument and analog board POLAR CEPPAD
Cosmic RAy Telescope for the Effects of Radiation
CRaTER Science TeamCRaTER Science Team and and Key PersonnelKey Personnel
NameName InstitutionInstitution RoleRole
Harlan E. Spence BU PI
Larry Kepko “ Co-I (E/PO, Cal, IODA lead)
Justin Kasper MIT Co-I (Project Scientist)
Bernie Blake Aerospace Co-I (Detector lead)
Joe Mazur “ Co-I (GCR/SCR lead)
Larry Townsend UT Knoxville Co-I (Modeling lead)
Michael Golightly AFRL Collaborator (Biological effects)
Terry Onsager NOAA/SEC Collaborator (CR measurements)
Rick Foster MIT Project Manager
Bob Goeke “ Systems Engineer
Brian Klatt “ Q&A
Chris Sweeney BU Instrument Test Lead
Cosmic RAy Telescope for the Effects of Radiation
Science/Measurement OverviewScience/Measurement OverviewCRaTER 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. ”
Cosmic RAy Telescope for the Effects of Radiation
So What? Powerful Solar Variability. So What? Powerful Solar Variability. • 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. KoemanJanuary 15, 2005
Cosmic RAy Telescope for the Effects of Radiation
Who Cares? Astronauts, s/c Operators Who Cares? Astronauts, s/c Operators dt < 30 minutes
Cosmic RAy Telescope for the Effects of Radiation
• 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
Magnitude and Scope of Effects?Magnitude and Scope of Effects?
Cosmic RAy Telescope for the Effects of Radiation
How Big is Big? Potentially Fatal.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 eventBig Bear Solar Observatory
Cosmic RAy Telescope for the Effects of Radiation
Why Characterize Radiation Sources? 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
Cosmic RAy Telescope for the Effects of Radiation
Galactic Cosmic Rays: Another SourceGalactic Cosmic Rays: Another Source
Crab Nebula (ESO) Advanced Composition Explorer
Cosmic RAy Telescope for the Effects of Radiation
When Is It Safe? Almost never.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
SolarMinimum
At solar minimum:•Min SEP occurrence•Max GCR flux
Cosmic RAy Telescope for the Effects of Radiation
Cosmic RAy Telescope for the Effects of Radiation
CRaTER As-Proposed Traceability MatrixCRaTER As-Proposed Traceability Matrix
Cosmic RAy Telescope for the Effects of Radiation
Science Measurement ConceptScience Measurement Concept
Cosmic RAy Telescope for the Effects of Radiation
• 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
Rationale for LET SpectraRationale for LET Spectra
Cosmic RAy Telescope for the Effects of Radiation
• 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 TradesScience Trades
Cosmic RAy Telescope for the Effects of Radiation
Example Science Trade Study Modification Example Science Trade Study Modification from As-proposedfrom As-proposed
Five-element detector stack with 3 volumes of
TEP sandwiched between
Six-element detector stack with 2 volumes of TEP sandwiched
between
D6
D5
A2
D4
D3
A1
D2
D1
Moon
Space
Cylindrical telescope rather
than conical