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
Cosmic RAy Telescope for the Effects of Radiation
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
Cosmic RAy Telescope for the Effects of Radiation
POLAR CEPPAD
CRaTER Science Team and Key Personnel
Name
Institution
Role
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 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. ”
Cosmic RAy Telescope for the Effects of Radiation
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
Cosmic RAy Telescope for the Effects of Radiation
Who Cares? Astronauts, s/c Operators
dt < 30 minutes
Cosmic RAy Telescope for the Effects of Radiation
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
Cosmic RAy Telescope for the Effects of Radiation
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
Cosmic RAy Telescope for the Effects of Radiation
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 Source
Crab Nebula (ESO)
Advanced Composition Explorer
Cosmic RAy Telescope for the Effects of Radiation
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
Cosmic RAy Telescope for the Effects of Radiation
Cosmic RAy Telescope for the Effects of Radiation
CRaTER As-Proposed Traceability Matrix
Cosmic RAy Telescope for the Effects of Radiation
Science Measurement Concept
Cosmic RAy Telescope for the Effects of Radiation
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
Cosmic RAy Telescope for the Effects of Radiation
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
Cosmic RAy Telescope for the Effects of Radiation
Moon
Example Science Trade Study Modification D6
from As-proposed
D5
A2
Cylindrical
telescope rather
than conical
D4
D3
A1
Six-element detector
stack with 2 volumes
of TEP sandwiched
between
D2
D1
Five-element detector
stack with 3 volumes of
TEP sandwiched between
Cosmic RAy Telescope for the Effects of Radiation
Space