Cosmic Ray Telescope for the Effects of Radiation

(CRaTER)

Harlan E. Spence, Principal InvestigatorHarlan E. Spence, Principal InvestigatorBoston University

Department of Astronomy and Center for Space Physics

• What do we know?What do we know?• Pristine GCR and SEP spectra (well enough) in near-lunar (and

other nearly interplanetary environments)• What don’t we know?What don’t we know?

• How GCR/SEP particles are transported through matter and how energy is desposited (e.g., LET), particularly the heavy ions and at high energy – these are needed to validate models which are currently nearly our only resource for this biologically important ionizing radiation component. What is actual LET spectrum from GCR/SEP at moon (interplanetary space)?

• What do we need to do?What do we need to do?• Instruments like CRaTER on LRO providing missing link

between model/theory-data closure on effects; RAD on MSL providing data for validating SEP/GCR models

• Modeling efforts like BBFRAG, HETC-HEDS, FLUKA, etc.• Better connection with radiation biology and EE communities to

provide measurements of value to their needs

2008 Lunar Reconnaissance Orbiter (LRO)2008 Lunar Reconnaissance Orbiter (LRO)First Step in the Robotic Lunar Exploration ProgramFirst Step in the Robotic Lunar Exploration Program

Robotic Lunar Exploration ProgramRobotic Lunar Exploration Program

LRO Objectives

• Characterization of the lunar radiation environment, biological impacts, and potential mitigation. Key aspects of this objective include determining the global radiation environment, investigating the capabilities of potential shielding materials, and validating deep space radiation prototype hardware and software.

• Develop a high resolution global, three dimensional geodetic grid of the Moon and provide the topography necessary for selecting future landing sites.

• Assess in detail the resources and environments of the Moon’s polar regions.

• High spatial resolution assessment of the Moon’s surface addressing elemental composition, mineralogy, and Regolith characteristics

LRO Mission OverviewOrbiter

LRO Instruments

• Lunar Orbiter Laser Altimeter (LOLA) Measurement Investigation – LOLA will determine the global topography of the lunar surface at high resolution, measure landing site slopes and search for polar ices in shadowed regions.

• Lunar Reconnaissance Orbiter Camera (LROC) – LROC will acquire targeted images of the lunar surface capable of resolving small-scale features that could be landing site hazards, as well as wide-angle images at multiple wavelengths of the lunar poles to document changing illumination conditions and potential resources.

• Lunar Exploration Neutron Detector (LEND) – LEND will map the flux of neutrons from the lunar surface to search for evidence of water ice and provide measurements of the space radiation environment which can be useful for future human exploration.

• Diviner Lunar Radiometer Experiment – Diviner will map the temperature of the entire lunar surface at 300 meter horizontal scales to identify cold-traps and potential ice deposits.

• Lyman-Alpha Mapping Project (LAMP) – LAMP will observe the entire lunar surface in the far ultraviolet. LAMP will search for surface ices and frosts in the polar regions and provide images of permanently shadowed regions illuminated only by starlight.

• Cosmic Ray Telescope for the Effects of Radiation (CRaTER) – CRaTER will investigate the effect of galactic cosmic rays on tissue-equivalent plastics as a constraint on models of biological response to background space radiation.

SOLAR ARRAY

PROPULSION MODULE

AVIONICS MODULE

INSTRUMENT MODULE

Mini-RF

LOLA

LAMP

LROC

CRaTER

SOLAR ARRAY

HGA

PROPULSION MODULE

AVIONICS MODULE

INSTRUMENT MODULE

Diviner

LEND

LAMP

LRO Preliminary Design

Preliminary LRO Characteristics

Mass 1317 kgDry: 603 kg

Fuel: 714 kg

Power 745 W

Measurement Data Volume

575 Gb/day

Competitively Selected LRO Instruments Provide Broad Benefits

1000’s of 50cm/pixel images (125km2), and entire Moon at 100m in UV, Visible

~50m scale polar topography at < 1m vertical, roughness

Hydrogen content in and neutron radiation maps

from upper 1m of Moon at 5km scales, Rad > 10 MeV

Maps of frosts in permanently shadowed

areas, etc.

300m scale maps of Temperature, surface

ice, rocks

Tissue equivalent response to radiation

Measurement

Resource evaluation, impact flux and

crustal evolution

Safe landing sitesthrough hazard

identification; some resource identification

LROC

Geological evolution of the solar system by geodetic topography

Safe landing site selection, and

enhanced surface navigation (3D)

LOLA

Improved understanding of

volatiles in the solar system - source,

history, migration and depositionLocate potential water-

ice in lunar soil and enhanced crew safety

LEND

Locate potential water-ice (as frosts) on the

surface

LAMP

Determines conditionsfor systems operability and water-ice location

Diviner

Radiation conditions that influence life

beyond Earth

Safe, lighter weight space vehicles that

protect humans

CRaTER

ScienceBenefit

ExplorationBenefit

INSTRUMENT

1000’s of 50cm/pixel images (125km2), and entire Moon at 100m in UV, Visible

~50m scale polar topography at < 1m vertical, roughness

Hydrogen content in and neutron radiation maps

from upper 1m of Moon at 5km scales, Rad > 10 MeV

Maps of frosts in permanently shadowed

areas, etc.

300m scale maps of Temperature, surface

ice, rocks

Tissue equivalent response to radiation

Measurement

Resource evaluation, impact flux and

crustal evolution

Safe landing sitesthrough hazard

identification; some resource identification

LROC

Geological evolution of the solar system by geodetic topography

Safe landing site selection, and

enhanced surface navigation (3D)

LOLA

Improved understanding of

volatiles in the solar system - source,

history, migration and depositionLocate potential water-

ice in lunar soil and enhanced crew safety

LEND

Locate potential water-ice (as frosts) on the

surface

LAMP

Determines conditionsfor systems operability and water-ice location

Diviner

Radiation conditions that influence life

beyond Earth

Safe, lighter weight space vehicles that

protect humans

CRaTER

ScienceBenefit

ExplorationBenefit

INSTRUMENT

(BU+MIT)Cosmic Ray Telescopefor the Effects of Radiation

(UCLA)

(SWRI)Lyman-Alpha Mapping Project

(Russia)Lunar Exploration Neutron Detector

(GSFC)Lunar Orbiter Laser Altimeter

(NWU+MSSS)Lunar Recon Orbiter Camera

Science/Measurement OverviewScience/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. ”

• GCR/SEP 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

Classical ionizing radiationClassical ionizing radiation

• Energy loss: Electromagnetic (electrons and nucleus) and nuclear (spallation)

• Nuclear interactions occur in a fraction of events

• Above plots are from a SRIM-2003 simulation of 50 MeV protons in human tissue

Science Measurement ConceptScience Measurement Concept

CRaTER Traceability MatrixCRaTER Traceability Matrix

Current energy spectral range:• 200 keV to 100 MeV (low LET); and • 2 MeV to 1 GeV (high LET)

This corresponds to:• a range of LET from 0.2 keV/ to 7 MeV/ (stopping 1 Gev/nuc Fe-56) • good spectral overlap in the 100 kev/ range (key range for RBEs)

CRaTER Telescope ConfigurationCRaTER Telescope Configuration

Nuclear fragmentation of 1 GeV/nuc FeNuclear fragmentation of 1 GeV/nuc Fe

Evolution of proton spectrum through stackEvolution of proton spectrum through stack

January 20 2005

Energy [MeV]

Pro

ton

flux

[p c

m-2 s

-1 s

r-1 (

MeV

/nuc

)-1]

Ene

rgy

depo

site

d in

com

pone

nt [

MeV

]

Energy [MeV]

Maximum singles detector ratesMaximum singles detector ratesCRaTER gets 100kbits/sec!!CRaTER gets 100kbits/sec!!

Extra slides

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)

Bern 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

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 20Image credit: J. KoemanJanuary 15, 2005

Who Cares? Astronauts, s/c Operators Who Cares? Astronauts, s/c Operators

dt < 30 minutes

• 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?

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 event

Big Bear Solar Observatory

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

Galactic Cosmic Rays: Another SourceGalactic Cosmic Rays: Another Source

Crab Nebula (ESO)

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

SEP events

SolarMinimum

At solar minimum:•Min SEP occurrence•Max GCR flux

• 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

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