Our Link to the Orbiter

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The Cosmic RAy Telescope for the Effects of
Radiation
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Presentation Goals

• Sources and Effects of Radiation in Space
• Designing and Testing a of a Space Craft
  Instrument
• Initial Results and Expected Goals of this Work

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Energetic Particles in Space

• Energetic particles can be, electrons, protons
  and heavier ions such as oxygen, carbon, and
  iron.
• The particles are charged and have enough energy
  to break chemical bonds such as those that hold
  together DNA.
• Damage to DNA is a major source of medical
  problems due to radiation exposure.

4
Solar Energetic ParticlesSEPs

• SEPs are mainly protons.
• Some SEPs are accelerated during a solar flare.
• Others are created as a result interactions in
  the solar wind.
• SEPs come in short bursts.
• Particle energies can vary from KeV to MeV(eV
  stands for electron volt)

Solar Flare that accelerates charged particles to
near light speeds
Flare Movie http//sohowww.nascom.nasa.gov/galler
y/Movies/flares.html
Webcam Movie http//www.youtube.com/watch?vvCFQZ
qSxWns
5
Galactic Cosmic Rays (GCRs)

• Sources outside of the solar system

• Supernovas can accelerate heavy ions particles to
  very high energies.
• GCRs are a mix of electrons and protons along
  with heavier elements.
• GCRs come from many different sources and so are
  constantly raining in from outside the solar
  system.

Particle energies can vary from 10s of MeV to
GeVs and higher
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SEPs and GCRs are tied to the solar cycle

• SEP events happen more frequently during solar
  maximum
• But..
• GCRs are deflected more by the Suns magnetic
  field during solar maximum

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Protection on Earth
Atmosphere Absorbs High Energy Particles
Earths Magnetic Field Traps Charged Particles
http//radbelts.gsfc.nasa.gov/outreach/outreach.ht
ml
8

• Effects of Ionizing Radiation

• Ionizing radiation can cause cell damage
• The damage is particularly harmful if DNA is
  broken apart
• Top
• Images of cellular nuclei that have been
  bombarded by ionizing radiation
• Green spots are places where DNA was split
• Bottom
• Visualization of DNA strand breaks from an x-ray
  and a cosmic ray

Image Credits A. Cucinotta / NASA,JSC,SRAG
9

• Measuring Cosmic Rays

• This ionization effect is used by instruments to
  measure the particles
• Radiation ionizes atoms in our detector
• Electric field accelerates electrons into our
  electronics
• We measure the amount of energy deposited by each
  particle (LET)

• How much energy is deposited?
• Not all the particles energy is deposited
• Low energy particles leave more energy then high
  energy particles

10

• Measuring Cosmic Rays with CRaTER

Warning The animators creative license has LRO
pointing the wrong way. Dont worry thoughthe
spacecraft operators know which way to point it!
Spacecraft Animation
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• Prototype

Same electronics as we would use in flight, but
easy to use (they plug into the wall!)
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• Protype Testing

Need a source similar to the one we will measure,
e.g. Brookhaven National Lab, where they can
accelerate ions to very high energies
Shadow of CRaTER prototype detector
Image taken with Iron nuclei at Brookhaven
National Lab
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Data Rate
But whats the real limitation?
Power
Mass Launch Costs
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• Engineering Model Testing

Need sources similar to the one we will measure
in space
Radioactive Sources
Cobalt-60 Source (gamma rays)
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• Engineering Model Testing

Particle accelerators, e.g. Brookhaven National
Lab
Ion Beam
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• Flight Model

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• Flight Model Calibration

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• Flight Model Environmental Testing

Make sure that instrument can survive in space
environment Thermal Large temperature
gradients in space Vibration Huge vibrations
during launch Acoustic Launch causes large
sound waves
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Integration with LRO
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• Testing of Entire Satellite

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• Launch!

http//www.nasa.gov/mission_pages/LRO/launch/index
.html
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CRaTER Science Goals

• Originally driven by exploration goals (measure
  energy deposited at different depths in the human
  body)
• Exploration Enables Science!
• High-data-rate and uniquely capable galactic
  cosmic ray (GCR) and solar energetic proton (SEP)
  science instrument

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CRaTER Sees the Moon!
When spacecraft is closer to the Moon, the moon
shields more cosmic rays coming from deep space
Altitude above the Moon
CRaTER Count Rates
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Periodic Table as Seen by CRaTER

• Iron Ion Beam at Brookhaven National Labs
• Iron factures in material placed in front of the
  detectorcreating smaller ions

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Flight Data
Why we do the experiment Because this is what
is really out there!
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Two Detector Histograms
Comparing Energy transfer to different detectors

• Particles deposit energy as they travel through
  material
• Lower energy particles leave more energy

• Each ion species leaves its owncharacteristic
  plot.

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Keeping Track of CRaTERhttp//crater.bu.edu/monit
or/
Time of Upload
- no data is available when the spacecraft is
out of communication
Instrument Power Usage
- CRaTER runs on the same power as 6
mini-Christmas lights
Counts for Each Detector
- 3 pairs of detectors separated by Tissue
Equivalent Plastic (TEP)
Total Counts
- some detector counts are deemed noise by the
instrument electronics.
Instrument Temperature
- instrument is warmed by the Sun but cools off
in the Moons shadow using electric current
warms circuitry
Dosimeter Reading
- reading of medical dosimeter on board the
instrument