The Cosmic R A y Telescope for the Effects of Radiation

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

Energetic Particles in Space SEP’s GCR’s 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.

Solar Energetic Particles SEP’s SEP’s are mainly protons. Some SEP’s are accelerated during a solar flare. Others are created as a result interactions in the solar wind. SEP’s 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: Webcam Movie:

Galactic Cosmic Rays (GCR’s) Sources outside of the solar system Supernovas can accelerate heavy ions particles to very high energies. GCR’s are a mix of electrons and protons along with heavier elements. GCR’s come from many different sources and so are constantly raining in from outside the solar system. Particle energies can vary from 10’s of MeV to GeV’s and higher

SEP’s and GCR’s are tied to the solar cycle SEP events happen more frequently during solar maximum But….. GCR’s are deflected more by the Suns magnetic field during solar maximum SEP’s GCR’s

Protection on Earth Quebec, Canada Aug. 19, Atmosphere Absorbs High Energy Particles Earth’s Magnetic Field Traps Charged Particles

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

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) Step 1: Electrons freed from atoms by incident radiation Step 2: Electrons collected and measured. More electrons = more energy deposited Electric Field CRaTER Electronics Incident Cosmic Ray How much energy is deposited? Not all the particles energy is deposited Low energy particles leave more energy then high energy particles

Measuring Cosmic Rays with CRaTER Detectors 1 & 2 Detector 3 & 4 Detectors 5 & 6 Particles from Deep Space TEP Particles from the Moon Warning: The animator’s creative license has LRO pointing the wrong way. Don’t worry though…the spacecraft operators know which way to point it! Spacecraft Animation

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

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 Image taken with Iron nuclei at Brookhaven National Lab Shadow of CRaTER prototype detector

Power: Payload: 98 Watts CRaTER: 6 Watts The Rest of LRO: 690 Watts The Rest of LRO: 2092 lbs Fuel: 1774 lbs Payload: 190 lbs CRaTER: 13 lbs Entire Satellite: 100 Mbps : about the same as a wireless router…not bad! CRaTER: ~90 kbps (~0.1% of LRO rate!): better than dial-up connection, but not much! But what’s the real limitation? $ Mass = Launch Costs: $ Data Rate:

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

Engineering Model Testing Particle accelerators, e.g. Brookhaven National Lab

Flight Model

Flight Model Calibration

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

Integration with LRO Who are those masked men??

Testing of Entire Satellite

Launch!

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 CRaTER Science Goals

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

Periodic Table as Seen by CRaTER Iron Ion Beam at Brookhaven National Labs Iron factures in material placed in front of the detector creating smaller ions

Flight Data Why we do the experiment: Because this is what is really out there!

Two Detector Histograms Detectors 1 & 2 Detector 3 & 4 Detectors 5 & 6 Particles from Deep Space TEP 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 own characteristic plot.

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