Centre for Electronic Imaging
The Challenges Associated with Imaging Technology in Space Jason Gow 30th October 2012
Radiation Damage Workshop 2012 Image credit: NASA
Contents • Radiation Environment • Radiation Effects • Radiation Damage Assessment
• Past and Current Missions • Future Missions
Imaging Technology in Space
Contents • Radiation Environment • Radiation Effects • Radiation Damage Assessment
• Past and Current Missions • Future Missions
Imaging Technology in Space
Three main sources of radiation •
Radiation Belts – High flux environment – High radiation dose
•
Solar Particle Events – Damaging events are sporadic in nature
•
Galactic Cosmic Rays – Low flux – High energy Image Credit: E. Daly ESA
Imaging Technology in Space
Radiation Belts •
Inner belt – – –
Dominated by protons Approximately static 100’s of MeV
•
The Slot – –
Low intensity of electrons Occasional injections of more particles
•
Outer belt – – –
Dominated by electrons Very dynamic Few MeV
Imaging Technology in Space
Radiation Belts Io
An ultraviolet image of Jupiter's aurora taken with the Hubble Space Telescope in 2007 Europa Ganymede
Jupiter's radiation belts as mapped by Cassini, based on the strength of their radio emissions
Imaging Technology in Space
Solar Particle Events •
The Sun (images from NASA Solar Dynamic Observatory)
Image credit: Imaging Technology in Space NASA
Solar Particle Events •
The Solar Wind – – – –
A stream of charged particles from the Sun’s Corona Velocity of around 670,000 to 2,000,000 mph The solar wind consists of protons and electrons of a few MeV Typically less than 2 keV.nucleon-1, therefore not generally a problem for spacecraft components – Extends over a region of space known as the heliosphere which extends out past the orbit of Pluto.
Solar wind resulting in a geomagnetic storm Credit: NASA
Imaging Technology in Space
Solar Particle Events •
Solar Flares – – – –
During a solar flare the sun ejects radiation across the entire electromagnetic spectrum The flares are classified by the peak X-ray flux in units of Watts per square metre (W.m-2) The soft X-ray flux of large flares can interfere with short-wave radio communication, Hard X-rays can be damaging to spacecraft electronics.
Credit: NASA Stereo
Credit: NASA SOHO
Imaging Technology in Space
Solar Particle Events •
Coronal Mass Ejections – Release around 110 tons of material into space – Often associated with solar flares – The size of an event can be approximated by the soft X-ray emission which precedes them, • Typically the proton shower reaches maximum intensity two or more hours after the soft X-ray emissions • However in January 2005 a shower of protons peaked after only fifteen minutes
Credit: NASA SOHO
Credit: NASA SOHO
Imaging Technology in Space
Solar Particle Events
Imaging Technology in Space
Galactic Cosmic Rays •
Credit: MIT OpenCourseWare
Typically composed of – – – –
85% protons 14% alpha particles 1% nuclides with Z greater than 4 Heavy ions with Z greater than 26 are rare
•
Cosmic rays are omnidirectional
•
Accelerated by supernova
•
Flux rate outside of the Earths magnetic field at 1 AU – 4 protons.cm-2.s-1 – 0.4 helium ions.cm-2.s-1 – 0.04 HZ.cm-2.s-1
•
Interact with the interstellar medium to produce -rays
Credit: NASA
Credit: Energetic Gamma Ray Experiment Telescope Imaging Technology in Space
The Space Radiation Environment Cumulative dose per mission phase for JUICE
~100 krad
~42 krad ~30 krad
~34 krad
~6 krad Imaging Technology in Space
The Space Radiation Environment Cumulative dose per mission phase for JUICE
~100 krad ~150 mrad one year on the International Space Stattion ~2 krad one year in low Earth orbit ~5 krad one year in Mars orbit
~42 krad ~30 krad
~34 krad
~6 krad Imaging Technology in Space
The Space Radiation Environment Cumulative dose per mission phase for JUICE
~100 krad
~50% chance of nausea (5% chance of death within 8 weeks)
~30 krad
~42 krad ~34 krad
~6 krad Imaging Technology in Space
The Space Radiation Environment Cumulative dose per mission phase for JUICE
~100 krad 50-100% chance of nausea, mild headache, slight fever, cognitive impairment (5-95% chance of death within 6 weeks)
~50% chance of nausea (5% chance of death within 8 weeks)
~30 krad
~42 krad ~34 krad
~6 krad Imaging Technology in Space
The Space Radiation Environment Cumulative dose per mission phase for JUICE
~100 krad 50-100% chance of nausea, mild headache, slight fever, cognitive impairment (5-95% chance of death within 6 weeks)
~50% chance of nausea (5% chance of death within 8 weeks)
~30 krad
~42 krad ~34 krad
75-100% chance of nausea, moderate headache, moderate fever, cognitive impairment, 95-100% chance of death within 4 weeks
~6 krad
Imaging Technology in Space
The Space Radiation Environment Cumulative dose per mission phase for JUICE
~100 krad 50-100% chance of nausea, mild headache, slight fever, cognitive impairment (5-95% chance of death within 6 weeks)
~50% chance of nausea (5% chance of death within 8 weeks)
~30 krad
~42 krad ~34 krad
75-100% chance of nausea, moderate headache, moderate fever, cognitive impairment, 95-100% chance of death within 4 weeks
~6 krad
Beyond 3 krad is likely to cause death within 1-2 days
Imaging Technology in Space
Contents • Radiation Environment • Radiation Effects • Radiation Damage Assessment
• Past and Current Missions • Future Missions
Imaging Technology in Space
Radiation Effects Decrease in solar panel efficiency
Component failure
False stars identified in star trackers
Spacecraft components become radioactive
Spacecraft charging
Single event effects in microelectronics
Decrease in instrument performance, e.g. CMOS and CCD imagers
Surface erosion
Imaging Technology in Space
Radiation Effects
Gate
SiO2
n-type buried channel
p-type epitaxial layer Figure adapted from Janesick 2001 Imaging Technology in Space
Radiation Effects Incoming Radiation
Hole Trap Surface trap (flat band voltage shift) (dark current)
Si interstial
Gate P-V trap (CTI)
Ionisation
Displacement damage (dark spike) SiO2
n-type buried channel
p-type epitaxial layer Figure adapted from Janesick 2001 Imaging Technology in Space
What Image Sensor to Use? •
Often dependant on the mission objectives – Full well capacity – Noise performance – Readout speed
•
The impact of radiation is dependant on the environment that could be experienced
•
Charge Coupled Device (CCD) or Complementary Metal Oxide Semiconductor Imaging Sensor? 0V
+ 10 V
0V
0V Electrode or gate
Channelstop
Insulator about 0.1 µm thick Buried channel (n-type) about 1 µm deep Substrate (p-type) typically 600 µm thick
Figure courtesy of David Burt (e2v) Substrate connection (SS)
Stored electrons
Imaging Technology in Space
What Image Sensor to Use? Drive Pulse Connections
Ø1 Ø2 Ø3
Bus lines
+10V
Ø1 Drive Pulses Or “Phases”
0V +10V
Ø2
0V +10V
Ø3
Figure courtesy of David Burt (e2v)
0V
Time
The drive waveforms are sometimes called “clock pulses” with charge transfer achieved by “clocking” the device. Imaging Technology in Space
What Image Sensor to Use? Control region
Irradiated region
X-ray image showing an un-irradiated and irradiated region of a CCD
The CCD was irradiated with protons to level equivalent to 250 years spent at L2. Imaging Technology in Space
Contents • Radiation Environment • Radiation Effects • Radiation Damage Assessment
• Past and Current Missions • Future Missions
Imaging Technology in Space
Radiation Damage Assessment •
Step 1 – Assess the environment
Imaging Technology in Space
Radiation Damage Assessment Step 2 – Estimate the dose to the sensor 10,000.0 2016 launch, science phase 1,000.0
Dose (krad)
•
100.0
10.0
1.0
0.1 0
2
4
6 8 10 Aluminium Shielding (mm)
12
14
16
Model of the ESA ExoMars Spacecraft Imaging Technology in Space
Radiation Damage Assessment •
Step 3 – Perform a pre-irradiation characterisation of the sensor
Imaging Technology in Space
Radiation Damage Assessment •
Step 4 – Irradiate the sensor to different levels up to and above the predicted dose
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Radiation Damage Assessment Step 5 – Perform a post-irradiation characterisation of the sensor
CCD204 2.5E-04 Un-Irradiated
Irradiated with 100% end of life
Serial Charge Transfer Inefficiency
•
2.0E-04
Irradiated with 200% end of life
1.5E-04
1.0E-04
5.0E-05
0.0E+00 -135
-125
-115
-105 -95 -85 -75 Temperature (oC)Imaging Technology in Space
Radiation Damage Assessment •
Step 6 – Make recommendations for changes to device operation and structure
•
Change to operating conditions – Change temperature – Change operating speed – Charge Injection
Reduction in serial CTI achieved by the decrease in register width from 50 µm to 20 µm 8.0E-05 7.0E-05
CCD204 CCD273 CCD204 Fit CCD273 Fit
• •
Change to the device structure Change to the mission – Increase shielding – Change orbital parameters
Serial CTI Parallel CTI
6.0E-05 5.0E-05 4.0E-05 3.0E-05 2.0E-05 1.0E-05
Demonstrates a factor 1.7 improvement in the serial CTI
0.0E+00
0.0E+00 2.0E+09 4.0E+09 6.0E+09 8.0E+09 1.0E+10 1.2E+10 1.4E+10 1.6E+10 1.8E+10 10 MeV equivalent proton fluence (protons.cm-2)
Imaging Technology in Space
Contents • Radiation Environment • Radiation Effects • Radiation Damage Assessment
• Past and Ongoing Missions • Future Missions
Imaging Technology in Space
Hubble •
Hubble Space Telescope 1990 – Wide Field and Planetary Camera (WF/PC) – Wide Field and Planetary Camera 2 (WFPC2), 1993 – Advanced Camera for Surveys (ACS), 2002
•
M. Sirianni et al, “Radiation Damage in Hubble Space Telescope Detectors”, Radiation Effects Data Workshop, 2007 – Hubble's cameras undergo a monthly anneal to +20 C – A room temperature irradiation would result in these defects not being identified
Imaging Technology in Space
GAIA • • • • •
Catalogue a billion stars with a billion pixel digital camera over a 5 year mission at L2 Launched 2013 Largest array of CCDs ever launched >3Gb/s data generation Requires on-board compression for 3-8Mb/s downlink
106 CCDs forming the GAIA focal plane array Image credit: Airbus Imaging Technology in Space
GAIA •
Increasing charge loss as a result of radiation damage to the CCDs Payload heated
Payload heated
Crowley et al., Radiation effects on the Gaia CCDs in Space after 30 months at L2, Proc. Imaging of SPIETechnology Vol. 9915
Rosetta •
Formation of defects identified by Dr. Neil Murray in images taken with the e2v technologies CCD47-20 used in the NAVigation CAMeras (NAVCAMs)
Image credit: ESA/Rosetta/NAVCAM
Image credit: ESA
Imaging Technology in Space
Contents • Radiation Environment • Radiation Effects • Radiation Damage Assessment
• Past and Current Missions • Future Missions
Imaging Technology in Space
JUpiter ICy moons Explorer (JUICE) • •
JUICE is the first L-class launch slot in the European Space Agencies Cosmic Vision Program foreseen in 2022. The objective of the JUICE mission is the investigation of Jupiter and its icy moons
e2v CIS115
Image credit: Airbus Imaging Technology in Space
Euclid •
Euclid will spend 6 years at L2 where it will study the geometry and nature of the dark Universe through the combination of several techniques of investigation, including – Weak Gravitational Lensing – Baryonic Oscillations
•
The payload consists of a single telescope and two instruments, the visible imager (VIS) and the near-IR photo-spectrometer (NISP)
Demonstration model of the optical assembly for NISP Image Credit: CNES
Demonstration model of the VIS focal plane array Image Credit: CEA Imaging Technology in Space
Euclid •
Weak Lensing – Measures the change in ellipticity of galaxies to a few percent – Requires the use of multiple galaxies to calculate the amount and distribution of intervening matter 3D reconstruction of the dark matter distribution
Galaxy cluster Abell 2218 and its gravitational lenses, captured by Hubble in 1999
Image courtesy of Richard Massey, R. Massey et al., Dark matter maps reveal cosmic scaffolding, Nature 445 (2007) Imaging Technology in Space
Summary •
It is important to understand the environment in which the sensor will operate to minimise the exposure to extremes. – Increased shielding. – Modify orbital parameters.
•
By understanding the radiation damage to the sensor it is possible to reduce their impact. – Optimisation of the device operation. – Changes to the design of future devices.
•
Radiation damage assessments should be performed under mission operating conditions, i.e. temperature, to give the best insight into in-flight performance.
•
What will the future hold for both CCD and CIS technology for space applications?
Imaging Technology in Space
