Miniaturized X-ray telescope for
VZLUSAT-1 nanosatellite with Timepix
detector
T. Bacaa, M. Platkevicb, J. Jakubekb, A. Innemanc, V. Stehlikovaa,
M. Urbana, O. Nentvicha, M. Blažeka, R. Filgasb, V. Danield
a
b
Faculty of Electrical Engineering, CTU in Prague
Institute of Experimental and Applied Physics, CTU in Prague
c
Rigaku Innovative Technologies Europe s.r.o., Prague
d
Aerospace Research and Test Establishment, Prague
The work has been done within Medipix2 collaboration.
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Outline
● About the mission
● X-ray telescope
● Detector selection
● Timepix board payload
● X-ray optics
● Data outputs
● Modes of operation
● Tests and experiments
● Conclusion
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Mission
● 2-U cubesat, expands to 3-U
after launch
● Part of QB-50 mission
● 2-year life expectancy
● ~500 km SSO LEO
● Mission experiments
○ FIPEX (measurement of
molecular oxygen)
○ Health monitoring
(material properties,
volatiles)
○ X-ray telescope
● Active electromagnetic
stabilization
● Radiation-hardened composite
housing
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X-ray telescope
Lobster eye optics
● 250 mm focal length
● 4 - 20 keV energy range
● Pantograph based mechanism for
the optics deployment
● X-ray beam goes through 5 other
electronic boards
Timepix board
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Detector selection
USB Lite interface with Timepix detector
● Hybrid semiconductor pixel detector with 256 x 256 55 μm pixels, 14×14 mm2
● USB interface developed in frame of the Medipix Collaboration at the Institute
of Experimental and Applied Physics (IEAP) of the CTU in Prague
● Satisfies constraints for cubesat use, i.e. is small and lightweight, has
moderate power consumption and low-level communication interface
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Timepix board payload
● Houses Timepix USB Lite interface
● 8-bit Atmel μ-controller for readout,
processing and communication
● 2x UV, 1x IR sensors for automatic
exposure triggering
● Aluminium cooler mounted directly
in between Lite interface and Timpix
● Tungsten radiation shielding behind
the detector
Thermometer
Power switches
USB Lite interface
Timepix Detector
xMega μ-controller
Tungsten shielding
Aluminum heatsink
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X-ray optics
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1D optics inspired by lobster’s eye
250 mm focal length, 3° field of view
Aperture 29 x 19 mm
50 coated double-sided gold-plated glass
foils
● Source position in 2nd axis provides
simple coded mask
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X-ray optics
The source’s focus
FWHM 20 arcmin
@4.5keV
Coded mask produces shadow
UV sensors for automatic
triggering
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X-ray optics
● Optics gain depends on energy
● For harder X-rays works as a
Soller slit (gain = 1)
● Photon attenuation of 300um Si
detector matches the optics
efficiency
Lobster eye gain
Observation candidates
● The Sun
○ The strongest
○ 1/6 of the FOV
● The Moon
○ Fluorescent in
x-ray
● Other sources
○ Sco X-1, Crab,
Mrk 421
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X-ray optics
Optics deployment mechanism
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Ground segment and communication
● 435 MHz radio
● Ideal maximum bandwidth 1 kbit/s
● Transmission every 90 minutes for ~5
minutes
● Automated data download and script
upload
Location: Pilsen, Czech Republic
GPS: 49°43'25.778"N,
13°20'58.626"E
LOC: JN69QR
400 m above sea
Scripts for controlling payloads
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Data outputs
Metadata (1 packet)
●Number of pixels hit
●Time
●Min and Max value in pixels
●Attitude and position
●Exposure parameters (threshold,
bias, exposure time)
●Measuring mode (TOT, MPX)
●Filtering (0/1)
●Data format
●Data address
●Heatsink temperature
Full Image (up to 3300 packets)
●Each non-zero pixel is encoded and
saved
Image energy histogram (1 packet)
●16 energy bins
Image projections (16 packets)
●Horizontal and vertical projection
Binning 32 (1 packet)
●8 x 8 resulting image
Binning 16 (4 packets)
●16 x 16 resulting image
Binning 8 (16 packets)
●32 x 32 resulting image
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Single photon event filtering
Onboard filtration of unwanted events of background radiation (alpha, electrons,
protons, ...) is based on eliminating events with clusters larger than 1 pixel.
α
e-
μ-
�
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Observation modes
Simple imaging
●Scheduled or directly controlled
exposure with predefined settings.
●Detector completes single exposure
per command.
●Preparation of the detector and
readout times are approx. 20 s
Scanning mode
●Can be scheduled, triggered
directly or set for repeating in regular
intervals
●Saves the image only when pixel
count exceeds set threshold.
●Metadata are saved every time long term dosimetry
Adrenaline mode
●“Hunt” for the Sun
●Detector is prepared to start
the exposure immediately
on demand within 1 minute
time span.
●Waits for a signal from widefield
and narrowfield UV sensors
●Exposure starts after UV signal
exceeds set threshold.
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Testing and experiments
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Assembled in clean room
Shock tested
Vibration tested
Thermal vacuum cycled
Long range communication field
tested
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Testing and experiments
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1 s exposure
Au, 40 kV, 0.05 mA
No filtering
Mild background
radiation
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Testing and experiments
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1 s exposure
Au, 40 kV, 0.05 mA
Filtering on
Mild background
radiation
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Testing and experiments
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Testing and experiments
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The last photo before delivery
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Launch
● Indian Space Research Organization
● PSLV rocket
● May 2017, within two weeks
● With 40 other cube sats
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Conclusion
● 1st Czech cubesat to be launched
● ~500 km low Earth orbit
● Launch planned for May 2017
● X-ray telescope for 4 - 20 keV range
● Timepix sensor with USB Lite interface
● UV trigger for ‘hunting’ the Sun
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Towards a rocket experiment
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Rocket experiment
Timepix for suborbital rocket experiment
● Granted: Much looser constraints on size
and power consumption then with small
satellites
● Needed: Online data processing with
feedback to control measurement
parameters
Off-the-shelf components and high-level computer
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Rocket experiment
Off-the-shelf technologies
Odroid XU4, ARM
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Rocket experiment
Software solution? Pixelman..
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Rocket experiment
Software solution? Embedded
Thermometer
Power switches
USB Lite interface
Timepix Detector
xMega μ-controller
Tungsten shielding
Aluminum heatsink
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Rocket experiment
Borrow a solution from robotics!
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Robot Operating System
Visualization
ROSpix
Logging
Debugging
State machines
etc
Exposure control
Robot Operating System
Linux Operating System
Hardware, Odroid PC computer
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Who needs it?
● Czech Academy of Sciences
– A need for automated measurement with Timepix.
– A desire for simple deployment into practice.
● University of Pennsylvania, USA
– Collaborative experiment of radiation mapping in Fukushima plant.
– Integration of Timepix into unmanned robotic drone.
● Faculty of Electrical Engineering, CTU Prague
– Distributed measurement of radiation using a swarm of micro
unamanned aerial robots.
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Thank you for your attention
We acknowledge the support provided
by TA ČR project TA03011329 and TA
ČR project TA04011295
The work has been done within
Medipix2 collaboration.
Tomáš Báča
Faculty of Electrical Engineering,
CTU in Prague
Czech Republic
[email protected]
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