Scientific Payloads for Pico
and Nanosatellites
Motivation
 The recent situation in experimental satellite high energy
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astrophysics is not very promising
LOFT was not selected as ESA M3 mission
ESA XEUS, NASA Cons X, ESA/NASA/JAXA IXO all cancelled
Hope remains with Athena+ but that’s distant future
QUESTION: IN WHAT EXTEND MAY VERY SMALL SATELLITES
FILL THE GAP?
Pico (Cube) and Nanosatellites
 In development at many Universities,
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mostly with involvement of students,
education
CubeSat Standard size 1 Liter Volume
i.e. 10 x 10 x 10 cm and typically 1.3 kg
Multiple modules possible i.e. 3U = 3 modules/units
i.e. 10 x 10 x 30 cm, typically up to 12U
Picosatellite 0.1 to 1 kg, Femtosatellite 10-100 g
Nanosatellite 1-10 kg, Microsatellite 10-100 kg
Recent technological progress allows use in astrophysics
 R. Hudec and V. Šimon, Astronomical Institute
Ondrejov, and Czech Technical University in
Prague, Faculty of Electrical Engineering
 V. Tichý and A. Inneman, Czech Technical University
in Prague, Faculty of Electrical Engineering
 L. Pína , Faculty of Nuclear Science, Czech Technical
University, Prague, Czech Republic
 V. Maršíková, D. Černá, RITE, Prague, Czech
Republic
Detector Medipix
Medipix is a family of photon
counting pixel detector
developed by an international
collaboration, hosted by CERN.
CTU Prague is member/
Space distribution of most X-ray binaries
If pointing possible, the LE should
monitor the center of our Galaxy
 The field of the center of the Galaxy (20x80 deg). The
positions of known LMXBs and HMXBs (Liu et al. 2007, 2006)
are marked. The field proposed for the monitoring by
lobster is marked by the oblong – it contains a number of the
already known objects.
 LMXBs (both transient and persistent) concentrate toward
the Galactic plane and the Galactic bulge.
Examples of objects within
sensitivity limit of LE
Scientific Payload for Picosatellite
 Must fit the small volume typically 30 x 10 x 10 cm or less
(3U i.e. 3 cubesat modules)
 Low weight < 1 kg
 Low power consumption ~ 10 Watts or less
 Technological tests: TRW increase, flight demonstration,
etc.
 Reasonable science
 Not easy to find such instrumentation
Miniature X-Ray/Telescope - Monitor
Lobster-Eye (LE)
KS 1731–260
The Medipix detector represents
suitable imaging detector for use
in space LE telescopes
But:
1. Not yet space qualified, 2.
Spectral coverage >3 keV
Tests LE X-ray Optics & Medipix detector at 8 keV
CTU Prague
Detector
member of
Medipix
Collaboration
It works!
8 keV on axis
Schmift design
ASM/RXTE 1.5-3 (12) keV …
similar to LE
LE Telescope for Picosatellite
Angel design
 Novel Wide Field X-ray Telescopes
 FOV of 100 sq. deg. and more easily
possible (classical X-ray optics only 1
deg or less)
 Analogy with lobster eyes
Transient and persistent LMXB,
CVs
Optics
Feasibility study
of small LE
X-ray telescope
for Picosatellite
GK Per / 1A 0327+43
8 keV off axis
Based on UWE concept, Univ of Wurzburg, DE
LE module: F=25 cm,L=30 cm
LE f=25 cm, L=30 cm
Picosatellite 10 x 10 x 30 cm
Technological experiment but still some science
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Outbursts of dwarf novae in X-rays
SS Cyg / 3A 2140+433
Optical
Optical
Soft X-ray
(E<0.5 keV)
Hard X-ray
(E=1.5–12 keV)
Hard X-ray
(E>2 keV)
LE Telescope for a Picosatellite: Example
“Real” Lobster Eye
Eye of small Czech river crayfish
SS Cyg / 3A 2140+433
Energy 4.5keV = 7,2 . 10-6 erg
Focal length 250 mm
h=30mm
Weight < 1 kg (optics 50 g, detector 50 g)
=> FOV 2˚x 2˚, gain=820
Daily mimimal flux=9,2 . 10-10 erg /s cm2
Arrow: LE limit 1 module,
measured Wheatley et al. (2003)
 Complicated relation
between the optical and
X-ray profile of outburst
 Large structural changes of the emitting regions occur during
outburst
 Strong brightening often only in very soft X-rays (but it may
differ from system to system) – the proposed band of
lobster is suitable for this purpose
Spacecraft – 6U CubeSat
Focal plane
detector
LE and GRBs
LE modules
(4 pcs.)
Micro LE:
3 x 3 x 14 mm
module glass
The front wiew of the mini lobster module, Schmidt
arrangement, based on 100
micron thick plates spaced by
300 microns, 23 x 23 mm each,
weight only 50 grams
Foils 30 µm thick
separated by 70 µm
Focal image
8 keV
Science objectives
Primary
The X-ray measurement at 8
keV in comparison with
mathematical simulation
measured
Optics
Space for
another
Star tracking
systems (power,
camera
communication,
etc.)
 Attitude control and sensing of accuracy in order of arcmins is
necessary
 Data rate ca. 1MB per orbit – deconvolution can be performed on
Earth
 Long-term (months) measurement of light curves of bright
persistent X-ray binary stars in the centre of the Galaxy at soft Xray energies
model
Modular concept to
achieve large FOV.
Picosatellite 1 module,
Nanosatellite 4
modules
Arrow:
LE limit 1
module,
measured
Arrow: LE limit
30 modules,
expected
Examples of X-ray LC of GRBs in
0.3-10 keV (OBrien et al. 2006)
Independent GRB
detection by X-ray
emission
Even the available LE module mini
able to detect and to follow for ~
15 minutes X-ray emission of GRBs
Conclusion
The Lobster Eye X-Ray Telescope can contribute
to various regions of recent astrophysics
 Detection and measurement of light curves of bright transient
events of X-ray binary stars in the centre of the Galaxy at soft Xray energies
The necessary technical background is already available
Secondary
 Discovery of X-ray counterparts of GRBs and X-ray flashes
Even small LE X-ray telescopes/monitors on pico/nano
satellites have scientific justification
 Monitoring and detection of transient and flaring X-ray sources
VZLUSAT the 1st cubesatellite with LE and Medipix detector t
Even the small recently tested LE module can deliver valuable
scientific outputs