Preliminary imaging tests of Preliminary imaging tests of lobster eye optics forlobster eye optics for

nano-satellite nano-satelliteVladimír Tichý, Marco Barbera, Alfonso Collura, Martin Hromčík, René Hudec, Adolf Inneman, Jiří Maršík, Veronika Maršíková,

Ladislav Pína, Vojtěch Šimon

Czech Technical University in PragueUniversitá degli Studi di Palermo

INAF-Osservatorio Astronomico di PalermoRigaku Innovative Technologies Europe, s.r.o.Academy of Sciences of the Czech Republic

Lobster eyeLobster eye

Grazing incidence Grazing incidence reflective X-ray opticsreflective X-ray optics

Schmidt designSchmidt design11: two sets : two sets of reflective surfaces - of reflective surfaces - each set focuses in one each set focuses in one planeplane

Wide field of view: up to Wide field of view: up to ~100 square degrees~100 square degrees

Can have small mass and Can have small mass and dimensionsdimensions Prototype lobster eye P-25, manufactured

and provided by Rigaku Innovative Technologies Europe, s.r.o.

[1] W. H. K. Schmidt, ”A proposed X-ray focusing device with wide field of view for use in X-ray astronomy”, Nucl. Instr. Meth. 127, 285-292 (1975)

One-dimensional system:One-dimensional system: Flat mirrors are arranged in an uniform radial pattern around the perimeter of a cylinder.

Another LE prototype, also manufactured byRigaku Innovative Technologies Europe, s.r.o.

Lobster eye principleLobster eye principle

Two Two orthogonally arranged systems in sequence form double-focusing device

or

Prototype Lobster Eye P-25Prototype Lobster Eye P-25

Manufactured and provided by Rigaku Innovative Technologies Europe, s.r.o.

Focal length 250mmFocal length 250mm

Outer dimensions 35Outer dimensions 35GG3535GG50 50 mmmm

Consists of 2Consists of 2GG60 mirrors of 60 mirrors of diameters 24diameters 24GG2424GG0.1 mm 0.1 mm

Optimal efficiency at 1 keV X-Optimal efficiency at 1 keV X-ray photon energyray photon energy

Similar parameters we suppose Similar parameters we suppose for LE for nano-satellitefor LE for nano-satellite

Proposed applicationProposed application

X-ray all-sky monitor like ASM/RXTEX-ray all-sky monitor like ASM/RXTE

Preparatory goalPreparatory goal

Smaller and cheaper nano-satellite mission givingSmaller and cheaper nano-satellite mission giving

the practical proof of the LE technology.the practical proof of the LE technology.

QuestionsQuestions

Is that mission Is that mission technologicaltechnologicallly y feasible?feasible?

Could nano-satellite lobster eye mission acquireCould nano-satellite lobster eye mission acquire

scientifically relevant data?scientifically relevant data?

What the nomenclature “nano-What the nomenclature “nano-satellite” does meansatellite” does mean

Usually, the nomenclature nano-satellite means satellite of dimesions of orderof 10 cm and maximum mass of few kilograms.Especially, the platform called CubeSat defines the base unit as a cube of dimensions of 10×10×10 cm3 and its maximal mass is limited to 1 kg.Moreover, it is allowed to build specified multiples of the base unit, possible sizes are 0.5, 1.5, 2 and 3 times of the base unit. So, the whole spacecraft can have total dimensions 30×10×10 cm3 and total mass up to 3 kg.

Tests of P-25 in X-raysTests of P-25 in X-rays

Lobster eye P25 was tested in quasi parallel beam full imaging mode using the 35 meters long X-ray beam line in XACT facility of INAF-Osservatorio Astronomico di Palermo (Italy). X-ray images at the focal plane have been taken with a MCP detector with spatial resolution 100μm.

Experimental setupExperimental setupTested lobster eye

was placed on device allowing

remote controlled rotations figured

by red color. MCP detector was

placed on device allowing remote

controlled translations in all

directions.

SimulationsSimulations

One-dimensional system: The sufficient problem is to One-dimensional system: The sufficient problem is to calculate shades and reflections of individual mirrorscalculate shades and reflections of individual mirrors

D1 = M1b − (M1z − Dz) tan() D2 = M4b − (M4z − Dz) tan()

D1b = M1b − (M1z − I1z) tan(2 + )D2b = M2b − (M2z − I2z) tan(2 + ) = − = arctan[(M2b −M1b)/(M2z −M1z)]

Shading between mirrorsShading between mirrors

M’1z = (N2b − q1)/tM’1b = M2b

M’2z = (q1 − q2)/tM’2b = t M’2z + q1

t = (M2b −M1b)/(M2z −M1z)q1 = M1b − t M1z

q2 = N1b − 2t N1z

One-dimensional system => one-dimensional martrixTwo-dimensional system => outer product of these matrices

Basic imagesBasic images

1500eV1500eV930eV930eV280eV280eV

8000eV8000eV4500eV4500eV2900eV2900eV

GainGainCalculated as Calculated as measured ratio between the flux incoming to LE and the measured average flux of X-rays measured in the projection of the central chamber of size 300×300μm

Experiment Simulations

Spatial resolutionSpatial resolutionEstimation of spatial resolution at energy 930eV

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

-5 -4 -3 -2 -1 0 1 2 3 4 5

x-position [mm]

Inte

nsit

y

Measured data shiftedleft

Measured data shiftedright

Sum of both

Estimated FWHM spatial resolution 13±1 arcmin.If sum profile of the image with the shifted one to simulate profile of image of two point sources and if we find the limit when the intesity between peaks fall to 80% of intesity of peak level, we get the same value. Theoretical value is 5.5 arcmin.

Field of viewField of view

Experimentally found boundary positions =>FOV = 2.9±1º

Yaw = -1.4˚ Yaw = +1.5˚

Angle between boundary chambers is 2.8º

Gain as function of yaw @930eV

0

10

20

30

40

50

60

70

80

-4 -2 0 2 4

Yaw [°]

Gai

n

At the boundary positions, gain is decreased to approx. 1/2

ExplanationExplanation

There are some manufacturing deviation causing the smearing of the image. However, it is a common problem of any technology.

Question: Can we still do some astronomical observations withthis or similar lobster eye?

Field of viewField of viewMeasured value is in agreement with the theoretical. So, we can belive our Measured value is in agreement with the theoretical. So, we can belive our model. Supposing manufacturing of larger LE, with active area of 8model. Supposing manufacturing of larger LE, with active area of 8GG8cm, we 8cm, we could reach could reach FOV of 5FOV of 5GG55ºº..

SensitivitySensitivityThe effective active area calculated from the incoming flux and the total The effective active area calculated from the incoming flux and the total amount of photons focused to spot (defined via FWHM) reaches 0.38cmamount of photons focused to spot (defined via FWHM) reaches 0.38cm22. We . We are conservative and we will suppose this value is unchanged. Also, we are conservative and we will suppose this value is unchanged. Also, we suppose 30% quantum efficiency of a used detector achievable for example suppose 30% quantum efficiency of a used detector achievable for example using an MCP. We simply suppose the object is detected if at least 100 using an MCP. We simply suppose the object is detected if at least 100 photons are focussed into spot.photons are focussed into spot.

These very conservative assumptions based on measured values gives the These very conservative assumptions based on measured values gives the minimal flux to be detected using 1ks exposure time asminimal flux to be detected using 1ks exposure time as

1.4 × 10−9 erg cm−2 s−1 ≈ 60 mCrab

Mission assumptionsMission assumptions

Relevant scientific goalRelevant scientific goalWe could monitor low- and high-mass X-ray binaries (LMXBs and HMXBs) in area of 5G20º around the Galactic center. For this goal, also measured angular resolution around 13 arcmin is sufficient.

The field of the center of the Galaxy (20×80º). The positions of known LMXBs and HMXBs are marked. The field proposed for the monitoring by lobster is marked by the oblong. It contains a number of the already known LMXBs and HMXBs.

Example #1: The light curve of a persistent source GX 3+1 observed by ASM/RXTE isin the 1.5-3 keV band.

Example #2: The outburst of a transient source Aql X-1 observed by ASM/RXTE in the 1.5-3 keV band.

ConclusionsConclusions

Although we reported differences between the theoretical and measured values, presented results still indicate that the proposed lobster eye nano-satellite mission is feasible using known and verified technologies.

Low and high mass X-ray binaries (LMXBs and HMXBs) laying in the center of the Galaxy seem to be good targets for the observations.

AcknowledgnmentsAcknowledgnments

Thanks Prof. Salvatore Sciortino, director of INAF-Osservatorio Astronomico di Palermo

Thanks to Rigaku Innovative Technologies Europe s.r.o. for providing of the lobster eye specimen.

Thank you for Thank you for your attentionyour attention