juhani huovelin and lauri alha observatory, university of helsinki finland

Spaceborne X-ray observations of the Sun and sky background : Analysis of data from the XSM onboard SMART-1

Juhani Huovelin and Lauri AlhaObservatory, University of Helsinki

Finland

J.Huovelin, Patras, 19th May 2006

University of HelsinkiUniversity of Helsinki


University of HelsinkiUniversity of Helsinki SMART-1The first European mission to

the Moon Project startedProject started in 1999 in 1999 LaunchLaunch:: 27 Sept. 27 Sept. 20020033. as . as

a piggybag on Ariane 5 at a piggybag on Ariane 5 at Kourou, French GuianaKourou, French Guiana

MissionMission: ~15 : ~15 months months cruise cruise and 9 and 9 + 12+ 12 months months at Moon orbitat Moon orbit ( (******))

Main taskMain task: Test of Solar : Test of Solar electric propulsion (SEP) electric propulsion (SEP) for future planetary for future planetary missionsmissions (***) Controlled crash to Moon in September, 2006


University of HelsinkiUniversity of Helsinki SMART-1Space Craft (S/C)

Manufacturer: Swedish Space Corporation (SSC)

• Volume: ~1 m x 1 m x 1 m• Mass: 370 kg • Primary propulsion: A plasma thruster:

Sunlight electric power by solar cells/panels a strong electric field inside thruster engine acceleration of ions from thruster S/C acceleration

• Fuel: 82 kg of Xenon-plasma• Thrust force: 70 mN (~weight of one A4

sheet of paper !)- Accelerated SMART-1 to Moon

orbit in 1.5 years • Payload: 19 kg (7 instruments)


University of HelsinkiUniversity of Helsinki SMART-1Payload

7 instruments operating during the whole mission

10 different scientific experiments

D-CIXSD-CIXS (Demonstration of a Compact Imaging X-ray Spectrometer)

XSMXSM (X-ray Solar Monitor)

SPEDE SPEDE (Spacecraft Potential Electron and Dust Experiment)

AMIEAMIE (Advanced Moon micro-Imager Experiment)

Laserlink and OBAN

EPDP EPDP (Electric Propulsion Diagnostic Package)

KKATE ATE (Ka-Band TT&C Experiment)

RSIS (Radio-Science Investigations for SMART-1)

SIRSIR (SMART-1 Infrared Spectrometer)



SMART-1 Science and Technology WorkingTeam (STWT)

B. Foing (ESA project scientist), J.L. Josset, M. Grande (D-CIXS), J. Huovelin (XSM), U. Keller, A. Nathues, G. Noci, A. Mälkki, Z. Sodnik, P. McMannamon

STWT & STOC Flight Operations Team



PI: Manuel Grande, (Rutherford Appleton Laboratory,) UK

Mapping of chemical elements on the Moon (Mg, Si, Al, Fe),

Absolute chemical abundances using XSM data

SMART-1

Demonstration of a Compact Imaging X-ray Spectrometer (D-CIXS)

Science task of D-CIXSScience task of D-CIXS



D-CIXS observations

SMART-1

Centre facet

All detectors on a facetobserve at the same directionwith a ~8 degrees FoV The effective area of a facet is ~5 cm2

Credit: M. Grande et al.



D-CIXS observations of the Moon

SMART-1

Mg Al

Si

Ca Fe

1 keV

10 keV

Credit: M. Grande et al.

• Observations of the X-ray illumination on the sunlit Moon surface (= solar X-ray spectrum)- Needed for Moon science: determination of elemental abundances from X-ray fluorescence spectra measured by D-CIXS on SMART-1- Very useful new information on the hot solar corona solar science- Also other applications: full sky X-ray background, including local intra-solar-system emission

Today’s topicToday’s topic• X-ray spectroscopy of the Sun (and sky

background) with XSM• Search of axion-related X-ray emission

XSM measures theX-ray spectrum of thewhole Sun with good spectral and timeresolution

ETask of XSM

SMART-1


I

X-ray Solar Monitor (XSM)

XSM specifications

Instrument Detector: - HPSi PIN, diameter 2mm - X-ray photon counter - Circular Field-of-View, 52o radius

- Entrance filter: 25 micron Be- Aperture stop, Au, inner diameter 1.5 mm- Electromagetic shutter, 0.4 mm W

(Tungsten)Features - Energy range: 1.5 - 20 keV (effective range) - Energy resolution: ~250 eV @ 6 keV (2003)

~350 eV @ 6 keV (2006)- Effective area (on-axis): 0.0145 cm2

Data Counts sampled to energy spectra: - 1 spectrum/16 s (512 energy channels)

SMART-1


Sensor unit - Dimensions: 81 x 40 x 26 mm3

- Mass: approx. 190 g - Box material: Aluminium- Contents: Detector Cooler (Peltier) Front end electronics Shutter mechanism Calibration source (55Fe+Ti)

1.5

mm

XSM sensitivitySMART-1


On- Axis effective area

Sensitivity: 1cps ~ 10-9 W/m2

XSM observations 2004-5 SMART-1

Observations of the Sun- 351 h total (78933 sp. !)- 42 full flares - 20 partial flares- Flare coverage: B2 – M2+ periods of quiescence (withperiods of quiescence (withaxion-induced emission ?)axion-induced emission ?)

Observations of sky background- 129 hours total- one field covers 1/5 of the whole sky- different offsets from the Sun- Includes all targets, X-ray sky background + possible axion-related X-possible axion-related X-ray emissionray emission


A flare with XSM SMART-1


SMART-1

Observations of the Sun1. Sensitivity

160 s exposure at quiescence, 1-2 x 10-7 W/m2

160 s exposure of a C5 flare, 5 x 10-6 W/m2


SMART-1

Observations of the Sun 2.Rising phase of an X-flare

16 s exposure of a flare 15th January, 2005Flux (1-8 Å)= 10-5 W/m2 (M1 level, a few minutes after onset)

Analysis: Indicative of filling–up of spectrum with denselypopulated line emission, or (non-thermal ?) continuum emission.Temperature > 20 MK.


SMART-1

Observations of the Sun 3. Flare spectra and models

Model: thermal bremsstrahlung + linesC1.5 flare: T = 17 MK (from BS model)- Fe K-alpha vs. K-beta visible and strong enough for comparative temperature analysis- Coronal abundances for several elements below 5 keV

exposure time: 16 s


SMART-1

Model: thermal bremsstrahlung + linesC 5 flare: T = 20 MK (from BS model)- Fe K-alpha vs. K-beta visible and strong enough for comparative temperature analysis- Coronal abundances for several elements below 5 keV

exposure time: 16 s

Observations of the Sun 3. Flare spectra and models


SMART-1

Question 1

J.Huovelin, EGU 2006

WHAT DO WE EXPECT TO SEE, AND WHERE ? Axion-induced X-ray emission1. In the Solar corona1. In the Solar corona - best visible during quiescence (or quiescent regions)- How to distinguish from the solar X-ray spectrum ?2. At ~ 5 RSun away from the Sun- visible all the time- how to distinguish from the sky X-ray background ?3. Elsewhere in the Solar System-how to minimise other sources of X-rays and background ? e.g. measurements of emission between a S/C and a celestial body that is a weak emitter of X-rays

SMART-1

Question 2

J.Huovelin, EGU 2006

X-ray emission from axions in the solar system originated in the Sun

At which energies we expect to see such emission ?At which energies we expect to see such emission ?

What is the expected spectral disribution ?

What is the strength of the expected emission ?

SMART-1

Question 3HOW COULD SMART-1 HELP IN THIS ?1. In the Solar corona1. In the Solar corona - XSM observations of the Sun during coronal quiescence- Accurate modelling of coronal X-ray emission and surrounding sky spectrum (very wide FoV !) needed2. Towards ~ 5 RSun away from the Sun- All off-Sun observations with XSM- Accurate modelling of sky background far away from theSun, and study of deviations for different off-Sun angles3. Elsewhere in the Solar System- XSM observations of the sky background.- D-CIXS observations of the Moon ?


SMART-1

1. XSM observations of quiescent solar corona


Solar X-ray spectrumDate: 30 June 2005Exp. time: 960 soff-axis/Sun: 9 degCount rate: 250 cpsFlux (2-10 keV): 7.1 10-8 W/m2

Model: -Thin thermal plasma (Sun)- Broken powerlaw (sky/bkg)

SMART-1



Solar X-ray spectrumDate: 06 Jan 2006Exp. time: 1120 soff-axis/Sun: 3 degCount rate: 48 cpsFlux (2-10 keV): 1.1 10-8 W/m2


SMART-1



Solar X-ray spectrumDate: 25 Mar 2006Exp. time: 1600 soff-axis/Sun: 9-12 degCount rate: 74 cpsFlux (2-10 keV): 1.8 10-8 W/m2


SMART-1

X-ray sky observationwith XSM

Average signal rate (1-20 keV): ~ 1 cps

Fit result (Note: includes all X-ray sources in a 2.4 sterad sky field):Flux (E, keV) = 111.0 x E –1.06 x exp(-E/11.7) photons/cm2/s/keVFlux (2-10keV) = 8 x 10-7 erg/cm2/s (~ 1/5 of full sky)Estimate: ~ 4 x 10-6 erg/cm2/s for full sky (TBC by analysis of all data) ~ 3.3* 10-7 erg/cm2/s/sr average

3.4 h integration(762 spectra)


SMART-1

2. XSM observations towards ~ 5 RSun away from the Sun


Solar X-ray spectrumDate: 21 June 2004Exp. time: 4416 soff-axis/Sun: 53-54 degCount rate: 0.7 cpsFlux (2-10 keV): 5.3 10-10 W/m2

Model: - Broken powerlaw (sky/bkg)

SMART-1

3. Observations elsewhere in the Solar System


Solar X-ray spectrumDate: 13 June 2004Exp. time: 20752 soff-axis/Sun: 75-79 degCount rate: 1.0 cpsFlux (2-10 keV): 8.0 10-10 W/m2

Model: - Broken powerlaw (sky/bkg)

SMART-1

Conclusions


There may be weak signs on some residual emissionThere may be weak signs on some residual emission at some energies

- Interpretation: may be due to inaccurate modelling of

- Solar X-ray spectrum

- Sky X-ray background spectrum

However, it is possible to derive an upper limit to the axion-related component.

- Reliable, since instrument background very low

SMART-1

Future ?


Idea: XSM observation towards the Moon before SMART-1 crashes on the Moon

- Possible to make accurate quantitative analysis of the observation

- Large FoV, thus large volume of space between S/C and Moon surface compensates for the small size of detector

Future space missions with our involvement (for more data):

- Chandrayaan-1 (ISRO): Moon mission on 2007-8 with XSM2

- BepiColombo (ESA): Mercury mission (2013-20) with SIXS and MIXS X-ray instruments (similar task as for SMART-1 D-CIXS/XSM)

juhani huovelin and lauri alha observatory, university of helsinki finland

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