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Phenomena in the Solar Phenomena in the Solar System: System: need of network of need of network of observationobservation

J.E. Arlot, M. StavinschiJ.E. Arlot, M. Stavinschi

IMCCE/CNRS/observatoire de ParisIMCCE/CNRS/observatoire de ParisInstitut astronomique de l’académie roumaineInstitut astronomique de l’académie roumaine

Antalya, March 2006Antalya, March 2006

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SummarySummary

• The observations of the natural planetary satellites

• The phenomena• The occurrences of the phenomena• What is a mutual event• The difficulties of the observations• The infrared observations• The network of observers• The Uranian satellites• The scientific goals

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For dynamical studies

flux

time (hours)

The mutual events (occurring each 6 years)

Two kinds of observationTwo kinds of observation

Astrometric observations

Photometric observations

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The accuracy depending on the kind of observationThe accuracy depending on the kind of observation

Example: the Galilean satellites

Kind of observation Accuracy in mas

Accuracy in km

Eclipses by Jupiter 150 450

Old photographic plates

100 300

Transit circle 60 180

Plates newly reduced 50 150

CCD observations 40 120

Mutual events 15 45

Interest of observing the mutual events

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The accuracy depending on the kind of observationThe accuracy depending on the kind of observation

Kind of observation Accuracy in mas Accuracy in km

CCD observations 40 400

Mutual events 6 60

The case of the Uranian satellites

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The most common eventsThe most common events

• The most common events are the eclipses by the planet

The atmosphere on the planet leads to a poor astrometric accuracyThe atmosphere on the planet leads to a poor astrometric accuracy

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Rare eventsRare events

The Mutual events (Galilean satellites of Jupiter) The Mutual events (Galilean satellites of Jupiter)

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Opportunities for mutual eventsOpportunities for mutual events

Mutual events occur when the planetocentric declination of the Earth and the Sun is zero: for example for the Galilean satellites, it happens in 2003 and in 2009

This occurrence should be at the opposition of the planetThis occurrence should be at the opposition of the planet

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Rare eventsRare events

Occurrence of mutual events:

Uranus: 2007-2008 (every 42 years)Jupiter: 2009 (every 6 years)Saturn: 2010 (every 15 years)

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What is an observation of a mutual event?What is an observation of a mutual event?

The direct astrometric measurementThe direct astrometric measurementis replaced by a photometric measurement against is replaced by a photometric measurement against timetime

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What is an observation of a mutual event?What is an observation of a mutual event?

It is a light curve which includes physical properties It is a light curve which includes physical properties of the surface of the body and dynamical parameters of of the surface of the body and dynamical parameters of the motion of both satellites. The light curve must be the motion of both satellites. The light curve must be referred to UTC within 0.1 second of time.referred to UTC within 0.1 second of time.

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What happens during a mutual eventWhat happens during a mutual event

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Observation of a mutual eventObservation of a mutual event

An occultation of a satellite by anotherAn occultation of a satellite by another

The satellites are slightly out of focus to improve The satellites are slightly out of focus to improve thethephotometric accuracy and avoid saturation of the photometric accuracy and avoid saturation of the receptorreceptor

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Examples of lightcurvesExamples of lightcurves

Non-symetrical lightcurveNon-symetrical lightcurve Non-symetrical lightcurveNon-symetrical lightcurve

Deep event near totalDeep event near totalFaint event grazingFaint event grazing

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Sky and meteorological problemsSky and meteorological problems

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Infrared observationsInfrared observations

• An example of infrared observation: the measurement of the thermal emission of a satellite

• The case of Io

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Infrared observationsInfrared observations

Occultation of Io by EuropaOccultation of Io by Europa

The first ground-based detections of the volcanoesThe first ground-based detections of the volcanoesof Io were made through occultations of Ioof Io were made through occultations of Io

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Observing sitesObserving sites

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Past observationsPast observations

Galilean Satellites of JupiterGalilean Satellites of Jupiter

The last campaigns of observations provided numerous dataThe last campaigns of observations provided numerous data

1985 1991 1997 2003

Number of sites of

observations

28 36 42 34

Number of observation

s made

166 401 255 271

Number of events

observed

64 115 122 104

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The Uranian satellitesThe Uranian satellites

These satellites are difficult to observe, more easily observablein infrared:

Ariel: magnitude 14.4Umbriel: magnitude 14.8Titania: magnitude 13.8Oberon: magnitude 14.2Miranda: magnitude 16.5Puck: magnitude 20

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Example: events observable from TurkeyExample: events observable from Turkey

Year Mth Day Hr mn sec Event2006 5 18 1 7 48. 5 O 1 2006 7 15 0 8 12. 5 O 1 2007 8 1 2 9 7. 1 E 5 2007 8 15 23 58 52. 5 E 3 2007 8 17 1 13 56. 5 O 2 2007 8 26 1 51 48. 2 E 5 2007 8 29 2 20 47. 1 O 5 2007 9 22 18 26 19. 1 O 5 2007 9 30 17 39 10. 1 E 5 2007 10 19 19 22 53. 5 E 4 2007 11 17 17 8 2. 1 E 5 2007 12 6 16 39 59. 5 E 1 2007 12 18 18 4 41. 5 E 1 2008 2 2 15 53 10. 5 E 1 2008 7 14 22 24 31. 5 E 1 2008 9 10 22 26 41. 5 E 1

Event:

5 O 1 means that satellite 5 occults satellite 1

2 E 5 means that satellite 2 eclipses satellite 5

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The scientific goalsThe scientific goals

• Study of dynamics of systems of natural satellites

• They are small solar systems allowing to understand formation and evolution of such systems

• Making models including all gravitational effects and dissipation of energy

• Need of a high astrometric accuracy to quantify all physical and dynamical parameters and measure accelerations

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A question to be solved with accurate astrometryA question to be solved with accurate astrometry

Tides from satellite to planet

Tides from planet to satellite

Tidal effects in the jovian system

planetsatellite

a, e

a, esatellite

planet

Satellite escapesSatellite escapes

Satellite fallsSatellite falls

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First estimations of the acceleration of the Galilean satellitesFirst estimations of the acceleration of the Galilean satellites

Galilean Satellites of Jupiter: Galilean Satellites of Jupiter:

Purpose of the increasing astrometric accuracy:Purpose of the increasing astrometric accuracy:- measure of the tidal effects- measure of the tidal effects

n’1/n1 n’2/n2 n’3/n3

De Sitter, 1928 +33 (+/- 5) +27 (+/- 7) -15 (+/- 6)

Greenberg, 1986

+32 (+/- 8) -16 (+/- 4.5) -16 (+/- 4.5)

Goldstein, 1996 +70 (+/- 75) +56 (+/- 57) +28 (+/- 20)

Vasundhara, Arlot, 1996

+22.7 (+/- 7.9) -6.1 (+/- 9.3) +10.6 (+/- 10.6)

Aksnes, Franklin, 2001

+54.7 (+/- 16.9)

+27.4 (+/- 8.4)

-27.4 (+/- 8.4)

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ConclusionConclusion

• Rare events are coming soon• We need a network of observers

• Please join us for these observations !

• Web site: http://www.imcce.fr/pheura07• e-mail: arlot@imcce.fr

• Workshop to be held in Paris on November 16-18, 2006

• Web site: http://paris2006.imcce.fr