GAIA - BORDEAUX WS 17-18 November 2002 Solar System Working Group 2nd Meeting ----- F. Mignard.

GAIA - BORDEAUX WS 17-18 November 2002

Solar System Working Group

2nd Meeting

-----

F. Mignard


AGENDA 17/10

09h00 Welcome and administrative matters of the WG, membership F. Mignard 09h30 Status of the GAIA programme M. Perryman 10h00 Impacts of the new design : geometry, detection F. Mignard

10h30 Coffee

10h45 Orbit prediction and determination K. Muinonen, J. Virtanen 11h30 Orbit improvements M. Carpino

12h15 lunch break

14h00 The NEO population model- Observations from space A. Morbidelli 14h30 Simulations of the MPs and NEOs passages with the new design F. Mignard 15h00 Update on a possible ground based network W. Thuillot 15h30 Design of an automatic instrument: the ARAGO project M. Boer 16h00 The asteroid data base by 2010 E. Zappala

16h30 coffee

17h00 Simulation of images of asteroids by GAIA A. Dell'Oro 18h00 Signal produced by gaia from asteroids D. Hestroffer (scattering, shape, photocenter shift) 18h30 Interactions with the simulation group all


AGENDA 18/10

9h00 Taxonomy with the photometric data : status E. Dotto 9h30 Asteroids radial velocity E. Dotto 10h15 The data base for GAIA E. Zappala

10h45 Coffee

11h00 Masses of asteroides from ground based observations. M. Rapaport The present situation. Perspectives.

11h45 Statistics of close approaches in 2011-2016. F. Mignard

12h15 lunch break

14h00 Conclusions and actions, next meeting

16h00 End of the Meeting


The Solar System Science with GAIA

The Solar System Working GroupThe Solar System Working Group


Science Goals

• Systematic survey down to 20 mag ~ 5x105 objects

• Main belt

• NEOs

• Orbits : virtually all object observed - x30 better than now

• Masses from close encounters ~ 100 masses expected

• Diameter for over 1000 asteroids : shape, density

• Photometric data in several bands : albedo, taxonomic classification

• Space distribution vs. physical properties

• Perihelion precession for 300 planets


Objectives of the task

• Assess observability of :

– minor planets, NEOs, satellite, comets, KBO

• Set the constraints on the CCDs for the best detection of moving

sources

• Determine the algorithms for the orbit reconstruction (known or new

objects)

• Assess the requirements on photometry for the best science return

• Assess the needs of and provide solar system ephemeris

• Provide recommendations for the quick alert mode

• Investigate the organisation of follow-up observations


• M. Carpino• A. Cellino• A. del'Oro• E. Dotto• D. Hestroffer• E. Hoeg• S. Klioner• F. Mignard• K. Muinonen• M. Rapaport• P. Tanga• W. Thuillot• E. Zappala

• C. Bailer-Jones• P. Bendjoya• J. Berthier• F. Colas• A. Doressoundiram• W. Evans• C. Fabricius• P. Hjorth• J. Kovalevsky• P. Kroll• C.I. Lagerkvist• R. Michelsen• A. Morbidelli• V. Vansevivius• J. Virtanen• S. Wolff

Core members Associates

Membership


Activities

Tasks identified Leader

- Asteroid size and shape A. Cellino

- Simulation and detection F. Mignard

- Orbit determination K. Muinonen

- Surface properties P. Tanga

- Photometry & Taxonomy E. Dotto

- Data base E. Zappala

- Mass determination D. Hestroffer

- Ground based follow-up W. Thuillot


Review of Actions (Feb 02)

• Provide a reference orbit for GAIA about L2 (FM)

• Investigate the possibility to obtain radial velocities (ED)

• Short note on the Monte Carlo method for orbits (KM)

• Algorithms for the orbit determination with GAIA data (KM, MC,DH)

• Investigate the propagation of orbit uncertainty to positions (MC)

• Outline of a global solution for mass determination (FM, DH)

• Investigate the photocenter offset vs. scattering model (AC)

• State of the art in the knowledge of asteroid masses (MR)

• How many objects and orbits by 2010 ? (EZ)

• Web pages on-line (FM)

• Discussion area and common storage zone (PT)


Relevance of the new design for Solar System


ASTRO-1 secondary mirror

Astro-2 Primary mirror

Astro-1 Primary mirror

Basic angle monitoring

GAIA : Optical system

ASTRO focal plane

reflectors)


Parameters of the main optics

• Aperture Aperture 1.4 x 0.5 m1.4 x 0.5 m22

• Focal length Focal length 47 m47 m

• Scale Scale 1 mas = 0.2 µm 1 mas = 0.2 µm

• Basic angleBasic angle 106°106°

• Spin periodSpin period 6 h 6 h

• Astro Fi eld of viewAstro Fi eld of view

0.66 x 0.66 deg0.66 x 0.66 deg 2 2

• ExtendedExtended 0.92 x 0.66 deg0.92 x 0.66 deg22


Astro Focal plane

~ 750 mm, 0.92 deg

600 mm0.74 deg

ASM2ASM1 AF1-11 BBP

Astro FieldAstro Field

• Cell size : 49 x 60 mmCell size : 49 x 60 mm22

• CCD size : 45 x 59 mmCCD size : 45 x 59 mm22

• 4.5 k x 2 k4.5 k x 2 k

• Pixel size 10 x 30 µmPixel size 10 x 30 µm22

• = 44 x 133 mas= 44 x 133 mas22

• TDI : 0.735 msTDI : 0.735 ms

• Airy (along) 103 masAiry (along) 103 mas

• Integration time : 3.3 sIntegration time : 3.3 s

• For ASM : 1.9 sFor ASM : 1.9 s

FOV 2FOV 1


Photo and spectro telescope15:36:36

Along scan disp. - Horizontal telescope Scale: 0.10 AsF 11-Mar-02

255.10 MM

Scan axis

15:36:36


255.10 MM

Scan axisScan axis

15:36:36


255.10 MM

Scan axis

15:36:36


255.10 MM

Scan axisScan axis

Focal length Focal length 2.1 m2.1 m

ApertureAperture 0.5 x 0.5 m0.5 x 0.5 m22

Airy spotAiry spot ~ 300 mas~ 300 mas

Field of viewField of view 2° x 4.8 °2° x 4.8 °

UnvignettedUnvignetted 2° x 3.2 °2° x 3.2 °

ScaleScale 10 µm = 1"10 µm = 1"


MBP and Spectro Fields

1.6°60 mm

2° = 120s = 74 mm

1.6°60 mmMBP2

1.6°60 mm

RVS

RVSM

MBPSM

MBP1

CCDsCCDs

MBP : 336 x 3932 pxsMBP : 336 x 3932 pxs

RVS : 1100 x 3932 RVS : 1100 x 3932 pxspxs

Pixel sizePixel size

10 x 15 µm10 x 15 µm22

1 x 1.5 arcsec1 x 1.5 arcsec22

Integration timeIntegration time

RVSM ~ 3 x 5.5sRVSM ~ 3 x 5.5s

MBPSM : 5.5 sMBPSM : 5.5 s

ResolutionResolutionR ~ 10000 = 0.4 R ~ 10000 = 0.4 Å/pixelÅ/pixel

V =19%


Detection of moving objects


Detection and recognition

• Solar system objects are moving relative to the stars

• Internal detection from motion: field crossing ~ 30 s,

• Observations in the 2 astro FOVs and in the spectro FOV

– NEO ~ 50-100 mas/s

– Main belt ~ 10 mas/s

– Trojan ~ 5 mas/s – Kuiper belt ~ 1 mas/s


Astro and Spectro Focal planes

~ 750 mm, 0.92 deg

600 mm0.74 deg

ASM2ASM1 AF1-11 BBP

FOV 2FOV 1

1.6°60 mm

2° = 120s = 74 mm

1.6°60 mmMBP2

1.6°60 mm

RVS

RVSM

MBPSM

MBP1

V =19%


Detection-I

Airy Pixel Integration

mas mas s

ASM 100 40 1.9

AF1 100 40 3.3

RVSM 300 1000 5.5*3

MBPSM 300 1000 5.5


Detection II

• Signature : relative motion of the image wrt TDI'ed image

• Measure : comparison of abscissa in different CCDs• Average alon-scan speed :

– 10 mas/s main-belt– 30 mas/s neo

ASM1

ASM2

AF1

s mas pixels

MB NEO MB NEO

ASM1 AF1 4.5 45 135 1.1 3.3ASM2 AF1 2.6 26 78 0.7 2.1

AF1 AF11 33 330 1000 8 24

RVSM1 RVSM3 12 120 360 0.12 0.4


Detection III

• Motion between Prec and Foll FOV

• No direct comparison of position

• But shift wrt to the stars shift in crossing time

• 106° ~ 6000 s

MB NEO

~ 60 180"

t ~ 1s 3s


Detection IV

0.7°

~ 3s = 180 " 0.25° max

t t+ 6000 s


Simulations and tools available


Simulation for the Solar System

• Goal : to provide realistic sequences of observations of moving sources

• Method : Computing the crossing time in the 3 FOVs of minor planets

• Crossing over 5 years of the scanning law and several 104 asteroids (main belt, neos)

• Output : for each object– t1, t2, … tn : crossing times– v1, v2, … vn : crossing speed ( along scan and transverse)– Apparent magnitude


Structure of the output file

1 Ceres 310 2 2 0 1 -1 0 2 2 15.5200 15.7708 16.0217 16.0731 16.1475 16.2725 16.5234 36.5252 8.0 8.0 8.0 8.0 8.0 8.0 8.0 7.6 21.45 21.43 21.40 21.40 21.37 21.37 21.34 17.87 2.30 2.20 2.11 2.11 2.01 2.01 1.91 -3.05 6.05 6.03 6.01 6.01 5.99 5.99 5.97 -1.52

Planete ID, N_obs

Fields (0 : spectro, 1: astro leading, -1 : astro trailing , 2 : MBP)

Crossing time (days)

Apparent magnitude

Phase angle in deg.

Inertial speed along scan in mas/s

Inertial speed cross scan in mas/s


Other tools

• Scanning law of GAIA as a callable subroutine– call scanning(XMJD, XSI,XKK,ETAZ, XLSUN, PSI, TETA,PSIP,TETAP, SUN, EPS)

! input!! xmjd : date in modified julian days! xsi : sun aspect angle (50 deg)! xkk : precession frequency (5.25 rd/yr)! etaz : initial phase!! output!! xlsun : longitude of the sun in degrees! psi : ascending node/sun of the scanning

circle in deg! teta : inclination of the scanning circle in deg! psip : dpsi/dt in "/s! tetap : dteta/dt in "/s! sun : heliotropic abscissa of the node! eps : latitude of the sun /scanning circle (pi/2-

xi)


Other tools

• A realistic orbit of Gaia about the L2 point (file or

subroutine)

– Lissajous orbit with 6 - 7 years quasi-period

• Motion of the barycenter wrt the Sun

– Surbroutine with an accuracy of 1000 km


Overall Statistics


Number of observations


Number of Epochs


Phases of minor planets with GAIA

Statistics on the first 20 000 planets


Solar elongation of minor planets



Apparent magnitude



Apparent Magnitudes

V = H + m


Along and across-scan proper speed

MB

MB NEOs

NEOs


Distance to Sun and Earth

MB

MB


How many Close Approaches ?


Close approach : impulse approximation

Perturbed motion of a minor planet

m

2

2

V

Gm

m D V Msol km ua km/s mas

10-10 ~500 0.1 3 400.05 3 80

10-11 ~200 0.1 3 40.05 3 8

V


Close approaches 2010.5 - 2016

• List of close approaches between

– the first 500 minors planets and 20 000 targets

• Criteria used for an effective close approach

– distance

– relative speed

– angular deflection

– impulse change of orbital elements

• Ouptut :

– each close approach (date, geometry, efficiency)

– global statistics per deflector


dmin < 0.2 0.1 0.05 0.02 0.01 au

1 Ceres 356 82 14 3 0

2 Pallas 181 46 9 1 1

3 Juno 531 125 23 3 0

4 Vesta 597 159 37 5 2

5 Astraea 577 141 41 5 1

6 Hebe 512 134 34 4 2

7 Iris 556 136 34 1 0

8 Flora 626 155 35 6 1

9 Metis 597 141 38 8 2

10 Hygiea 238 56 14 3 2

11 Parthenope 603 153 43 6 2

12 Victoria 532 129 36 4 2

13 Egeria 287 86 12 1 0

14 Irene 408 108 22 5 2

15 Eunomia 473 115 25 1 0

Number of closest approaches < dmin


Statistics


Number of deflections > lim

> 1 5 20 100 mas 1 Ceres 8738 4828 1518 163

2 Pallas 275 18 1 0

3 Juno 162 6 0 0

4 Vesta 5772 1575 314 30

5 Astraea 41 6 0 0

6 Hebe 66 9 0 0

7 Iris 382 51 7 1

8 Flora 188 22 2 2

9 Metis 3369 773 144 16

10 Hygiea 3675 901 193 26

11 Parthenope 377 48 8 0

12 Victoria 34 8 2 0

13 Egeria 93 5 2 0

14 Irene 1874 195 24 3

15 Eunomia 377 27 6 0

N > 5 305 120 40 11


Actions for the next six months


Actions (Oct 02)Pending from the last meeting

• Outline of a global solution for mass determination (MR, FM, DH)

• Web pages on-line (FM, PT)

– available documents, presentations ...

New actions

• Initial error model for the astro observations of moving objects (FM)

• Simulated observations in the astro fields over short timespan (FM)

• Contact with C. Jordi for the photometric band (ED)

• Algorithms for detection for moving objects (SW, FM, PH, EH)

• Contact with IAU WG on GB astrometry (WT)

• Determination of physical parameters from photometry (EZ)

• Observability of planets and satellites (PT)

• Add planets in the simulation file (FM)


Actions (Oct 02)

New actions (ctd)

• Radial velocities in the simulation file (FM)

• List of minor planets and pieces of software for Sim WG (AM)

• Observations of very faint objects with input catalogue ()

• GB observations vs. GAIA for orbit improvement (MC) • Non gravitational forces (AM, ....)


= 1.7 au = 3.7 au

D

km

H

magN ( < H)

mag

mas

V

mag

mas

Vmag

250 7.3 5 200 10.6 90 12.3100 9.2 200 80 12.6 40 14.2

50 10.7 2000 40 14.1 20 15.725 12.5 10 000 20 15.6 10 17.3

10 14.2 5 x 104 8 17.6 4 19.25 15.7 2 x 105 4 19.1 2 20.7

2 17.7 10 6 1.6 21.0 0.8 22.71 19.2 5 x 106 0.8 22.6 0.4 24.2

5

D : diameter - H : abs. mag. - : angular diameter - V : apparent mag.

Some useful numbers

Albedo = 0.05

GAIA - BORDEAUX WS 17-18 November 2002 Solar System Working Group 2nd Meeting ----- F. Mignard.

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Transcript of GAIA - BORDEAUX WS 17-18 November 2002 Solar System Working Group 2nd Meeting ----- F. Mignard.