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GAIA - BORDEAUX WS 17-18 November 2002
Solar System Working Group
2nd Meeting
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F. Mignard
GAIA - BORDEAUX WS 17-18 November 2002
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
GAIA - BORDEAUX WS 17-18 November 2002
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
GAIA - BORDEAUX WS 17-18 November 2002
The Solar System Science with GAIA
The Solar System Working GroupThe Solar System Working Group
GAIA - BORDEAUX WS 17-18 November 2002
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
GAIA - BORDEAUX WS 17-18 November 2002
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
GAIA - BORDEAUX WS 17-18 November 2002
• 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
GAIA - BORDEAUX WS 17-18 November 2002
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
GAIA - BORDEAUX WS 17-18 November 2002
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)
GAIA - BORDEAUX WS 17-18 November 2002
Relevance of the new design for Solar System
GAIA - BORDEAUX WS 17-18 November 2002
ASTRO-1 secondary mirror
Astro-2 Primary mirror
Astro-1 Primary mirror
Basic angle monitoring
GAIA : Optical system
ASTRO focal plane
reflectors)
GAIA - BORDEAUX WS 17-18 November 2002
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
GAIA - BORDEAUX WS 17-18 November 2002
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
GAIA - BORDEAUX WS 17-18 November 2002
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
Along scan disp. - Horizontal telescope Scale: 0.10 AsF 11-Mar-02
255.10 MM
Scan axisScan axis
15:36:36
Along scan disp. - Horizontal telescope Scale: 0.10 AsF 11-Mar-02
255.10 MM
Scan axis
15:36:36
Along scan disp. - Horizontal telescope Scale: 0.10 AsF 11-Mar-02
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"
GAIA - BORDEAUX WS 17-18 November 2002
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%
GAIA - BORDEAUX WS 17-18 November 2002
Detection of moving objects
GAIA - BORDEAUX WS 17-18 November 2002
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
GAIA - BORDEAUX WS 17-18 November 2002
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%
GAIA - BORDEAUX WS 17-18 November 2002
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
GAIA - BORDEAUX WS 17-18 November 2002
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
GAIA - BORDEAUX WS 17-18 November 2002
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
GAIA - BORDEAUX WS 17-18 November 2002
Detection IV
0.7°
~ 3s = 180 " 0.25° max
t t+ 6000 s
GAIA - BORDEAUX WS 17-18 November 2002
Simulations and tools available
GAIA - BORDEAUX WS 17-18 November 2002
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
GAIA - BORDEAUX WS 17-18 November 2002
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
GAIA - BORDEAUX WS 17-18 November 2002
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)
GAIA - BORDEAUX WS 17-18 November 2002
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
GAIA - BORDEAUX WS 17-18 November 2002
Overall Statistics
GAIA - BORDEAUX WS 17-18 November 2002
Number of observations
GAIA - BORDEAUX WS 17-18 November 2002
Number of Epochs
GAIA - BORDEAUX WS 17-18 November 2002
Phases of minor planets with GAIA
Statistics on the first 20 000 planets
GAIA - BORDEAUX WS 17-18 November 2002
Solar elongation of minor planets
Statistics on the first 20 000 planets
GAIA - BORDEAUX WS 17-18 November 2002
Apparent magnitude
Statistics on the first 20 000 planets
GAIA - BORDEAUX WS 17-18 November 2002
Apparent Magnitudes
V = H + m
GAIA - BORDEAUX WS 17-18 November 2002
Along and across-scan proper speed
MB
MB NEOs
NEOs
GAIA - BORDEAUX WS 17-18 November 2002
Distance to Sun and Earth
MB
MB
GAIA - BORDEAUX WS 17-18 November 2002
How many Close Approaches ?
GAIA - BORDEAUX WS 17-18 November 2002
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
GAIA - BORDEAUX WS 17-18 November 2002
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
GAIA - BORDEAUX WS 17-18 November 2002
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
GAIA - BORDEAUX WS 17-18 November 2002
Statistics
GAIA - BORDEAUX WS 17-18 November 2002
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
GAIA - BORDEAUX WS 17-18 November 2002
Actions for the next six months
GAIA - BORDEAUX WS 17-18 November 2002
GAIA - BORDEAUX WS 17-18 November 2002
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)
GAIA - BORDEAUX WS 17-18 November 2002
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, ....)
GAIA - BORDEAUX WS 17-18 November 2002
= 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
Recommended