1. 21 Lutetia: Overview of Results
10/3/2017
21 Lutetia: Overview of Results
from OSIRIS Images
H. Sierks1, C. Barbieri2, D. Koschny3, P. Lamy4,
H. Rickman5, R. Rodrigo6, and the OSIRIS team
1 Max-Planck-Institut für Sonnensystemforschung, Katlenburg-Lindau, Germany
2 CISAS, University of Padova, Padova, Italy
3 Research and Scientific Support Department, ESTEC, Noordwijk, The Netherlands
4 Laboratoire d’Astrophysique de Marseille, Marseille, France
5 Department of Astronomy and Space Physics, Uppsala, Sweden
6 Instituto de Astrofísica de Andalucía - CSIC, Granada, Spain
6 lead scientists, 9 contributing institutes to Osiris h/w, 35 CoIs, 15 associate scientists, 50 team scientists plus local scientists, post docs, phd students

2. Outline OSIRIS – Scientific Camera System
10/3/2017
Outline
OSIRIS – Scientific Camera System
Observation Geometry and Sequence
Approach Sequence
Opposition Images
Closest Approach
Shape Prediction & Observation
Lutetia Map Projection & Coordinate System
Surface Geomorphology
Boulders and Landslides
Ejecta Thickness from Craters
Lutetia Reflectance Spectrum
Summary
Bridge from Rita intro and Sonia asteroid context talk to observations by Osiris
Instrument, observation geometry, approach, opposition, CA, farewell, science: shape vs predict, map, geomorphology, boulders, ejecta, spectrum

3. OSIRIS - Scientific Camera System
10/3/2017
OSIRIS - Scientific Camera System
NAC – Narrow Angle Camera
FOV 2.2°, IFOV 18.6 µrad/px
2k x 2k BI E2V CCD, AB
60m px CA, f/8, 717mm
23 Filters 250 to 1000 nm (UV to IR)
2 high performance cameras, an optimized couple, both off axis imagers, optimized for comet observations
WAC – Wide Angle Camera
FOV 12°, IFOV 100 µrad/px
2k x 2k BI E2V CCD, AB
300m px CA, f/5.6, 140mm

4. Observation - Geometry and Sequence
10/3/2017
Observation - Geometry and Sequence
OSIRIS fly-by sequence from closest approach (CA) -9h to CA +16 min
234 NAC images, 228 WAV images, total of 462 images with ~1 GB of image data
show observation geometry and sequence of events, zero phase angle at 18 min before CA, got down to 0.15deg phase angle
CA is at 3170km, so 10km off
(plot courtesy ESA)

5. km -9:30h
km -7:30h
10/3/2017
km –5:30h
km -4:00h
km -1:30h
km -3:00h
km -0:46h
km -1:10h
distances and time to CA, s/c flip is corrected for, see Lutetia rotation, upper left, 2 px dia, lower right 24px dia, disk 300px total

6. Opposition Images phase angles 4.1°, 2.0°, 0.6°, 0.15°
10/3/2017
Opposition Images
km -0:30h
km -0:22h
Zero phase angle crossing
km -0:19h
km -0:18h
phase angles 4.1°, 2.0°, 0.6°, 0.15°
Work by Stefan Schroeder, MPS

7. Opposition Image Stretched
10/3/2017
Opposition Image Stretched
Opposition Spot
NAC phase angle ~0.15°
Albedo variation in
landslide area ~7%
Line features are visible
Small impact feature
Opposition spot crossing surface
See opposition spot running over the surface
No s/c shadow ;-)
Features: fresh crater, land slide, stripes, small new crater ejecta
Work by Stefan Schroeder, MPS

8. Closest Approach 10/3/2017 All NAC, all orange
3.600 km -0:02h
3.170 km CA
All NAC, all orange
Upper left at 15:42, 3604km, CA upper right at 15:44:48, mid from 3207 to 3667km. Low 3915, 4628, 6072, 6304 km, lower right 15:50:39, CA +5min
CA –2min to CA +5min, 3604 to 3169 to 6304 km
6.300 km +0:06h

9. 10/3/2017
Closest Approach
Highest resolution 60m px resolution, see large impact craters of size comparable to radius of the asteroid, smooth near craterless regions indicate recent impacts and ejecta. Regional units show craters, grabens, scarps, pits, ridges, contacts, large boulders. Craters with sharp and steep walls, some with land slides, some with irregular shape, and others almost filled with regolith are found.
Add scale bar, add arrows
10 km

10. Shape Prediction & Observation
10/3/2017
Shape Prediction & Observation
3.902 km distance
size Frascati: 134 x 102 x 94 km3, 1 sigma error 3 x 2 x 8 km
B Carry volume 5.94 ± 0.90 x 10^20 cm^3
T Morley mass ^18 kg -> density 3.6 (3.1 to 4.2) g/cm3
Excellent agreement with the predicted
shape based on light curve inversion and
AO observation with OSIRIS images.
(see B. Carry et al., this conference)
km (top), km distance (bottom)

11. Lutetia Coordinate System
10/3/2017
Lutetia Coordinate System
Use Osiris/LAM shape by
silhouette based on WAC
limb images
Project NAC highres images
on shape
Project grid of
coordinates on shape to
create coordinate system
Identify features by
latitude/longitude
Will be improved by use of
final shape from photo-
clinometry (see Lamy et al.,
this conference)
Work by Jean-Baptiste Vincent, MPS
Use WAC images for coarse shape model (shape by silhouette)
Move down to backup (tbc)

12. Lutetia Coordinate System
10/3/2017
Lutetia Coordinate System
More than 50% seen by Osiris, we cover up to -10 to -20 deg
Cylindrical projection, checkout Mercator JBV, redo psf deconvolved
Work by JBV, MPS

13. Surface Geomorphology
10/3/2017
Surface Geomorphology
Started to do cartography
Work of Matteo Massironi, UPD
Work by Matteo Massironi, UPD

14. Boulders and Landslides
10/3/2017
Boulders and Landslides
Boulders in 2 regions (Montmatre and Trocadero)
Total of 237 boulders identified of size of min 100m
3 landslides in Montmatre; gravitational talus in Trocadero
Work by Richard Moissl, MPS
Boulders not of size of Ayers Rock, but of impressive size up to 300m
5 km
Work by Richard Moissl, MPS

15. 10/3/2017
Regolith Thickness
First estimation of d/D for different "old" regions between 0.13 and 0.3, similar to what has been measured on other planetary surfaces.
"Young" region shows craters completely buried under the regolith blanket.
If the region was similar to the rest of the asteroid before the resurfacing, these craters must be at least 600m deep, which gives a lower limit on the regolith thickness.
Crater diameter: 70 pixels ~ 4.5 km
Blanket thickness:
~600 m (for d/D = 0.13)
Work by Jean-Baptiste Vincent, MPS
Work by Jean-Baptiste Vincent, MPS

16. Lutetia Reflectance from OSIRIS
10/3/2017
Lutetia Reflectance from OSIRIS
Distance km
NAC ~100 px dia
WAC ~20 px dia
Disk integrated
Phase angle 7.74°
TNG spectrum
from15/16 Nov 2004
(Belskaya et al. 2010)
Match UV with ALICE
Match IR with VIRTIS
Want to match to UV with ALICE, IR to VIRTIS, to come
Work by Sonia Fornasier, LESIA

17. Summary Asteroid fly-by was very successful
10/3/2017
Summary
Asteroid fly-by was very successful
Lutetia is a piece of rock, too dense for a rubble pile
Old and young regions, young with ‘fresh’ blanket
Blanket in North Pole region suggests a thick layer
of regolith/ejecta
Lutetia exposes fascinating morphology with many
craters, grooves, ridges, graben, etc. that lead to
speculations about Lutetia’s history
Craters suggest Lutetia is very old
(see Marchi et al., this conference)
No satellites found, size limit 160m from WAC images
(see Bertini et al., this conference)
No exosphere found (Na)
Nature paper in preparation
M-type by mass
C-type by
X-type

18. Lutetia in Perspective
10/3/2017
Lutetia in Perspective
Collection by E. Lakdawalla, APOD 26 July 2010
Collection by E. Lakdawalla, APOD 26 July 2010

19. Farewell Lutetia
Thank you.

20. Talks to Come Martin Pätzold et al. on mass from radio tracking
Nick Thomas et al. on surface geomorphology
Simone Marchi et al. on age from crater counting
Stubbe Hviid et al. on color variegation
Philippe Lamy et al. on shape and physical properties

21. Backup Slides

22. Phase function ALBEDO UV375 0.15956 phase=0.15°

23. 21 Lutetia
Belskaya & Shevchenko 1999