NGAO- Solar System Science Cases

Transcription

1 NGAO- Solar System Science Cases F. Marchis (UC-Berkeley) Members: A. Bouchez (Caltech), J. Emery (NASA-Ames), K. Noll (STSCI), M. Adamkovics (UC-Berkeley)

2 General introduction Planetary science from the ground Complementary with space mission (if any) AO because need for high angular resolution Variability & good temporal monitoring (over several years) to understand variable events (volcanism, atmosphere, resurfacing)

3 Science Cases A. Multiple Asteroidal Systems A Sylvia - a Main-Belt multiple system A EL61 - a TNO multiple system A.3 Size and shape (-> density?) A.4 Spectroscopy of moonlets (origin?) B. Titan and other Giant Planet Satellites B.1. Titan surface and its atmsophere B.2 Io Volcanism Smaller Giant Planet Satellites? C. Atmosphere of Giant Planets

4 Minor Planets ~300,000 minor planets known Small apparent size (largest MB-> 1 Ceres D app =0.7arcsec <-> seeing limit Building blocks of the Solar System linked to its formation L5-Trojan Main-Belt L4-Trojan Centaurs TNOs Thomas et al. 2005

5 What are asteroids made of? (a) Shape of NEA * Toutatis observed with radar Internal structure? (b) Monolith (c ) Contact Binary (d) Rubble Pile From E. Asphaug, 1999, Survival of the weakest * NEA= Near Earth Asteroid

6 Binary Asteroids A Family Portrait MB 45 Eugenia & Petit-Prince (AO, 1998) TNO 1998WW31 (Classical, 2000) MB Ida and Dactyl (Galileo 1993) MB 87 Sylvia and its 2 moons (AO, 2005) NEA 2000DP107 (2002, radar) MB 90 Antiope (AO, 2001) Binary Asteroids - 85 systems known Astronomical prize for astronomers and theorists Mass, density, formation of solar system

7 Multiple asteroid system: 87 Sylvia 87 Sylvia was discovered in Aug, Rprimary = 143 km, Rremus= 3.5 km, Rromulus=9 km add 2 more moonlets. 1 closer (6km) at 480 km and one smaller (1.75 km) at 1050 km

8 Simulations NIRC-2 H band Positions is calculated based on orbital parameters Images generated Blurred by convolution No noise added yet (TBD) Positions estimated by fit with Gaussian Dynamical model to fit the orbital paramters -> COMPARISON

9 Simulations NGAO-R band

10 Simulations NGAO-H band Close-up innermost moon can be seen all the time Positions is calculated based on orbital parameters Images generated Blurred by convolution No noise added yet (TBD) Positions estimated by fit with Gaussian Dynamical model to fit the orbital paramters -> COMPARISON (TBD)

11 Preliminary analysis S_Romulus S_Remus S_New1 S_New2 Det. rate Dm Det. Rate Dm Det. Rate Dm Det. Rate Dm init 100% % % % 9.56 NIRC2-H 100% 6.5±0.2 75% 6.1±1.0 58% 5.0±1.9 20% 9.7±0.5 NGAO-H 100% 5.94± % 8.3±0.9 76% 6.6±1.4 70% 11.1±1.4 NGAO-R 100% 6.02± % 8.3± % 6.7± % 9.6±0.2 HST-R? Detection of fainter moonlet & closer moonlet Better photometry (size & shape)

12 Future task Use our dynamical model to estimate the orbital elements And their accuracy + precision Will it be possible to see second order interaction such as: -Forced eccentricity due to resonance -Precession effect Work in progress.

13 AO Imaging of Asteroids Directly measure size, shape, albedo, rotation Clues to planet formation mechanisms Collisional history of Solar System Endogenic and exogenic processes active on individual and groups of asteroids Complement spacecraft missions Temporal coverage, cost effective

14 Close-up pictures of asteroids Itokawa

15 Cases in point Vesta... Imaging reveals 460 km basin strong constraint in collisional models (e.g. Bottke et al. 2005)...and Elektra Dark albedo marks endogenic or exogenic process?

16 How many asteroids observable w/ NGAO? MB, Troj, Cen, TNO assume observed at perihelion and opposition NEA assume observed at close-approach (MOID) Populations by brightness (numbered and unnumbered asteroids) Orbital type Total number V < < V < < V < < V < 18 Near Earth Main Belt Trojan Centaur TNO Other

17 How many asteroids observable w/ NGAO? Populations by brightness (numbered asteroids only) Orbital type Near Earth Main Belt Trojan Centaur TNO Other Total number V < < V < < V < < V <

18 Resolved asteroid shape Diameters from IRAS or from H with assumed albedo No blurring for V<15, some blurring for fainter Require angular diameter > 2 resolution elements Resolvable asteroids in each band (numbered and unnumbered) Orbital type V R I J H K Near Earth Main Belt Trojan Centaur TNO Other

19 Multiple Trans-Neptunian Object

20 Kuiper Belt Object satellite systems Recent detections suggest that most large KBOs may have multisatellite systems. 3 bright KBOs observed with Keck 2 LGS, 3 satellites were detected. Satellite orbits give primary mass, and constrain the formation and collisional history of the Kuiper Belt 2003 EL61 A Charon-sized KBO with 2 satellites in non-coplanar orbits. (Brown et al. 2006)

21 NGAO planetary science case A.2: A survey of KBO satellite systems Simulation Give 2003 EL61 a hypothetical faint inner satellite, and determine how many satellites would be detectable in a 30-minute integration, as a function of heliocentric distance (EL61 is at 51.4 AU).

22 NGAO planetary science case A.2: Preliminary conclusions and questions Conclusions: Both NGAO systems simulated would be extremely effective! One can use either the KBO or off-axis NGS for tip-tilt. Choice depends on AO configuration. An MCAO/MOAO system is somewhat preferred due to better sky coverage with moderate J band Strehl (~30% is sufficient for inner satellite detection). Nyquist-sampled J band imaging appears optimum for nm NGAO systems. Need: RMS tip-tilt error vs. on-axis TT magnitude (simulation used only very rough estimates) Better understanding of Strehl vs. sky coverage, for non-scao configurations. For example, would a 2-chanel MOAO system (science and TT star) be ideal for this science case? to compare apples to apples

23 Spectroscopy of Asteroids and their companions Characterization of the surface composition mafic silicate minerals (pyroxene, olivine, spinels), hydrated silicate? C-type asteroid - what are they? Space weathering? Comparison moonlet vs primary for Origin moonlet is an infant of the primary (same composition) or is a captured asteroid?

24 Mineralogy Silicate absorption band centered at 1 and 2 µm (Gaffey et al. 2004) -> need to be fully sampled - up to 0.7 µm 0.7 µm hydrated feature (Rivkin et al. 2004) low contrast & up to 0.6 µm Still controversial LOW SPECTRAL RESOLUTION R~

25 Summary Science case A Which AO -> KPAO up to visible But MCOA/MOAO for binary TNO (TBC) Which instrument -> visible+nir imaging+spectroscopy. This AO will be the best tool for this scientific subject (no space mission scheduled, need for numerous observations, ) Density & composition of minor planet is the key to understand the formation of the solar system

26 Science Cases A. Multiple Asteroidal Systems A Sylvia - a Main-Belt multiple system A EL61 - a TNO multiple system A.3 Size and shape (-> density?) A.4 Spectroscopy of moonlets (origin?) B. Titan and other Giant Planet Satellites B.1. Titan surface and its atmsophere B.2 Io Volcanism Smaller Giant Planet Satellites? C. Atmosphere of Giant Planets

27 Mysterious Titan Satellite of Saturn - D~5150 km Surface mostly hidden by an opaque prebiotic atmosphere Studied with Cassini spacecraft (4 flyby already) and Huygens lander (Jan. 2004) Spatial resolution of global observations up to 9km in NIR

28 Titan Surface and its Atmosphere Goals: Observations of an extended object - imaging and spectroscopy of its atmosphere. Comparison with previous NGS AO systems. Illustration of the variability of solar system phenomena (volcanism, clouds) Inputs from TCIS: Simulated short exposure On-Axis PSFs (~2-4s) (x10) at various wavelength (NOT YET DEFINED) in good seeing conditions for a bright reference (mv=8.5). Should we expect a degradation due to the angular size of Titan (D=0.8") Method:We will create a fake Titan observations considering also the haze component in visible and NIR and using global map (with R= km) of Cassini spacecraft. We will focus on atmospheric windows for which the surface can be seen (tools are ready MA & FM). Wavelength not defined yet.- Deconvolution with AIDA may be included (algorithm 95% ready FM)- Comparison with Keck NGS AO, VLT AO, and Cassini will be included- Good temporal coverage from the ground vs spacecraft will be discussed and illustrated by surface changes due to a cryo-volcano (and/or clouds in the troposphere?)- Spectroscopy to detect N2+ species in the atmosphere (high R) and measure winds in Titan atmosphere at various altitudes (extremely high R).

29 Titan Surface and its Atmosphere First results - Comparison of H band observations 0.8 FWHM= 44 mas FWHM= 34 mas FWHM= 34 mas About the fake image of Titan based on Cassini map at 0.94 µm, 600 pixels across, spatial resolution of 9 km (1 mas) near disk center, Minnaert function reflectivity, long=150w, lat=23s

30 Titan Surface and its Atmosphere Multi-wavelength observations PSF used : NFAO - no blurring Prebiotic atmosphere Not completely transparent in visible- NIR µ c m Atm. window

31 Blurring due to haze scattering Cassini/VIMS Spectra Baines et al., Science, 2005 Haze scattering efficiency is getting higher in visible. So the contrast on the feature will be low (less than 2%) See Voyager 600 nm data in Richardson et al

32 Titan Surface and its Atmosphere Comparison HST-ACS/HRC & Keck NGAO Clear progress in angular resolution compared with HST

33 Surface Changes on Titan HST/ACS R KNGAO-R Cryovolcanic-style surface change are detectable with KNGAO in J band. In R band morphology is better estimated -> volcano caldera, lava flow?

34 Titan 5 µm bright terrain Three regions with high Reflectivity at 5 µ m located South of Xanadu (Barnes et al. 2006). No change of intensity with phase -> surface feature KNGAO up to 5 µm? In progress. TBD

35 Volcanism of Io Satellite of Jupiter - R~1800 km The most volcanically active place in the solar system Studied with Galileo spacecraft (5 successful flyby only) Spatial resolution of global observations km

36 Io Volcanism Goals: Observations of an extended object - imaging of its surface. Comparison with previous NGS AO systems. Illustration of the variability of solar system phenomena (volcanism). Comparison with Keck NGS AO anisoplanetic and KPAO (widerfield AO systems such as MCAO & MOAO). Inputs from TCIS: - Simulated short exposure On-Axis PSFs (~1s) (x10) at various wavelength (0.7, 0.9, 1.2, 1.6, 2.2 microns) under good seeing conditions for a bright reference (mv=5.5).- Simulated short exposure Off-Axis PSFs (~1s) (x10) at various wavelength (0.7, 0.9, 1.2, 1.6, 2.2 microns) under good seeing conditions for a bright reference (mv=6) located at 25" (or more...).- possibility to discuss NIR WFS (to close the loop on Io itself in eclipse?) Method: two set of fake Io images with various active eruptive centers using Galileo/Voyager global map (R~35 km). One in sunlit (on axis reference) and the second one in eclipse (off axis reference at 25"). Observations at 0.7, 0.9, 1.2, 1.6, 2.2 microns will be considered not finalized yet

37 Io volcanism Surface change & hot spots 1 Up to 0.9 µm, thermal output of outburst can be detected (T>1450 K) Up to 0.7 µm, -> mafic absorption band (centered at 1 µm) L and M band imaging capabilities are necessary

38 Comparison with HST Io Volcanism PSF HST/ACS (HRC) from tinytim (simulated PSF) Better spatial resolution (~50 km) than Galileo spacecraft image

39 Io Volcanism Io in eclipse Need off-axis PSF Simulation using NFAO convolved with gaussian Point out the problem of glare from Jupiter RESULT (image here) comparison with real observations (de Pater et al. 2005) Photometric accuracy on hot spot flux (then temperature) Spectroscopy to better estimate the nature of the active center

40 Other satellites Satellite name Ang. Size (mas) Distance planet mv comments Mimas 60 Enceladus Volcanic activity (science, 2006) Tethys 170 Dione 180 Rhea 250 Titan 830 Cryo-volcanoes? Iapetus 230 Io Basaltic volcanic activity Europa 1000 Young surface - ocean beneath? Ganymede 1700 Ocean? Callisto 1600 Himalia 60 Reminder: FWHM PSF(NGAO-R) = 12 mas

41 Other satellites Consider high resolution spectral analysis (R>1000) for atmospheric features. Example geysers on Enceladus Problem due to giant planet halo contribution on the WFS? 80 mas Reminder: FWHM PSF(NGAO-R) = 12 mas

42 Summary for science case B KPAO NIR+visible is Science drivers for Titan & Io And other satellites (TBD) AO technology & Instrument KPAO (LTAO) Priority: Visible camera (important progress compared with HST), super NIRC2 (including L&M bands)

43 Best AO technology & KPAO but Instruments for Solar System 100, 120, 200 nm? Impact on design? <0.7 µm is necessary? Not sure Instruments 1. Visible camera + spectro low R (400) 2. Super Osiris 3. Super NIRC2