Temperatures of Marco Polo Mission Targets

Transcription

1 Temperatures of Marco Polo Mission Targets Marco Delbo, Patrick Michel June 5, 2008 Observatoire de la Côte d Azur; Laboratoire Cassiopée with contributions from: A. Barucci, D. Koschny Marco Delbo, Patrick Michel () Temperatures of Marco Polo Mission Targets June 5, / 24

2 Table of contents Temperature of Marco Polo s targets: Outline 1 Parameters that influence surface temperatures 2 Thermophysical parameters geology of the surface 3 How do we derive/calculate temperatures: thermophysical models 4 Surface and sub surface (regolith) temperature (surface operations, sample extraction) 5 Thermal evolution (orbital evolution) 6 Discussion, future observations and instruments needs Marco Delbo, Patrick Michel () Temperatures of Marco Polo Mission Targets June 5, / 24

3 Parameters that influence asteroid surface temperatures Parameters that influence asteroid surface temperature Heliocentric distance (r) Bolometric Albedo (A) Rotation period (T) Direction of rotation axis (λ P,β P ) Thermal inertia (Γ = ρκc) heat diffusion in the regolith Surface roughness (e.g. craters) small scale multiple scattering Gross shape (shadows) Marco Delbo, Patrick Michel () Temperatures of Marco Polo Mission Targets June 5, / 24

4 Parameters that influence asteroid surface temperatures Asteroid surface temperature vs. heliocentric distance 1400 Low thermal inertia High thermal inertia Temperature (K) Heliocentric distance (AU) Marco Delbo, Patrick Michel () Temperatures of Marco Polo Mission Targets June 5, / 24

5 Surface temperature of Marco Polo s targets Surface temperature of 1999 JU 3 for different values of Γ Effect of thermal inertia and asteroid rotation TI=0 TI=50 TI=300 TI= Surface Temperature (K) Thermal Inertia 50: Moon soil 300: km-sized NEAs 2500: Basalt Rotation phase Marco Delbo, Patrick Michel () Temperatures of Marco Polo Mission Targets June 5, / 24

6 Thermal inertia and regolith Thermal inertia (Γ) and asteroid surface nature Thermal inertia gives information about the presence (or absence), depth and thickness of regolith, and the presence of exposed rocks on the surface of atmosphere less bodies (Γ in SI units: Jm 2 s 0.5 K 1 ) Itokawa 433 Eros The moon 1 Ceres Γ = 600 Γ = 150 Γ = 50 Γ = 10 Coarse regolith Finer and thicker Mature and Very fine and boulders regolith fine regolith regolith?? Marco Delbo, Patrick Michel () Temperatures of Marco Polo Mission Targets June 5, / 24

7 Thermal inertia and regolith Close up of asteroids regolith: Itokawa Marco Delbo, Patrick Michel () Temperatures of Marco Polo Mission Targets June 5, / 24

8 Thermal inertia and regolith Close up of asteroids regolith: Itokawa Marco Delbo, Patrick Michel () Temperatures of Marco Polo Mission Targets June 5, / 24

9 Thermal inertia and regolith Close up of asteroids regolith: (433) Eros Marco Delbo, Patrick Michel () Temperatures of Marco Polo Mission Targets June 5, / 24

10 Thermal inertia and regolith Close up of asteroids regolith: (433) Eros Marco Delbo, Patrick Michel () Temperatures of Marco Polo Mission Targets June 5, / 24

11 Thermophysical Models Thermophysical Models 1 Thermophysical Model ( 96-07) Lagerros 1996; Delbo 2004; Mueller ρc T(r i,t) t k 2 T(r i,t) r 2 i = 0 3 Parameters: size, albedo, thermal inertia (Γ), surface roughness (θ). 4 Required: shape, spin state. Marco Delbo, Patrick Michel () Temperatures of Marco Polo Mission Targets June 5, / 24

12 Thermophysical Models How thermal inertia is derived: thermophysical modeling Models parameters are: 1 object size 2 surface roughness 3 thermal inertia Chi squared no roughness low roughness medium roughness high roughness They are adjusted to yield the best fit to the IR data Thermal Inertia (SI units) Delbo and Tanga, 2008; Mueller, 2007 (Ph.D. thesis) Marco Delbo, Patrick Michel () Temperatures of Marco Polo Mission Targets June 5, / 24

13 Thermophysical Models Surface temperature of 1989 UQ 500 (65679) 1989 UQ 400 Temperature (K) Perihelion Aphelion 100 Midday Rotational phase Marco Delbo, Patrick Michel () Temperatures of Marco Polo Mission Targets June 5, / 24

14 Sub soil temperature Subsoil temperature (1999 JU 3 ): Γ = 300Jm 2 s 0.5 K Regolith temperature of 1999JU3 (Gamma=300 S.I.; r=0.96 AU; T=7.5h) Midday Midnight 340 Temperature (K) Regolith depth (m) Marco Delbo, Patrick Michel () Temperatures of Marco Polo Mission Targets June 5, / 24

15 Orbital evolution of Marco Polo targets 2001 SG 286 Variation of the orbital elements with time (1 clone). 2.5 Semimajor axis (AU) Semimajor axis (AU) Semimajor axis (AU) Orbital eccentricity (e) e+06 2e+06 3e+06 4e+06 5e+06 6e+06 Time (years) e+06 2e+06 3e+06 4e+06 5e+06 6e+06 Time (years) Marco Delbo, Patrick Michel () Temperatures of Marco Polo Mission Targets June 5, / 24

16 Thermal evolution of Marco Polo targets 2001 SG Temperature Perihelion distance Max surface Temperature (K) Perihelion distance (AU) e+06 2e+06 3e+06 4e+06 5e+06 6e+06 0 Time (years) Marco Delbo, Patrick Michel () Temperatures of Marco Polo Mission Targets June 5, / 24

17 Thermal evolution of Marco Polo targets 2001 SK Temperature Perihelion distance Max surface Temperature (K) Perihelion distance (AU) e+06 4e+06 6e+06 8e+06 1e e e e e+07 Time (years) Marco Delbo, Patrick Michel () Temperatures of Marco Polo Mission Targets June 5, / 24

18 Thermal evolution of Marco Polo targets 2001 SK Temperature Perihelion distance Max surface Temperature (K) Perihelion distance (AU) Time (years) Marco Delbo, Patrick Michel () Temperatures of Marco Polo Mission Targets June 5, / 24

19 Conclusion Concluding remarks 1 Knowledge of target temperature is important for surface operation: landing, sample collection... 2 Information about physical (e.g. spin state) and thermophysical parameters (e.g. thermal inertia) are required for accurate thermophysical modeling. Marco Delbo, Patrick Michel () Temperatures of Marco Polo Mission Targets June 5, / 24

20 Conclusion Concluding remarks 1 Knowledge of target temperature is important for surface operation: landing, sample collection... 2 Information about physical (e.g. spin state) and thermophysical parameters (e.g. thermal inertia) are required for accurate thermophysical modeling. Follow up observations important! Marco Delbo, Patrick Michel () Temperatures of Marco Polo Mission Targets June 5, / 24

21 Conclusion Concluding remarks 1 Knowledge of target temperature is important for surface operation: landing, sample collection... 2 Information about physical (e.g. spin state) and thermophysical parameters (e.g. thermal inertia) are required for accurate thermophysical modeling. Follow up observations important! On board thermal IR photometer/spectrometer! see O. Groussin s tomorrow talk! Marco Delbo, Patrick Michel () Temperatures of Marco Polo Mission Targets June 5, / 24

22 Conclusion Concluding remarks 1 Knowledge of target temperature is important for surface operation: landing, sample collection... 2 Information about physical (e.g. spin state) and thermophysical parameters (e.g. thermal inertia) are required for accurate thermophysical modeling. Follow up observations important! On board thermal IR photometer/spectrometer! see O. Groussin s tomorrow talk! Marco Delbo, Patrick Michel () Temperatures of Marco Polo Mission Targets June 5, / 24

23 Back up slides Backup slides Marco Delbo, Patrick Michel () Temperatures of Marco Polo Mission Targets June 5, / 24

24 Asteroids thermal inertia The thermal inertia of asteroids Marco Delbo, Patrick Michel () Temperatures of Marco Polo Mission Targets June 5, / 24

25 Asteroids thermal inertia Subsoil temperature (1999 JU 3 ): Γ = 300, 1000Jm 2 s 0.5 K Regolith temperature of 1999JU3 (Gamma=300 and 1000 S.I.; r=0.96 AU; T=7.5h) Midday (Gamma=300) Midnight (Gamma=300) Midday (Gamma=1000) Midnight (Gamma=1000) 340 Temperature (K) Regolith depth (m) Marco Delbo, Patrick Michel () Temperatures of Marco Polo Mission Targets June 5, / 24

26 Asteroids thermal inertia Subsoil temperature (1989 UQ): low thermal inertia Low TI; Perihelion; 3.0cm Low TI; Perihelion; 5.0cm Low TI; Aphelion; 3.0cm Low TI; Aphelion; 5.0cm Sub-Soil Temperature (K) Time (hours) Marco Delbo, Patrick Michel () Temperatures of Marco Polo Mission Targets June 5, / 24

27 Asteroids thermal inertia Subsoil temperature (1989 UQ): high thermal inertia High TI; Perihelion; 3.2cm High TI; Perihelion; 5.4cm High TI; Aphelion; 3.2cm High TI; Aphelion; 5.4cm Sub-Soil Temperature (K) Time (hours) Marco Delbo, Patrick Michel () Temperatures of Marco Polo Mission Targets June 5, / 24