1. Jian-Yang Li, University of Maryland Marc Kuchner, NASA Goddard Space Flight Center Ron Allen, Space Telescope Science Institute Scott Sheppard, Carnegie Institution of Washington, DTM 7/24/2009Li et al., BDEP, Shanghai, China 1

2. Precision astrometry on stars to V=20. Optical interferometer on a 6 m structure. –One science interferometer. –One guide interferometer (4.2 m baseline) and one precision guide telescope to stabilize the fringes. Global astrometric accuracy: 4 µas. –At end of 5 year mission lifetime. Narrow-field astrometric accuracy: 1 µas, in a single measurement. –Current state of the art is HST/FGS at ~500 µas. –Ground-based differential astrometry will reach ~20 µas. Typical observations take about 1 minute; ~ 5 million observations in 5 years.

3. RV will press on icy planets and close-in planets. Transit & microlensing will provide statistical census of rocky planets (e.g., Kepler @ 1 kpc, and microlensing @ 5 kpc. Together with some other instruments, SIM probes 1-10 M Earth  (0.4 - 6.0 AU for nearby stars). It provides orbital parameters and masses for RV planets.

4. 7/24/2009Li et al., BDEP, Shanghai, China4 The outer solar system objects (KBOs and Centaurs) will help us understand the characteristics and formation of big planets far away from the star

5. 7/24/2009Li et al., BDEP, Shanghai, China5

6. 7/24/20096Li et al., BDEP, Shanghai, China

7. D=34.3 mas D=40.4 mas 7/24/20097Li et al., BDEP, Shanghai, China

8. Brown et al. 2006 Shape+ Period  Density T Radius Size  Escape Velocity 7/24/20098Li et al., BDEP, Shanghai, China Density+shape => internal structure Iapetus: Brightness variations

9. 7/24/2009Li et al., BDEP, Shanghai, China9 109 KBOs + 26 Centaurs in total: 20 KBOs and 18 Centaurs are identified to be observable for SIM SIM can measure the: Size Shape Rotational status

10. 7/24/2009Li et al., BDEP, Shanghai, China10 2 Jinc(2πR) Three visibilities, solve for two axes and one angle  B1B1 B3B3 B2B2  B1B1 B2B2 B3B3 Inverse jinc function to get the size of a circular disk with uniform brightness distribution

11.  Rotation period 3.92 hr (Rabinowitz et al., 2006)  Jacobi ellipsoid  Axial ratio b/a=0.86, c/a=0.54 (Lacerda and Jewitt, 2007)  Density 2551 (+115, -10) km m-3 (Lacerda and Jewitt, 2007)  Mass from two satellites  Size 1960-2500 km (Rabinowitz et al., 2006)  Albedo ~0.6  Dark red spots from photometric lightcurves (Lacerda et al., 2008)  Almost pure water ice on the surface (Trujillo et al., 2007)  Strong limb-darkening, k=0.85 7/24/2009Li et al., BDEP, Shanghai, China11

12. 7/24/2009Li et al., BDEP, Shanghai, China12 1% uncertainty of visibility from SIM Size can be determined to better than 5% uncertainty

13. 7/24/2009Li et al., BDEP, Shanghai, China13 SIM can achieve ~10 µas in visibility phase SIM tracks the photocenter of the object precisely. Rotational period Pole orientation Sense of rotation

14. 7/24/2009Li et al., BDEP, Shanghai, China14 Complicated pattern for a surface with albedo features: Not a problem for period determination Should not be a problem for pole orientation determination May be used to track surface features

15. k=0.4 k=0.5 k=0.8 Low albedo objects SSA < 0.2, Moon Minnaert limb-darkening model: I/F = A cos k (i) cos (k-1) (e) High albedo, high roughness objects SSA = 0.99, Θ=50 deg, g=0 High albedo, low roughness objects Triton: SSA=0.99, Θ=14 deg, g=-0.38 7/24/2009Li et al., BDEP, Shanghai, China15

16. 7/24/2009Li et al., BDEP, Shanghai, China16 Stellar limb-darkening from simultaneously visibility measurement at multiple λ/B (e.g. Quirrenbach et al., 1996) Limb-darkening from k=0.5 (uniform disk) to k=1 (strongest limb-darkening) Visibility uncertainty 1% Simultaneously measurement of visibility at multiple wavelengths from 0.4-0.9 µm Guide interferometer can be used to extend the λ/B range

17.  Outer solar system object help us understand planetary system formation at large distances from the star.  Fundamental properties of KBOs and Centarus, such as their sizes, shapes, and rotations, can only be measured to be good at 20% level from radiometry.  SIM can observe about 40 KBOs and Centaurs  Better than a few percent in size  Determine 3-D shape  Constrain rotational status, including pole orientation and sense of rotation  Limb-darkening can be measured by SIM through simultaneously visibility measurements at multiple λ/B. 7/24/2009Li et al., BDEP, Shanghai, China17