1. MDI, 9/25

2. Orbital Motions and SAS Error Terms H. S. Hudson Sep. 29, 2003

3. Representative SAS radii, one orbit, one limb

4. SDS as a chronometer (Sofia et al., ApJ 427, 1048, 1994)

5. Solar Disk Sextant sensor layout

6. Oblateness values (radius) Allen, ApQ~ 10.4 ppm Solar Disk Sextant8.6 +- 0.9 ppm MDI (SOHO)8.8 or so

7. SAS-related facts (epoch July 23, 2002) A.U./10 13 cm (Allen)1.495985 +- 0.000005 1.471/1.521 Earth orbital velocity~29.8 km/s RHESSI orbital radius6960 +- 15 km RHESSI orbital velocity~7.57 km/s SAS wavelength670 +- 6 nm

8. Correction terms Earth orbital motion~3.34 % Lorentz contraction (Earth’s motion) ~0.5 ppb  RHESSI orbital motion <46.5 ppm Lorentz contraction<0.3 ppb  Relativistic beaming<50 ppm 1+2  cos  Doppler effect (RJ assumption) <50 ppm 1+2 

9. Prospects for oscillation studies The p-modes have an integrated amplitude of about 50 ppm in total sunlight SAS can see higher-l modes, and their amplitudes should be greater The observations will show a highly model- dependent mixture of propagation effects To detect g-modes would be highly unlikely, but we must give it a shot

10. What are p-modes and g-modes? Eigenmode classification by Cowling: “p-mode” is like a standing sound wave, periods ~ 5 minutes “g-mode” is like an internal gravity wave, periods ~ tens of minutes If one can observe g-modes, one will become rich and famous because they directly measure the solar core, but these waves are evanescent in the convection zone.