1. Ground-Based Observations of Mars and Venus Jeremy Bailey, Sarah Chamberlain, Andrew Simpson (Australian Centre for Astrobiology, Macquarie University, Sydney) David Crisp, Vikki Meadows (Jet Propulsion Laboratory/Caltech) 2. Polarimetric Detection and Characterization of Extrasolar Planets Jeremy Bailey (ACA) Jim Hough, Phil Lucas (University of Hertfordshire)

UKIRT – Excellent image quality.Excellent image quality. IR spectrograph with R up to 4000 and long slit.IR spectrograph with R up to 4000 and long slit. Ability to scan across Mars while guiding (correcting automatically for the motion of Mars).Ability to scan across Mars while guiding (correcting automatically for the motion of Mars). Spectroscopic Imaging data. Narrow-band filter images.

UKIRT Mars Images (2003) Long exposure image (Mauna Kea natural seeing) Selected best short exposure image Further image processing (unsharp masking and smoothing) UKIRT/UIST 0.06 arc sec pixels  m 1Kx1K InSb detector windowed to 512x512, 90ms exposure.

HST / Ground- Based Comparison HST Aug , ACS UKIRT Sep , 1.64  m

Mars 2.12  m Imaging

Spectral Cubes arcsec pixels arcsec pixels 1024 spectral pixels

Spectra

Aug 17 Sep  m Atmospheric CO 2 absorption 2.00  m CO 2 ice absorption 2.29  m Water ice absorption 2.10  m

UKIRT 2.2  m albedo UKIRT CO 2 band depth MGS MOLA topography Aug Sep 4th 2003

UKIRT MOLA

CO 2 band pressure measurement Complications –Dust. –CO 2 in Earth atmosphere. –Topography removal. Sensitivity –4-5 Pa (in total pressure of ~700 Pa).

Mars Earth Light passes twice through Mars atmosphere and once through Earth’s atmosphere

White - Earth Red - Earth+Mars Green - Earth White - Mars CO 2 bands have unresolved structure

Model Building Approach Solar spectrum Mars atmosphere radiative transfer model Earth atmosphere transmission model High resolution spectrum spectrum Observed spectrum Compare Bin to observed resolution Correct for Mars atmosphere Correct for Earth atmosphere Observed spectrum Surface reflectance

Venus night side spectra in the near-IR Spectra with SPEX on the 3m IRTF (R ~ 2000) - Feb 19th 2001

H 2 SO 4 clouds (2.3  m) (40-70km altitudes) Images: AAT 3.9m IRIS2, Jul 9th 2004 Spectra: IRTF SPEX, Feb 19th 2001

Venus O 2 airglow at 1.27  m Image: ANU 2.3m CASPIR, Sep 26th 2002 Spectrum: IRTF SPEX, Feb 19th 2001 (>100km altitudes)

1.27  m Airglow Variability Images: ANU 2.3m CASPIR, Sep 20-26th 2002

Our Future Plans Instrument Development –Demonstrate HST resolution or better from ground-based telescopes. –IR Spectroscopy R ~ 2000 and R > 100,000. Continued observing program of Mars and Venus. –Long sequences of CO 2 observations of Mars to look for weather systems. –High spectral resolution observations to measure winds and trace gases. Development of modeling and analysis software –Techniques for Earth Atmosphere correction. –Retrieval algorithms for pressure, temperature, dust etc.

Polarimetric Detection of Hot Jupiters Light from planet is polarized and polarization varies around orbit as scattering angle changes. Seager, Whitney and Sasselov, 2000, Ap. J. 540, 504. “…. Polarization signatures … are well under the current limits of detectability which is a few x 10 –4 in fractional polarization” (Seager et al. 2000). Star - unpolarized Planet polarized at 5- 10%, <10 –4 of star Combined light polarized at <10 –5

Photoelastic Modulators (PEMs)

PEM Aperture Wheel Wollaston Prism (3 wedge cemented) Two Filter Wheels Fabry Lenses Avalanche Photodiode Modules Star Channel Sky Channel Calibration Slide Each channel (blue section) rotates about its axis Entire instrument rotates about star channel axis

Edwin Hirst Phil Lucas Jim Hough David Harrison JeremyBailey PLANETPOL

Telescope polarization is measured by tracking stars over a range of hour angle. With an altazimuth mounted telescope the telescope tube rotates relative to the sky. Residual instrument polarization effects are removed by a “second-stage chopping” achieved by rotating the polarimeter channels (wollaston + detectors) relative to the PEM from +45 to –45 degrees.

“Unpolarized” Stars StarQ/I (10 –6 )U/I (10 –6 ) HR 5854 (  Ser, K2IIIb, V=2.6, 22pc) 0.44 ±  ± 1.76 HR 5793 (  CrB, A0V, V = 2.2, 22pc) –1.50 ± ± 0.93 HD (  Vir, F8V, V = 3.6, 11pc) 1.26 ± ± 1.93 Procyon (  CMi, F5IV-V, V = 0.4, 3.5pc) 4.5 ± 3.0–0.1 ± 2.3 HR 6075 (  2 Oph, G9.5IIIb, V = 3.2, 33pc) 45.4 ± 1.3–5.7 ± 2.3

Polarized Stars StarQ/I (10 –6 )U/I (10 –6 ) HD ± 3.0–710 ± 2.7 u Her (Eclipsing binary) ± 6.8–169.0 ± 7.3 U Sge (Eclipsing binary) –1362 ± ± 10 HD (Standard P = 1.8%) 3074 ± 4–12734 ± 20 HD (Standard P = 2.8%) 4819 ± ± 164

Tau Boo Data Fig 7(a) Q residuals and (b) U residuals (the brown points are the averages of each block of data)

What the Polarization Can Tell Us Position angle variation through orbit gives us the inclination. –and hence the mass of the planet removing the sin I uncertainty. The presence or absence of Rayleigh scattering polarization provides information on the pressure at the cloud tops. The orbital variation of polarization tells us about particle size and composition. We will have some idea of the albedo and this will assist other direct detection techniques (e.g. photometry and spectrscopy).

Summary of Results PLANETPOL works and delivers repeatable polarization measurements at the 10 –6 level. The telescope polarization of the WHT is low and seems stable (over a few days at least). –Good news for us — It could be much more difficult to get reliable results in the presence of a telescope polarization at the 10 –3 to 10 –4 level. Normal nearby stars have very low polarization (~3 x 10 –6 or less). –Also good for us — We shouldn’t have too many problems from star polarization in interpreting the data from our extrasolar planet systems. We are measuring  Boo to an accuracy of about 2-3 x 10 –6 for a 24 minute integration. –More extended observations should be sufficient for a detection or a significant upper limit. –We have a 13 night run on the WHT in April/May 2005.

Imaging Polarimetry Similar polarization techniques using an imaging system can be used for detection and characterization of resolved planetary images. –e.g. From Adaptive Optics systems on large ground-based telescopes. –Space instruments such as TPF-C. Polarimetry can be used as a differential technique to pick the planet out of the speckle noise halo around the star. Polarimetry can be used to help characterize any detected planet.