Report - School of Physics
Report - School of Physics
Report - School of Physics
Create successful ePaper yourself
Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.
A<br />
Space Precursors: Interferometers, Coronographs<br />
and Apodizers<br />
The McKee-Taylor Decadal Survey Committee (McKee & Taylor, 2000) qualified its<br />
endorsement <strong>of</strong> the TPF mission with the condition that the abundance <strong>of</strong> Earthsize<br />
planets be determined prior to the start <strong>of</strong> the TPF mission. Many ideas for<br />
scientific and technological precursors for TPF have been examined. The main<br />
contenders are summarised here for completeness, although with the recent (April<br />
2004) NASA announcement on TPF strategy, it seems unlikely that any <strong>of</strong> these<br />
concepts will be developed further:<br />
Eclipse (coronography) is a proposed NASA Discovery-class mission to perform a<br />
direct imaging survey <strong>of</strong> nearby planetary systems, including a complete survey for<br />
Jovian-sized planets orbiting 5 AU from all stars <strong>of</strong> spectral types A–K within 15 pc<br />
<strong>of</strong> the Sun (Trauger et al., 2003). Its optical design incorporates a telescope with an<br />
unobscured aperture <strong>of</strong> 1.8 m, a coronographic camera for suppression <strong>of</strong> diffracted<br />
light, and precision active optical correction for suppression <strong>of</strong> scattered light, and<br />
imaging/spectroscopy. A three-year science mission would survey the nearby stars<br />
accessible to TPF. Eclipse may be resubmitted for NASA’s Discovery round in 2004.<br />
Jovian Planet Finder (JPF) was a MIDEX proposal to directly image Jupiter-like<br />
planets around some 40 nearby stars using a 1.5-m optical imaging telescope and<br />
coronographic system, originally on the International Space Station (ISS) (Clampin<br />
et al., 2002). Its sensitivity results from super-smooth optical polishing, and should<br />
be sensitive to Jovian planets at typical distances <strong>of</strong> 2–20 AU from the parent star,<br />
and imaging <strong>of</strong> their dusty disks – potentially solar system analogues. A 3-yr mission<br />
lifetime was proposed.<br />
Extra-Solar Planet Imager (ESPI) is another proposed precursor to TPF (Lyon<br />
et al., 2003). Originally proposed as a NASA Midex mission as a 1.5 × 1.5 m 2<br />
apodized square aperture telescope, reducing the diffracted light from a bright central<br />
source, and making possible observations down to 0.3 arcsec from the central<br />
star. Jupiter-like planets could be detected around 160–175 stars out to 16 pc, with<br />
S/N > 5 in observations lasting up to 100 hours. Spectroscopic follow-up <strong>of</strong> the<br />
brightest discoveries would be made. The Extra-Solar Planet Observatory (ExPO)<br />
is a similar concept proposed as a Discovery-class mission (Gezari et al., 2003).<br />
Self-luminous Planet Finder (SPF) is a further TPF precursor under study by<br />
N. Woolf and colleagues, aiming at the search for younger or more massive giant<br />
planets in Jupiter/Saturn like orbits, where they will be highly self-luminous and<br />
bright at wavelengths <strong>of</strong> 5–10 µm, where neither local nor solar system zodiacal glow<br />
will limit observations. SPF will demonstrate the key technologies <strong>of</strong> passive cooling<br />
associated with interferometric nulling and truss operation that are required for a<br />
TPF mission. SPF targets young Jupiter-like planets both around nearby stars such<br />
as ɛ Eri, and around A and early F stars.<br />
75