Report - School of Physics

(Shao): this major SIM survey programme comprises a deep survey of about 75
nearby main-sequence stars within about 10 pc of the Sun, of which one third are
G dwarfs and the remainder are inactive main-sequence stars of other spectral types
(mostly K and M but including a few A and F). Over the mission lifetime, each target
will be observed some 70 times, each of twenty 1-minute observations resulting in
a final accuracy of about 1 micro-arcsec. Each pointing will be accompanied by the
observation of typically 28 additional bright nearby stars (within 25 pc), with single
1-minute observations leading to some 2000 stars observed with accuracies of about
4 micro-arcsec. These will be from diverse types: all main-sequence spectral types,
binaries, a broad range of age and metallicity, dust disks, white dwarfs, planets
from radial velocity surveys, etc. Preparatory programmes for this survey include
radial velocity monitoring and adaptive optic imaging. The total expected number
of new detections from SIM, for any given planetary mass and orbital radius is again
not straightforward to predict, and depends on the (unknown) mass distribution of
exo-planets versus orbital radius at a ∼ 1 AU. Estimates are given in Table 5.
The NASA SMEX proposal AMEX (which followed on from the FAME study)
aimed at 150 micro-arcsec accuracy at 9 mag and 3 milli-arcsec at 15 mag and, with
a proposed launch in 2007–08, would have provided limited prospects for planet
detection through the comparison of proper motions with Hipparcos, including some
600 detections to 30 pc down to K5V stars, and transits to V =11 mag. AMEX was
not selected by NASA in 2003. In mid-2004 NASA announced the selection of
nine studies for future mission concepts within its ‘Astronomical Search for Origins
Program’, including the ‘Origins Billion Star Survey’ (OBSS) focussing on a census
of giant extra-solar planets using the principles of Gaia. If OBSS is selected, its
contribution to astrometric exo-planet research would not surpass those of Gaia.
The Japanese mission JASMINE, and a potential prototype nano-JASMINE, have
been under discussion at a low level in Japan for several years (Gouda et al., 2002).
Originally conceived as a mini-Gaia but able to concentrate on the Galactic centre
by operating in the infrared, the mission’s technical feasibility has been improved
in the past few months (although its scientific niche has been weakened) with the
move to CCD detector technology.
2.2.3 Space-Based Microlensing: MPF
Proposals for exo-planet detection through their microlensing signatures have been
made. GEST (Galactic Exo-Planet Survey Telescope (Bennett & Rhie, 2002)) was
proposed for a NASA mission in 2001–02 (a Survey for Terrestrial Exo-Planets
(STEP) was also submitted to NASA’s Extra-Solar Planets Advanced Concepts
Program at the same time). It was not selected in 2002, but was re-submitted
during 2004 under the name of Microlensing Planet Finder (MPF), using HgCdTe
and Si-PIN detectors in place of the earlier CCDs (Bennett et al., 2004).
A 1.2-m aperture telescope with a 2 deg 2 field of view continuously monitors 10 8
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