Astronomy and Astrophysics – Astronomy
Scientific paper
Apr 1998
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998exdu.work..292w&link_type=abstract
Exozodiacal Dust Workshop, p. 292
Astronomy and Astrophysics
Astronomy
Zodiacal Light, Signal Detection, Terrestrial Planets, Space Missions, Spaceborne Telescopes, Infrared Interferometers, Light Emission, Thermal Emission, Solar System, Infrared Radiation, Angular Resolution
Scientific paper
Is there a configuration which matches the potential scientific and technical interest in a planet finder precursor? There were many telescopes in space before HST, yet we nearly blew it! There have been no interferometers in space before SIM and DS3 and neither of them will be much like TPF. We have never previously attempted to control a long floppy structure so precisely. And we have never attempted to get control information so precisely, to get phase and amplitude precision correct to a fraction of 1/10 of 1%. It would be helpful if a smaller, faster, simpler, cheaper version of TPF could be tried first. Likewise the angular resolution of a planet finder, and its ability to explore very faint regions not far from very bright sources is a new kind of tool for astronomy. There would seem to be an opportunity to make some kind of novel astronomy study simultaneously with making the technical advance. What would a precursor be like that attempted to measure exo-zodiacal emission (EZE), and what else might be done with such a device? A precursor would be at 1 AU, and would have only two mirrors, approx. 15 m apart. There is no need to make them more than 1 m diameter despite the strong solar system zodiacal background. To avoid radiation from Sun, Earth, and Moon in different directions, it would be in a fall-away orbit like SIRTF or at L2. Passive cooling could get to 40 K, which is enough for a 5 micron InSb detector but not for sensitive 10 micron observations. Detector cooling is one version of the price of making a precursor detect EZE. Alternatively, we might try to detect the EZE at 5 microns, where the strongest signal will come from about 0.4 AU from the star. However, 2-element interferometers "leak" starlight because they partially resolve a star, and a 2-element interferometer to see emission 0.4 AU from a star would leak too much radiation from a star 0.01 AU diameter. The 5 micron EZE is relatively fainter relative to the star radiation, and at 10 microns the leak is less important compared with solar system ZE. So an alternative "price" to detector cooling at 10 microns is a 4-element interferometer with ambient detector at 5 microns. Neither is a simplest, cheapest approach. In terms of current lack of experience, the cooled detector seems the preferable approach. Such a device would also be able to detect the radiation of giant planets of approx. 100 million years old, where the system dust had largely gone. Such planets could be found around stars of the Pleiades cluster or nearby star formation regions.
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