ACCESS: Enabling an Improved Flux Scale for Astrophysics
msra(2010)
摘要
Improvements in the precision of the astrophysical flux scale are needed to
answer fundamental scientific questions ranging from cosmology to stellar
physics. The unexpected discovery that the expansion of the universe is
accelerating was based upon the measurement of astrophysical standard candles
that appeared fainter than expected. To characterize the underlying physical
mechanism of the "Dark Energy" responsible for this phenomenon requires an
improvement in the visible-NIR flux calibration of astrophysical sources to 1%
precision. These improvements will also enable large surveys of white dwarf
stars, e.g. GAIA, to advance stellar astrophysics by testing and providing
constraints for the mass-radius relationship of these stars.
ACCESS (Absolute Color Calibration Experiment for Standard Stars) is a
rocket-borne payload that will enable the transfer of absolute laboratory
detector standards from NIST to a network of stellar standards with a
calibration accuracy of 1% and a spectral resolving power of R = 500 across the
0.35-1.7 micron bandpass.
Among the strategies being employed to minimize calibration uncertainties
are: (1) judicious selection of standard stars (previous calibration heritage,
minimal spectral features, robust stellar atmosphere models), (2) execution of
observations above the Earth's atmosphere (eliminates atmospheric contamination
of the stellar spectrum), (3) a single optical path and detector (to minimize
visible to NIR cross-calibration uncertainties), (4) establishment of an a
priori error budget, (5) on-board monitoring of instrument performance, and (6)
fitting stellar atmosphere models to the data to search for discrepancies and
confirm performance.
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关键词
spectrophotometry,nir spectroscopy,vega,standard stars,calibration,access,hd37725,photometry,sub-orbital,sir- ius,nist,rocket,bd+17 � 4708,optical spectroscopy,dark energy,spectrum,atmospheric modeling
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