 |
| Titel |
Spectroscopic Observations of Uranus and Neptune by the Herschel SPIRE Experiment: Constraints on Global-Mean Temperature Structure and Composition |
| VerfasserIn |
Glenn Orton, Bruce Swinyard, Matthew Griffin, Trevor Fulton, Ed Polhampton, Cos Hopwood, Raphaël Moreno, Emmanuel Lellouch, Paul Hartogh |
| Konferenz |
EGU General Assembly 2011
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250047867
|
|
|
|
|
|
| Zusammenfassung |
| The Herschel SPIRE Fourier Transform Spectrometer (FTS) covers the hitherto relatively
unexplored spectral region from 15 to 50 cm-1 (200 to 670 μm) with a spectral resolution of
0.048 cm-1. In order to calibrate the instrument we primarily rely on the measurement of the
spectrum of Uranus along with corroborating observations of Neptune and other solar system
bodies. Accurate models of the spectral emission from Uranus and Neptune are therefore
critical to the calibration and interpretation of all SPIRE photometric and spectroscopic
data as well as being of significant scientific interest in themselves. In order to
probe the sub-millimeter spectrum of Uranus and Neptune as deeply as possible,
long disk-averaged spectra of Uranus and Neptune were obtained by the Herschel
SPIRE FTS on 7 October 2010 (Herschel Operation Day (OD) 423) and 9 June 2010
(Herschel OD 392), respectively. These observations were made in the context
of the investigations of the Herschel Key Project “Water and Related Chemistry
in the Solar System”. Additional calibration of the instrument response function
was derived from observations of the airless Jovian satellite Callisto on 5 January
2011 (Herschel OD 602). For both planets, the continuum in most of this spectral
range is controlled by the collision-induced absorption of H2, and it is sensitive to
temperature at atmospheric pressures up to 1.5 bars. Models for their disk-averaged
radiances have been derived from measurements of the temperature structure and
composition by Voyager, as well as independent observations by the Infrared Space
Observatory and the Spitzer Space Telescope at shorter wavelengths, and Herschel
PACS measurements of lines of well mixed HD (Lellouch et al. 2010, Astron. &
Astrophys., 518, L152). These models will be compared with independent evaluations
of the flux calibrated against emission from the Herschel telescope itself, whose
temperature is continually monitored, assuming a wavelength-dependent emissivity
based on measurements obtained before launch (Fischer et al. 2004, Appl. Opt. 43,
3765). At the long wavelength end of the SPIRE FTS, an evaluation will be made of
the need for additional opacity sources, such as H2S or PH3, aided by supporting
ground-based observations in the SPIRE spectral range and longer wavelengths. |
|
|
|
|
|
|