J/MNRAS/449/2274 Characterization of Herschel SPIRE FTS (Hopwood+, 2015)
Systematic characterization of the Herschel SPIRE Fourier Transform
Spectrometer.
Hopwood R., Polehampton E.T., Valtchanov I., Swinyard B.M., Fulton T.,
Lu N., Marchili N., Van Der Wiel M.H.D., Benielli D., Imhof P.,
Baluteau J.-P., Pearson C., Clements D.L., Griffin M.J., Lim T.L.,
Makiwa G., Naylor D.A., Noble G., Puga E., Spencer L.D.
<Mon. Not. R. Astron. Soc., 449, 2274-2303 (2015)>
=2015MNRAS.449.2274H 2015MNRAS.449.2274H (SIMBAD/NED BibCode)
ADC_Keywords: Photometry, sequences
Keywords: instrumentation: spectrographs - methods: data analysis -
space vehicles: instruments
Abstract:
A systematic programme of calibration observations was carried out to
monitor the performance of the Spectral and Photometric Imaging
REceiver (SPIRE) Fourier Transform Spectrometer (FTS) instrument on
board the Herschel Space Observatory. Observations of planets
(including the prime point-source calibrator, Uranus), asteroids, line
sources, dark sky and cross-calibration sources were made in order to
monitor repeatability and sensitivity, and to improve FTS calibration.
We present a complete analysis of the full set of calibration
observations and use them to assess the performance of the FTS.
Particular care is taken to understand and separate out the effect of
pointing uncertainties, including the position of the internal beam
steering mirror for sparse observations in the early part of the
mission. The repeatability of spectral-line centre positions is
<5km/s, for lines with signal-to-noise ratios >40, corresponding to
<0.5-2.0 percent of a resolution element. For spectral-line flux, the
repeatability is better than 6 percent, which improves to 1-2 percent
for spectra corrected for pointing offsets. The continuum
repeatability is 4.4 percent for the SPIRE Long Wavelength
spectrometer (SLW) band and 13.6 percent for the SPIRE Short
Wavelength spectrometer (SSW) band, which reduces to ∼1 percent once
the data have been corrected for pointing offsets. Observations of
dark sky were used to assess the sensitivity and the systematic offset
in the continuum, both of which were found to be consistent across the
FTS-detector arrays. The average point-source calibrated sensitivity
for the centre detectors is 0.20 and 0.21Jy [1σ; 1h], for SLW
and SSW. The average continuum offset is 0.40Jy for the SLW band and
0.28Jy for the SSW band.
Description:
Tables summarizing the FTS observations used.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tableb.dat 69 408 AFGL2688, AFGL4106, CRL618, NGC7027, NGC6302,
R Dor, CW Leo, VY CMa, Uranus, Neptune, Mars,
Saturn, Ceres, Hebe, Hygiea, Juno and Vesta
observations taken after OD 189 (tables B1-B20)
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Byte-by-byte Description of file: tableb.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Name Source name
11- 23 A13 --- Mode Mode (1)
25- 28 I4 --- OD Herschel operational day
30- 39 A10 "date" Date Observation date (DD-MM-YYYY)
41- 43 I3 --- Reps Number of repetitions
45- 54 I10 --- obsId Herschel observation ID
55- 57 A3 --- n_obsId Note on obsId (2)
59- 60 A2 --- Res Commanded resolution
62- 65 F4.1 arcsec Poff ? Pointing offset (3)
67- 69 F3.1 arcsec e_Poff ? rms uncertainty on Poff
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Note (1): Modes as follows:
CR = CR nominal sparse
CR/HR bright = CR/HR bright sparse
HR = HR nominal sparse
HR/CR = HR/CR nominal sparse
HR/CR bright = HR/CR bright sparse
HR/CR full = HR/CR nominal full
H+LR = H+LR nominal sparse
LR = LR nominal sparse
LR int = LR nominal intermediate
LR nscm = LR nominal special calibration map
LR full = LR nominal full
MR = MR nominal sparse
Note (2): Note on obsId as follows:
* = Science observation
+ = Known outlier
P0 = Pointing offset reference observation
D = Special calibration. Two pointing offsets are given for the
special calibration observation, which is comprised of two
pointings - one with the BSM set at zero-zero and one with it
is set to the Before offset position.
** = Continuum peak and pointing offset reference observation
Note (3): For CW Leo, No pointing offset is given, due to CW Leo's intrinsic
variability, which precludes the v14 relative method. CW Leo is also known as
IRC+10216, with FIR/submm domain variability (Cernicharo et al.,
2014ApJ...796L..21C 2014ApJ...796L..21C). Observations made prior to OD209 are not included
For Vesta, No offset is given when the source is positioned in an off-axis
detector or for the bright mode observation.
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 07-Dec-2015