J/A+A/630/A101 Multi-frequency celestial reference frame (Karbon+, 2019)
Realization of a multi-frequency celestial reference frame through a
combination of normal equation systems.
Karbon M., Nothnagel A.
<Astron. Astrophys. 630, A101 (2019)>
=2019A&A...630A.101K 2019A&A...630A.101K (SIMBAD/NED BibCode)
ADC_Keywords: Fundamental catalog ; Positional data
Keywords: catalogs - astrometry - reference systems
Abstract:
We present a celestial reference frame (CRF) based on the combination
of independent, multifrequency radio source position catalogs using
nearly 40 years of very long baseline interferometry observations at
the standard geodetic frequencies at SX band and about 15 years of
observations at higher frequencies (K and XKa). The final catalog
contains 4617 sources.
We produce a multifrequency catalog of radio source positions with
full variance-covariance information across all radio source
positions of all input catalogs.
We combined three catalogs, one observed at 8GHz (X band), one at
24GHz (K band) and one at 32GHz (Ka band). Rather than only using the
radio source positions, we developed a new, rigorous combination
approach by carrying over the full covariance information through the
process of adding normal equation systems. Special validation routines
were used to characterize the random and systematic errors between the
input reference frames and the combined catalog.
The resulting CRF contains precise positions of 4617 compact radio
astronomical objects, 4536 measured at 8GHz, 824 sources also observed
at 24GHz, and 674 at 32GHz. The frame is aligned with ICRF3 within
±3µas and shows an average positional uncertainty of 0.1mas in
right ascension and declination. No significant deformations can be
identified. Comparisons with Gaia-CRF remain inconclusive, nonetheless
significant differences between all frames can be attested.
Description:
File contains the combination product of the catalogs referenced in
the name in the IERS-format.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
combkx.dat 104 4567 Coordinates for 4567 sources in S/X, and K band.
Corresponding Qxx matrix in kx-qxx.dat
combkxka.dat 104 4617 Coordinates for 4617 sources in S/X, K band,
X/Ka band.
Corresponding Qxx matrix in kxka-qxx.dat
kx-qxx.dat 81 13909560 *co-variance matrices of the combination
Combo_KX catalog (combkx.dar)
kxka-qxx.dat 81 14215743 *co-variance matrices of the combination
Combo_KXKa catalog (combkxka.dar)
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Note on kx-qxx.dat and kxka-qxx.dat: It is given as a decomposed lower
triangle matrix.
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See also:
I/323 : International Celestial Reference Frame 2, ICRF2 (Ma+, 2009)
Byte-by-byte Description of file: combkx.dat combkxka.dat
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Bytes Format Units Label Explanations
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1- 16 A16 --- ICRF ICRF Designation (JHHMMSS.s+DDMMSS) (1)
18- 25 A8 --- IERS IERS Designation (HHMM+DDd) (2)
27- 36 A10 --- IVS IVS Designation (HHMM+DDd)
38- 39 I2 h RAh Right ascension (J2000)
41- 42 I2 min RAm Right ascension (J2000)
44- 54 F11.8 s RAs Right ascension (J2000)
56 A1 --- DE- Declination sign (J2000)
57- 58 I2 deg DEd Declination (J2000)
60- 61 I2 arcmin DEm Declination (J2000)
63- 72 F10.7 arcsec DEs Declination (J2000)
74- 83 F10.8 s e_RAs rms uncertainty on RA
86- 95 F10.8 arcsec e_DEs rms uncertainty on DE
96-102 F7.4 --- RA-DE Correlation between Right Ascention and
Declination
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Note (1):ICRF Designations, constructed from J2000.0 coordinates with the format
ICRF JHHMMSS.s+DDMMSS or ICRF JHHMMSS.s-DDMMSS. They follow the
recommendations of the IAU Task Group on Designations.
Note (2): IERS Designations, previously constructed from B1950 coordinates.
The complete format, including acronym and epoch in addition to the
coordinates, is IERS BHHMM+DDd or IERS BHHMM-DDd
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Byte-by-byte Description of file: kx-qxx.dat kxka-qxx.dat
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Bytes Format Units Label Explanations
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3- 6 I4 --- Row Row number (1)
9- 12 I4 --- Col Column number
16- 35 E20.14 mas+2 Val1 Matrix Estimated Value
39- 58 E20.14 mas+2 Val2 ? Matrix Estimated Value 2
62- 81 E20.14 mas+2 Val3 ? Matrix Estimated Value 3
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Note (1): Odd Row-numbers correspond to the right ascension, even to the
declination of the respective source.
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Acknowledgements:
Maria Karbn, maria.karbon(at)obspm.fr
(End) Patricia Vannier [CDS] 27-Aug-2019