Reference Frame of GAOUA

Main Astronomical Observatory of the National Academy of Sciences
of Ukraine

The Main Astronomical Observatory of the National Academy of Sciences of Ukraine has elaborated this frame [RSC (GAOUA) 01 C 01]. Radio source coordinates have been calculated by the combination of the four individual VLBI solutions submitted to the IERS and analyzed in the IERS Annual Report for 2000 (IERS, 2001). The Kyiv arclength method (Yatskiv and Kur'yanova, 1990) has been applied for the catalogue compilation. The axes of the compiled frame are aligned to the ICRS with an accuracy of 0.01 mas by the 202 ICRF defining sources present in RSC (GAOUA) 01 C 01.

Reference Frame Characteristics :

Table 1 gives the number of sources and their mean standard error of this Reference Frame according to following classification :

• "defining", "candidate" and "other" sources correspond to the classification of ICRF sources,
• "new" are the sources added in ICRF-Ext.1,
• "additional" is for sources not present in ICRF-Ext.1 and observed in this VLBI program.
  

Total	Defining		Candidate		Other		New		Additional
N	N	m	N	m	N	m	N	m	N	m
670	211	0.06	277	0.09	102	0.02	59	0.14	21	0.22

Table 1 : N = number of sources, m = mean standard error (Unit: mas).

Comparison of this celestial frame to ICRF-Ext.1 :

Under the assumption that ICRF-Ext.1 is free from deformations, the systematic effects detected in the comparison indicate the existence of deformations in the individual frame.

The algorithm of comparison is the one currently used at the ICRS Centre; the coordinate difference between two frames is modelled by a global rotation of the axes, represented by the three angles A1, A2, A3, and by a deformation represented by three parameters : two slopes (Da) and (Dd), and one bias (Bd).

Table 2 gives the global orientation between axes of this catalogue and those of the ICRS.

N	A1	A2	A3	ra	rd
211	-0.003±0.016	-0.020±0.016	-0.022±0.021	0.17	0.22

Table 2 : A1, A2, A3 are the small angles which transform coordinates from this frame into ICRF; N is the number of the common defining ICRF sources used for the comparison; ra and rd are the weighted mean residuals in acos(d) and d respectively. Unit: 0.001".

Table 3 shows the systematic effects in this frame detected by their comparison to ICRF-Ext.1.

Da	Dd	Bd
-0.001±0.001	+0.000±0.000	+0.014±0.017

Table 2: Da, Dd are the slopes in right ascension and in declination, respectively. Bd is the bias in declination. Units: 0.001"/degree for the slopes, 0.001" for the bias.

Remark : No deformations are detected in this frame when compared to ICRF.