Institut of Applied Astronomy
of St. Petersburg
The VLBI research group of the IAA Laboratory of New Methods in Astrometry and Geodynamics (NMAG) in St. Petersburg has elaborated this celestial frame [RSC (IAA) 02 R 03]. The solution has been obtained with the new software QUASAR (version QUASAR_LSC) for VLBI data analysis by Least Squares Collocation Technique. NEOS-A VLBI data for the period 1993-2001 has been analysed for this solution. . RSC (IAA) 02 R 03 has been aligned to the ICRS by not-net translation and no-net rotation constraints applied to source positions with respect to ICRF-Ext.1. Tropospheric gradients have been adjusted in the solution.
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 323 85 0.11 115 0.10 68 0.06 47 0.23 8 0.45
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 85 -0.009±0.024 +0.018±0.025 -0.023±0.036 0.15 0.23
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 -0.001±0.001 -0.005±0.038
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.