VLBI  Data  Analysis  Centre

Software

The unique software SteelBreeze, developed by Sergei Bolotin (the Main Astronomical Observatory of the National Academy of Sciences of Ukraine), is used for geodetic VLBI data analysis.

The development of the software SteelBreeze was started in 1992. Originally, it was developed for the MS DOS operating system, and then it was adapted to Windows 3.1. The software is written on Pascal programming language using Object Oriented Design. This version is called SteelBreeze ver.1.

In 1998, the development of the SteelBreeze ver.2 software was started. The current version of the software reflects considerable changes in the software development (e.g., SteelBreeze ver.2 written on the C++ language, running on Linux, Solaris, FreeBSD and other operating systems, uses Qt widget library for graphics user interface). In addition, many subsystems of the software (observation data processing, estimation, logging, results output, etc.) were improved and optimized. At present, SteelBreeze ver.2 is used for VLBI data analysis.

The SteelBreeze software makes least-squares estimation of various geodynamical parameters with the Square Root Information Filter (SRIF) algorithm (see Biermann, 1977). The SRIF uses Householder's transformation for matrix triangularization which makes it fast and intensive for computer roundoff. Besides, the SRIF makes possible to introduce the stochastic model for parameter estimation.

The SteelBreeze software analyses the VLBI data (time delay) of single and multiple set of sessions. The time delay is modeled according to the IERS Conventions 2003. Additional models can also be used (tectonic plate motions, nutation models, wet and hydrostatic zenith delays, mapping functions, etc). The software makes estimations for the following parameters: the Earth's orientation parameters, coordinates and velocities of a selected set of stations, coordinates of a sample of radio sources, Love numbers, clock function and wet zenith delay and their gradients.

Various investigations on the stability of the Celestial Reference Frame were carried out with SteelBreeze software. Some studies of variations of tropospheric zenith delays and comparison of GPS- and VLBI-derived zenith delays were performed. Now, an analysis of time variations of Love and Shida numbers is conducted.

The following list of models is implemented in the software for time delay calculating.

List of models
 

	Tectonic Plate motion	NNR Nuvel-1A Nuvel-1A
	CRF<->TRF System Transformation	Equinox based (classical) NRO (IAU 2000 Resolutions)
	Precession-Nutation Theory	IAU 1976 Precession + IAU 1980 Nutation Theory IAU 1976 Precession + IAU 1996 Nutation Theory IAU 2000A Precession-Nutation Model
	Planetary Ephemeris	DE200/LE200 DE403/LE403 DE405/LE405
	Ocean Loading	based on GOT00.2 Ocean tide model provided by H.G. Scherneck
	Solid Tides	only degree 2 tides displacements (IERS Standards 1992) degree 2 and 3 tides displacements with latitude and frequency dependence of the Love and Shida numbers (IERS Conventions 2003)
	Atmospheric Loading	Petrov and Boy Atmospheric Loading Ephemeris
	Diurnal and subdiurnal EOP variations	Ocean tide model (Ray et al, 1994) Non-tidal variations in oceanic angular momentum (de Viron et al) Atmospheric tides (Brzezinski, Bizouard and Petrov, 2002)
	Tropospheric zenith delay	Saastamoinen, 1972 Hopfield, 1977
	Tropospheric mapping functions	Chao, 1974 CfA-2.2 Ifadis global mapping function, 1986 MTT, Herring, 1992 NMF2, Niell, 1996