Features
> Home
> About
> History
> Instrument Shop
> Telescopes
Projects
> Double Stars
> OBSS
> FAME
> FTS
> ICRF
> ICRF-2
> UCAC
> VLBI
Catalogs
> Recommended
> AC2000
> ACT
> CPC2
> CPIRSS
> Double Stars
     -WDS
     -Orbit
     -Interferometric
     -Delta M
> ERLcat
> OID
> RORF
> RRFID
> TAC
> Tycho-2
> UCAC2
> VLBI
Miscellaneous
> Astronomy Events
Naval Meteorology and Oceanography Command U.S. Naval Observatory
Thursday November 23, 2017

Home About History Instrument Shop Telescopes

USNO Global VLBI Solution crf2001a

Presented here is the U.S. Naval Observatory's crf2001a global solution. Parameterization of this solution follows that of the International Celestial Reference Frame (ICRF) solution (Ma et al. 1998, AJ, 116, 516) but includes several analysis improvements, the most important of which are 1) using the Niell Mapping Function to model the troposphere and 2) more frequent estimation of troposphere gradients (once every 6 hours instead of once every 24 hours as was done for the ICRF). The solution also includes more than 6 years of new data (including the VLBA RDV data from experiments RDV01 to RDV24).

The resultant global SOLVE solution includes all available VLBI observations at 8.4 GHz (X-band) and 2.2 GHz (S-band) from 3 August, 1979 through 23 October, 2001. This includes a total of 3237 diurnal sessions encompassing 3,122,879 measurements of group delay and phase delay rate. The weighted root-mean-square residuals of the solution were 24.556 ps in delay and 73.196 fs/s in delay rate. The SOLVE batch control file crf2001a.cnt.gz was used to generated this solution with an output spool file crf2001a.spl.gz. Tabulated below are the global and session values for the solution.

Source and Station Positions

Positions of 548 sources were estimated as global parameters. Sources which participated in 2 or more sessions separated by at least 2 years, had 20 or more good observations, had normalized residual delays less than 1.2 in preliminary solutions, and were not galactic or transient qualified for the list of global sources. Positions for an additional 155 sources were estimated for each session independently as local parameters. A total of 85 sources with either less than two good observations or with bad data were excluded from the solution. Positions of all 121 stations were estimated as local parameters.

Tabulated data.

Global source positions crf2001a.sou.gz format description
Local source positions crf2001a.lso.gz format description

Earth Orientation Parameters

Daily nutation offsets in longitude and obliquity were estimated for each session separately.

Tabulated data.

Nutation angles crf2001a.nut.gz format description

Comparisons

Shown below is a comparison of the USNO crf2001a solution with the ICRF Ext.1 source positions. The weighted rms differences are at the end of the difference tables.

Tabulated data and plots.

crf2001a minus ICRF Ext.1 Defining Difference Table Aitoff Plot: PS, JPG
crf2001a minus ICRF Ext.1 Difference Table Aitoff Plot: PS, JPG

Position Time Series

Three additional solutions were made with identical parameterization and data as for crf2001a. In each of these three solutions, one third of the sources were estimated as "arc" parameters (all other sources were treated as global). The SOLVE BATCH control files for these additional solutions are available here (pts2001a1.cnt.gz, pts2001a2.cnt.gz, pts2001a3.cnt.gz). Daily nutation offsets in longitude and obliquity were estimated for each session separately. Results are presented in the following tables.

Tabulated data.

pts1 Nutation angles pts2001a1.nut.gz format description
pts2 Nutation angles pts2001a2.nut.gz format description
pts3 Nutation angles pts2001a3.nut.gz format description

Tabulated statistics and plots.

Min obs/pos: 1; Max Sigma/pos: NONE (i.e. all data)
Wrms Table, PS, JPG; "arc" wrms and Chi^2/df (df=degree of freedom)
Positions Table (in gsnoop format); "arc" weighted mean and wrms
"Arc" Position Plots (PS, one file ~9.0 MByte)

Min obs/pos: 3; Max Sigma/pos: 1 mas
Wrms Table, PS, JPG; "arc" wrms and Chi^2/df (df=degree of freedom)
Positions Table (in gsnoop format); "arc" weighted mean and wrms
"Arc" Position Plots (PS, one file ~7.4 MByte)

"Arc" weighted mean minus crf2001a global Difference Table Aitoff Plot: PS, JPG

Please read this Privacy and Security Notice and this Disclaimer for External Links.

This is an Official U.S. Navy Web Site Need Help?