General information

[iers at hpvlbi.obspm.fr]

To IERS users

>From: IERS Central Bureau (iers at obspm.fr)

Subjects : New format in the permanent EOP(IERS)97 C 04 solutions for 1998
	 : Removal of the previous EOP(IERS) C01, C01, C03 and C04 in CB ftp
	 
	 
Dear Colleagues,


Please note the following changes in the EOP solutions of the IERS Central 
Bureau:  
  
  
1 - New format in the permanent EOP(IERS)97 C 04 solutions for 1998

To align to the format used by USNO VLBI analysis center and those
recently adopted by the IGS, the IERS Central Bureau will adopt a new 
format with an extra digit for polar motion and UT/LOD.

This change starting from July 1998 will be first applied to the permanent
EOP(IERS)97 C 04 for 1998 and the combined IERS/CB GPS solution (IERS)97 P 01.
It will progressively be applied for other previous years of C04 and also to 
all combined solutions C01, C02 and C03.

 The new format for the C04 solution is the following:

=>  FORMAT(2X,A4,I3,2X,I5,2F9.6,F10.7,2X,F10.7,2X,2F9.5)

Note: 
   The precision in the determination of Earth Orientation Parameters has
dramatically increased over the latter few years thanks to the improvement in 
techniques and in data analysis. 
   The IGS community has recently decided to add an extra digit to Polar Motion 
and UT/LOD estimates primarily for the sake of meaningful formal solution sigmas.
GPS Analysis centers are progressively introducing this new format.
   It is clear however that the accuracy of 1 micro-arcsecond in polar motion 
and 0.1 micro-second for UT/LOD (corresponding to 0.3 mm on the earth surface) 
is not yet reached.

2 - EOP(IERS) C 01, C02, C03 and C04 which were the current solutions before the 
adoption of the "1997 system" (see gazettes 8 and 16) will be removed from the 
web/ftp site on 1 September, 1998. These series will still be available on 
request (iers at obspm.fr).