|
CDDIS Bulletin - April 1990
Volume 5 No. 4
In this issue:
On the cover: Global DORIS
Site Locations
As reported in previous issues of the DIS Bulletin, the Bendix
Data Services group has been generating test sets of LAGEOS normal
points for 1988 and 1989. Recently, Hermann Hauck of IfAG has detected
errors in the wavelength used to compute refraction in these data
sets. In the 1988 data set, 40 passes out of 4734 passes for which
normal points were computed contained an incorrect wavelength in
the normal point field and an incorrect refraction value.. An additional
25 passes contained an incorrect wavelength in the field, but the
normal points were computed using the correct wavelength. In the
1989 data set, 20 passes out of 2011 passes for which normal points
were computed contained an incorrect refraction value and an incorrect
wavelength in the normal point field; an additional 13 passes contained
an incorrect wavelength, but the normal points were computed using
the correct wavelength.
Table Ia lists the passes in the 1988
normal point data set that contained an incorrect wavelength and
an incorrect refraction value. The column Wavelength Applied is the
wavelength that was incorrectly used to compute the refraction for
each normal point in the pass. The column Correct Wavelength is the
correct value to be used to properly compute the refraction. Table
Ib lists the normal points that contained an incorrect value
in the wavelength field. Once again, the refraction value is correct;
only the wavelength value is in error. The column Correct Wavelength
is the wavelength that was used to compute refraction. Similarly, Table
IIa lists the passes in the 1989 normal point data set that contained
an incorrect wavelength and an incorrect refraction value; Table
IIb lists those passes that contained an incorrect value in the
wavelength field only.
This section is designed to give brief notices of special events
or problems encountered in recent months.
The Bendix Data Services group reports that all MOBLAS-7 data for
the time period October 12, 1989 through December 31, 1989 will be
recalled. The data is artificially short and has a range bias of
100 picoseconds (1.5 centimeters). Bendix will repair the data by
adding 100 picoseconds to all of the time-of-flight values. Data
Services used an old calibration distance for processing; a new survey
was performed on October 12, 1989.
SLR data analysts report that selected HOLLAS passes during 1988
are off by approximately 50 microseconds. Further research is required;
the DIS will inform SLR data users as more information becomes available.
DGFI has recently sent their DGFII 89L03 analyzed results to the
CDDIS. This solution contains station coordinates, station velocities,
and earth orientation parameters computed using five years of LAGEOS
SLR data. These data sets can be viewed through the DIS by using
pre-programmed data base queries.
|
