DORIS data format description
Format change: January 2004
An improved tropospheric delay computation algorithm is
introduced in the data preprocessing.
Slight change (Jan 2004) Nr 301
Starting arc/cycle: JASON-1 cycle 73 ja1data073...
TOPEX/POSEIDON cycle 417 topdata417...
ENVISAT arc 76 en1data076...
SPOT-5 arc 65 sp5data065...
SPOT-4 arc 251 sp4data251...
SPOT-2 arc 498 sp2data498...
Format change: January 2002
Data are delivered under either of two versions of the file content,
depending of the date of the observations. The change of format is not
reflected in the data filenames.
Starting dates for the adoption of the 2.1 format
The 1.0 format that was first used to distribute the data is acceptable
only for the pre-Jason receivers. Times t1 and t2 (start and end of
observations) are given in TAI. The Doppler count is converted from
cycles to mm/s based on frequency values that are the best estimates
(polynomial model for the onboard Ultra Stable Oscillator (USO),
pass by pass solutions for ground beacons) derived in the
Precise orbit determination (POD) process.
The 2.1 format is a slight modification of the 1.0 format,
with the following characteristics. Times t1 and t2 are in TAI.
The Doppler count is converted from cycles to mm/s based on
the timing polynomial for the onboard frequency and nominal
values for the ground beacons.
The 2.1 format better fits the analysts needs, in particular in the
context on multi-satellite solutions.
JASON-1 cycle 1 (15-24 Jan 2002) ja1data001...
TOPEX/POSEIDON cycle 344 (15-24 Jan 2002) topdata344...
ENVISAT arc 7 en1data001...
SPOT-5 arc 1 sp5data001...
SPOT-4 arc 168 (11-20 Jan 2002) sp4data168...
SPOT-2 arc 413 (11-17 Jan 2002) sp2data413...
The change from formats 1.0 to 2.1 may be summarized as follows.
Columns 46-56: Range rate is computed with
f(bea)= nominal (instead of best estimate) beacon frequency
Column 90: Channel indicator
Users should also check column 35: preprocessing indicator.
With format 1.0, CNES only measurements considered to be good
were delivered (value = 0).
With format 2.1 edited measurements may also be delivered
(value=1 for preprocessing, value=2 for postprocessing)
More on the change in DORISMail