New DORIS/ENVISAT data available

[Vincent Patrick <Patrick.Vincent@cnes.fr>]

Dear all,


This message is to inform you about the availability of new DORIS/ENVISAT
data for the OVT use.

The new data set has a 12 day length: It corresponds to the June 12, 10:00 
pm
to June 24, 00:00 period.


Let me now take the opportunity to recall you some elements.


A. About the RA-2/OVT web site maintained by ESA:

Some of you asked me to recall you the coordinates of the RA2/OVT website
maintained by ESA. Here are these elements:

Location is: http://styx.esrin.esa.it:8060
Login: ccvt
Pwd:  ra2mwr


B. About the DORIS data themselves

B. 1. Where to get the data: no change with respect to previous information

Data are available from the following ftp server:
        ftp spike.cst.cnes.fr (IP: 132.149.10.3)
        name: anonymous
        password: your email address

Then, change directory to /pub/ENVIS

B. 2. Architecture of the ENVIS directory: No change with respect to 
previous
information

Three sub-directories and a series of 4 README files may be found:

B.2.1. Sub-Directory DORIS

It contains:

the DORIS Doppler data expressed as the nominal ENVISAT project products
which are thus provided in the ESA/PDS format (note that these are zipped
files).

In addition to the previous list of data, you can find:

DOR_DOP_1POF-P20020612_....N1.Z
DOR_DOP_1POF-P20020613_....N1.Z
DOR_DOP_1POF-P20020614_....N1.Z
DOR_DOP_1POF-P20020615_....N1.Z
DOR_DOP_1POF-P20020616_....N1.Z
DOR_DOP_1POF-P20020617_....N1.Z
DOR_DOP_1POF-P20020618_....N1.Z
DOR_DOP_1POF-P20020619_....N1.Z
DOR_DOP_1POF-P20020620_....N1.Z
DOR_DOP_1POF-P20020621_....N1.Z
DOR_DOP_1POF-P20020622_....N1.Z
DOR_DOP_1POF-P20020623_....N1.Z

and the DORIS doppler data in the usual CDDIS format:

en1data006_arc5.dat.Z, which contains all DORIS Doppler data which were 
used
for the 5-th orbital arc of ENVISAT cycle 6.
en1data007_arc1.dat.Z, which contains all DORIS Doppler data which were 
used
for the 1-st orbital  arc of ENVISAT cycle 7.

2 Notes about the CDDIS DORIS doppler data files:

* They contain the same data as the ones in the ESA PDS format.

* For the usual operational POE processing in nominal conditions, a 35 day
ENVISAT cycle results in 5 seven day POE arcs. DORIS data are gathered in
packages corresponding to each POE orbital arc. This is the reason why an 
arc
number has been added to the naming just after the ENVISAT cycle number. 
This
arc number may vary from 1 to 5 in normal conditions: it may be greater 
than
5 when some orbit events strongly disturb the orbit computation, so that
smaller POE arc may have to be computed.


You will also find 4 files named:

DOR_CON_AXVF-P20020702_125400_20020612_xxxxxx_20020617_yyyyyy
DOR_CON_AXVF-P20020702_151000_20020618_xxxxxx_20020623_yyyyyy

and

DOR_INS_AXVF-P20020702_125200_20020612_xxxxxx_20020617_yyyyyy
DOR_INS_AXVF-P20020702_150800_20020618_xxxxxx_20020623_yyyyyy

which respectively contain the orbit computation configuration information,
and the information about the DORIS instrument, for the 2 POE orbital arcs
computed for the June 13 to June 17, and June 18 to June 23 periods. The
ESA/PDS format is used.


B.2.2. Sub-Directory COM

No Center of Mass and Mass information updates.


B.2.3. Sub-Directory ORBITS

It contains the orbit ephemeris:

Under the ORBITS directory, a so-called CNES subdirectory has been 
initiated.

Under the CNES subdirectory, two subdirectories have been created. A first
one is named MOE: It contains the MOE files; a second one is named POE and
contains the POE files.

* POE directory:

In addition to the previous files, the POE directory has been filled in 
with
the following new files (note that these are zipped files):

DOR_VOR_AXVF-P20020702_xxxxxx_20020612_221528_20020614_002328.Z
DOR_VOR_AXVF-P20020702_xxxxxx_20020613_215528_20020615_002328.Z
DOR_VOR_AXVF-P20020702_xxxxxx_20020614_215528_20020616_002328.Z
DOR_VOR_AXVF-P20020702_xxxxxx_20020615_215528_20020617_002328.Z
DOR_VOR_AXVF-P20020702_xxxxxx_20020616_215528_20020618_002328.Z
DOR_VOR_AXVF-P20020702_xxxxxx_20020617_215528_20020619_002328.Z
DOR_VOR_AXVF-P20020702_xxxxxx_20020618_215528_20020620_002328.Z
DOR_VOR_AXVF-P20020702_xxxxxx_20020619_215528_20020621_002328.Z
DOR_VOR_AXVF-P20020702_xxxxxx_20020620_215528_20020622_002328.Z
DOR_VOR_AXVF-P20020702_xxxxxx_20020621_215528_20020623_002328.Z
DOR_VOR_AXVF-P20020702_xxxxxx_20020622_215528_20020624_002328.Z

and

eph_envis1_20020612_215128_20020618_012128.sp1.Z
eph_envis1_20020617_215128_20020624_012128.sp1.Z

The so-called DOR_VOR files are the nominal ENVISAT project products: they
are thus provided with the ESA/PDS format (one segment per day extending 
over
26 hours).

The eph_envis1_*.sp1.Z  files have been provided in the sp1 format, which 
is
the format used for the Jason-1 exchanges in the frame of the Jason-1 orbit
verfication activities.

* MOE directory:

For those of you interested in qualifying the MOE orbits, the MOE directory
has been filled in with 14 files that provide the daily MOEs from June 12 
to
June 25, 2002.
Format of the MOE files is exactly the one of the ESA POE file (that is the
so-called PDS format).
The MOE files are named DOR_POR instead of DOR_VOR for the POEs.


B.2.4. The 4 README files: No change with respect to the previous 
information


B.3. Additional information

3.1. The new data set correspond to the June 12, 10:00 pm to June 24, 00:00
period.

MOE are computed as 1 day arcs.
POE have been computed in two separate arcs: * one is for the June 12 10:00
pm to June 18 00:00 period, * the second is for the June 17, 10:00 pm to 
June
24, 00:00 period.

B.3.2. Format of files: No change with respect to previous information


C. How to exchange orbits within the group

Any group of the OVT may deliver orbits by putting files in the 
/depot/ENVIS
directory using the same ftp server.

Please send an e-mail to me with a copy to Berthyl Duesmann after any
delivery of POE solutions to the ftp site (at least during the next weeks; 
we
will then revisit the organization later).

The orbits you make us available will then be made available to any member 
of
the OVT for the comparison/validation exercise.

A message will be sent soon to tell you how/where to retrieve the solutions
made available by each group in order to perfom cross-comparisons.


D. Summary of DORIS data availability since launch

Some of you have asked some details about DORIS data availability since 
DORIS
has been turned on.
In order to answer this question, we are preparing:

* the list of events having impacted the DORIS data collection,
* a table providing information about the percentage of data that has been
made available through the ENVISAT Ground Segment.

Once we have compiled this information, we will of course make it available
to the OVT by mail and through the RA2/OVT web site, so that every member 
of
the OVT group can have the full information on the DORIS data availability.



I hope this information is useful.

Would you encounter any difficulty, please send an e-mail to:

Patrick.Vincent@cnes.fr, with a copy to
bduesman@estec.esa.nl

We will take care of your comments and questions as far and as quickly as 
we
can.

With my best regards,

Patrick