##### Minutes ILRS/AWG Workshop #11

##### June 5, 2004, San Fernando, Spain

#### **1. Opening**

Welcome by Noomen. Approval of agenda (Table 1). The names and e-mail
addresses of the participants are listed in Table 2.

**2. Pilot project "positioning and earth orientation"**

Noomen gave a short introduction of this ILRS AWG pilot projects, in
particular on the customers (IERS Bulletin A, IERS Combination Pilot
Project) and the most recent refinements (after the AWG meeting in Nice,
April 2004).

**2.1. Individual contributions**

In the discussion that took place during the AWG meeting in Nice, a
number of criteria were selected to document and evaluate the quality of
the solutions for station coordinates and EOPs. The ones for
documentation (like number of stations, number of passes, etcetera; cf.
Table 4 of minutes AWG meeting Nice 2004) are not addressed here any
further. The ones that have been identified for quality evaluation
purposes in particular are reflected in tabular form in Table 3.

The various contributors to the ILRS products were given the opportunity
to comment on their most recent activities. The providers of individual
solutions present here (ASI, DGFI, JCET and NSGF) as well as the
combination centers present (ASI and DGFI) gave a few remarks, where
appropriate. The time for this agenda item was mainly filled with the
completion of Table 3. This gives an overview of the various numerical
estimates of various quality aspects, both of the individual solutions
and of combination solutions. After each entry, the name of the source
of the specific number is given; in principle, a particular aspect may
have been addressed by more than one group. The table has been completed
as much as possible.

**2.2. Comparisons and combinations**

See remarks under 2.1 "individual contributions".

**2.3. External evaluation of combination solutions**

##### IGN

On behalf of Altamimi, Noomen presented the IGN evaluation of the
combination solutions generated by ASI. Because of time constraints,
Altamimi was unable to address any of the other (individual and/or
combination) solutions, and the evaluation of the ASI solutions, too,
was restricted to a few aspects only.

Altamimi compared the ASI combination solution with an intermediate
combination solution, which is based on 10 years of SLR, 6 years of GPS,
14 years of VLBI and 10 years of DORIS data. This may introduce an
offset w.r.t. the other comparisons which used ITRF2000 as a reference,
and therefor, the results are not included in Table 3, but will be
reported in this part of the minutes only. The following ranges were
observed for the origin differences of ASI's combination solution versus
this internal IGN solution: -15 - 35 mm (X), -35 -- 20 mm (Y) and 0 --
40 mm (Z). Neither clear signals nor significant outliers were detected.
As for scale, the values typically range between --15 and 0 mm
(corresponding to about --2 -- 0 ppb), with an individual outlier of
--40 mm (or 6 ppb). The differences w.r.t. this new IGN combination
solution show values of, on average , 10 - 20 mm for 2D WRMS, and a
similar range (and pattern) for the up component (making the total 3D
difference 15 - 30 mm WRMS).

##### OdP

Based on input provided by Altamimi, Gambis showed a plot of the EOP
residuals for x-pole and y-pole of the ASI combination solution w.r.t.
IERS C04 (Gambis was not present; Noomen presented on his behalf). The
rms value of these differences amounts to about 0.3 mm for the
x-component and about 0.4 mm for the y-component (ignoring a small group
of individual outliers at the level of up to 20 marcsec).

**2.4. Selection of ILRS combination center and backup**

In this part of the meeting, two main questions needed to be answered:
(*i*) is the quality of the combination solutions better than that of
the individual solutions, and (*ii*) which institute will act as the
official primary ILRS combination center, and what will be the role for
the others?

The first question can be answered positively by inspecting Table 3:
there is a small improvement in the residual rms w.r.t. ITRF2000, but
this can possibly be explained by imperfections in this reference model
at the level of a few mm. More striking, however, is that the Helmert
parameters (in particular those for our unique products, *i.e.* origin
and scale) when mapping into ITRF2000 show a much better consistency
(cf. Table 3). Also, EOP statistics for the combination solution (ASI's
solution could be evaluated only) turn out to be significantly better
than those for the individual solutions. In conclusion, there was a
positive conclusion on this part of the evaluation.

The second question proved a bit harder to answer, if only because the
information that was present to evaluate and compare the 3 combination
solutions was sparse. There was a debate on whether to postpone this
important decision or not, but in view of the requirements of our
external clients (IERS, with various products) and the likely date for a
next AWG meeting, it was generally accepted that a decision was to be
made here.

At this point, it was generally agreed by the members present that ASI
has done an outstanding performance throughout the pilot phase
(history), and has taken a large variety of roles within the ILRS
analysis community, always with a positive attitude. After some debate,
it was decided to give the role of official primary ILRS combination
center to ASI, and the role of official backup ILRS combination center
to DGFI. Representatives of the two institutes present agreed with this
outcome. It was emphasized by the chairman that it requires strict
adherence to the timelines as followed now during the testing phase of
the operational procedures, irrespective of the actual role. Holidays
and other occasions cannot be taken as an excuse to not have a
particular analysis done, by neither of the centers. Since NCL was not
present, no information was available on the actual performance of this
combination product, and the combination product information to the
analysis community has been difficult sometimes, it was decided to give
NCL the status of ILRS combination center in development; NCL is
strongly encouraged to further develop their procedures and results.

There are a number of action items that come out of this decision:
Noomen will iron out the exact details of the combination products
(computer location, naming etc.) and will convey the outcome to IERS.
The decision will be formalized by sending an official letter on the
outcome to ASI and DGFI representatives (*action item Noomen,
Pearlman*). The current selection will be effective until the next
International Workshop on Laser Ranging, to take place in Canberra in
October 2006. Then, the performance of the current two (plus additional
candidates, like NCL) combination centers will be evaluated again. It
was decided to retain this performance evaluation, of ASI and DGFI as a
minimum, as a standard agenda item in upcoming AWG meetings.

Although the decision has been made, Altamimi and Gambis will be asked
to complete their evaluation of the results as they are now (*action
item Noomen*). Irrespective of the outcome, this will not change the
decision made here, but it will be used as additional monitoring input.
Preferably this should be ready by July 15. Kelm and Altamimi need to
get in contact on technical problems of the DGFI solutions (*action item
Kelm*).

**2.5. Other issues**

No issues here.

**3. Next meeting**

The next AWG workshop has not been scheduled yet. Very likely, there
will be one in conjunction with the EGU meeting in Spring 2005 (Vienna,
Austria). If deemed necessary, an additional AWG meeting may be
organized in the mean time, but if possible preference will be given to
email correspondence.

**4. Action items**

In view of the time, no overview of the standing and new action items
was given. All standing action items remain, and new ones are added (cf.
Table 4).

**5. Closure**

Noomen thanked the participants for their contributions and their input
in the discussions.

June 25, 2004

R. Noomen, G. Appleby, P.J. Shelus

**Table 1: Agenda.**

# ILRS Analysis Working Group workshop #11

San Fernando, Spain, June 5, 2004

1\. opening

2\. pilot project \"positioning + earth orientation\"

2.1. individual contributions

. ASI

. DGFI

. GFZ

. JCET

. NSGF

2.2. comparisons and combinations

. ASI

. DGFI

. NCL

2.3. external evaluation of combination results

. IGN

. OdP

2.4. selection of ILRS combination center and backup

2.5. other issues

3\. next meeting

4\. action items

5\. closure

**Table 2: Attendance.**

Graham Appleby <graham.appleby@nerc.ac.uk>

Giuseppe Bianco <giuseppe.bianco@asi.it>

David Coulot <david.coulot@obs-azur.fr>

Mark Davis <mdavis@ssdd.nrl.navy.mil>

Bud Donovan <howard.donovan@honeywell-tsi.com>

Maury Dube <mdube@pop900.gsfc.nasa.gov>

Richard Eanes <eanes@csr.utexas.edu>

Werner Gurtner <gurtner@aiub.unibe.ch>

Julie Horvath <julie.horvath@honeywell-tsi.com>

Rainer Kelm <kelm@dgfi.badw.de>

Cinzia Luceri <cinzia.luceri@asi.it>

John Luck <jmckluck@optusnet.com.au>

Horst Müller <mueller@dgfi.badw.de>

Ron Noomen <ron.noomen@deos.tudelft.nl>

Toshi Otsubo <otsubo@nict.go.jp>

Erricos Pavlis <epavlis@jcet.umbc.edu>

Mike Pearlman <mpearlman@cfa.harvard.edu>

Riccardo Sala <riccardo.sala@telespazio.it>

Peter Shelus <pjs@astro.as.utexas.edu>

Mark Torrence <mtorrenc@magus.stx.com>

##### Table 3: Overview of aspects for evaluation of individual and combination solutions and their values; institute names after numbers represent source of data.

<table>
<colgroup>
<col style="width: 12%" />
<col style="width: 15%" />
<col style="width: 9%" />
<col style="width: 9%" />
<col style="width: 9%" />
<col style="width: 10%" />
<col style="width: 10%" />
<col style="width: 8%" />
<col style="width: 8%" />
<col style="width: 8%" />
</colgroup>
<tbody>
<tr class="odd">
<td>aspect</td>
<td>parameter [unit]</td>
<td>ASI (ind)</td>
<td>DGFI (ind)</td>
<td>GFZ (ind)</td>
<td>JCET (ind)</td>
<td>NSGF (ind)</td>
<td>ASI (cmb)</td>
<td>DGFI (cmb)</td>
<td>NCL (cmb)</td>
</tr>
<tr class="even">
<td>3D WRMS wrt ITRF2000</td>
<td>[mm]</td>
<td><p>11 asi</p>
<p>10 dgfi</p></td>
<td>10 dgfi</td>
<td>10 dgfi</td>
<td><p>10 jcet</p>
<p>12 dgfi</p></td>
<td><p>12 nsgf</p>
<p>18 dgfi</p></td>
<td>10 asi</td>
<td>9 dgfi</td>
<td></td>
</tr>
<tr class="odd">
<td>3D WRMS wrt comb</td>
<td>[mm]</td>
<td>9 asi</td>
<td>10 asi</td>
<td>9 asi</td>
<td>9 asi</td>
<td>19 asi</td>
<td>-----</td>
<td>-----</td>
<td>-----</td>
</tr>
<tr class="even">
<td rowspan="4">Helmert wrt ITRF2000</td>
<td>mean X [mm]</td>
<td><p>-2 asi</p>
<p>5 dgfi</p></td>
<td><p>-2 asi</p>
<p>5 dgfi</p></td>
<td><p>0 asi</p>
<p>4 dgfi</p></td>
<td><p>2 asi</p>
<p>4 dgfi</p></td>
<td><p>-3 asi</p>
<p>2 dgfi</p></td>
<td>-1 asi</td>
<td>4 dgfi</td>
<td></td>
</tr>
<tr class="odd">
<td>mean Y [mm]</td>
<td>-4 asi</td>
<td>-6 asi</td>
<td>-3 asi</td>
<td>-3 asi</td>
<td>-13 asi</td>
<td>-4 asi</td>
<td></td>
<td></td>
</tr>
<tr class="even">
<td>mean Z [mm]</td>
<td>-8 asi</td>
<td>-10 asi</td>
<td>-8 asi</td>
<td>-11 asi</td>
<td>-15 asi</td>
<td>-9 asi</td>
<td></td>
<td></td>
</tr>
<tr class="odd">
<td>scale [ppb]</td>
<td>-0.6 asi</td>
<td>0.8 asi</td>
<td>-0.3 asi</td>
<td>0.13 asi</td>
<td>-0.25 asi</td>
<td>-0.09 asi</td>
<td></td>
<td></td>
</tr>
<tr class="even">
<td rowspan="4">Helmert wrt comb</td>
<td>mean X [mm]</td>
<td>-1 asi</td>
<td>0 asi</td>
<td>1 asi</td>
<td>1 asi</td>
<td>-3 asi</td>
<td>-----</td>
<td>-----</td>
<td>-----</td>
</tr>
<tr class="odd">
<td>mean Y [mm]</td>
<td>1 asi</td>
<td>-3 asi</td>
<td>2 asi</td>
<td>0 asi</td>
<td>-5 asi</td>
<td>-----</td>
<td>-----</td>
<td>-----</td>
</tr>
<tr class="even">
<td>mean Z [mm]</td>
<td>1 asi</td>
<td>-4 asi</td>
<td>0 asi</td>
<td>0 asi</td>
<td>-3 asi</td>
<td>-----</td>
<td>-----</td>
<td>-----</td>
</tr>
<tr class="odd">
<td>scale [ppb]</td>
<td>-0.2 asi</td>
<td>0.68 asi</td>
<td>-0.3 asi</td>
<td>0.06 asi</td>
<td>0.5 asi</td>
<td>-----</td>
<td>-----</td>
<td>-----</td>
</tr>
<tr class="even">
<td rowspan="6">internal continuity EOPs</td>
<td>mean Xpole [μasec]</td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td>-8 asi</td>
<td></td>
<td></td>
</tr>
<tr class="odd">
<td>mean Ypole [μasec]</td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td>13 asi</td>
<td></td>
<td></td>
</tr>
<tr class="even">
<td>mean LOD [μs]</td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td>0.55 asi</td>
<td></td>
<td></td>
</tr>
<tr class="odd">
<td>sigma Xpole [μasec]</td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td>261 asi</td>
<td></td>
<td></td>
</tr>
<tr class="even">
<td>sigma Ypole [μasec]</td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td>265 asi</td>
<td></td>
<td></td>
</tr>
<tr class="odd">
<td>sigma LOD [μs]</td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td>72 asi</td>
<td></td>
<td></td>
</tr>
<tr class="even">
<td rowspan="6">diff wrt IERS Bulletin A</td>
<td>mean Xpole [μasec]</td>
<td>54 asi</td>
<td>-2 asi</td>
<td>77 asi</td>
<td>-62 asi</td>
<td>-31 asi</td>
<td>40 asi</td>
<td></td>
<td></td>
</tr>
<tr class="odd">
<td>mean Ypole [μasec]</td>
<td>216 asi</td>
<td>255 asi</td>
<td>230 asi</td>
<td>304 asi</td>
<td>39 asi</td>
<td>256 asi</td>
<td></td>
<td></td>
</tr>
<tr class="even">
<td>mean LOD [μs]</td>
<td>-32 asi</td>
<td>-111 asi</td>
<td>4 asi</td>
<td>-44 asi</td>
<td>222 asi</td>
<td>-21 asi</td>
<td></td>
<td></td>
</tr>
<tr class="odd">
<td>sigma Xpole [μasec]</td>
<td><p>204 asi</p>
<p>200 dgfi</p></td>
<td><p>258 asi</p>
<p>230 dgfi</p></td>
<td><p>334 asi</p>
<p>200 dgfi</p></td>
<td><p>232 asi</p>
<p>180 dgfi</p></td>
<td><p>385 asi</p>
<p>400 dgfi</p></td>
<td>180 asi</td>
<td></td>
<td></td>
</tr>
<tr class="even">
<td>sigma Ypole [μasec]</td>
<td><p>206 asi</p>
<p>150 dgfi</p></td>
<td><p>235 asi</p>
<p>180 dgfi</p></td>
<td><p>342 asi</p>
<p>200 dgfi</p></td>
<td><p>277 asi</p>
<p>250 dgfi</p></td>
<td><p>333 asi</p>
<p>250 dgfi</p></td>
<td>180 asi</td>
<td></td>
<td></td>
</tr>
<tr class="odd">
<td>sigma LOD [μs]</td>
<td>89 asi</td>
<td>71 asi</td>
<td>117 asi</td>
<td>71 asi</td>
<td>135 asi</td>
<td>50 asi</td>
<td></td>
<td></td>
</tr>
</tbody>
</table>

##### Table 4: ILRS AWG action items.

Appleby/Otsubo complete and provide satellite center-of-mass correction
table (station dependent); in coordination with ILRS SPWG chair?

####### Bianco check conversion of 1-wavelength data plus streak camera data into dual wavelength data

####### Eanes implement ITRF2000 in QC analysis

Glotov implement ITRF2000 in QC analysis

Gurtner check stations in "slreport"

Husson finalize (other than 1999), keep up-to-date and announce table
with LAGEOS data problems (SINEX format). - action item to be taken over
as combined action by analysts (detecting), stations (actual physical
assessment) and CB (inclusion in table)

Husson/Torrence (??) develop references for benchmarking (100% "D")

Husson (??) evaluate individual benchmark solutions

Husson (??) develop autom. system for assessing "Core" stations for AWG
purposes

Kelm/Altamimi resolve technical problems with DGFI SINEX files

Mareyen check why TIGO dual-wavelength data output is low

Noll/Seemueller modify SLR and LLR data file structure and contents

Noll/Noomen inform analysts of changes in data file naming convention
and contents

Noomen install new TDF

Noomen/Appleby/Shelus minutes of meeting

Noomen/Appleby/Shelus update CfP "pos+eop"

Noomen inform data centers and analysts of new naming "pos+eop"
solutions

Noomen/Altamimi generate list of most reliable ITRF2000 stations to be
used for mapping

Noomen/Pearlman write official letter to ASI and DGFI on selection of
primary and backup combination center

Noomen inform Nurutdinov on selection of primary/backup combination
center

Noomen iron out technical details of primary/backup combination; inform
IERS

Noomen ask Altamimi and Gambis to complete their evaluation of "pos+eop"
products (July 15 deadline for their action)

Pavlis determine status of (semi)diurnal geocenter and loading models

Pavlis update benchmarking: selection of 2^nd^ 30-day period for
evaluation, plus update of description

Pearlman contact IGS for retro's on GPS-III

Pearlman modify ILRS mission request form to emphasize credits

Pearlman arrange automatic message for credits when doing an ftp to
CDDIS and/or EDC

Seemueller/Noomen modify EDC data file structure and contents, to be
exact copy of CDDIS

Shelus (new) distinguishment between ILRS ACs and AACs

Torrence station report card 1^st^ quarter 2004

all send electronic version of presentations to Noomen

analysts update weekly solutions for test phase "pos+eop" (associate
stations, 7810/7824 ref., naming conventions) (May 9)

analysts if possible, participate in evaluation of new Mt. Stromlo data

CB ask stations for check/update site log and configuration file

combination centers check treatment of individual station outliers

combination centers redo combinations (May 19)

QC analysts get in direct contact with stations in case of detected
problems and make sure they correct

QC analysts verify that reports are sent to "slreport"

QC analysts report updates in used coordinates

CB ask stations for check/update site log and configuration file