First ILRS AWG Workshop (Frankfurt 2000)

Minutes of Analysis Working Group Workshop #1,
Frankfurt, Germany
January 17 - 19, 2000

Attendees (detailed list Appendix 1):

  • Zuheir Altamimi IGN
  • Detlef Angermann DGFI
  • Graham Appleby NERC
  • Richard Biancale GRGS
  • Richard Eanes CSR
  • Ramesh Govind AUSLIG
  • Van Husson HTSI (formerly ATSC)
  • Mark Kaufman IMVP
  • Rainer Kelm DGFI
  • Dirk Kuijper ESOC
  • Cinzia Luceri ASI
  • Maria Mareyen BKG
  • Juergen Mueller IAPG
  • Ron Noomen DEOS
  • Axel Nothnagel Univ. Bonn; IVS analysis coordinator
  • Mike Pearlman SAO
  • Bernd Richter BKG
  • Stefan Riepl BKG
  • Philippe Yaya GRGS
  • Rene Zandbergen ESOC

Agenda (Appendix 2)

Monday, January 17, 2000

1. Opening

Introductory remarks are given by Bernd Richter and Ron Noomen.

2. Agenda

The agenda is briefly explained by Ron Noomen.

3. Minutes and results of Florence AWG meeting (September 22, 1999)

3.1 Unification of QL analysis results

Van Husson presents the results of his comparison concerning the four currently distributed QL reports (CRL, CSR, DEOS, MCC). The QL reports are mainly used as a quality check and for problem detection by the SLR stations. The QL reports are not unique. This may lead to confusion if one doesn't know how to interpret them. An unsymmetric distribution in the time bias plots for LAGEOS-1 vs. LAGEOS-2 indicates a position error. The analysis centers are encouraged to ascertain that their model of station coordinates is accurate to within a few mm. The range bias comparison between LAGEOS-1 and LAGEOS-2 should be the same for each station. Herstmonceux does not show a similar behavior for both satellites, which indicates a problem in the analyses. Van Husson will continue with his activities in this respect.

3.2 Internet science page update

Cinzia Luceri will write an introductory page for some of the science products derived from laser ranging data: earth orientation and station positions and velocities.

3.3 E-mail exploders

After the Florence meeting, Carey Noll has developed some new e-mail exploders at CDDIS, now also covering the Analysis Working Group (ilrsawg@ilrs.gsfc.nasa.gov), the Analysis Centers (ilrsac@ilrs.gsfc.nasa.gov) and the Associate Analysis Centers (ilrsaac@ilrs.gsfc.nasa.gov). As a result of a computer problem at CDDISA the exploder service did not work as of the 28th of December 1999. The ftp service is available.

4. ILRS pilot projects

4.1. Ron Noomen gives an introduction to the EOP and station positioning pilot projects as defined in Florence.

4.2. The individual contributors present their results:

  • - Cinzia Luceri derived station positions and 3-day EOP values from Lageos-1 data processed with GEODYN.
  • - Ramesh Govind presents EOP estimates done with MICROCOSM and SOLVE which are in good agreement with the Bulletin B values. The analysis group uses data of all geodetic satellites for estimating station positions.
  • - Maria Mareyen presents the 1 arc results obtained with UTOPIA. Special remarks are given concerning the datum choice and the interpolation and detrending of the EOP values.
  • - Detlef Angermann uses the DGFI DOGS_4.04 software to obtain his results. There appears to be a saw-tooth pattern in the X-component of the pole position solutions, which is related to the computation with weekly arcs.
  • - Philippe Yaya presents results obtained with GINS/DYNAMO, and addresses the various steps that were taken to come to the final results.
  • - Mark Kaufman presents an EOP solution parameterized by the earth rotation vector and it's temporal derivative.
  • - Graham Appleby presents his results obtained with SATAN. He found that a range bias of 1 to 2 cm is not significant for short period solutions. He compared his EOP results with quadratic interpolated Bulletin B values.
  • - Graham Appleby (on behalf of Toshi Otsubo) presents the CRL results obtained with CONCERTO.

4.3. Comparisons of the solutions

- Cinzia Luceri presents a mapping of all obtained station positions to ITRF97, estimating 7 Helmert parameters. Some solutions had to be rejected altogether. An estimation of Helmert parameters based on both station positions and EOPs is left as a future task. - Rainer Kelm gives some comments on constraints handling and summarizes the different methods. Kelm makes a recommendation for unconstrained solutions. - Philippe Yaya compared the EOP data. A bias adjustment leads to an improved rms. There are unremoved tidal effects. In addition, there occurred a problem with fixing UT1, which is discussed in point 12 of the agenda. - Zuheir Altamimi presents a comparison of station positions and pointed out the following items: SINEX format compliance. removal of constraints. distribution of stations impacts comparison and/or combination of results. ties for some stations are missing. use of the full covariance matrix is to be preferred. solutions for Tx and Ty are realistic, but those for Tz are not: high correlations between the scale factor and Tz (result of lack of southern hemisphere stations). up to 3ppb scale factor agreement between solutions and ITRF. comparison of pole coordinates rms. Overall conclusion: don't constrain solutions. A constrained solution is only artificially better than an unconstrained one. - Van Husson gives a report of: format integrity check. coordinate difference w.r.t. ITRF97. comparison of different solutions. DOMES number is recommended for use instead of the CDP number. - Graham Appleby gives notes on: solution strategy. CDP/DOMES number problem. combined solution estimation approach. methodology. supply of SINEX verification software. Appleby recommends to stick to a small dataset of SLR observations at this stage of the pilot projects. - Ron Noomen gives a report on comparisons done by institutes not present in Frankfurt: a comparison in terms of baselines (Peter Dunn). a full mapping of network solutions, which showed problems with some of the stations (by N.V. Shuigina).

The generation of an official, combined product will be a future task.

Tuesday, January 18, 2000

After a short summary by Ron Noomen the meeting proceeds with

6. Better incorporation of LLR

Juergen Mueller points out the lack of LLR stations, which leads to difficulties in including LLR data into an overall analysis.

Remarks:

  • - SLR and LLR solutions can be compared.
  • - LLR can be used to derive relativistic parameters if other earth related parameters are provided.
  • - LLR can be integrated in global solutions on a long time-scale since observations are available as of the early 1970s (Richard Eanes).
  • - the SELENE mission (laser transponder) would give a good link budget for SLR stations. Combination with VLBI is also possible due to a microwave transmitter on the SELENE platform.
  • - LLR and SLR analysis should use the same standards and models.

7. SLR/LLR analysis: other/new parameters?

Richard Eanes leads the discussion on parameters, beyond station positions and EOPs. First candidates for new parameters are GM and force model parameters. There is a necessity for standard orbits for determination of time and range biases. This could also serve as a reference for SLR station residual calculations (quality check). A standardized center of mass correction could be determined from an orbit comparison. In conclusion the results are: - Publication of orbits would be useful. - Standardized set of station positions should have high priority. - There are customers for tabulated satellite ephemeris. - Richard Eanes will propose an additional pilot project dealing with standard orbits in SP3 format.

Notes by Mike Pearlman:

  • - Comparison (benchmarking) of different programs is an important exercise.
  • - Need for testing programs with standard parameters.

8. ILRS contribution(s) to IERS

Zuheir Altamimi informs about the standard solution (i.e. ITRF2000). It will include SLR, VLBI, GPS, DORIS and LLR results, preferably at least 3 independent contributions from each technique. The sites are densified by GPS and other markers tied to space geodetic ones. The following items are discussed:

  • - reference points.
  • - DOMES numbers instead of CDP 4-digit numbers.
  • - check and, if necessary, revision of eccentricities, on a regular basis.
  • - A general recommendation for eccentricities should be made. There should be 1 unique file containing eccentricities in cartesian and geodetic coordinates w.r.t. a fixed reference ellipsoid.
  • - Contributions should be loosely constrained or unconstrained.

9. ILRS contribution(s) to ITRF2000

This has been discussed under item (8). In addition, IERS has initiated a pilot project on time-series of position solutions, contributed by different techniques, which could become a standard product. The participants are invited to provide periodical solutions. At this moment, there is no official ILRS contribution. Analysts are encouraged to contribute individually.

10. Miscellaneous

10.1 Permanent tide

Juergen Mueller: The recommendation in the IERS 1996 Conventions („subtract") is not being followed by anyone, so therefor it is recommended to eliminate this from the text of the convention in order to avoid any confusion, and ask analysts to keep doing what they have always been doing.

10.2 Tides working group

The tides working group (for SLR: chair Wu Bin) is asking how the SLR-AWG treats the tides. Richard Eanes will provide an official ILRS answer.

10.3 UTC leap second

The geodetic community was asked whether the leap seconds should be abolished. At the meeting in Frankfurt no unique opinion could be found, so all analysts are invited to submit their individual ideas to originator of the question, dr. D.N. Matsakis (dnm@orion.usno.navy.mil).

10.4 ILRS web site

  • - Van Husson asked for new inputs.
  • - Van Husson will distribute an announcement of the ILRS reference card.

10.5 ILRS presentations AGU Fall Meeting 1999, San Francisco:

  • - Richard Eanes gave an official ILRS presentation on EOPs.
  • - the paper was well received - people were enlightened by the AWG pilot projects EGS 2000, Nice:
  • - Ron Noomen will give an official ILRS presentation on station positioning.
  • - Also, a review paper on SLR satellite orbits will be given by the same author. Special issue of Journal of Geodesy: "New methodologies for EOP combinations"
  • - the ILRS has been invited to make a contribution.
  • - who?
  • - Cinzia Luceri will consider it and discuss it with her colleagues.

10.6 IVS

  • - The ILRS has been invited to contribute to a joint IGS/ILRS/IVS working group to resolve analysis and reference issues. After some debate, the AWG proposes 2 candidates for this to the ILRS General Board: Graham Appleby and Richard Biancale.
  • - Ron Noomen will participate in the IVS Analysis meeting in Koetzting, Germany (February 24, 2000).

11. ILRS annual report

Various people were asked by Mike Pearlman to provide or to coordinate contributions to the ILRS Annual Report. Everyone is encouraged to stick to the description, the maximum number of pages and the deadline.

12. Future of ILRS pilot projects (discussion)

12.1 Parameters

One of the issues brought up repeatedly is the choice of the 3rd component of the EOPs: UT or LOD. The former is by definition impossible to estimate in absolute value by satellite techniques, but it is easier to handle (additional information is needed). The second representation better follows the physical possibilities of the technique, although both have their limitations. After lengthy debate, it was decided to stick to the UT representation (which was already agreed upon in Florence).

12.2 Standards

IERS Conventions are recommended as usual. Analysts are encouraged to develop and use improvements.

12.3 Official ILRS products

Too premature yet, considering the status of the pilot projects. However,likely candidates for the first official products are station coordinates and EOPs.

12.4 Data format

Ron Noomen reviewed the various elements in the SINEX format. Consensus was reached what to include in ILRS submissions and what not (no conflict with standard). Solutions with problems in the SINEX format will be rejected completely.

12.5 Dataflow for ILRS solutions

There was some discussion on the dataflow for submissions to the pilot projects and possible follow-ups: testing, naming, adhering, replacing etc. Phil Moore will continue to work on a testing tool, whereas Ron Noomen will initiate an e-mail discussion on naming conventions.

12.6 ILRS solutions (general)

In the following (table 1) the SINEX format used within the activities of ILRS will be described.

Table 1. Overview of the SINEX blocks and their use by the ILRS

  • 1. Header line mandatory
  • 2. FILE/REFERENCE mandatory
  • 3. FILE/COMMENT recommended
    Editor's Note: FILE/COMMENT Block was changed to be mandatory at the Delft AWG Meeting
  • 4. INPUT/HISTORY recommended
  • 5. INPUT/FILES optional
  • 6. INPUT/ACKNOWLEDGEMENTS optional
  • 7. SITE/ID mandatory
  • 8. SITE/DATA optional
  • 9. SITE/RECEIVER not relevant
  • 10. SITE/ANTENNA not relevant
  • 11. SITE/GPS_PHASE_CENTER not relevant
  • 12. SITE/ECCENTRICITY mandatory
  • 13. SOLUTION/EPOCHS mandatory
  • 14. SOLUTION/STATISTICS mandatory
  • 15. SOLUTION/ESTIMATE mandatory
  • 16. SOLUTION/APRIORI mandatory
  • 17. SOLUTION/MATRIX_ESTIMATE mandatory
  • 18. SOLUTION/MATRIX_APRIORI mandatory
  • 19. Footer line mandatory

12.7 Future activities

Discussion on more satellites, a longer time span, a reprocessing of the current dataset, and timelines. For results of this discussion: see notes on item 13.

13. Future of ILRS pilot projects (conclusions)

The pilot projects on positioning and earth orientation will be combined into one. The dataset will be expanded with 2 days w.r.t. the previous pilot projects, and now run from September 5, 1999 (0.00 hrs) until October 4, 1999 (24.00 hrs). Analysts are invited to contribute 2 solutions: one with 2-day EOP intervals, and one with 3-day intervals (station positions estimated simultaneously). The beginning of the first EOP interval must coincide with the beginning of the data arc.

Deadline for analysis and comparison: March 1 and April 15, respectively.

Ron Noomen will write an official invitation and distribute it.

In addition, there will be a new pilot project "orbit" on comparing orbit solutions (SP3 format). Richard Eanes will coordinate this. Deadlines: February 15 (invitation), April 1 (analysis) and May 15 (comparison).

Finally, the meeting expressed the usefulness of a new pilot project "benchmarking", to compare various software packages. A few days after the meeting in Germany, Van Husson volunteered to coordinate this. No deadlines yet.

14. Next meeting

There are a number of options for a follow-up of the Frankfurt meeting:

  • - the weekend of April 29/30 (in conjunction with the EGS, in Nice).
  • - 2 days in the 4th week of May, in Delft.
  • - June 17/18, in conjunction with the Conference 2000 in St. Petersburg.
  • - July, in conjunction with COSPAR in Warsaw. - September, in conjunction with the WEGENER meeting in San Fernando.
  • - October, in conjunction with the International Laser Workshop + ILRS General Assembly and Governing Board meeting, in Matera.

Elements that play a role in the selection are the availability of a meeting place, the amount of time that people can really devote to the meeting, the timeliness in relation to the pilot project activities (momentum, usefulness) and the travelling options for Russian colleagues. No consensus could be obtained in Frankfurt, although June seemed to be the latest possible date. Ron Noomen will inquire the preferences of the community by e-mail.

15. Questions

16. Conclusions

17. Closure

Stefan Riepl, Bernd Richter, Maria Mareyen, Ron Noomen

Appendices

1.List of participants

2. Agenda of the ILRS /AWG meeting in Frankfurt, January 17-19, 2000

January 17, 1999 14:00 h - 15:35 h Session 1  
  15:35 h - 16:00 h Coffee break  
  16:00 h - 17:30 h Session 2  
Session 1    
1. opening 5 minutes
2. agenda 5 minutes
3. minutes Florence; old action items 15
     
3.1 unification of QL analysis results  
3.2 web page "science update"  
3.3 ILRS e-mail exploders  
     
4 ILRS pilot projects (current):  
4.1 introduction 10
4.2 contributions (presentations of the individual solutions) 60
     
Session 2    
4.3 comparisons (presentations by each of the comparisongroups) 90
     
January 18, 1999 9:00 h - 10:40 h Session 3
11:00 h - 12:30 h Session 4
12:30 h - 14:00 h Lunch break
14:00 h - 15:40 h Session 5
15:40 h - 16:10 h Coffee break
16:10 h - 18:00 h Session 6		  
Session 3    
6. better incorporation of LLR 30
7. SLR/LLR analysis: other/new parameters? 10
8. ILRS contribution(s) to IERS 30
9. ILRS contribution(s) to ITRF 2000 30
9.1. requirements by IERS/ITRF  
9.2. individual contribution(s)  
9.3. combined product(s)  
     
Session 4    
10. miscellaneous 30
10.1. permanent tide  
10.2. tides WG  
10.3. UTC leap second  
10.4. ILRS web site  
10.5. ILRS presentations  
  - AGU, San Francisco, December 1999
- EGS, Nice, April 2000
- "New methodologies for EOP combinations" (special issue of Journal of Geodesy)		  
10.6. IVS  
  - representation in joint working group ILRS/IGS/IVS - participation in 1st IVS Analysis Workshop Koetzting (near Wettzell), Feb 24, 2000  
     
11. ILRS annual report 5
     
Session 5    
12. Future of ILRS pilot projects (discussion):  
12.1. parameters 30
  - EOPS: UT vs. LOD  
12.2. standards 15
12.3. official ILRS product(s) 30
12.4. data format: 30
  - checking
- description
- mandatory/optional elements
- definition of parameters		  
     
Session 6    
12.5. dataflow for ILRS solutions: 30
  - naming
- replacements
- testing before sending
- procedure within CDDIS		  
12.6. ILRS solutions (general): 30
  - rejections of solutions
- modifications/corrections on solutions (by whom?)
- deadline		  
12.7. future activities 30
  - more satellites?
- longer time span?
- redo current set?
- timeline?		  
     
January 19, 1999 9:00 h - 10:30 h Session 7
10:30 h - 10:50 h Coffee break
10:50 h - 12:00 h Session 8		  
     
Session 7    
13. Future of ILRS pilot projects (conclusions)  
     
Session 8    
14. next meeting 5
  - invitation for AWG meeting during Conference 2000, June 19-24, St. Petersburg (IAA)  
     
15. questions 15
     
16. list of 10
  - conclusions
- recommendations
- action items (names + schedule)		  
     
17. closure 5