Minutes ILRS/AWG Workshop #9
October 25-26, 2003, Koetzting, Germany

Agenda

Sunday October 25, 2003

Opening

Welcome by Appleby. Thanks to Schreiber for making the arrangements for the meeting. Appleby   asked for a moment of silence for Matti Paunonen who passed away. Comment that Ron Noomen is recovering from back problems, but has been in contact with Graham Appleby. Additionally Van Husson and Mike Pearlman are attending the meeting at their own expense because of severe funding problems, and Van cannot formally make any comments.

Each of the attendees introduced themselves

IERS Matera survey meeting

Richter reviewed summarized the IERS survey meeting October 23-24 that was held in Matera, Italy. There are now 72 space geodetic sites for which there are multiple technologies present. The local survey for these sites can be described in three levels: full characterization; no information; inconsistent information. The meeting recommended that the local survey for all space geodetic sites be fully characterized and accurate to the millimeter level.

A discussion ensued about what the correct IERS 2003 conventions for loading and Earth center of figure motion are, and what should be incorporated into the station position determination. Pavlis was given an action item to resolve this issue.

Benchmark

Pavlis introduced this agenda topic. Pavlis suggested benchmark "D" be used in the evaluation, and benchmark "C" be graded as pass/fail.   Torrence suggested there be an additional benchmark, benchmark "0", consisting of integration of the initial state vector with GM and C20, C30 and C40 only, no other force model perturbations. The final group concensus was to use benchmarks "0", "A", "C" and "D" in the assessment. A suggested weighting critera is: [ 30% "0" + 10% "A" + 10% "C" + 50% "D" ].

ASI: Luceri presented results of ASI's benchmark version D comparison with solutions from GFZ, ASI, and JCET. There was a brief discussion about whether the EOP rates were to be included in the solutions; there are to be no EOP rate adjustments included in the solutions, partial derivatives for the rates can be constructed to be included in the SINEX file, but not adjusted in the solution.

GEOS: Ramesh Govind reported that 28 day very weakly constrained solutions have been submitted to CDDISA using Starlette   and Stella with the   CHAMP/GRACE gravity models.

NERC: Graham Appleby reported that NERC intends to do benchmark solutions "0", "A", "C" and "D" by November, 2003.

Any analysis groups that have not yet submitted solutions for the benchmark test need to do so to be considered for participation in official ILRS AWG products. It was strongly suggested that groups make benchmark contributions before the end of November 2003.

ILRS Announcements: Mike Pearlman

Mike Pearlman talked a bit about NASA's future funding profile for SLR activities. The funding projection was based upon the axiom of SLR2000 deployment in the current time frame resulting in decreased network operation costs. Mike asked that any detailed questions be addressed to David Carter during the ILRS meeting in few days.   The 13 th Laser Ranging Workshop report and the ILRS 2002 Annual Report should be published in November 2003.

Mike presented the current   station qualification criteria, and solicited comments from the AWG with respect to the definition and use of "associate station". The group generally agreed with the definition. Details are at http://ilrs.gsfc.nasa.gov/reports/ilrs_reports/ilrs0310/ilrsmtg_0310_session1.pdf

Mike gave a brief presentation on the results of an ILRS Central Bureau science analysis survey. The results are presented at http://ilrs.gsfc.nasa.gov/reports/ilrs_reports/ilrs0310/ilrsmtg_0310_session18.pdf

CFP, formerly pilot project "positioning + earth orientation": Graham Appleby

Graham introduced this agenda item. Many analysis centers have submitted the 28 day station position and daily EOP solutions to the ILRS. The analysis centers from ASI and DGFI have also performed preliminary combination solutions with those solutions.

Contributions for the CFP:

ASI: Cinzia Luceri reported that ASI has automated the solution process so that every Tuesday a solution is "pushed" to the CDDIS. The solutions submitted, up to this point, do not use data from stations that have fewer than 50 LAGEOS normal points per week, nor from associate stations. Cinzia reported finding differences between data downloaded from CDDIS and EDC, so ASI downloads data from both data centers and then merges the data into a file that is used for their analyses.

The attendees discussed whether to use the data from associate stations and simply down weight (at perhaps 1000m) or not. There could be "political" ramifications due to the use or not of the data from associate stations. Additional comments were that the IERS EOP products should be "first-class"; the best that the ILRS AWG can produce, and, as such, questionable data probably should not be used for those products. Werner Gurtner suggested that a "second tier" of solution be based upon the standard IERS EOP product which would include data from associate stations, and from lower data yield stations.

A discussion ensued about the need for timely submission of data to have the data included in the IERS EOP product solutions.

DGFI: Horst Mueller reported DGFI has been doing weekly solutions beginning in June 2003. Analysis of EOP interpolation schemes show jumps of about 0.2 microsec comparing linear and Hermite interpolation.

GFZ:   Rolf Koenig reported their analysis is almost automatic. GFZ identified a need to automate   QC checks of input SINEX files to determine whether there are any implicit constraints. Further participation in the CFP project has enabled the identification of subtle errors in the processing.

Also (cf.ASI) showed different values of EOP.

NERC: Graham Appleby reported that NERC is now automating procedures for producing 28 day solutions.

BKG: Mareyen Maria reported BKG has recently updated their processing computers to a Linux environment working on PC. The change requires updates to the UTOPIA orbit determination and parameter estimation system and other supporting software package.

JAXA: Toshimichi Otsubo is working on upgrading JAXA's processing software and will submit solutions to the CFP pilot project.

Geoscience Australia: Ramesh Govind reported that he intends to submit benchmark solutions soon, and then contribute to the CFP pilot project.

JCET: Erricos Pavlis reported JCET has not submitted solutions to the CFP pilot project as JCET is making 7-day EOP solutions for NEOS and JPL in an ITRF2000 frame. Erricos' suggestion of establishing a new product for the CFP and combination projects; a 7 day EOP solution within a fixed ITRF2000 frame. JCET will be able to submit weakly constrained weekly solutions to the ILRS in the near future.

The attendees discussed the suggestion to move to a 7-day arc length, as the IERS is the main customer for rapid product. Marcus Rotheracher had given a presentation to the previous AWG meeting (Nice, France, April 2003) on the IERS establishing a combination research center which wishes to use 7 day solutions from each of the space geodetic techniques to produce time series of EOP and site locations. The current CFP 28 day arc length was established to follow-on to the benchmark project.   DGFI showed a 10 year time series of latitude, longitude and height of Yaraggadee from 7 day solutions as evidence for stable site position recovery using 7 day arcs instead of 28 day arcs. Graham Appleby reported there seems to mounting evidence that stable 7 day solutions are achievable.   Following more discussion, the attendees agreed to begin submitting 7 day solutions instead of 28 day solutions to the ILRS/CDDIS for use by the ILRS combination groups. There was general agreement that this transition should begin a soon as possible.

Combination Centers:

ASI: Has automated the combination analysis procedure and uses MatLab to form the combination solution.

DGFI: Rainer Kelm reported that the combination of normal equations is done automatically. The solution is formed by using minimal constraints over three core stations.

NCL :   Konstantin Nurutdinov reported using the TANYA software to compare 28 day solution series from NERC, ASI, DGFI, GFZ and the DGFI, ASI and NCL combination solutions with the IGS EOP time series.

IERS/ITRF Analysis of SLR products: Zuheir Altimimi

Zuheir presented his analysis of the ASI SLR solution. He emphatically stated the need for SLR site positions information for the determination of Earth center of figure in the ITRF.

Future Pilot Projects : Graham Appleby

Graham opened a discussion about whether the ILRS should try to develop other products such as orbits in SP3 format, or a geocenter time series.

Business Meeting : Graham Appleby

The attendees discussed when the next AWG meeting should take place: either before the EGU meeting in Nice, France on 22-23 April 2004 and/or before the SLR Workshop, San Fernando, Spain, in June 2004.

The consensus was to have a meeting before both meetings at times to be determined later.

ILRS AWG action items

ILRS AWG Attendees

Responsible Government Official: Carey Noll
NASA's Privacy Policy and Important Notices

Send us your comments

Last modified date: Wednesday, November 01, 2006
Author: Ron Noomen
Author: Graham Appleby
Author: Peter Shelus
Maintained by: Carey Noll