Message-Id: Date: Wed, 28 Feb 2001 17:31:01 -0800 To: igsmail@igscb.jpl.nasa.gov From: "Ruth E. Neilan" Subject: [IGSMAIL-3216]: Summary, IGS LEO Pilot Project Meeting Feb. 6-8, 2001 Sender: owner-igsmail Precedence: bulk ****************************************************************************** IGS Electronic Mail 28 Feb 17:31:03 PST 2001 Message Number 3216 ****************************************************************************** Author: Chris Reigber, Ruth Neilan, Angie Moore and Mike Watkins Subject: Summary, IGS LEO Pilot Project Meeting Feb. 6-8, 2001 Dear colleagues, This message provides a summary of the recent IGS LEO Pilot Project meeting held February 5-8 at the GeoForschungsZentrum, Potsdam, Germany. The general conclusion of the attendees was quite positive for this effort as you will see from the summary. The meeting agenda is detailed in IGSMail message #3193 and can be accessed at: http://op.gfz-potsdam.de/D1/LEOW/LEOW_index.html The participant list is also attached below for completeness. Following the LEO PP meetings was an ad-hoc meeting concerning real-time activities within the IGS. At the last IGS Governing Board meeting in December there was a strong consensus that the IGS should establish a Real-Time Working Group (RTWG) to address and assess issues involving the IGS moving towards real-time infrastructure and processes. Generally, an IGS working group is established when a group develops a charter, project plan and designates a chair, and then comes to the Board for approval. In this case, the GB identified this as a critical new activity, proposed a draft charter, and asked the CB to organize the ad-hoc meeting during the venue of the LEO PP meetings in Potsdam to explore and initiate the formation of such a working group. Additional information on this productive meeting will be forthcoming in the very near future. Message Contents ---------------------------- Overview Summary Tuesday February 6 Wednesday, February 7 Overview Proposal Descriptions Analysis/Associate Analysis Center Discussion Summary Network/Station & Data Center Proposals and Plans Format Discussions Data Center Issues LEO PP Designated Agency/Points of Contact IGS LEO Working Group Members LEO Project Meeting Participants List Overview -------------------------------------- The primary purpose of this meeting was devoted to understanding upcoming LEO missions carrying GPS flight receivers, with particular emphasis on CHAMP, in order to develop the goals, objectives and structure for the IGS LEO Pilot. There were over 70 people attending this meeting and it was quite evident that this project has sparked great interest within agencies planning LEO missions, as well as the IGS components that are well positioned to be involved in these new activities. This ranges from ground network support, to data handling, to analyses of the flight data, POD, etc. It is clear that the spaceborne GPS will revolutionize atmospheric and ionospheric science over the next decade, similar to the revolution experienced in Earth geodesy in the last. Summary Tuesday, February 6 --------------------------------------- The morning of the first day was devoted to an overview of the CHAMP mission. Details on the satellite state and performance were provided with an overview of each, the satellite, science instruments, ground support and data archive, provided by the responsible member of the CHAMP Team. The overview by the CHAMP Team provided insight into the technical aspects, challenges and successes of the mission. Since the launch in July 2000 all satellite subsystems, payload instruments, mission operations and mission control are performing very well. The science ground segment is in the final stage of the accommodation and calibration/validation phase. RO capability has been enabled only recently with the upload of the new GPS receiver software. For this task the calibration/validation phase has just started. The CHAMP rapid science orbit determination is achieving 10cm orbits for the GPS satellites and produces 15cm to 30cm CHAMP orbits, 1/2 day and one day arc lengths respectively. SLR data are employed for operationally producing CHAMP orbit predictions and for CHAMP GPS POD validation with an independent data source. Since the meeting, the GPS radio occultation data have successfully been received and analyzed, see the CHAMP website for details. As this new capability becomes routine it is expected that CHAMP will produce about 200 occultations per day. From only a few days' worth of of CHAMP GPS and accelerometer data it has been possible to tune the global Earth gravity field model resolution taking into account terms up to degree/order 70, already resulting in a considerable accuracy improvement for a 5x5 degree geoid representation. Earth magnetic field models have also already been derived successfully from the scalar magnetometer data and are compared with OERSTED and MAGSAT results. Work is going on to include vector and magnetometry data now. The afternoon was devoted to presentations of LEO Missions Status and Plans and LEO Flight GPS Analysis. Overviews and science objectives were presented on SAC-C, GRACE, ICESat/GLAS, Jason, COSMIC and the various requirements of each. There was collective agreement that IGS clocks at 30s or 10s would be of great value to these missions. The GPS flight instrument onboard these missions as well as CHAMP is the JPL Blackjack receiver. Members of the JPL team described the characteristics of the receiver. The SAC-C, a joint Argentine-US LEO mission, successfully launched in November 2000 uses this same receiver, and data are available from JPL. SAC-C is at an altitude of ~700 km and preliminary orbit determination results from JPL are below 10cm level. GRACE and JASON which both launch later this year will also carry the Blackjack. In November 2000, a CHAMP data set was released for August 7, 2000 (DOY 220) containing complete files of the operating instruments. This public data set is available at the CHAMP website. The last session of the day included presentation on analysis of this data set, and plans for future analysis, software tools, and methodology. Representatives from CNES noted that JASON will provide a good data set for POD studies, it will have both GPS and DORIS on-board as well as SLR tracking. JASON and ICESat/GLAS do not plan occultation measurements. Summary requirements: - IGS 10-30sec clocks - JASON 1cm radial orbit accuracy - Retrieval of occultation profiles require <0.1mm/sec velocity determination and ~10cm LEO POD - 10-15 minute latency of ground data eventually required for numerical weather prediction - Use accelerometer data to accurately account for drag and other surface forces - Improved gravity field needed for analysis of CHAMP data Wednesday, February 7 Overview ----------------------------------------- Mike Watkins, Chair of the LEO Working Group, gave an overview and history of the IGS LEO activities thus far. The call for Participation had highlighted POD of LEOs, evaluation of improvements to IGS "classic" products, and data flow and management given the required high-rate, low-latency requirements of LEO analysis. This was the largest CFP since the inception of the IGS. He noted that it will be important to review IGS Analysis Standards and the new IERS standards, enlisting the assistance of the new IGS Analysis Coordinator, Robert Weber. It was noted that model refinements, e.g. concerning Earth tide, phase lags, Love numbers, etc. get very important for lower Earth satellites. A proposed phased approach to the pilot project was presented: * Begin with SAC-C data ASAP (1 Mar?): producing LEO orbits, acquire selected periods of high-rate ground data for RO support to test data flow * Add CHAMP data as it becomes available in May/June: Improve orbit determination & study impact on IGS classic products, refining data flow for full occultation support * Add JASON (Nov '01): Compare GPS orbits to SLR and DORIS; study effect on IGS classic products The pilot project should have a defined end; 31 Dec 01 was suggested. The morning was devoted to brief proposal descriptions from the groups participating in analysis efforts for the LEO project, and the afternoon focusing on network and data center proposals. Proposal Descriptions ------------------------------ JPL/Webb Frank Webb described activities with respect to JPL's role as an IGS Analysis Center, generating the 'classic' products on a daily basis. JPL will upgrade more sites to hourly or better availability with a significant number offering high-rate data. As a data center, JPL will provide hourly & high rate data. Production of the IGS ultra product (igu) will resume, improving with long arcs and reducing latency from 12hr to 6hr. Currently they provide 30s clocks from 5min estimates; proposed 1s from 5 min estimates & 1s ground data. Now that SA is off, a new proposal is to investigate interpolation & extrapolation for 1s GPS clocks from 5 min estimates & high rate ground data. JPL/Muellerschoen Ron Muellerschoen described JPL's proposed role as an Associate analysis Center for the LEO pilot project. He anticipates POD daily or subdaily final within one month. Usage is to extract atmospheric refractivity of occulting signal. Velocity should be known to 0.1mm/s (for occultation) and position to ~10cm. Also looking to gravity recovery & magnetometer. Current latency (CHAMP) of 3 weeks to be reduced to ~3 days with a dual approach for rapid products (for s/c validation; goal 6hrs for atmospheric studies) and final products. LEO phase ambiguity resolution is done with ground stations. CHAMP star tracker & accelerometer data help; 4cm pitch error gives a 10cm radial offset. A run every 6 hrs to get predicts will provide ephemerides for NWP (troposphere to be ingested every 6 hrs). Current real-time GPS orbit results are at ~30-40cm. A question on the velocity results will be verified. GFZ/Koenig Rolf Koenig described GFZ role as an Associate Analysis Center (AAC) to provide predicted, rapid science, and postprocessed science orbits for CHAMP and the GPS satellites. Rapid science orbits are computed with a 3 hour turn-around time to support RO activities. Postprocessed science orbits include 30s clocks and are primarily used for gravity recovery. POD may be done for other data (e.g., SAC-C, JASON, etc.) but CHAMP activities must take priority. Presently used software version in use is GFZ's EPOS-V5.2OC. ASI/Vespe Francesco Vespe said that MATE, the station at Matera station is proposed as a high rate station. AAC was also proposed. Since submitting proposal: - ASI plans for POD and radio occultation remote sensing mission in the next few years (GPS/GLONASS receiver, Lagrange). Italy provides the attitude control of SAC-C - Also planning a climatology mission, not yet selected, with GPS/GLONASS receiver for POD + occultations, and an infrared spectrometer. Other stations to be added: MALI (GPS/GLONASS) and Peru due to other missions (but high-rate uncertain). Can process CHAMP data in calendar 2001. On SAC-C Lagrange L2 SNR is not good, nor is the second frequency the GLONASS channels. Improvements expected in next version on other satellites. AIUB/Hugentobler Bern's main interest is POD via epoch-wise code & phase differences and clock extractions from IGS ephemerides. Propose: pilot phase LEO POD when quality data is available to demonstrate real-time LEO POD, and improve models & data editing. After the pilot phase, AIUB will make a decision about continuing support. They plan to - evaluate impact on IGS products when combination available (not near future) - not prepared for combination of LEO orbits due to Springer's departure but ready to develop tools for comparison - study predict quality & necessary update frequency for desired accuracy. Standard gravity model is needed for comparison. ACCs should address (consider GRIM5 & new CHAMP model). CSR/Schutz Address impact to IGS orbits, reference frame, EOP. Motivation is GRACE & ICESAT preparation. CSR will tune the gravity field and evaluate force models. They can participate in PP in 2001. CNES/Mercier CNES main interest is altimetry of the JASON mission. Can participate certainly until June but not continuously. For JASON require GPS ephemerides & daily precise GPS clocks. ESOC/Dow John Dow described the participation of ESA/ESOC and agreed to assume the responsibility of the analysis coordination for the project, and will designate the actual point of contact by the end of March They will provide high rate data from some stations, act as an AAC and improve latency & quality of IGS AC products. His approach will be to request specific project boundaries (select periods or months of data), comparison of 1 or 2 satellites and that this would be a part time activity this year. In a few months ESOC will focus on standards etc, then ramp up the analysis. OSU/Schutz for Shum Ohio State proposes two stations: Lake Erie & OSU. They plan to develop AAC capability using kinematic OD for GPS & LEO using triple differencing (no ambiguities) OD & atmospheric profiling latency. He noted that near-real time (NRT) stations are possible. CISAS/Caporali Station UPAD can become an hourly stations. They are trying CHAMP data for improving OD and developing software. Analysis/Associate Analysis Center Discussion Summary ---------------------------------------------------------------- Watkins questioned whether SAC-C should be a part of PP. Dow felt that it would be better to prepare standards, details, etc. in preparation for the CHAMP data release in May. It was agreed that those interested could experiment voluntarily with the SAC-C data available from JPL, but it would not be an official part of the project as yet. Schutz noted that there was little information on the SAC-C s/c, and Yunck agreed to try to obtain this. Reigber stated that the IGS participants need not respond to the upcoming CHAMP AO for general data access. Network/Station & Data Center Proposals and Plans ------------------------------------------------------------ JPL/Stowers 15 minute data of 1sec data available online at JPL for 2 weeks, nearline thereafter. GFZ/Reigber 8 sites of GFZ network are 1Hz data in 15m files and in GFZ's CHAMP-ISDC data centerin GFZ-BINEX. All stations are available to the LEO PP and have reliable meteorology instruments with links to WMO. There are 5 reliable stations for hourly, 30sec data and 3 more potential. Pecny/Simek GOPE station has an operating GPS/GLONASS receiver producing hourly 30 sec data files. They started a 1Hz sample experiment in Jan 2000 (following Aug 99 solar eclipse campaign). They also propose to be an AAC for NRT troposphere, with subdaily orbits, and hourly orbits. Their DC supports NRT data & products. They participate in the COST 716. NRCan/Caissy NRCan plans to continue hourly 30s stations, with 12 stations operating at 1Hz transmitting data to Ottawa. A possible new site far north is being considered. 15min 1sec files in tcomp (designed exchange format for GFZ-JPL CHAMP Network) are ready to go from three stations. They propose AAC for subdaily orbits. Since March, they produce orbits twice daily via Bernese processing every 3 hours. KMS/Madsen High rate data from Thule THU2 is already operating at 1Hz for Oersted. A new station in southern Greenland is planned this summer. HERS/Wood Herstmonceux is already operating hourly and can possibly operate at 1sec. rate. Format Discussions ------------------------------------------ Werner Gurtner guided the discussion and separated two issues, how the IGS will handle LEO data for the project, and how the IGS will move towards a real-time data handling. The latter would be discussed in the ad-hoc meeting scheduled for February 8. At the Oslo workshop a 'formats' group was established, co-chaired by Werner Gurtner and Angie Moore. This discussion focused on file oriented RINEX and RINEX modifications for the LEO s/c data. Oslo Network Workshop | Two data format issues | |________________________________________|Real-time File Oriented RINEX | | | Real-time Working Group | Ground Network |_______________________________________| LEO s/c Data | | |_______________|_______________| | 15m 1hr 1 day | 1s 30s 30s | | |___________________|_______________| Occultation POD Auxiliary 1s 30s ? Orbit exchange, SP3? Proposed modification to RINEX to support LEO flight data were discussed. How to handle multiple antennas on the LEO could either have separate files for each antenna, or could define antenna # and cross-references in the header. The group prefers separate files. SP3 needs only to have "L" code defined for LEO. Comments on the proposed RINEX would be accepted until 23 February with a final proposal due 1 March. Zumberge questioned whether the clock RINEX format could handle LEO clock information. (ftp://igscb.jpl.nasa.gov/pub/data/format/rinex_clock.txt) Hugentobler noted that analysis needs maneuver information and how to include this. Caporali: wondered if there could be an event flag for maneuver, but Gurtner was not sure whether such information is available at the time of RINEXing data. GFZ suggests using the CHAMP orbit format (CH-ORB) over SP3. They also recommend to use the CH-ACC rather than a new AUX file. For description and contents see: ftp://ftp.gfz-potsdam.de/pub/champ/chftp1/public/champ_data_format_description.txt The project AACs and the IGS ACs are to be informed of these discussions and asked for comment until 23 Feb to determine consensus. Noll said that a naming convention is needed for subhourly files. Data Center Issues --------------------------------------- Carey Noll at GSFC/CDDIS proposes to be DC for LEO data for the PP. This is still to be sorted out since CHAMP data will only be available from the CHAMP DC at GFZ. There was some discussion about linking, however, there is no such thing as "linking" in FTP, the accepted protocol for automated data download. It is expected that AACs will request unattended automatic transfer of newly received data. The GFZ in response to the LEO PP CfP proposed to also be a DC for the project. Bernd Ritschel reported that registration is required for first access to the CHAMP Information System and Data Centre (ISDC). Product archiving, administration and retrieval are organized by the CHAMP ISDC at GFZ Potsdam, which also is the users' www- and ftp-based interface for access to all scientific data and products. There is no support for a "new requirement" of unattended automated download. A "Batch Agent" to be active for regular operations is under development. Tom Yunck gave an overview of the new GPS Environmental & Earth Science Information System GENESIS. This information system is a member of the Federation of Earth Science Information Partners (ESIP) see: http://genesis.jpl.nasa.gov/ Access is unrestricted for GENESIS, however in the future it is expected that users will register (no cost) so that access statistics can be compiled. It was decided that Moore, Noll, Ritschel, Yunck, and Stowers will compile access instructions for various data types analogous to current .dcn files located at the Central Bureau (which may need alteration). A LEO PP mail listing has been established for the project by the Central Bureau and on-going communications can be viewed at IGSLEO Mail: http://igscb.jpl.nasa.gov/mail/mailindex.html LEO PP Designated Agency/Points of Contact: ------------------------------------------------------------- Proposal received: Agenzia Spaziale Italiana, Matera, Italy/Francesco Vespe Astronomical Institute, University of Bern, Switzerland/Urs Hugentobler Center for Space Research, Univ. of Texas-Austin, USA/Bob Schutz CNES, Toulouse, France/ Analysis: Jean-Paul Berthias, Stations: Louis Duquesne, (David Assemat) ESA/ESOC, Germany/John Dow GeoForschungsZentrum Potsdam, Germany/Ch. Reigber Indian Space Research Organization, Tracking and Command Network/K. Elango (S.K. Shivakumar) Institut Cartographic de Catalunya, Spain/Julia' Talaya Jet Propulsion Lab/Jim Zumberge Jet Propulsion Lab, & Univ. Sth. California/Tom Yunck Korean Astronomy Observatory,/Pil-Ho Park Laboratory for Space Geodesy and Remote Sensing - Ohio State, USA/C.K. Shum NASA Goddard Space Flight Center, CDDIS, USA/Carey Noll Natural Resources of Canada, Geodetic Survey /Mark Caissy,(Norman Beck) National Survey and Cadastre - Denmark/Per Knudsen Norwegian Mapping Authority/Rune Hannsen Research Institute of Geodesy, Pecny, Czech Republic/Jaroslav Simek NERC Space Geodesy Facility, UK/Roger Wood University of New Brunswick, Dept. of Geodesy and Geomatics Engr./Richard Langley, Sunil Bisnath University of Padua, Center for Space Studies (CISAS), Italy/Stefano Casotto University of Padua, CISAS, Italy/Alessandro Caporali US Naval Observatory, USA/Jim Ray Letter of Intent received: Australian Surveying and Land Information Group/Ramesh Govind University Consortium for Atmospheric Research/Chris Rocken Joint Center for Earth Systems Technology, Univ. Maryland/Erricos Pavlis IGS LEO Working Group Members --------------------------------------------- John Dow Ruth Neilan, IGS CB Christoph Reigber Chris Rocken Markus Rothacher Bob Schutz Tom Yunck M. Watkins (WG chair) R. Weber, IGS ACC LEO Project Meeting Participants List, Feb 6-8, 2001 ----------------------------------------------------- 1. Gerald Baustert, TeleOrbit, Germany (gbau@gfz-potsdam.de) 2. Georg Beyerle, GFZ, Germany (gbeyerle@gfz-potsdam.de) 3. Heike Bock, AIUB, Switzerland (heike.bock@aiub.unibe.ch) 4. Ralf Bock, GFZ, Germany (ralf.bock@gfz-potsdam.de) 5. Mark Caissy, NRC, Canada (caissy@nrcan.gc.ca) 6. Alessandro Caporali, University of Padova, Italy (alex@geol.unipd.it) 7. Stefano Casotto, University of Padova, Italy (casotto@pd.astro.it) 8. Wolfgang Dick, BKG, Germany (dick@ifag.de) 9. John Dow, ESA/ESOC, Germany (john.dow@esa.int) 10. Louis Duquesne, CNES, France (louis.duquesne@cnes.fr) 11. Lou Estey, UNAVCO/UCAR, USA (lou@unavco.ucar.edu) 12. Kevin Fleming, GFZ, Germany (kevin@gfz-potsdam.de) 13. Christoph Foerste, GFZ, Germany (foer@gfz-potsdam.de) 14. Roman Galas, GFZ, Germany (galas@gfz-potsdam.de) 15. Carlos Garcia, ESOC, Germany (Carlos.Garcia-Martinez@esa.int) 16. Gerd Gendt, GFZ, Germany (gendt@gfz-potsdam.de) 17. Gianluca Graglia, Alenia Spazio, Roma, Italy (g.graglia@roma.alespazio.it) 18. Serge Gratton, CNES, France (serge.gratton@cnes.fr) 19. Ludwig Grunwaldt, GFZ, Germany (grun@gfz-potsdam.de) 20. Werner Gurtner, AIUB, Switzerland (gurtner@aiub.unibe.ch) 21. Phillip Hartl, Germany (ph.hartl@t-online.de) 22. Finn Hass, Terma, Denmark (fah@terma.com) 23. Stefan Heise, DLR, Germany (stefan.heise@dlr.de) 24. Urs Hugentobler, AIUB, Switzerland (urs.hugentobler@aiub.unibe.ch) 25. Klaus-Peter Johnsen, GKSS, Germany (johnsen@gkss.de) 26. Zhigui Kang, CSR, USA (Kang@csr.utexas.edu) 27. Wolfgang Koehler, GFZ, Germany (wolfk@gfz-potsdam.de) 28. Rolf Koenig, GFZ, Germany (koenigr@gfz-potsdam.de) 29. Jakub Kostelecky, Pecny Obs., Czech Republic (gope@asu.cas.cz) 30. Jan Kostelecky, Prague Techn. Univ., Czech Republic (kost@fsv.cvut.cz) 31. Gerhard Kruizinga, JPL, USA (Gerhard.Kruizinga@jpl.nasa.gov) 32. Hermann Luehr, GFZ, Germany (hluehr@gfz-potsdam.de) 33. Finn Bo Madsen, KMS, Denmark (bm@kms.dk) 34. Christian Marquardt, GFZ, Germany (marq@gfz-potsdam.de) 35. Franz-Heinrich Massmann, GFZ, Germany (fhm@gfz-potsdam.de) 36. Charles Meertens, UNAVCO/UCAR, USA (chuckm@unavco.ucar.edu) 37. Bill Melbourne, GFZ/JPL, Germany/USA (wgm@gfz-potsdam.de, william.g.melbourne@jpl.nasa.gov) 38. Flavian Mercier, CNES, France (flavien.mercier@cnes.fr) 39. Angelyn W. Moore, JPL, USA (Angelyn.W.Moore@jpl.nasa.gov) 40. Ron Muellerschoen, JPL, USA (rjm@cobra.jpl.nasa.gov) 41. Antonio Nardi, Telespazio, Roma, Italy (antonio@sidus.mt.asi.it) 42. Ruth E. Neilan, JPL, USA (ruth.neilan@jpl.nasa.gov) 43. Roland Neuber, AWI, Germany (neuber@awi-potsdam.de) 44. Karl-Hans Neumayer, GFZ, Germany (neumayer@gfz-potsdam.de) 45. Carey Noll, GSFC, USA (noll@cddis.gsfc.nasa.gov) 46. Kurt Oppitz, BKG, Germany (kop@potsdam.ifag.de) 47. Markus Ramatschi, GFZ, Germany (maram@gfz-potsdam.de) 48. Christoph Reigber, GFZ, Germany (reigber@gfz-potsdam.de) 49. Hyung-Jin Rim, CSR, USA (rim@csr.utexas.edu) 50. Bernd Ritschel, GFZ, Germany (rit@gfz-potsdam.de) 51. Chris Rocken, UNAVCO/UCAR, USA (rocken@unavco.ucar.edu) 52. Uwe Schaefer, BKG, Germany (ufer@potsdam.ifag.de) 53. Torsten Schmidt, GFZ, Germany (tschmidt@gfz-potsdam.de) 54. Bob Schutz, CSR, USA (schutz@csr.utexas.edu) 55. Volker Schwieger, GFZ, Germany (schwieg@gfz-potsdam.de) 56. Peter Schwintzer, GFZ, Germany (psch@gfz-potsdam.de) 57. Jaroslav Simek, Pecny Obs., Czech Republic (gope@asu.cas.cz) 58. Dave Stowers, JPL, USA (dstowers@jpl.nasa.gov) 59. Drazen Svehla, TU Munich, Germany (svehla@step.iapg.verm.tu-muenchen.de) 60. Byron Tapley, CSR, USA (tapley@csr.utexas.edu) 61. Francesco Vespe, ASI, Italy (vespe@asi.it) 62. Pieter Visser, TU Delft, Netherlands (Pieter.Visser@lr.tudelft.nl) 63. Michael M. Watkins, JPL, USA (Michael.M.Watkins@jpl.nasa.gov) 64. Frank Webb, JPL, USA (Frank.H.Webb@jpl.nasa.gov) 65. Robert Weber, Univ. of Technology, Austria (rweber@luna.tuwien.ac.at, robert.weber@aiub.unibe.ch) 66. Andreas Wehrenpfennig, DLR, Germany (Andreas.Wehrenpfennig@dlr.de) 67. Jens Wickert, GFZ, Germany (wickert@gfz-potsdam.de) 68. Roger Wood, NERC, UK (rw@slrb.rgo.ac.uk) 69. Thomas Yunck, JPL, USA (tom.yunck@jpl.nasa.gov) 70. James F. Zumberge, JPL, USA (james.f.zumberge@jpl.nasa.gov) -- ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ IGS Central Bureau/Jet Propulsion Laboratory tel: 818-354-8330, fax: 818-393-6686