From feissel@ensg.ign.fr Thu Jun 17 12:46:30 2004 Date: Tue, 2 Apr 2002 16:45:58 +0200 (Paris, Madrid) From: Martine Feissel To: Doris/IDS data analysts biancale , exertier , Jean-François Crétaux , Jean-Jacques Valette , Jean-Paul Berthias , Jean-Michel Lemoine , jries@csr.utexas.edu, kra@ipa.rssi.ru, Laurent Soudarin , Pascal Bonnefond , Pascal Willis , skuzin@inasan.rssi.ru Cc: Henno Boomkamp , Robert Weber , Gilles Tavernier , feissel@ensg.ign.fr Subject: Comparing DORIS orbits Dear colleagues As you will see in the appended message from Henno Boomkamp (ESA), we are offered the possibility to associate DORIS orbit comparisons, at least for JASON and possibly for T/P, with an IGS ongoing project. Not withstanding developing our own activities for other satellites (e.g. Spot) or complementary objectives (e.g. reference systems), this gives an excellent opportunity to interact with this part of the world. I encourage you to take this opportunity and to contact Henno to work out the content/format issues, keeping me informed. As far as the campaign dates and duration are concerned, it would certainly be advisable to coordinate them with the GPS side. Best regards Martine -- Martine Feissel Internet: feissel@ensg.ign.fr Observatoire de Paris and Institut Geographique National Telephone: 33 (0) 1 64 15 32 83 ENSG/LAREG Fax: 33 (0) 1 64 15 32 53 8 Av. Blaise Pascal, Champs sur Marne 77455 Marne la Vallee Cedex 2, France -- ---------- Forwarded message ---------- Date: Tue, 2 Apr 2002 16:32:00 +0100 From: Henno.Boomkamp@esa.int To: Martine Feissel Cc: feissel@ensg.ign.fr, Jean-Jacques Valette , Jean-Michel Lemoine , John.Dow@esa.int, Pascal Willis , Robert Weber Subject: Re: DORIS LEO orbits Dear Martine, The future plans for the IGS LEO pilot project include an orbit campaign for JASON similar to that of CHAMP. For that purpose, I plan to install JASON webpages similar to those of CHAMP (... which, by the way, will be updated soon with the latest results - I'll add a header as well). It is possible that the objectives of the IDS and IGS LEO are not strictly the same, but regardless of that I can offer to start a JASON orbit webpage as soon as possible, and do the comparisons for your campaign. The system here is almost automatic. It will not be a major effort to adapt it for JASON, and this was foreseen anyway. If there is sufficient interest in TOPEX/Poseidon, I can do that as well. Even if some of your solutions may not include GPS data, or some of our solutions will not have DORIS, it will be useful to compare all such orbits. With regard to the contributed orbits, I would prefer the following: (1) Earth-fixed orbit files in SP3 format, preferably 1-day arcs but this is not critical. If velocity vectors are present in both compared files of a pair, the velocity differences will also be generated. For CHAMP we have installed an orbit repository at CDDIS, it seems practical to do the same for JASON. (2) A small READ.ME file to describe the POD method. For TOPEX and JASON most orbits will be from dynamic solutions, but what is important in this case is to indicate (A) all tracking data that has been used (GPS, DORIS, SLR, altimetry, ...). (B) the terrestrial reference frame in which the orbit has been estimated (3) The aim is to have a longer JASON campaign than for CHAMP. JASON POD is already more mature so that we don't expect a lot of re-processing. I would suggest a period of at least two repeat cycles, but we might as well do a full month. If you have already chosen a campaign duration, please let me know. It will probably not be a problem to run periods even longer than one month. If possible, SLR data should not be used in the POD so that we can keep it as an independent check. However, if the SLR is needed to reach the required precision it would be a nonsense to leave it out. Solutions that include SLR may come out of our analysis slightly better than they really are, but in the end the GPS and DORIS data will probably dominate the POD. Please note that I will be in the IGS workshop next week, and on holidays the week after. This week you can still reach me at ESOC, after that I will answer your mails from day 22/4. Best regards, Henno Boomkamp >----------------------------------------------------------------------------| | | | To: Henno Boomkamp/esoc/ESA@ESA | | cc: Robert Weber , John | | Dow/esoc/ESA@ESA, Jean-Jacques Valette ,| | Jean-Michel Lemoine , Pascal Willis | | , feissel@ensg.ign.fr | | Subject: DORIS LEO orbits | >----------------------------------------------------------------------------| Dear colleague I visited your webpage http://nng.esoc.esa.de/gps/campaign.html which shows comparisons of a number of GPS-derived CHAMP orbits. I found it quite informative and useful - it would be even nicer if the page had a Heading, so that it gets a name in the list of users bookmarks. The DORIS Pilot Experiment is set up to prepare a future International DORIS Service (IDS), parallel to the IGS, the IVS (for VLBI) and the ILRS (for laser ranging). In this framework, several analysis centers produce precise orbits of DORIS-tracked satellites (Spot-n, Topex/Poseidon, Jason 1, Envisat). We are looking for possibilities of comparing these orbits, in parallel to what is done in the context of the altimetry missions. In preparation for the DORIS-IDS Workshop on June 13-14 (see http://www.cta-congres.com/BIARRITZ2002/twodori.html), we would like to be able to show some DORIS orbit comparisons for, e.g., Jason 1 or Topex/Poseidon. The standard procedure you apply to the CHAMP orbits could meet this need. Could you devote some time to perform such comparisons, if orbits would be provided to you in the SP3 format? The number of analysis centers would be probably around five. Looking forward to your response. Best regards. Martine Feissel Analysis Coordinator, DORIS Pilot Experiment -- Martine Feissel Internet: feissel@ensg.ign.fr Observatoire de Paris and Institut Geographique National Telephone: 33 (0) 1 64 15 32 83 ENSG/LAREG Fax: 33 (0) 1 64 15 32 53 8 Av. Blaise Pascal, Champs sur Marne 77455 Marne la Vallee Cedex 2, France --