From: Henno.Boomkamp@esa.int To: igsleo@igscb.jpl.nasa.gov Message-ID: <41256B61.00596103.00@esocmail2.esoc.esa.int> Date: Fri, 15 Feb 2002 17:11:25 +0100 Subject: [IGSLEO-40] IGS LEO report Sender: owner-igsleo Precedence: bulk ****************************************************************************** IGS LEO Mail 15 Feb 08:11:42 PST 2002 Message Number 40 ****************************************************************************** Author: Henno Boomkamp Dear Colleagues, Please find attached a report on the IGS LEO meeting in Potsdam, January 2002. Based on the conclusions of the meeting some concrete actions are proposed. As part of these actions the report contains an invitation for presentations in a dedicated IGS LEO session during the Ottawa Workshop. if you would like to present on that occasion, please reply as soon as possible with a title and short abstract. Best regards, Henno Boomkamp ------------------------------------------------------------------------------------------------------------------------------------------ IGS LEO meeting - Potsdam 23/01/2002 ------------------------------------------------------------------------------------------------------------------------------------------ The IGS LEO meeting in Potsdam was well attended, which shows that a wide interest exists in applications of LEO GPS data. With the release of the CHAMP data in May last year and several other operational LEO missions arriving soon, the IGS LEO centres can gear up their activities. The technical analysis within the IGS LEO pilot project has so far been dominated by CHAMP POD. During the CHAMP Science Meeting separate sessions were dedicated to that topic, so that the IGS LEO meeting mainly focussed on a discussion about its future policy. Agenda of the meeting ---------------------------------- (I) Status and policy: * Proposed development of IGS LEO processing (Henno Boomkamp) * Discussion on proposed development versus current status of IGS LEO analysis (All) (II) Technical presentations: * Presentation on the CHAMP Orbit Comparison campaign (Henno Boomkamp) * Presentation on TUM fine ambiguity resolution orbits (Markus Rothacher) Summary of the discussion ---------------------------------------- From the discussions during and after the meeting it became clear that different centres have different expectations of the IGS LEO pilot project. The following points of view on future IGS LEO activities were brought forward: (1) The value of LEO GPS data must still be established more clearly. The main task of the pilot project would be to do this kind of analysis, which could be done off-line without needing much in terms of additional infrastructure or processing capability. (2) The lack of LEO GPS data - at least until recently - and the lack of processing capability or data infrastructure still prevent proper GPS LEO analysis. To enable adequate study of the impact of LEO data on IGS products, the IGS LEO pilot project should stimulate the development of the processing capability of LEO GPS data at a substantial number of Associate Analysis Centres. (3) The IGS LEO pilot project could give more priority to applications of GPS to the LEO satellites and not mainly concentrate on benefits of using LEO data for IGS processing. Some IGS LEO products could be considered if there is a genuine demand for it. In general terms these views are not incompatible, but they set different priorities. What seems to be lacking is a clear definition of the scope and objectives of the IGS LEO pilot project. For creating some clarity on this point, the initial intentions of the IGS LEO working group can be briefly recalled here. The call for participation in support of LEO missions (IGS mail 2669) invited proposals related to LEO POD, to a high performance IGS ground station network and to the development of processing capability for high rate and / or LEO flight receiver data at data centres and analysis centres. This same announcement mentions a pilot project as one of the suggested activities, with the following objectives: "Generating scientific POD for the LEO satellites ...; AACs will demonstrate POD for these satellites as data is made available ..;. AACs will investigate and asses potential improvement of the suite of IGS classic products". The Pilot Project activities have so far focussed on POD for CHAMP, but the orbit comparison campaign suggests that CHAMP POD will soon reach a mature status. Logical next steps for the pilot project will be to extend the CHAMP campaign over a longer period of time and/or to involve other satellites (notably JASON). On the other hand, the availability of more LEO data and adequate POD will make it possible to initiate projects related to the second objective of the pilot project, i.e. assessing the impact of the LEO data on the classic IGS products, as brought up under point (1) above. Other areas of interest that were expressed by the IGS LEO working group in the call for proposals have not received much attention so far (i.e. high performance ground network, developing processing capability at data centres and analysis centres). The availability of adequate analysis capabilities is a necessary condition for assessing the impact of LEO data on the classic IGS products, and it would be a natural task for the current pilot project to ensure that this analysis capability is present. This is what point (2) of the discussion was about, and it was also the essence of the initial presentation on proposed IGS LEO processing. The third point of view illustrates that the applications of IGS LEO data and products may be wider than originally anticipated. The call for proposals for IGS LEO naturally aimed at improving the classic IGS products, which is why it is an IGS initiative in the first place. However if intermediate LEO products appear, notably LEO orbits and clocks, IGS could consider the distribution of such products among the further IGS outputs. A tentative suggestion of commercialising this kind of output was made, but this opens up another discussion entirely. Conclusions from the meeting --------------------------------------------- * Different views appeared on the way in which IGS LEO should develop. On the grounds of the initial call for proposals, the current pilot project could limit itself to analysis, reflected under (1) above. In practice the IGS LEO Pilot Project is the only form in which IGS LEO activities are being implemented. This means that it may be inevitable to extend the scope of PP activities to also include the development of analysis capabilities and data infrastructure. This is the view that was noted under point (2). Then, many of the centres that are currently working on the CHAMP data have a primary interest in LEO missions rather than IGS/GPS, which understandably leads to the view mentioned under (3). * Because of these different opinions, it seems useful to define the scope of the IGS LEO pilot project more clearly and to consolidate a common set of objectives and priorities. * Data availability and LEO POD are improving rapidly, which means that concrete projects should be started to analyse the impact of LEO data on IGS products, at least within those centres that already have combined LEO+GPS analysis capability. * It will also be good to capitalise on the success of the CHAMP orbit campaign in some form by extending the campaign period and/or by setting up a similar campaign for other satellites. Actions ------------ 1. For creating clarity on the scope and objectives of the IGS LEO pilot project, I offer to prepare a draft version of a more or less formal IGS LEO charter or working plan, along the lines set out in ftp://igscb.jpl.nasa.gov/igscb/resource/workgroups.txt. Inputs to this draft will be the initial call for proposals, the proposals themselves and the recommendations from the various LEO meetings in the past, including the 2002 meeting in Potsdam. After review by interested parties this draft can be put forward for approval during the IGS Governing Board meeting in Ottawa. 2. Technical analysis for assessing the impact of LEO data on the classic IGS products can gradually gain priority over LEO POD. A primary objective of the Ottawa meeting will be to define the areas in which concrete projects can be initiated and coordinated through IGS LEO. Please note the suggestions for presentations during the Ottawa workshop further below. 3. A follow-up project for the CHAMP Orbit Comparison campaign will be organised (...soon). Invitations for presentations during the Ottawa workshop ------------------------------------------------------------------------------------ Following up on action 2 above, concrete projects should be started soon to gain insight in the impact of LEO GPS data on the IGS products. Some relevant knowledge will already be available, other potential benefits of the LEO GPS data may not yet have been acknowledged to full extent. I would like to invite technical presentations related to this topic for a dedicated IGS LEO session during the IGS workshop in Ottawa (8-11 April). The main goal of this session will be to determine the areas in which subsequent IGS LEO projects can be organised, i.e. to assess what relevant knowledge is available, what processing capability is available, and what areas need to be developed further. Suggested subjects for presentations: * As mentioned in Potsdam, the presence of LEO data should improve the separability of the Z-component in the rapid as well as in the final products. Using CHAMP data, this effect can be quantified by centres that have combined GPS+LEO processing capability. Perhaps it is also possible to use simulated data for LEOs at different heights and inclinations, while validating the quality of these simulations via CHAMP or other LEO, for which simulations can be compared with results from real data. * Differenced data involving a LEO and a ground station or combinations of LEOs can provide advantages over pure ground-based difference combinations (longer base lines, no atmosphere, variable LEO geometry). Using CHAMP or SAC-C these effects can be quantified with real data. * Perhaps there has been relevant analysis in the past based on TOPEX GPS data that can now be repeated with CHAMP data and/or SAC-C data to provide more precise results. * Incorporation of LEO data in IGS processing may improve EOP and station coordinates observability via links with other Earth-based tracking data (SLR, DORIS). Presentations are invited that demonstrate benefits of reference frame or EOP estimation based on GPS in combination with other tracking data types. * Any other contribution that can illustrate potential benefits of LEO GPS data on the further GPS products is welcome, of course. There is not much time left until the Ottawa workshop, but some of the topics above can be investigated with relatively modest effort. Please reply as soon as possible if you are interested in presenting something in Ottawa, so that a LEO session agenda can be produced. Best regards, Henno Boomkamp