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Support for the Orbit Visualisation Tool (OVT)

Introduction

This web page gives access to updates of various data files needed by the Orbit Visualisation Tool-2 for Cluster, which has been developed by the Swedish Institute for Space Physics, Uppsala and ESA. The OVT code (currently version 2.3) and documentation are available from the OVT web site.

Geomagnetic field

OVT supports the tracing of magnetic field lines within the magnetosphere. This tracing is based on various external and internal magnetic field models including the International Geomagnetic Reference Field. OVT 2.3 includes the IGRF 8th generation model (formerly known as IGRF2000) while the current IGRF is the 12th generation model. To update the field model in OVT:

  • Download the updated data file igrf.d
  • Go to the mdata directory within your OVT installation (e.g. on a typical Windows installation this is C:\Program Files|Orbit Visualisation Tool 2.3\mdata). See figure below.
  • Rename the existing igrf.d file, e.g. as igrf_old.d
  • Copy the new igrf.d into the mdata directory
  • Re-start OVT to use the new file

    ESOC has now produced a set of Cluster LTOFs extending to January 2022, but IGRF12 is formally defined only to end of 2019. To ensure that OVT works with these LTOFs, the igrf.d file has been extended by linear extrapolation to end of 2024 (the IGRF code works in 5-year blocks). This is just a mathematical extension and is not, in any way, a future representation of IGRF - but is sufficient to enable use of OVT with any current Cluster orbit files.

    Further IGRF updates will be put on this site when available.

    Cluster orbit data

    OVT can read the Cluster orbit files provided by ESA. These files are available from a variety of sources with varying lengths of time coverage. For comprehensive coverage of the mission it is recommended to use the Super-LTOF files compiled by JSOC. These cover the whole period from launch to the end of mission. They are updated weekly as new reconstituted data for the past mission becomes available. They are also updated with new predicted data as ESOC implement the detailed plans developed by the Cluster Science Operations Working Group. See below for advice on how to check the provenance of a Cluster orbit file.

    The Super-LTOFs include the latest good long-term predictions from ESOC. These include accurate predictions of the spacecraft configuration up to autumn 2011 and the subsequent orbit evolution to January 2015. Further release information is as follows:

    • The version available from 20 March 2009 to 7 May 2009 contained inaccurate data for December 2009 to December 2012.
    • The version available from 7 May 2009 contains accurate data for the period through to December 2012.
    • This was extended to January 2015 in the version released on 22 December 2009.
    • A new version released on 26 March 2010 updates the orbits from 13 July 2009 through to January 2015.
    • A new version released on 3 March 2011 updates the orbits from 20 July 2010 through to January 2015.
    • A new version released on 28 October 2011 adds reconstituted data to 26 October 2011 and updates the predicted data through to 1 February 2017.
    • A new version released on 12 December 2011 includes manoeuvres for the guest investigator formations now planned for 2012 and early 2013 and other changes agreed at or following the Nov 2011 SOWG at ESTEC. Orbits are then projected forward through to 2 January 2017.
    • A new version released on 11 September 2012 includes updates to manoeuvres for the Foullon and Pu guest investigator formations planned for November 2012 and February 2013. Orbits are then projected forward through to 2 January 2017.
    • A new version released on 20 March 2013 includes updates to manoeuvres to refine the close configuration of C1, C3 and C4 in the inner magnetosphere during August-September 2013 and a preliminary planning of the Pitout guest investigator formation in November/December 2013. Orbits are then projected forward through to 3 January 2017.
    • A new version released on 21 June 2013 includes updates to manoeuvres to refine the Pitout guest investigator formation in November/December 2013, to set up the ring current formation in spring 2014, and a draft planning for the tail formation in Autumn 2014. Orbits are then projected forward through to 3 January 2019.
    • A new version released on 16 April 2014 includes changes from mid October 2014: (a) manoeuvres to a repetition of the Pitout guest investigator formation in October/November 2014, and(b) manoeuvres to set up a bow shock 5km formation in January 2015 (lasting at least till mid February 2015). Orbits are then projected forward by free drift propagation till end of 2019. The bow shock 5km formation 2015 is final for C3/C4. It might be changed for either C1 or C2 by shifting one satellite backwards by up to 20 minutes (to be decided in September 2014 at the SWT in Rhodes).
    • A new version released on 17 October 2014 includes changes decided at the September 2014 SWT in Rhodes.
    • A new version released on 06 March 2016 includes changes implemented by ESOC in August 2015 and February 2016. It now includes orbit data to January 2022.

    To update the Cluster orbit data in OVT, first download the updated orbit files:

  • Cluster1.ltof (20 Mbytes)
  • Cluster2.ltof (19 Mbytes)
  • Cluster3.ltof (19 Mbytes)
  • Cluster4.ltof (20 Mbytes)

    Then go to the odata directory within your OVT installation (e.g. on a typical Windows installation this is C:\Program Files|Orbit Visualisation Tool 2.3\odata). See figure below.

  • Rename the existing orbit files, e.g. as Old_cluster1.ltof
  • Copy the new orbit files into the odata directory
  • Re-start OVT to use the new file

    Double Star orbit data

    Double Star orbit are also available as Super-LTOF files. To update these orbit data in OVT, first download the updated orbit files:

  • Double_Star_1.ltof (26 Mbytes)
  • Double_Star_2.ltof (32 Mbytes)

    Then proceed as for Cluster orbit files

    Checking the provenance of Cluster & Double Star orbit files

    The Cluster & Double Star orbit files are divided into blocks where each block specifies the spacecraft orbit for a particular period. Thus each orbit file is built up of contiguous blocks in order to cover an extended period. Each block is labelled with a data type (R for reconstituted and P for predicted) and a generation time; these can be used as an indication of the provenance of the orbit data.

    To generate a list of orbit block provenance records, you may use the Unix script orbit_block_list. This takes the orbit file name as its only argument and lists records to standard output. Each record gives a data type, generation time and the range of times covered by blocks with that provenance; this range will generally be more than one block.

    This script runs under Solaris so you may need to adapt for other systems.

    Swarm orbit data

    Swarm orbit are available as both Super-LTOF files and as TLE-format files (see below). More details on the JSOC support page for Cluster-Swarm coordination.

    Other mission orbit data

    OVT can also read orbit data in the NORAD Two-Line Element (TLE) format. This is the recommended method by which OVT can ingest and display orbit data for other magnetospheric missions, e.g. Polar, THEMIS. A number of historical TLE datasets are available as part of the OVT 2.3 installation kit. Additional TLE data are available from a number of sources:

  • The official source of Two-Line Elements is the Space Track web site run by the US Air Force. This requires a username/password for login and the downloaded data are provided for your personal use only. Thus you are recommended to apply for a personal account via the Space Track web site above.
  • Historical (1957-2004) elements are freely available via the Celestrak web site together with a small amount of more recent data. This web site also provides extensive information on the history and use of Two-Line Elements. To update other orbit data in OVT:
  • Obtain the Two-Line Elements as described above.
  • Go to the odata directory within your OVT installation (e.g. on a typical Windows installation this is C:\Program Files|Orbit Visualisation Tool 2.3\odata). See figure below.
  • Place the new TLE file in the odata directory with name xxxx.tle, where xxxx is a suitable description (no blanks)
  • Re-start OVT to use the new file

    Caveat: Experience shows that OVT has problems in using some TLE datasets. These are being investigated. Possible sources of problems are:

  • Missing checksums in TLE records - causes a read error in OVT
  • Large time gaps between TLE records

    OVT directory structure and file installation

    The figure below shows the standard OVT directory structure and the location of the odata and mdata directories in which the files above should be installed. Important note: If you cannot save files directly from the web page to the relevant directory, it may be that you need to administrator privilege to load files into these directories. If so it is recommended to save the files to an intermediate directory, then copy from there to the directories shown below, confirming/supplying administrator privilege when prompted.

    OVT directory structure

    Last updated by  Mike Hapgood ( mike.hapgood@stfc.ac.uk), 12 March 2016.


     
     

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