Support for the Orbit Visualisation Tool (OVT)

ESOC has now produced a set of Cluster LTOFs extending to nominal re-entry of each spacecraft (August 2024 for C2, November 2025 for C1, and April 2026 for C3 and C4). However, IGRF13 is formally defined only to end of 2024. To ensure that OVT works with these LTOFs, the igrf.d file has been extended by linear extrapolation to end of 2029 (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.

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.
• A new version released on 24 March 2017 includes changes implemented by ESOC in 04 January 2017. It now includes orbit data to January 2022.
• A new version released on 4 April 2018 includes orbit data now going up to Aug 2024 for C2 and end 2025 for C1, C3 and C4.
• A new version released on 7 August 2018 includes orbit data now going up to start of 2024. They cover the solar wind monitor formation in Spring 2019 and the tail formation in Autumn 2019. They include the manoeuvres planned for the associated formation changes between November 2018 and August 2019.
• A new version released on 19th February 2019 includes the LTOF files received from ESOC on 8th February. In these ESOC FD has implemented the proposed shifts of 4h by C1 and 1h by C3. The drift is started on 15th September 2019 and stopped on 10th December followed by a trim manoeuvre on 19th December 2019.
• A new version released on 1st August 2019 is unchanged up to 1st January 2024, but includes orbit data now going up to 31st Aug 2024 for C2, 6th November 2025 for C1 and up to 30th April 2026 for C3 and C4.
• A new version released on 15th August 2019 includes formations for the north hemisphere cusp crossing in Jan 2020, south hemisphere cusp in May 2020, looking at the sub-ion magnetic holes in the dipolarized plasma sheet Aug/Sep 2020, and a study of the magnetic reconnection at the Earth's magnetopause from end Nov 2020 onwards. Please note that the Aug/Sep 2020 formation implementation is still to be confirmed.
• A new version released on 15th October 2019 for Spacecraft 2 alone includes an update for manoeuvre optimisation and orbit prediction for the C2 manoeuvres on 22nd September and 13th November 2020. The new C2 LTEF/LTOF are practically identical to the previous ones except during 22nd September - 22nd November 2020 where the formation change manoeuvres take place. The maximum time difference is between four and five minutes along track.
• A new version released on 17th August 2020 for all spacecraft contains the 2021 manoeuvres for the hiss formation starting in June 2021. This update was contained in the LTEF and LTOF files received from ESOC on 7th August 2020. Manoeuvres to reach the formation will be performed between 29th March 2021 and 11th June 2021.
• A new version released on 4th August 2021 for spacecraft 3 implements the formation in April 2022, after the end of the short eclipse season, to measure the extent of high speed plasma jets in the magnetosheath. As only the SC.3 position changes along track, last years’ orbits of the other satellites remain valid.
• A new version released on 18th February 2022 for spacecraft 3 implements the magnetotail formation in 2022, for which C3 is shifted from 3000km distance to 1 Re from C4. As only the SC.3 position changes, last years’ orbits of the other satellites remain valid.
• A new version released on 13th July 2022 based on long-term orbit files received from ESOC on 20th June 2022 for all spacecraft, implements the formation to enable the campaign for studying the scale of foreshock bubbles in Spring 2023.
• A new version released on 13th October 2022 based on long-term orbit files received from ESOC on 15th September 2022, for spacecraft 1 and 2 only, implements both time shifts for the auroral acceleration region campaign involving manoeuvres on SC,1 and 2 up to 28th April 2023, and ending with a final trim manoeuvre on SC.2 on 17th November 2023. For SC. s 3 and 4 the LTOFs from June 2022 already contained the 20km configuration required.
• A new version released on 7th December 2022 is based on long-term orbit files received from ESOC on 25th November 2022, for spacecraft 1 and 2 only; corrects time shifts for the auroral acceleration region campaign involving manoeuvres on SC,1 and 2 in April 2023, and implements manoeuvres in September and November 2023. For SC. s 3 and 4 the LTOFs from June 2022 already contained the 20km configuration required.
• A new version released on 8th November 2023 for spacecraft 2 is based on long-term orbit files received from ESOC for spacecraft 2 only on 28th September 2023; it takes into account the air drag effect during the last few months of the mission for spacecraft 2 and considers the re-entry tuning manoeuvres for it in January 2024 .
• A new version released on 22nd March 2024, for spacecraft 3 only, now includes the SC.3 reconfiguration in April 2024. This comprises of several manoeuvres to facilitate the Northern AAR formation. However the differences wrt previous long term orbits from June 2022 are small; they remain below 25km radial/across track and less than 0.5 minutes along track during the whole year 2024.
• A new version released on 26th June 2024 for spacecraft 1 only, now includes the C1 re-entry tuning, involving two manoeuvres on 3rd August 2024 at 19:12z (main manoeuvre) and 10th August 2024 at 19:09z (trim manoeuvre).

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

Then go to the odata directory within your OVT installation (e.g. on a typical Windows installation this is C:\Users\XXX\.ovt\3.0\odata),where XXX is your user name. See figure below. .

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:

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

The ESA Earth Explorer mission Swarm was launched on 22 November 2013. It aims to provide the best ever survey of the geomagnetic field and its temporal evolution and to gain new insights about the Earth's interior and climate.

The Swarm mission is a constellation of three satellites in polar orbits, with two (A and C) in similar close orbits with initial altitude around 460 km and the third (B) in a different orbit with initial altitude around 530 km.

High-precision and high-resolution measurements of the strength and direction of the magnetic field are provided by each of 3 Swarm satellites. In combination, these magnetometers provide the observations that are required to model various sources of the geomagnetic field. GPS receivers, an accelerometer and an electric field instrument on each spcecraft provide supplementary information for these studies. The Swarm data are available via ESA's Swarm Data Access page.

Swarm also monitors the time-variability aspects of the geomagnetic field producing results that also have practical applications in areas such as space weather and radiation hazards. Data from Swarm are therefore of great interest to the solar-terrestrial physics (STP) community, especially if they can be combined with data from other STP instruments, such as those from Cluster. In order to do this, it is necessary to identify when Cluster and Swarm can make coordinated observations, e.g. when the two missions are observing in magnetically conjugate locations.

The Swarm orbit can be plotted with OVT which has access to the orbits of the heliophysics spacecraft through SSCweb .

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 installation kit. Additional TLE data are available from a number of sources:

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

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.

Last updated by  Anne Chadwick ( anne.chadwick@stfc.ac.uk), Yulia Bogdanova ( yulia.bogdanova@stfc.ac.uk) and Mike Hapgood ( mike.hapgood@stfc.ac.uk) 26th June 2024.