The INTERBALL Auroral PROBE orbital elements collections

| Instead of the introduction | Format of the orbital elements | Estimation of the extrapolation errors |

The orbital elements collections:

  • "Version 1" of the orbital elements collection, determined by KIAM during flight and used for operations planning
  • "Version 2" of the of the orbital elements collection, modified by IKI during flight and recommended for the orbital calculations during scientific data processing

  • "Version 3" - post-flight determined by KIAM orbital elements, recommended for apostriori orbit calculations
Three kinds of the INTERBALL Auroral probe (IB_AUR) orbital elements' collections are presented here.

  • The "Version 1" contains the orbital elements, determined by KIAM (Ballistic center at the Keldysh Institute of Applied Mathematics of Russian Academy of Sciences) during the treatment of the in-flight SC trajectory measurements. This data are connected with the last point of the used measuring time intervals. The orbit determination root mean square error (RMS) of 30-40 km inside the measuring intervals was estimated by KIAM.
    It have to be mentioned, that the IB_AUR motion is not passive one, it is subjected to non-gravitational accelerations generated by the work of the attitude control system.
    The later estimations show the discrepance between the predicted and real positions of the IB_AUR. The IB_AUR position prediction in 15 days give the RMS error 150 - 500 km.
    It is not possible to avoid this error during the IB_AUR positions prediction on the operations planning stage, but it is possible to avoid this error during such calculations for the next stage, connected with the scientific data processing. It was done via the orbital elements of the "Version 2"

  • For the "Version 2" orbital elements constructing the backward in time integration was fulfilled at IKI on the base of the the orbital elements "Version 1". For each epoche Tn the new state vector was obtained by integration from the old state vector, corresponding to the epoch Tn+1.
    The resulting modified orbital elements are valid to use for the standard scheme of the forward integration on the time interval Tn - Tn+1 with accuracy not worth then one obtained during orbit determination (with RMS error 30-40 km).
    "Version2" orbital elements ware used for all aposteriori orbital calculations presented up to now in the IKI servers and

  • The last orbital elements collection "Version 3" is a result of the post-flight reconstruction of the orbit fulfilled in the Ballistic Center of the Keldysh Institute of Applied Mathematics (KIAM) of Russian Academy of Sciences. This work was based on the statistical processing of the complete information related to the trajectory measurements summarised with the information concerning the spacecraft (SC) reorientation moments. The non-gravitational accelerations generated by the work of the attitude control system were taken into consideration.
    The root-mean-square (RMS) error of the SC position determination inside the measuring intervals is about 2-3 km (till 20 km on some sections of the orbit).

In all mentioned collections the orbital elements are presented in the same format F1, as a state vectors (the satellite position and velocity) in the inertial frame (Standard reference of the Earth's equator and Equinox J2000).

Dr. Victoria Prokhorenko
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Last modified 8 January 2000