Temporal Analysis of Envisat’s Rotational Motion

S. Sommer et al. (2017), JBIS, 70, pp.45-51

Refcode: 2017.70.45

Abstract:
The Earth-observing satellite ENVISAT failed in April 2012 and orbits with an uncontrolled attitude. In order to remove ENVISAT from space in a potential de-orbiting mission, the attitude state of the satellite has to be known. We present attitude estimations using ISAR images obtained with the Tracking and Imaging Radar (TIRA) during 2011 – 2017. By matching wire grid models to the 2D ISAR images, the rotation vector can be estimated. After loss of contact, the spin period of ENVISAT decreased and reached the minimum in 2013. Since then, the spin period increased by (75.0 ± 0.9) ms d^-1 and reached 226 s in March 2017. An analysis of the rotation axis shows, that ENVISAT tumbles, where the rotation axis describes a nutation with a cone opening of about 80°.