Spin motion determination of the Envisat satellite through laser ranging measurements from a single pass measured by a single station

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◦.

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Temporal analysis of Envisat&#039;s rotational motion

An estimation of Envisat’s rotational state accounting for the precession of its rotational axis caused by gravity-gradient torque☆

This work will discuss an ESA project “Debris Attitude Motion Measurements and Modeling” (ESA AO/1-7803/14/D/SR) dedicated to the attitude determination of large spacecraft and upper stages. Two major goals are defined for this project. First, the determination of the attitude motion vector in case of a contingency situation, when a short response time is required between the observations themselves and the attitude determination. The second goal is the long term prediction (e.g. 10 years) of the spin rate of selected targets for future potential Active Debris Removal (ADR) missions. The study should in particular fuse the results from passive optical, laser ranging and radar observations. We will discuss a highly modular software tool named ιOTA (In-Orbit Tumbling Analysis) which was 
developed during the presented activity. This tool performs short- (days) to long-term (years) propagations of the orbit and the attitude motion of spacecraft in 
Earth orbit and furthermore its post-processing modules will generate synthetic measurements, i.e. light curves, satellite laser ranging (SLR) residuals and synthet
ic radar images. Last but not least we will present results from a collaborative campaign when four priority targets have been selected for collaborative measurements with radar, SLR and light curves in order to test and validate the ΙOTA tool.

/pdf/debris-attitude-motion-measurements-and-modelling-by-3cihyprnsa.pdf

Debris Attitude Motion Measurements and Modelling by Combining Different Observation Techniques

Analysis of laser ranges and angular measurements data fusion for space debris orbit determination

The Astronomic Institute of the University of Bern (AIUB) in cooperation with other three partners is involved in an ESA study dedicated to the attitude determination of large spacecraft and upper stages. Two major goals are defined. First is the long term prediction of tumbling rates (e.g. 10 years) for selected targets for the future Active Debris Removal (ADR) missions. Second goal is the attitude state determination in case of contingencies, when a short response time is required between the observations themselves and the attitude determination. One of the project consortium partners, hypersonic Technology Goettingen (HTG), is developing a highly modular software tool ιOTA to perform short- (days) to long-term (years) propagations of the orbit and the attitude motion of spacecraft in space. Furthermore, 
ιOTA's post-processing modules will generate synthetic measurements, e.g. light curves, SLR residuals and Inverse Synthetic Aperture Radar (ISAR) images that can be compared with the real measurements. In our work we will present the first attempt to compare real measurements with synthetic measurements in order to estimate the attitude state of tumbling satellite E
NVISAT from observations performed by AIUB. We will shortly discuss the ESA project and ιOTA software tool. We will present AIUB’s ENVISAT attitude state determined from the SLR ranges acquired by the Zimmerwald SLR stati
on. This state was used as the initial conditions within the ιOTA software. Consequently the attitude of satellite was predicted by using ιOTA and compared with the real SLR residuals, as well with the high frame-rate light curves acquired by the Zimmerwald 1-m telescope.

Dominik Bodenmann

Papers

Comparison of ENVISAT’s attitude simulation and real optical and SLR observations in order to refine the satellite attitude model