The lightcurve inversion technique is used to find an object's rotation period, its shape and spin-axis orientation. It requires the availability of multi-epoch and multi-apparition lightcurve measurements in sufficient quality.

The field of spin and shape modelling of asteroids has seen a huge development in recent years. Since the lightcurve inversion technique (Kaasalainen & Torppa 2001; Kaasalainen at al. 2001) introduction at the beginning of the last decade, over 400 spin and shape models have been published (e.g. Hanus at al. 2013; Marciniak et al. 2012) and first attempts of multi-data inversion have been made (KOALA code, Carry et al. 2012; ADAM algorithm, Viikinkoski et al. 2015). Previously obtained shape models have also been size-scaled using data from stellar occultations (Durech et al. 2011). In this way, it was shown that many inversion solutions fit the data from independent methods. It has also been demonstrated recently, that lightcurves alone contain enough information for reliable non-convex modelling (the SAGE algorithm, Bartczak et al. 2014). Today, with many types of complementary data, there is a possibility to join different kinds of data for full physical models of asteroids, which would be an invaluable cornerstone for calibration of various methods and extrapolating gained knowledge to the whole range of objects, with less rich datasets available. For example with thermal data we see emission influenced by the thermal inertia of the surface and also sub-surface emission at submm/mm wavelengths, which makes a direct comparison with optical lightcurves more complex. Thermal data also bear contributions from non-illuminated, yet warm part of the surface. But if the relation of the two types of data was known on the basis of a few well-studied objects, then we would gain a tool with great potential to infer information on albedo, size, spin, thermal inertia, and large-scale surface and regolith properties. Physical properties of asteroid surfaces are the missing link in e.g. YORP effect modelling, which has been shown to change the spin frequencies and spin axis positions of small and medium-sized asteroids (Vokrouhlicky et al. 2003). However, widely applicable spin and shape modelling technique based on such varied sources (optical and thermal data) of data is still missing. Thus we are going to address these issues in the present project. This way we will prepare strong foundations for further studies of whole range of asteroid physical properties.

Shape models for two components of the binary asteroid (90) Antiope obtained with the inversion of lightcurves using the SAGE algorithm for non-convex shapes (Bartczak et al. 2014). An equatorial (left image) and polar (right image) views of the system are shown.