A new model to predict Ajisai satellite reflected sunlight flashes and application to the determination of its rotation parameters.

• Study of the Ajisai satellite rotation from sequences of flashes generated by sunlight reflected by its curved mirror. • A model capable of reproducing the observed sequence of flashes considering mirrors curvature. • Determination of the satellite rotation parameters (spin axis, rotation period, rotation angle). In this paper, we propose a model reproducing the sequences of flashes emitted by the Ajisai satellite by reflection of the sunlight on the mirrors all around its surface and received by an observing station. A decisive novelty was added by introducing the curvature of the mirrors, that allows the reconstruction of the observed light curve given the attitude of the satellite. Measurements of the Ajisai’s light flux have been acquired using a high frequency (5/10 kHz) linear-detection optical photometry technique from the MéO telescope at Grasse station on the Plateau de Calern site of Observatoire de la Côte d’Azur. A procedure to extract individual flashes from the observed flux and identify the associated mirror on which the reflection occurred has been developed. The analysis of the observed flashes confirmed the validity of the model and allowed us to reconstruct the attitude of the satellite. The satellite rotation has been expressed as a function of the rotation spin axis, the rotation period and the rotation angle around the axis. A method to determine each parameter directly from single pass observations is proposed to fully constrain the satellite attitude using photometry. A precise knowledge of the attitude of the satellite is essential to enable future interesting developments, among others, improving the precision of the synchronization of distant clocks by means of laser links involving Ajisai.