APPARENT COLOURS AS MANIFACTURING MARKERS FOR GEO SATELLITES

Alessandra Di Cecco(1), Alberto Buzzoni(2), Maddalena Mochi(3), Giuseppe Altavilla(4,5), Sara Brambilla(6), Marco Castronuovo(1), Fiore De Luise(7), Silvia Galleti(2), José Guichard(8), Cosimo Marzo(1), Gaetano Valentini(7),

(1) ASI, Italian Space Agency, via del Politecnico snc, Rome, IT

(2) INAF-OAS, via Gobetti 93/3, Bologna, IT

(3) Università degli Studi di Pisa, Largo Pontecorvo, Pisa, IT

(4) SSDC-ASI, via del Politecnico snc, Rome, IT

(5) INAF-OAR, Via Frascati 33, Monte Porzio Catone (RM), IT

(6) Aero Club Monte Comizzolo, Via San Miro 10, Suello (LC), IT

(7) INAF-OAAB, via Mentore Maggini snc, Teramo, IT

(8) INAOE, L.E. Erro 1, Tonantzintla, Puebla, 72840 (México)

alessandra.dicecco@asi.it

Abstract. We present a multi-band photometric analysis of GEO satellites, observed by using three optical telescopes in different observational sites. Our dataset consists of more than 1,200 scientific images acquired in the BVRI Johnson-Cousin filters. The observational strategy we adopted is based on alternating the filter-sequence, thus obtaining consecutive multi-band images, in order to reduce the color-indexes uncertainty. By using the color-color planes we investigated possible correlations between photometric colors and the satellites' structural features, obtaining that some of the considered parameters seem to significantly affect the color indexes.

Keywords: Photometry, GEO satellite

Introduction

Space debris pose a significant risk for operational satellites, astronauts and new launches, as well as for uncontrolled re-entry in the Earth’s atmosphere. The observational and tracking activities of space debris are currently on-going worldwide. Among different techniques used to characterize these objects, the multi-band photometry is a powerful tool for investigating their physical parameters (surface materials, shape, etc). Interesting results have been obtained by Schmitt 2020, Cowardin et al. 2010, Schildcknet et al. 2008. Following, we present a photometric analysis.

Observations and data analysis

We observe 23 GEO satellites from three different observational sites. In particular, the Cassini-Loiano and Teramo Normale Telescope are located in Italy and belong to the National Institute for Astrophysics (INAF), while the third telescope belongs to the Guillermo Haro Astrophysical Observatory (GHAO) located in Cananea, Mexico.
The entire dataset consist of more than 1,200 images acquired in the Johnson-Cousin BVRI filters. Bias, dark current and flat-field frames, as well as Landolt’s standard fields were also acquired for calibration process. We reduced the data by using the DAOPHOT software. By using VRI filter-sequence, we reconstructed the lightcurves for each GEO satellite in our sample (Fig.1, left). Moreover, we reconstructed the color-lightcurves by calculating the difference between two consecutive frames, and we estimated the mean color-index as the average value of the color-lightcurve. The obtained values were investigated through color-color planes (Fig. 1, right), where a search for possible correlations with the structural features (retrieved from the web) of the bus and model of each satellite is underway, showing promising results.

Fig. 1. Left: Light-curves obtained for the ASTRA 2F GEO satellite. Right: Subset of our sample in the V-I vs V-R color color plane, tagged with the satellites’ names and colored according to their bus family.

Conclusions.

We studied the photometric properties of GEO satellites by comparing observational color-indexes with different satellite structural parameters. Preliminary results suggest a possible correlation between some of the considered features (i.e. bus, model, etc) and photometric colors (V-I, V-R). However, before to impose firm conclusions several investigations are still required.

References

Cowardin, H. et al. 2010, Proceedings of the Advanced Maui Optical and Space Surveillance Technologies Conference, held in Wailea, Maui, Hawaii, September 14-17, 2010, Ed.: S. Ryan, The Maui Economic Development Board

Schmitt, H. R., 2020, Advances in Space Research 65, 326–336

Schildknecht, T. et al. 2008, Proceedings of the International Astronautical Congress, A6.1.4, Glasgow, Scotland, Great Britain, 29 Sep–3 October