Small-sat Platforms and Formation Flying : an opportunity for the gamma ray telescope MAX

Paper number

IAC-05-B5.2.06

Author

Mr. Jacques Borde, EADS Astrium, France

Coauthor

Dr. Peter Von Ballmoos, Centre d Etude Spatiale des Rayonnements (CESR - CNRS/UPS), France

Coauthor

Mr. Raymond Soumagne, Centre National d'Etudes Spatiales (CNES), France

Coauthor

Mr. Regnier Pascal, EADS Astrium, France

Year

2005

Abstract

This paper presents the results of a study performed by EADS Astrium in support to the Centre d’Etude Spatiale des Rayonnements (CESR, Toulouse, France) for the preliminary definition of the MAX space segment, based on a small-sat platform in the 200 kg range.

MAX is a new concept of gamma ray telescope with as prime objective the study of type Ia supernovae by measuring intensities, shifts and shapes of their nuclear gamma-ray lines. When finally understood and calibrated, these profoundly radioactive events will be crucial in measuring the size, shape, and age of the Universe.

The concept of MAX is radically different from the traditional gamma ray telescopes: gamma rays are focussed from the large collecting area of a crystal diffraction lens on a very small detector volume. Thus, the implementation of the MAX space mission consists in flying a lens-detector duo satellites in an active Formation Flying geometry. The lens satellite is kept inertial and pointing to the gamma ray source with an accuracy of 15 arcsec, while the detector satellite is controlled in position and attitude with respect to the lens at a constant distance of 86 m, within an accuracy of 1 cm in lateral and 10 cm in longitudinal.

This paper discusses and trades-off the various complex technical challenges of the MAX mission: GNC (Guidance Navigation Control) algorithms for the deployment, initialisation and control of the lens-detector geometry, accurate pointing of the lens to the gamma ray sources, definition and accommodation of the optical  metrology, mechanical and thermal accommodation of the 8200-crystal lens, fine attitude/position actuators sizing, FDIR (Failure Detection Isolation and Recovery) and collision avoidance algorithms.

This paper depicts a baseline mission derived from these analyses and provides a preliminary definition of the space segment. It relies on a 200 kg class platform for a launch envisaged in 2012.

The large experience gained by EADS Astrium in the GNC and optical metrology domains through numerous ESA and CNES studies and internal funding, allows the definition of the Formation Flying Payload (composed of RF and optical metrology and cold gas thrusters) that fulfills the requirements of the MAX mission with margins. Therefore, beyond its scientific interest for nuclear astrophysics, MAX is a good opportunity for demonstrating Formation Flying concepts and technologies in space.

The scientific payload composed of the lens and the detector is also described. Especially, the manufacturing and accommodation of the lens on one satellite, and the detector on the second satellite are analysed.

Abstract document

IAC-05-B5.2.06.pdf

Manuscript document

IAC-05-B5.2.06.pdf (🔒 authorized access only).

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