Planck is a scientific satellite that represents the next milestone in space-based research related to the cosmic microwave background, and in many other astrophysical fields. Planck was launched on 14 May of 2009 and is now operational. The uncertainty in the optical response of its detectors is a key factor allowing Planck to achieve its scientific objectives. More than a decade of analysis and measurements have gone into achieving the required performances. In this paper, we describe the main aspects of the Planck optics that are relevant to science, and the estimated in-flight performance, based on the knowledge available at the time of launch. We also briefly describe the impact of the major systematic effects of optical origin, and the concept of in-flight optical calibration. Detailed discussions of related areas are provided in accompanying papers.

No abstract

Abstract-We present an in depth look at the challenges involved in using analogue retrodirective arrays for satellite communications. The main technical issues surrounding the development of a retrodirective (self-steering) Satellite Communications (SATCOM) system are given and techniques for mitigating these issues provided. Detailed results are given for a prototype high performance circularly polarized retrodirective array architecture suitable for mounting on an un-stabilized mobile platform. The paper concludes with practical retrodirective L-band array results with the array used to acquire actual broadband satellite data signals from a commercial L-band satellite system. Received satellite signals as low as -130dBm at the antenna elements are tracked. Accurate self-tracking occurs over the azimuth range of up to ± ± ± ±40°°°°.

This article investigates the potential of additive manufacturing for the fabrication of complex antenna geometries with enhanced performance at K-band. Stereolithography is here used to 3D-print a novel topology of dual-polarized leaky-wave antenna that allows for the control of its aperture illumination both in phase and magnitude. The antenna consists of a modulated triple-ridge square waveguide perforated on its top wall with crossed slots of different sizes. An orthomodetransducer is integrated within the structure for dual-mode operation. Monolithic implementation of this compound threedimensional structure is only possible thanks to additive manufacturing. In addition, low weight and compactness are attained comparing to classical milling. The present proposal is validated through the manufacturing of a low sidelobe levels prototype suitable for intersatellite links. The corresponding measured results are in very good agreement with full-wave predictions.

No abstract