International Telemetering Conference Proceedings / October 28-31, 1996 / Town and Country Hotel and Convention Center, San Diego, California / This paper reviews the performance requirements that provided the baseline for development of the onboard data system, RF transmission system, and ground segment receiving system of the Midcourse Space Experiment (MSX) spacecraft. The onboard Command and Data Handling (C&DH) System was designed to support the high data outputs of the three imaging sensor systems onboard the spacecraft and the requirement for large volumes of data storage. Because of the high data rates, it was necessary to construct a dedicated X-band ground receiver system at The Johns Hopkins University Applied Physics Laboratory (APL) and implement a tape recorder system for recording and downlinking sensor and spacecraft data. The system uses two onboard tape recorders to provide redundancy and backup capabilities. The storage capability of each tape recorder is 54 gigabits. The MSX C&DH System can record data at 25 Mbps or 5 Mbps. To meet the redundancy requirements of the high-priority experiments, the data can also be recorded in parallel on both tape recorders. To provide longer onboard recording, the data can also be recorded serially on the two recorders. The reproduce (playback) mode is at 25 Mbps. A unique requirement of the C&DH System is to multiplex and commutate the different output rates of the sensors and housekeeping signals into a common data stream for recording. The system also supports 1-Mbps real-time sensor data and 16-kbps real-time housekeeping data transmission to the dedicated ground site and through the U.S. Air Force Satellite Control Network ground stations. The primary ground receiving site for the telemetry is the MSX Tracking System (MTS) at APL. A dedicated 10-m X-band antenna is used to track the satellite during overhead passes and acquire the 25-Mbps telemetry downlinks, along with the 1-Mbps and 16-kbps real-time transmissions. This paper discusses some of the key technology trade-offs that were made in the design of the system to meet requirements for reliability, performance, and development schedule. It also presents some of the lessons learned during development and the impact these lessons will have on development of future systems.

La Polymérisation Radicalaire par Ouverture de Cycle (R-ROP) est une méthode de synthèse de polymères contenant des fonctions chimiques de choix dans le squelette carboné grâce à un mécanisme d'addition-fragmentation. L'utilisation de monomères spécifiques, les Acétals Cétènes Cycliques (CKA), permet dans certaines conditions l'obtention de polyesters aliphatiques dont la propriété de (bio)dégradation présente de nombreuses applications. Cette méthode relativement peu étudiée depuis les années 1980 présente un fort potentiel mais également de nombreuses limites. Ce travail de thèse a consisté à comprendre l'origine de ces limites pour tenter d'y apporter des solutions, grâce à une approche combinée expérience-théorie.Nous avons montré que l'obtention exclusive de polyesters découle d'une compétition cinétique et que le comportement des différents monomères s'explique par des interactions orbitalaires dépendant de la géométrie, la flexibilité et la substitution des cycles. D'autre part, nous avons mis en évidence l'extrême difficulté de propagation des monomères propageant via des radicaux stabilisés par des cycles aromatiques. Cette faible réactivité inhérente à la double liaison riche en électrons des CKA est également la cause de l'incorporation restreinte des monomères cycliques en copolymérisation avec des monomères vinyliques usuels. La rationalisation de la copolymérisation a été mise à profit pour réaliser des copolymérisations de type statistique et alternée. Enfin, l'étude du contrôle de la R-ROP par les nitroxydes a montré la présence de réactions secondaires propres à ce système et permettant actuellement un contrôle partiel de la polymérisation. / The Radical Ring-Opening Polymerization (R-ROP) is a synthetic pathway to introduce chemical functions into a polymer backbone due to an addition-fragmentation mechanism. Using specific monomers like Cyclic Ketene Acetals (CKA) in the right conditions allows preparing aliphatic polyesters which have numerous applications thanks to their (bio)degradability. This method has been quite faintly investigated since the 1980s and even if it has a great potential, it suffers of numerous limitations. This PhD work consisted in the understanding of those limitations to try bringing solutions to them, with a combined approach of experiments and theory.We first demonstrated that the exclusive preparation of polyesters comes from a kinetic competition. The behavior of the distinct monomers is explained by orbital interactions depending on the geometry, flexibility and substitution of the cycles. Then, we highlighted the extremely difficult propagation of the monomers propagating with stabilized aromatic radicals. This low reactivity inherent to the electron-rich double link of the CKAs is also the cause of low polyester introduction during the copolymerization with usual vinyl monomers. We took advantage of the CKA copolymerization rationalization to realize statistical and alternate copolymerizations. At last, the study of the nitroxide mediated R-ROP demonstrated the occurrence of side reactions characteristic of this system that allow at present a partial control of the polymerization.

The large amount of non-degradable plastic waste has become a significant environmental concern, leading to an increased need for degradable plastics. Here in, to create degradable polymers, polyesters were produced through radical ring opening polymerization using cyclic ketene acetals. The cyclic ketene acetal monomer 5,6-benzo-2-methylene-1,3-dioxepane has been prepared for the synthesis of homo- and copolymers with methyl methacrylate, α-methylene-γ-valerolactone, α-methylene-γ-butyrolactone, cholesterol methacrylate and limonene acrylate. The polymerization was conducted using radical ring opening polymerization both in bulk and solution polymerization. The structural characteristics of the polymer were determined by different characterization methodologies, including TGA, DSC, SEC, FTIR and 1D 1H-NMR. The results obtained from 1H-NMR analysis showed the composition of the copolymers. TGA analysis revealed the thermal stability of the polymers and their degradation patterns. DSC analysis provided information about the glass transition temperatures (Tg’s) of the polymers. Moreover, the Tg indicated the presence and amounts of comonomers in the copolymers. Overall, the results showed the influence of different comonomers on the properties of the polymers by successfully incorporating the comonomers in the polymer. The thermal properties for polymers containing methyl methacrylate became more thermally stable. The Tg, analyzed with DSC, shifted from the Tg of homopolymers indicating the incorporation of both monomers. The polymers were successfully degraded via hydrolysis in alkaline conditions breaking them down into smaller pieces making them easier to recycle. To conclude, the results all indicate that the incorporation of BMDO and thereby possibly other CKA-monomers into the polymer chains of commonly used plastics could provide valuable tools in the recycling of said plastics.