Deployment requirements for deorbiting electrodynamic tether technology

In the last decades, green deorbiting technologies have begun to be investigated and have raised a great interest in the space community. Among the others, electrodynamic tethers appear to be a promising option. By interacting with the surrounding ionosphere, electrodynamic tethers generate a drag Lorentz force to decrease the orbit altitude of the satellite, causing its re-entry in the atmosphere without using propellant. In this work, the requirements that drive the design of the deployment mechanism proposed for the H2020 Project E.T.PACK—Electrodynamic Tether Technology for Passive Consumable-less Deorbit Kit—are presented and discussed. Additionally, this work presents the synthesis of the reference profiles used by the motor of the deployer to make the tethered system reach the desired final conditions. The result is a strategy for deploying electrodynamic tape-shaped tethers used for deorbiting satellites at the end of their operational life.Open Access funding provided by Università degli Studi di Padova. This work was supported by European Union’s H2020 Research and Innovation Programme under Grant Agreement No. 828902 (E.T.PACK Project). Gonzalo Sánchez-Arriaga's work is supported by the Ministerio de Ciencia, Innovación y Universidades of Spain under the Grant RYC-2014-15357

Multi-functional interface for flexibility and reconfigurability of future European space robotic systems

The capabilities of maximising standard payload modules’ functionalities for applications such as on-orbit satellite servicing or planetary exploration depend critically on the creation and availability of a standard interface (IF). Standard interface should provide, aside from the necessary mechanical interconnections, electrical power and data connections, as well as thermal transfer between “building block” payload modules. The overall flexibility enabled by such IF will allow endless reconfigurations of payload and other modules for different functional requirements. This can be considered a game changer technology, enabling transformation from the current approach to space missions, deploying single-use system with pre-planned and limited functionalities, to a radically new approach with multi-use, dynamically reconfigurable and multi-functional systems. Hence, SIROM aims to set a new research agenda for future affordable space missions. Within this context, the partners of the SIROM (Standard Interface for Robotic Manipulation of payloads in future space missions) project are developing the first standard IF solution that combines the four required functionalities in an integrated and compact form for future space missions. With a mass lower than 1.5 kg and having an external diameter of 120 mm and a height of 30 mm, this novel interface permits not only mechanical coupling but also electrical, data and thermal connectivity between so called Active Payload Modules (APMs), as well as other modules such as the robotic end-effectors. This multi-functional IF features an androgynous design to allow for replacement and reconfiguration of the individual modules in any combination desired. It consists of the following sub-assemblies: mechanical IF, electrical IF, data IF, thermal IF and IF controller. A clear advantage of SIROM design is that its mechanical IF consists of a latching and guiding systems for misalignment correction, capable of withstanding certain robotic arm positioning inaccuracies: ± 5 mm translation and ± 1.5° rotation in all axes. Regarding the electrical and data IFs, SIROM transfers up to 150 W electrical power and provides a data transfer rate of 100 Mbit/s via SpaceWire, plus command communication with speeds up to 1Mbit/s via CAN bus. The thermal IF provides fluidic ports for flow transfer and has the potential to transfer 2500 W between APMs accordingly provided with the corresponding close-loop heat exchange system. Although not envisaged for SIROM current design, a possible variation could be to use these ports for satellite re-fuelling. Apart from that, SIROM exhibits redundant coupling capabilities: it can match and couple another completely passive SIROM. It is provided with main and redundant connectors for thermal, electrical, data and control flow in case of one of the lines fails. All in all, SIROM will enable long duration missions with no logistic support, refurbishing, maintenance and reconfiguration of satellites, cost efficiency and simplification of the tool exchange in scientific exploration missions. SIROM is designed to be a common building block for European and possibly world future space robotics enabled missions

Characterization of topoisomerase II α and minichromosome maintenance protein 2 expression in anal carcinoma

The present study aimed to ascertain the significance of topoisomerase II alpha (TOP2A) and minichromosome maintenance protein (MCM) 2 expression in anal carcinoma. A total of 75 anal lesions were retrieved from the files of the Department of Pathology of Barretos Cancer Hospital (Barretos, Brazil) in order to verify the human papillomavirus (HPV) statuses of these lesions and characterize the immunohistochemical expression levels of TOP2A and MCM2 in anal carcinoma, as these are important markers for cervical HPV-induced lesions; their expression was also compared with respect to p16 and Ki-67. The vast majority of the cases tested positive for HPV16 (84%); 1 case tested positive for both HPV16 and HPV18. Positive HPV16 status was more frequent in early stages than in advanced stages (P=0.008). Positive immunohistochemical reactivity for MCM2 and TOP2A protein was observed in 71.6 and 100% of cases, respectively. Positive reactivity for p16 was significantly associated (P=0.001) with histological grade, and was more commonly expressed in squamous cell carcinoma than adenocarcinomas. HPV16 was strongly associated with positive p16 protein expression (76.6%). However, the high expression of Ki-67 combined with the high expression of p16 was predominantly observed in Stage III-IV cases. MCM2, TOP2A, p16 and Ki-67 exhibited intense positive staining in the anal lesions, indicating that these markers were significantly and constantly expressed in anal carcinoma.info:eu-repo/semantics/publishedVersio

Low work-function tether Deorbit Kit

This works presents a system level analysis of a Deorbit Kit (DK) based on electrodynamic tether technology. The analysis is focused on two relevant scenarios for deorbiting space debris: (i) Earth Observation (EO) satellites with mass in the range of 700 kg -1000 kg and initial orbital altitude of 800 km and 98° inclination, and (ii) Mega Constellation (MC) spacecraft in the order of 200 kg and initial orbit at 1200 km of altitude and 90° of inclination. The scenarios have been selected considering the orbits that are already suffering from the space debris problem or will suffer in the next future. The DK implements a bare electrodynamic tether for capturing electrons passively from the ambient plasma while three different methods are considered for emitting the electrons back to the plasma to reach a steady electrical current on the tether. The three studied options to close the electrical circuit are: (a) a hollow cathode, which has a high technological maturity but needs expellant and a little of power, (b) a thermionic emitter, which does not involve expellant but needs power, and (c) a Low Work-function Tether (LWT) that does not need neither expellant nor power because it has a segment coated with a special material that emits electrons passively through the thermionic and photoelectric effects. In order to provide a fully autonomous operation even in case of critical failure of the mother spacecraft, the DK includes a deployment mechanism, a telemetry and telecommand system, a complete Attitude Determination and Control System with attitude sensors (GNSS, sun sensors, magnetometer) and actuators (magneto torquers), solar panels and batteries. Upon activation, the DK autonomously de-tumbles the satellite, deploys a tether and carries out the satellite's de-orbiting. The study presents DK architectures, mass budgets and simulation results for the two scenarios. It is shown that a complete DK with mass below 6% the mass of the host spacecraft can deorbit EO and MC satellites in about 1.5 years and 10 years, respectively. The importance of the development of the LWT concept to enhance the simplicity and reduce the mass, power and volume budget is highlighted.This work was supported by the European Union's Horizon 2020 Research and Innovation Programme under grant agreement No.828902 (E.T.PACK project). GSA work is supported by the Ministerio de Ciencia, Innovación y Universidades of Spain under the Grant RYC-2014-15357