A New, Single Diode, Sequential Switching Shunt Regulator

This paper describes the design improvement of a Sequential Shunt Switching Regulator (S3R) based on a power cell composed of one switching FET and one Diode connecting the Solar Array (SA) section to the Main Bus. This topology allows to minimize the S3R cells dimensions, to optimize the efficiency figures and complies with the electrical Single Point Failure Free (SPFF) requirement on the Main Bus. The single switching FET can cause the loss of one Solar array section if it fails in short circuit, while its failure in open can be compensated by the presence of one additional (spare) shunt section positioned on Main Bus to drain the power eventually in excess. If the series redundancy of the Diode is removed, its failure in short circuit, causes overload on the Main Bus when the switching FET turns ON. To avoid the possible subsequent failure in short circuit of the switching FET due to over-heating, with permanent loss of Main Bus, the maximum current drawn by the FET in failure condition and the duration of this operation mode must be strictly controlled in order to avoid thermal overstress and consequently thermal failure propagation. The adopted solution foresees a circuitry that controls the current in the FET, both the peak in the first transient and the subsequent limited value, and forces the FET in permanent open status after a short period, compatible with the overheat of the FET junction. No spurious cause leads to the permanent loss of the S3R section due to permanent activation of the protection, causing the switching element (FET) to be continuously open. In fact a dedicated circuit, activated by sensing of the Error Signal, unlatches the section to restore the power control. The presented design has found its first application in the PCDU for the COSMO-SkyMed Second Generation (CSG) satellite power system. A dedicated Elegant Bread Board of the S3R, integrated with the board designed to control the Battery Current and Voltage has been tested in the design and development plan of CSG PCDU

A New, Single Diode, Sequential Switching Shunt Regulator

This paper describes the design improvement of a Sequential Shunt Switching Regulator (S3R) based on a power cell composed of one switching FET and one Diode connecting the Solar Array (SA) section to the Main Bus. This topology allows to minimize the S3R cells dimensions, to optimize the efficiency figures and complies with the electrical Single Point Failure Free (SPFF) requirement on the Main Bus. The single switching FET can cause the loss of one Solar array section if it fails in short circuit, while its failure in open can be compensated by the presence of one additional (spare) shunt section positioned on Main Bus to drain the power eventually in excess. If the series redundancy of the Diode is removed, its failure in short circuit, causes overload on the Main Bus when the switching FET turns ON. To avoid the possible subsequent failure in short circuit of the switching FET due to over-heating, with permanent loss of Main Bus, the maximum current drawn by the FET in failure condition and the duration of this operation mode must be strictly controlled in order to avoid thermal overstress and consequently thermal failure propagation. The adopted solution foresees a circuitry that controls the current in the FET, both the peak in the first transient and the subsequent limited value, and forces the FET in permanent open status after a short period, compatible with the overheat of the FET junction. No spurious cause leads to the permanent loss of the S3R section due to permanent activation of the protection, causing the switching element (FET) to be continuously open. In fact a dedicated circuit, activated by sensing of the Error Signal, unlatches the section to restore the power control. The presented design has found its first application in the PCDU for the COSMO-SkyMed Second Generation (CSG) satellite power system. A dedicated Elegant Bread Board of the S3R, integrated with the board designed to control the Battery Current and Voltage has been tested in the design and development plan of CSG PCDU

A New, Single Diode, Sequential Switching Shunt Regulator

This paper describes the design improvement of a Sequential Shunt Switching Regulator (S3R) based on a power cell composed of one switching FET and one Diode connecting the Solar Array (SA) section to the Main Bus. This topology allows to minimize the S3R cells dimensions, to optimize the efficiency figures and complies with the electrical Single Point Failure Free (SPFF) requirement on the Main Bus. The single switching FET can cause the loss of one Solar array section if it fails in short circuit, while its failure in open can be compensated by the presence of one additional (spare) shunt section positioned on Main Bus to drain the power eventually in excess. If the series redundancy of the Diode is removed, its failure in short circuit, causes overload on the Main Bus when the switching FET turns ON. To avoid the possible subsequent failure in short circuit of the switching FET due to over-heating, with permanent loss of Main Bus, the maximum current drawn by the FET in failure condition and the duration of this operation mode must be strictly controlled in order to avoid thermal overstress and consequently thermal failure propagation. The adopted solution foresees a circuitry that controls the current in the FET, both the peak in the first transient and the subsequent limited value, and forces the FET in permanent open status after a short period, compatible with the overheat of the FET junction. No spurious cause leads to the permanent loss of the S3R section due to permanent activation of the protection, causing the switching element (FET) to be continuously open. In fact a dedicated circuit, activated by sensing of the Error Signal, unlatches the section to restore the power control. The presented design has found its first application in the PCDU for the COSMO-SkyMed Second Generation (CSG) satellite power system. A dedicated Elegant Bread Board of the S3R, integrated with the board designed to control the Battery Current and Voltage has been tested in the design and development plan of CSG PCDU

The Cosmo-Skymed Second Generation Sar Antenna Electrical Power Chain and Platform Power Distribution

This paper presents the Electrical power Subsystem (EPS) of the COSMO-SKYMED SECOND GENERATION (CSG) spacecraft, regarding the design and development of the electronics for power generation, conditioning and distribution. It provides a detailed description of the power equipment’s and of the Photovoltaic Assembly (PVA). It will be also shown how the design of the power conditioning and distribution electronics has taken advantage of the Leonardo (former Finmeccanica) heritage on Power Management and Distribution (PMD) for scientific platforms [1], [3]. The design characteristics of the EPS elements are described. A summary of the main performances is given, including a glance to the EMC aspects, which are very important in the definition and characterization of the design of a high power SAR system

The Cosmo-Skymed Second Generation Sar Antenna Electrical Power Chain and Platform Power Distribution

This paper presents the Electrical power Subsystem (EPS) of the COSMO-SKYMED SECOND GENERATION (CSG) spacecraft, regarding the design and development of the electronics for power generation, conditioning and distribution. It provides a detailed description of the power equipment’s and of the Photovoltaic Assembly (PVA). It will be also shown how the design of the power conditioning and distribution electronics has taken advantage of the Leonardo (former Finmeccanica) heritage on Power Management and Distribution (PMD) for scientific platforms [1], [3]. The design characteristics of the EPS elements are described. A summary of the main performances is given, including a glance to the EMC aspects, which are very important in the definition and characterization of the design of a high power SAR system

Interferometric Missions: Applications within ASI Space Programs

The Italian Space Agency (ASI), together with Ministry of Defence (I-AD), is involved in the realization of the COSMO-Skymed program that foresees the deployment of a constellation of 4 SAR satellites in Low Earth Orbit, dedicated to the management, control and exploitation of Earth resources for civilian and defence applications. ASI is responsible for the definition, implementation and management of the Program, while Alcatel Alenia Space Italia is the Prime Contractor responsible for the design, development and verification of the entire system. The nominal phasing of the satellites on the orbit plane has been selected in order to achieve the optimisation of the performance in terms of accessibility and revisit time w.r.t. the number of satellites. Moreover COSMO-SkyMed system is able to perform interferometric acquisitions, which yield three dimensional images and/or provide various information on land conformation change, subsidence, land-slides and so on. Then, periodically, one of the four satellites will be moved to a fixed distance with respect to another for reaching the interferometric configuration. In order to increase the operating capacity of the COSMO-Skymed system, ASI intends to start the definition of a complementary civilian program with the purpose of covering bi-static and across-track/along-across interferometry applications. Such a mission will be referred as “SABRINA”, acronym of “System for Advanced Bistatic and Radar INterferometry Applications”, based on the use of a “passive” satellite (“BISSAT”, acronym for “Bistatic and Interferometric SAR SATellite”). This satellite will fly in formation with COSMO-Skymed and then a suitable strategy shall be determined for reaching and maintaining the interferometric configuration. The paper will describe the manoeuvre strategies necessary for reaching the interferometric configuration, both for COSMO-Skymed and for BISSAT. Such strategies have been defined taking into account all the constraints coming from the satellite (Δv size, minimum interval time between two consecutive manoeuvres, propulsion S/S performance, AOC requirements). After the description of the manoeuvres requested for achieving the interferometric configurations foreseen for COSMO-Skymed (tandem and “tandem-like”), the paper will focus on the configuration requested for the BISSAT satellite for flying in formation with a single COSMO-SkyMed satellite. Two formation configurations will be selected: pendulum or cartwheel. The mission will carry out interferometric acquisitions in the following configurations: 1. Across track interferometry 2. Along track interferometry The mission will carry out bistatic acquisition multi-angle and multi-polarization with a baseline variable in the range 100-500 km