Ultra-stable frequency and time sources play an important role in many modern applications, such as high-speed data transmission, time keeping, space navigation, and geodesy, and in supporting key elements of basic research in space. The areas covered by this topic include techniques and technologies for the generation, transfer and comparison of ultra-stable time/frequency signals, in both the RF/Microwave domain and in the optical domain (for dedicated payload without optical communications function).

- Time and Frequency generation: Space

• On-board oscillators
• Miniaturised atomic clocks
• Atomic clocks and Clock Monitoring and Control Units
• Microwave photonics

- Time and Frequency generation: Ground

• Microwave clocks
• Optical clocks and related technologies
• Timescale generation

- Time and Frequency transfer and dissemination

- GNSS time and frequency transfer

- Two-Way Satellite Time and Frequency Transfer

- Optical fibre links

- Optical free-space links

For frequency and time distribution over physical or telemetry layer of free-space optical communications links please see Optical Communications for Space.

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This topic is related to Functional Verification facilities used for development, assembly, integration and test in pre-launch and maintenance phases, and to Mission Operations Systems facilities for remote asset (e.g. satellite, rover, lunar base) monitoring and control during in-flight operations in post-launch phase. In particular, the topic addresses the following facilities and subsystems listed below.

- Functional Verification Bench

- Software Verification Facility

- Spacecraft AIV Simulator 

- Ground System Test Simulator 

- Training, Operations and Maintenance Simulator

- Electrical Ground Support Equipment systems, including Special Checkout Equipment / Front-end Equipment

- Mission Control Systems

- Data Archiving System

- Data Dissemination System

- Mission Planning Systems

- Ground Stations Monitor and Control System

- Subsystems and components used inside or across these facilities 

• Mission Database and Operations Preparation Environment 
• Automated Procedure Preparation, Execution and Post-processing Tools 
• Data archiving, analysis and distribution, including long term archive of large amount of data
• Simulators

- Process definitions, standards and reference architectures as well as supporting methodologies

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Ground station technology underpins critical services for the launch, deployment and operation of every space mission: telecommand transmission, telemetry reception from the platform or payload, and tracking and ranging. This topic mainly focuses on Ground Station technologies for the institutional applications, trying to also identify synergies with technologies for commercial services, if applicable.

• Data return via RF: large aperture ground antennas, real time and offline arraying for deep space, multi-frequency feed systems and antenna radome, cryogenically cooled receivers and feed systems, highly stable frequency converters, autonomous receivers with variable/adaptive coding and modulation, CCSDS protocol stack, advanced propagation modelling on link optimization, secure protocols, multiple downlink antenna.
• Data return via optical: optical ground stations for LEO, lunar and deep space direct-to-Earth (including adaptive optics), optical receivers and modems for ground, modulation and coding following CCSDS standard, planning and scheduling.
• Enhanced uplink: ground passive RF elements and feed systems for high power, pointing performance improvements, high-power amplifiers up to 100 kW, equipment for new frequency uplink bands, multiple uplinks in same beam, coding, forward Frame Cross Support Transfer Service (CSTS).
• Digital ground station: direct RF ADC sampling and DAC generation, intermediate frequency over IP, software defined radio, digital signal distribution, secure TTC processing, correlation and arraying of antennas, cloud computing and virtualization).
• Orbit determination accuracy and radio science: radiometric measurements equipment, Ka-band, first signal acquisition for critical operations, multi-frequency uplinks, radiometric calibration.
• Radar space objects observation: transmission and reception including signal synchronisation, calibration, signal processing architecture, correlation algorithms.
• Optical space objects observation: telescope and sensor technologies, active laser ranging technologies.
• Obsolescence and cost reduction: replacement of obsolete technology, monitoring and control for ground stations automation, next generation space link extension and CSTS, real time diagnosis tools.

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Temperature control of spacecraft requires the use of heat transport equipment and systems. This topic covers both Two-Phase and Single-Phase Heat Transport technologies.

Two-Phase Heat Transport Equipment

- Heat Pipes (HP)

• Constant Conductance Heat Pipes (CCHP), including low-CTE CCHPs and flexible heat pipes
• Variable Conductance Heat Pipes (VCHP)
• Heat Pipe Diodes (HPD)
• Pulsating Heat Pipe
• Two-Phase Structure

- Two-Phase Loop:

• Capillary Driven Loops (CDL): Loop Heat Pipes (LHP), including high, ambient, low and cryogenic temperatures; and Capillary Pumped Loops (CPL)
• Mechanical Pump Loops (MPL)
• Heat Pump Systems including high capacity refrigeration systems

Single Phase Heat Transport Equipment:

- Single Phase Mechanical Pump Loop

- Single Phase Electro-Hydro-Dynamic (EHD) Pump Loop

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Lidar instruments have become an important class of optical sensing tools which can be utilised in a vast number of Space and Ground applications, e.g. in scientific, military, environmental and commercial domains. This topic covers three key blocks based on application.

• Atmospheric Lidars: measurement of e.g. greenhouse gas molecules, particle and aerosol, wind doppler. Includes Differential absorption lidar (DIAL), doppler lidars, and frequency comb lidars.
• Altimetry Lidars: surface morphology and geology of planets and small bodies, measurements of vegetation canopy structure, bathymetry. Includes classical detection approach using a high power laser and a receiver detector.
• Imaging Lidars: close proximity guidance and navigation for applications such as rendezvous and docking, automated descents, orbital satellite servicing, navigation and control of robots and rovers, shape sensing or pointing of structures (e.g. deployable antennas). Includes flash lidars and scanning lidars.

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This topic covers technologies of bioreactors and membrane-based processes, which are needed for the implementation and execution of crewed exploration missions for lunar outposts or Mars transit missions, and planetary exploration (e.g. Moon habitat, crewed Moon rover, Mars habitat).

- Bioreactors

• CO2 processing into oxygen (for atmosphere and food management)
• Solid organic waste processing (for waste management)
• Urine processing (for atmosphere and food management)
• Cultured meat production (for food management)

- Membrane-based processes

• Oxygen or CO2 enrichment (gas-gas separation)
• Product extraction (gas-liquid interface)
• Culture medium recovery (liquid-solid separation)
• Water reclamation (liquid-liquid separation)

- Electrochemical technologies for production of oxygen, enhancement of organic waste degradation, compression of gases for storage, separation/purification of oxygen

• Electrolysis technologies
• Microbial electrolysis cell technology

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Micro-Electro-Mechanical Systems (MEMS) play a key role in the on-going miniaturisation of electronic modules and systems for space applications. MEMS components englobe a very large field of technologies and applications. Within Harmonisation three MEMS technologies for space applications are considered.

- MEMS Pressure Sensors

• Piezoresistive Pressure Sensors 
• Capacitive Pressure Sensors 
• Micromachined Pirani Sensors 

- MOEMS (Micro-Opto-Electro-Mechanical Systems)

• Optical switches and switching matrices
• Variable optical attenuators 
• Tilting micro-mirrors for fine optical beam steering 
• Tuneable spectral filters 

- RF MEMS

• RF MEMS switches and associated matrices 
• Micromachined RF filters (MEMS fabrication processes but no moving part) 
• RF MEMS varactor 
• Associated RF MEMS Hermetic packaging

- MEMS micro-coolers: devices made with MEMS technology for application in the packaging of high-power component

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Microwave passive devices are present in all kinds of satellite systems. The repertoire of on-board microwave passive technologies and equipment is very wide and it covers the units or components that do not have any active parts but permit essential payload functionality (filtering, connection, power splitting, routing, etc.). The coverage of this topic is classified as listed below.

• Low and high power filters, diplexers and multiplexers
• Power dividers, combiners, couplers and multiport couplers
• Ferrite devices: isolators, circulators, phase shifters
• RF harness: connectors, cables & cable assemblies, loads, attenuators and waveguides
• RF coaxial and waveguide relays and switches

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Model Based for System Engineering topic addresses the use of model-based technologies to support system engineering. It involves the structured application of modelling to support system requirements, design, analysis, verification and validation activities in space systems engineering context, covering the entire life cycle from needs identification to disposal.

Providing timely and direct access to consolidated, well-structured and interlinked data from different actors (specialist disciplines) creates digital continuity, which significantly improves communication between all stakeholders involved and therefore reduces the chances of late discovery of errors and costly rework. Moreover, data exchange based on a well-defined common vocabulary allows to seamlessly integrate powerful design and analysis tools, providing the capability to handle complex system designs more effectively.

For model-based techniques specifically for functional verification and for ground segment, in view of developing simulators, see Functional Verification and Mission Operations Systems.

For the specific modelling and simulation technology see System Modelling and Simulation Tools.

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Every modern spacecraft is equipped with an On–Board Computer & Data Handling System (OBCDHS), which is responsible for the command and monitoring. The OBCDHS implements spacecraft management and mission management functions as an extension of the Ground Control and Operation Centre. Complex Microelectronic circuits are of capital importance to achieve miniaturisation and performance levels demanded by today’s and future space OBCDHS modules, other platform systems and satellite instruments. This topic covers the areas listed below.

- Computer and Data Handling Systems (CDHS) architecture, units, modules and communication systems

• Platform and Payload CDHS Architectures background 
• CDHS units, modules and functions (PF+PL) 
• CDHS communication links, buses and networks 

- Microelectronic devices and enabling technology

• FPGA 
• Microprocessors, microcontrollers, Digital Signal Processing 
• Application Specific Standard Products (digital, analogue and mixed-signal) 
• ASIC platforms (rad hard cell libraries, IP, Design Kits, packaging, supply chain space quality) 
• IP Cores 

- CDHS EGSEs & Microelectronics Development methods and tools

• EGSE and tools for CDHS used at satellite level or instrument level 
• EGSE for CDHS Units 
• EGSE that are used to verify the proper functionality of a module to be then integrated in a CDHS unit. 
• Microelectronics development methods and tools 

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