麻省理工学院：《Satellite Engineering》Lecture 24 Ground System Design

Ground system design Col John Keesee 6/17/2004 Lesson objective The student will Be able to list the functions performed by a space systems ground support system 2. Know factors in ground station design 3. Know components of ground station architecture 4. Know capabilities of typical dedicated ground systems and common multi-user ground support systems 5. Know design considerations for specifying ground system elements

Ground System Design Col John Keesee 6/17/2004 1 Lesson Objectives The student will: 1. Be able to list the functions performed by a space systems ground support system. 2. Know factors in ground station design 3. Know components of ground station architecture 4. Know capabilities of typical dedicated ground systems and common multi-user ground support systems 5. Know design considerations for specifying ground system elements. 1

Oⅴ erview Ground Systems Support the space segment · Command and control Monitor spacecraft health Calculate spacecraft attitude Relay mission data to the users syste e ai d (uplink) func mission data)function

Overview • Ground Systems – Support the space segment • Command and Control • Monitor spacecraft health • Track • Calculate spacecraft attitude – Relay mission data to the users 6/17/2004 2 Ground systems have a command (uplink) function as well as a data (telemetry and mission data) function. 2

Ground station Design Location location location Coverage Data-user needs Accessibility availability Link data rates G/TS EIRP Requirements for data handling Communication between ground system elements and data users 6/17/2004 These are the important facto d station design. The spacecraft orbit and mission characteristics will drive available locations for ground systems Satellite transmitter characteristics and data rates will determine the ground stems transmitter and receiver operating characteristics Because the facilities that process data may not be co-located with the receiving system, the ground system will have its own terrestrial and space communication

Ground Station Design • Location, location, location – Coverage – Data-user needs – Cost – Accessibility – Availability • Link data rates – G/Ts, EIRP • Requirements for data handling • Communication between ground system elements and data users 6/17/2004 3 These are the important factors in ground station design. The spacecraft orbit and mission characteristics will drive available locations for ground systems. Satellite transmitter characteristics and data rates will determine the ground system’s transmitter and receiver operating characteristics. Because the facilities that process data may not be co-located with the receiving system, the ground system will have its own terrestrial and space communication links. 3

Ground system elements Mission elements and facility elements Ground station is where the earth-based end of satellite co on takes pla RF equ Transmit RF equipment Data-user interface TT&c equipment Station control center System clock The d system consists of both mission(functional)elements and facilities a ground station would usually consist of most of these elements

Ground System Elements • Mission elements and facility elements • Ground station is where the Earth-based end of satellite communication takes place – Antenna system – Receive RF equipment – Transmit RF equipment – Mission data recovery – Data-user interface – TT&C equipment – Station control center – System clock 6/17/2004 4 The ground system consists of both mission (functional) elements and facilities. A ground station would usually consist of most of these elements 4

Control centers Spacecraft Operations Control Centers Monitors and commands the spacecraft bus Analyzes spacecraft telemetry Coordinates and controls payload Control Center access Includes data monitoring equipment, commanding facilities and communications 6/17/2004 In most cases, the spacecraft operations control center controls the overall mission, even though the payload is the reason for the mission. The SOCC monitors the health and status of the bus and, in some architectures, the payload as well Sometimes it's a multi-mission facility, and many times is separated physically from the payload operations control center

Control Centers • Spacecraft Operations Control Centers – Monitors and commands the spacecraft bus – Analyzes spacecraft telemetry – Coordinates and controls Payload Control Center access – Includes data monitoring equipment, commanding facilities and communications 6/17/2004 5 In most cases, the spacecraft operations control center controls the overall mission, even though the payload is the reason for the mission. The SOCC monitors the health and status of the bus and, in some architectures, the payload as well. Sometimes it’s a multi-mission facility, and many times is separated physically from the payload operations control center. 5

Control centers continued Payload Operations Control Center Analyzes telemetry and mission data from instruments Issues commands to instruments Mission control center Plans and operates the space mission SOCC, Pocc and mcc may not be co-located May require hot spares to maintain high availability Survivability may dictate multiple ground system sites for coverage and redundancy 6/17/2004 The entire focus of the POCC is the payload, its monitoring, management and contro The mission control center would be responsible for the entire constellation of satellites The SOCC, the PoCc and the mcc are many times not co-located When the availability requirement is very high we may specify multiple systems running in parallel (hot spares )to minimize the downtime in case of a failure

Control Centers continued • Payload Operations Control Center – Analyzes telemetry and mission data from instruments – Issues commands to instruments • Mission Control Center – Plans and operates the space mission • SOCC, POCC and MCC may not be co-located • May require hot spares to maintain high availability • Survivability may dictate multiple ground system sites for coverage and redundancy 6/17/2004 6 The entire focus of the POCC is the payload, its monitoring, management and control. The mission control center would be responsible for the entire constellation of satellites. The SOCC, the POCC and the MCC are many times not co-located. When the availability requirement is very high we may specify multiple systems running in parallel (hot spares) to minimize the downtime in case of a failure. 6

Communication links Communication support required between ground system elements and data-users Landline and satellite connections International links through comsats and terminal equipment Intelsat. Telstar. Westar. DSCS. Milstar Internet protocols 6/17/2004 The communication links between the socc. the pocc and the mcc might be hrough landlines, satellite connections, or the internet. Typically military systems may use the defense Satellite Communication System to relay information between

Communication Links • Communication support required between ground system elements and data-users – Landline and satellite connections – International links through comsats and terminal equipment • Intelsat, Telstar, Westar, DSCS, Milstar – Internet protocols 6/17/2004 7 The communication links between the SOCC, the POCC and the MCC might be through landlines, satellite connections, or the internet. Typically military systems may use the Defense Satellite Communication System to relay information between nodes. 7

Data Handling Multiplex Demultiplex Encryption-Decryption Encoding-Decoding Data Compression Time Tagging · Data storage Data quality monitoring 6/17/2004 Data from the satellite are usually multi-plexed(usually Time division multiple access)to allow communication with multiple satellites over the same link We discussed these functions in the lesson on tt&c

Data Handling • Multiplex—Demultiplex • Encryption—Decryption • Encoding—Decoding • Data Compression • Time Tagging • Data storage • Data quality monitoring 6/17/2004 8 Data from the satellite are usually multi-plexed (usually Time division multiple access) to allow communication with multiple satellites over the same link. We discussed these functions in the lesson on TT&C 8

Defense Meteorology Satellite rogram Spacecraft uplink L-band(1.75 to 1.85 GHz)2 kb bps(command) Downlink S-band (2.2 to 2.3 GHz)1024 kbps(mission data) Command readout stations and aFscN Mission data transfer from ground stations to DMSP central facilities via domestic satellite and landlines Similar connections to large data processing centers Some data-users receive direct from the spacecraft 6/17/2004

Defense Meteorology Satellite Program • Spacecraft uplink – L-band (1.75 to 1.85 GHz) 2 kbps (command) • Downlink – S-band (2.2 to 2.3 GHz) 1024 kbps (mission data) • Command Readout stations and AFSCN • Mission data transfer from ground stations to DMSP central facilities via domestic satellite and landlines • Similar connections to large data processing centers • Some data-users receive direct from the spacecraft 6/17/2004 9 9

Alternatives to dedicated Ground Systems Host systems provide some or all parts of the ground system Saves money, has high reliability and availabilit However, may not be optimum for a specific mission Sharing resources requires scheduling coordination and Ly impact user mission 6/17/2004 10

Alternatives to Dedicated Ground Systems • Host systems provide some or all parts of the ground system – Saves money, has high reliability and availability – However, may not be optimum for a specific mission • Sharing resources requires scheduling coordination and prioritization – May impact user mission 6/17/2004 10 10