Subsystems Spacecraft

reaction control system thrusters on front of u.s. space shuttle



attitude control
a spacecraft needs attitude control subsystem correctly oriented in space , respond external torques , forces properly. attitude control subsystem consists of sensors , actuators, controlling algorithms. attitude-control subsystem permits proper pointing science objective, sun pointing power solar arrays , earth pointing communications.


gnc
guidance refers calculation of commands (usually done cdh subsystem) needed steer spacecraft desired be. navigation means determining spacecraft s orbital elements or position. control means adjusting path of spacecraft meet mission requirements.


command , data handling
the cdh subsystem receives commands communications subsystem, performs validation , decoding of commands, , distributes commands appropriate spacecraft subsystems , components. cdh receives housekeeping data , science data other spacecraft subsystems , components, , packages data storage on data recorder or transmission ground via communications subsystem. other functions of cdh include maintaining spacecraft clock , state-of-health monitoring.



communications
spacecraft, both robotic , crewed, utilize various communications systems communication terrestrial stations communication between spacecraft in space. technologies utilized include rf , optical communication. in addition, spacecraft payloads explicitly purpose of ground–ground communication using receiver/retransmitter electronic technologies.


power
spacecraft need electrical power generation , distribution subsystem powering various spacecraft subsystems. spacecraft near sun, solar panels used generate electrical power. spacecraft designed operate in more distant locations, example jupiter, might employ radioisotope thermoelectric generator (rtg) generate electrical power. electrical power sent through power conditioning equipment before passes through power distribution unit on electrical bus other spacecraft components. batteries typically connected bus via battery charge regulator, , batteries used provide electrical power during periods when primary power not available, example when low earth orbit spacecraft eclipsed earth.


thermal control
spacecraft must engineered withstand transit through earth s atmosphere , space environment. must operate in vacuum temperatures potentially ranging across hundreds of degrees celsius (if subject reentry) in presence of plasmas. material requirements such either high melting temperature, low density materials such beryllium , reinforced carbon–carbon or (possibly due lower thickness requirements despite high density) tungsten or ablative carbon–carbon composites used. depending on mission profile, spacecraft may need operate on surface of planetary body. thermal control subsystem can passive, dependent on selection of materials specific radiative properties. active thermal control makes use of electrical heaters , actuators such louvers control temperature ranges of equipments within specific ranges.


spacecraft propulsion
spacecraft may or may not have propulsion subsystem, depending on whether or not mission profile calls propulsion. swift spacecraft example of spacecraft not have propulsion subsystem. typically though, leo spacecraft include propulsion subsystem altitude adjustments (drag make-up maneuvers) , inclination adjustment maneuvers. propulsion system needed spacecraft perform momentum management maneuvers. components of conventional propulsion subsystem include fuel, tankage, valves, pipes, , thrusters. thermal control system interfaces propulsion subsystem monitoring temperature of components, , preheating tanks , thrusters in preparation spacecraft maneuver.


structures
spacecraft must engineered withstand launch loads imparted launch vehicle, , must have point of attachment other subsystems. depending on mission profile, structural subsystem might need withstand loads imparted entry atmosphere of planetary body, , landing on surface of planetary body.


payload
the payload depends on mission of spacecraft, , typically regarded part of spacecraft pays bills . typical payloads include scientific instruments (cameras, telescopes, or particle detectors, example), cargo, or human crew.


ground segment



the ground segment, though not technically part of spacecraft, vital operation of spacecraft. typical components of ground segment in use during normal operations include mission operations facility flight operations team conducts operations of spacecraft, data processing , storage facility, ground stations radiate signals , receive signals spacecraft, , voice , data communications network connect mission elements.


launch vehicle
the launch vehicle propels spacecraft earth s surface, through atmosphere, , orbit, exact orbit being dependent on mission configuration. launch vehicle may expendable or reusable.




^ rosetta ground segment . esa.int. 2004-02-17. archived original on 2008-03-11. retrieved 2008-02-11.