Spacecraft are complex machines comprised of numerous subsystems that must work in unison to complete their mission. There are seven main engineering subsystems involved, which must collaborate for successful operation: Structure, Attitude Determination & Control, Onboard Data Handling, Communication Power Thermal Propulsion.
Propulsion systems are required for altitude and orbit adjustments, drag make-up maneuvers, momentum management maneuvers and thermal control subsystem integration with propulsion subsystem. Preheating tanks, pipes and thrusters is monitored as part of this interface between propulsion subsystem and thermal control subsystem.
Propulsion
Propulsion subsystems provide thrust to move spacecraft through all stages of its mission. Their specific thrust generated depends on fuel availability, power output and mass-to-thrust ratios as well as conservation of momentum laws.
Specialized ion thrusters can deliver considerably more thrust per unit of propellant weight than chemical engines and at lower exhaust velocity. These systems operate using less costly oxidizers while still offering excellent thrust.
Many spacecraft rely on multiple thruster systems to correct launch vehicle injection errors and orbital perturbations from solar radiation pressure, atmospheric drag or inhomogeneities in Earth’s gravity field; and to execute planned maneuvers to alter their trajectory. They may also be used for stationkeeping, attitude control or interplanetary travel.
Communication
The structures subsystem assembles all spacecraft components and is tailored according to payload specifications and launch vehicle type. It serves to facilitate two-way communications between ground stations and satellites for command transmission and data dissemination, as well as handling ground commands, payload data transmission and dissemination as well as key software elements necessary for spacecraft mission control. Its primary function is providing two-way data dissemination. Meanwhile, communications subsystem handles ground commands, payload data transmission telemetry as well as mission control software elements essential to spacecraft operation.
This subsystem safeguards spacecraft against micrometeoroid impacts by covering it in protective blankets made of Kevlar or similar materials, and protects against micrometeoroid impacts using tough Kevlar blankets and other materials. In manned spacecraft this subsystem also includes life support systems providing oxygen, water, waste processing services, temperature control and ventilation within a pressurized crew compartment.
AOCS tracks and controls satellite orientation (attitude) and orbit using sensors such as star trackers, magnetometers, reaction wheels, and gyroscopes – as well as actuators like reaction wheels and gyroscopes – and actuators such as reaction wheels. It can even point payloads towards Earth.
Power
The Power Subsystem supplies energy to spacecraft components by creating, storing and dispersing electrical energy from solar arrays that convert sunlight to current, and batteries that store additional storage capacity. Operational units receive 28V power while an independent converter supplies other voltages. Any surplus is distributed among resistors known as Internal Power Dumpers (IPDs) within the spacecraft for general heating as well as heaters in tanks or thruster blocks as required for specific areas.
The AOCS is responsible for controlling the satellite’s orientation and orbit, using sensors like star trackers and gyroscopes to sense current orientation while acting upon it through actuators such as reaction wheels or magnetic torquers. Additionally, this component handles high-level fault protection routines as well as receiving commands from Earth while receiving housekeeping telemetry data from payload.
Attitude and Orbit Control
AOCS is an essential subsystem to ensure the spacecraft maintains its desired pointing and orbital positions. It is responsible for achieving centimeter pointing accuracy while managing asymmetrical orbits with complex dynamics like solar radiation, gravity gradients or atmospheric drag.
Sensors like gyroscopes and magnetometers generate signals to detect changes in attitude. These signals are processed by control algorithms to command actuators that counteract these forces and torques; many AOCS designs incorporate thrusters, reaction wheels and magnetorquers which exchange momentum in order to perform the requested slewing maneuvers.
Sensors, actuators and avionics selected and sized according to payload requirements, power and thermal requirements and accuracy needs. Additionally, AOCS performs telecommand and telemetry transmission to the ground segment.
Ground Segment
Communication systems deliver command and housekeeping data to spacecraft, receive telemetry from them, and transmit information between spacecraft. Telemetry systems play an integral part here by collecting health and status data from all other subsystems onboard before buffering and formatting it for transmission back to Earth via ground stations or relay satellites.
This team provides a vital interface between mission operations team, which develops command plans and simulates them to ensure they will accomplish desired tasks, and uploading and downloading of telemetry.
Communications networks enable this, usually comprised of an array of antennae covering an entire continent or part thereof, designed for reliability and bandwidth use while taking into account any delay-tolerant networking protocols that might exist.