Ch-4 Satellite Hardware

7/29/2019 Ch-4 Satellite Hardware

1/16

Ch-4: Satellite Hardwar


2/16

SATELLITE SYSTEM

Space Segment

Payload Bus

Structure Attitude Determination

And ControlThermal Propul

Data HandlingCommand and

TelemetryPower


3/16

SATELLITE SYSTEM(Contd)

A satellite system is composed of the spacecraft (bus) and payload(s)

A spacecraft consists of the following subsystems

Propulsion and Launch Systems

Attitude Determination and Control

Power Systems

Thermal Systems

Configuration andStructure SystemsCommunications

Command and Telemetry

Data Handling and Processing


4/16

SATELLITE SYSTEM (contd)

Propulsion and Launch SystemsLaunch vehicle: used to put a spacecraft into space.

Once the weight and volume of the spacecraft have beenestimated, a launch vehicle can be selected from a variety othe manufacturers.

If it is necessary to deviate from the trajectory provided bythe launch vehicle or correct for the errors in the initial

condition, additional force generation or propulsion isnecessary

On-board propulsion systems generally require a means todetermine the position and attitude of the spacecraft so ththe required trust vectors can be precisely determined and

applied.


5/16

SATELLITE SYSTEM (contd) Attitude Determination and Control System

(ADCS)ADCS are required to point the spacecraft or a

component, such as solar array, antenna,propulsion thrust axis, and instrument sensor, ina specific direction.

Attitude determination can be accomplished bydetermining the orientation w.r.t. the star, earth,inertial space, geomagnetic field and the sun.

Attitude control can be either passive or activeor combination.


6/16


Power SystemsSpacecraft power can be obtained from the

through solar cell arrays and thermal electrigenerators and from on-board devices such

chemical batteries, fuel cell, and nuclear theelectronic and therm-ionic converters.

Most satellites use a combination of solar cand chemical batteries.


7/16


Thermal Control SystemsThe function of the thermal control system is to m

temperatures to within specified limit throughoutmission to allow the onboard systems to functionand have a long life

Thermal balance can be controlled by using heatepassive or active radiators, and thermal blankets o

various emissivities on the exterior.


8/16


Configuration and Structure SystemsThe configuration of a spacecraft is constrained by the p

capability and the shape of the fairing of expendable lauvehicle.

Large structures, such as solar arrays and antenna are er

the space through deployable components.Explosive devices, activated by timing devices or comma

used to separate the spacecraft from the launch vehiclesand deploy mechanisms, and cut cables.


9/16


Command and TelemetryTheCommand and Telemetry system provide info

to and from the S/C respectively.

Commands are used to provide information to chthe state of the subsystems of the S/C and to se t

The Telemetry subsystem collects and processes of data and modulates the signal to be transmittethe S/C.


10/16


Data Handling and ProcessingData processing is important to help control and

reconfigure the spacecraft to optimize the overallperformance and to process data for transmissionConsists of processor(s), RAM, ROM, Data Storag

implemented by machine, assembly or high level Low mass, volume, and power requirements, insto radiation, and exceptional reliability are importcharacteristics of processor.


11/16


CommunicationsRadio frequency communication is used to transmit info

between the S/C and terrestrial sites and perhaps other

Information transmitted from the S/C include the state aof the subsystems in addition to data from the primaryinstruments.

Information transmitted to the S/C generally consists of stored by on-board processors and commands to changeof the on-board system either in real-time or through elelogic that execute them as a function of time or as requir


12/16

Engineering Procedures

Space Systems Engineering

System DefinitionSystem, Subsystem, Components, and Parts

A large collection of subsystems is called a segment.

In a space mission, the spacecraft, the launch vehicle, the tracthe mission control center, etc., may each be considered a systsegment by their principle developers but are subsystems of th

system.Value of a System

Systems ability to satisfy criteria generally called system level or standards for judgment.

P l i


13/16

PropulsionSubsystem

Purpose of the propulsion subsystem

Transfer spacecraft from launch vehicle parking orbit to spmission orbit

Maintain and control spacecraft orbit

Maintain and control spacecraft attitude

Types of spacecraft propulsion systems

Chemical Liquid, Solid or Hybrid

Solar Electric

Nuclear

Thermal or Electric


14/16


15/16


16/16

Documents

Ch-4 Satellite Hardware