Satellite Subsystems Ppt

7/23/2019 Satellite Subsystems Ppt

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Satellite

subsystemsMoitreya Adhikary

ID 210713016

1stSemester

M.E. ETC Mi!ro"a#e$

%ES&' Shib(ur


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Exploded view of SpinnerSatellite


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Spacecraft subsystem

overview1. Attitude and orbit Control System (AOCS)2.elemetry! rac"in#! Command! and $onitorin# (C%&. 'ower System. Communication Subsystem. Satellite Antennas


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1. A)CS Attitude * orbit!o+trol system$


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*eason for Attitude % Orbit control

At +EO orbit altitude t,e moon-s #ravitational force isabout twice as stron# as t,e sun-s

$oon orbit is inclined to t,e euatorial plane byapproximately de#rees

,e plane of t,e eart,-s rotation around t,e sun is

inclined to 2& de#rees to t,e euatorial plane

/et #ravitational force on t,e satellite tends toc,an#e t,e inclination of t,e satellite.

Also solar pressure actin# on solar cells and antennasof t,e satellite and eddy currents #enerated byeart,-s ma#netic 0eld cause rotation in t,e satellite.Orbital period of t,e satellite ma"es many eectscyclic! w,ic, can cause /utation3 ( a wobble) of t,esatellite.


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4nclined Orbit


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4nclination rate is approximately 5.67de#rees per year from t,e euatorial plane.

8EO satellites are less eected by t,is

#ravitational pull from t,e sun and moon At t,e euator t,ere are bul#es of about

7m at lon#itudes 172 de#rees East and&6 de#rees East.

,us Satellite is accelerated towards one oftwo stable points on +EO orbit at t,elon#itude of 9 de#ree E and 22 de#rees E

*eason for Orbit Correction (Contd..)


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:ine positionin#

wo ways to ma"e t,e satellite stablein orbit w,en it is wei#,tless.

Satellite can be rotated at a rate between&5 and 155 rpm to create #yroscopic forcet,at provides stability (spinner satellites)

Satellites can be stabili;ed by one or more

momentum w,eels! called t,ree


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Orbit insertion % $aintenance< +EO

wo types of motors used on satellites. raditional bipropellant t,ruster

=ipropellants used are $onoydra;ine and /itro#entetraoxide

,ey are ,ypo#olic! i.e.! t,ey i#nite simultaneously on contact

wit,out any catalyst or ,eater Arc ?ets or ion t,rusters

>i#, volta#e is used to accelerate ions

:uel stored in +EO satellite is used for twopurposes

Apo#ee "ic" motor (A@$) t,at in?ects t,e satellite into its0nal orbit

$aintain t,e satellite in t,at orbit over its lifetime.


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SpinnerSatellite


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& Axis Stabili;ed Satellite


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e0nition of axis


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/S Control of a Spinner Satellite Bsin# 4nfrared Eart,Sensors


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On =oard Control System


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2.TTC*M


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elemetry $odes


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rac"in#


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Command


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ypical C%$System


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3. ,o"er systems


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=ac"up 'ower System


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'ower systems(Contd..)

Typical battery voltages 20-50 Vwith 20-100 Ah capacity


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-. Commu+i!atio+subsystems


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'ayload functions


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*epeaters and ransponders


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ypes of payloadsransponders


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Sin#le Conversion =ent pipe ransponder


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ouble Conversion =ent pipe ransponder


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=asic ransponder elements


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Onboard 'rocessin# ransponder


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:actors aectin# payloaddesi#n


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. Satellite A+te++as

:our main types of antennas are used on satellites

/ire a+te++as Mo+o(oles a+d Di(oles$'rimarily used at D>: and B>: to provide communicationwit, t,e C%$ system.

or+ a+te++as Bsed at microwave freuencies w,enrelatively wide beams are reuired.

ee!tor a+te++as +enerally consist of 'araboloidreector illuminated by one or more >orns and providelar#er aperture t,an >orns.

Array a+te++as Bsed for #eneration of multiple spotscannin# beams.


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ypical Satellite Antenna 'atterns and Covera#e Fone


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Contour 'lot of t,e Spot =eam 'ro?ected onto t,e Eart


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4/E8SA D4 Satelliteon Station


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eployment Seuence ofSatellite Antenna


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*eferences

Satellite Communications3 by 'ratt!=ostian! Allnutt

Electronic Communications3 by*oddy! Coolen


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GuestionsH


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,an" IouJ

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Satellite Subsystems Ppt