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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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