 Hello everyone, today I will be explaining you what are satellite power subsystems and how they look as well as what are the contents of power subsystem and what are the hazards that create the power subsystems in satellites which are in space. Now learning outcome at the end of this session the students will be able to explain the constituents of power subsystems used in the satellites. Before going to the next slide let us see let us recall what are the AOCs. So AOCs are nothing but attitude and control subsystems so attitude and control subsystems are nothing but the subsystems that will decide the satellite behavior in the orbit. Now let us see the introduction to the satellite subsystems here there are different types of subsystems are available to make the satellite revolve around the earth in proper orbit with proper velocity they are as follows telemetry tracking command and monitoring system second one communication subsystems third one power subsystem fourth one antenna subsystems. Now before going to the next slide let us see a typical satellite which is going to have power subsystems on it you can see here the power subsystem they are nothing but the power sources so you can see the solar panels panels on the satellite as well as you can see the communications subsystem that is the antenna you can see here then the overall control system that is the computer so that you can see it here then also you can observe the attitude control subsystems so which is present in front of the satellite. Now let us go to the power subsystem so what does a power subsystem does the power subsystem mainly does the following jobs so those jobs are nothing but harness the power from the sun rays using high efficiency solar cells second one the collected power is supplied to the various systems board then third one the remaining energy is stored in batteries now let us see the first one the harnessing of power from the sun rays using high efficiency solar cells so these are nothing but the space grid solar cells that are needed to ensure a long life of the satellite similarly the batteries which are qualified for space applications are preferred over untested batteries second one the collected power that will be supplied to the various systems they are stored on the board so that is nothing but the batteries are used when the satellite consumes more power then the solar panels can provide that power so next one what happens the remaining energy which is stored in the batteries so that remaining energy it will be supplied to those circuits in satellites necessary for ground tracking and command now at the times that is the fourth point if you can see here conservation of power and allow battery recharging so at the times when there is no sunlight the power subsystems conserve power and allow battery recharging so the solar panels which are present on the spacecraft they are mainly for two main uses so first use is that the power to run the sensors active heating cooling and telemetry second one the power for spacecraft propulsion electric propulsion sometimes called solar electric propulsion to increase the specific power typical solar panels on spacecraft use close packed solar cell rectangles that cover nearly 100% of the sun visible area of the solar panels now let us see what are the threats to the power subsystem since the space we cannot predict the conditions of the space so there may be possibility that heavy solar wind may come and disturb the solar panels second thing is that there are meteroids which are present in space they can damage the solar panels so that is what we will be seeing it in critical condition so in the critical condition the satellites orbiting the earth pass through a shadow region on the opposite side of the earth from the sun depending on the type of orbit this can happen just a few times a year or every few hours the solar panels cannot produce electric energy and the satellite would not only be unable to operate but would also freeze to incredibly low temperatures eventually around minus 270 degree Celsius so the energy storage there are essentially two ways of storing electrical energy that are used on satellites both of which rely on reversible chemical reactions one is based on cells very similar to those found in portable phones so usually in mobile phones you can find those things the other uses so called the fuel cells a type of electrical accumulator now being used experimentally in cars and buses now let us look at the other methods for generating the power in satellites so if at all if the solar cells break down or if the batteries do not store the power then what are all other methods of generating the power in satellites so the method that will be there so this method is achieved by combining hydrogen and oxygen at a platinum membrane with water as a by-product this water can also be accumulated in a tank and successively divided into oxygen and hydrogen by electrolysis that is by letting a current flow through it there is another method called as RTGs so RTGs are nothing but nuclear power that is radioisotope thermoelectric generators RTGs so these are basically used in order to generate the nuclear power in the power subsystem you can see the references I have referred to textbooks first one the satellite communication textbook by Timothy Pratt that is the second edition so valley publications it is then the second textbook that you can refer that is introduction to satellite communication by Bruce Elbert that is also second edition so Pearson publications thank you