 Now, come to the design development of these systems. So, these are the actually key factors with try ups or design atmospheric conditions because at that height, we will encounter wind speed different wind speed at different locations and the power available due to solar energy and the envelope shape optimization because it will encounter a drag envelope technologies you have to optimize the systems we have to minimize the structural systems to maximize the payload station keeping and thermal compensation because temperature variations diurnal temperature variations is there which will affect the performance buoyancy and output of the solar systems and lightning and electrostatic charge protection because it might affect or distract the envelope and launch recovery and ground handling. These are the challenges while design. So, these are the requirement because hello you can see to control the buoyancy that this used to be a another systems because due to the temperature variation and the height and it will the height of the systems will vary. So, you have to take care of all that and to fight with the drag because the wind direction will change. So, there should be a proper first vectoring altitude control thermal protection these are the systems requirement. So, let us see the what are the actual scenario at that height. So, at the altitude of around 20-25 kilometers, you will see the temperature and density and the viscosity at that range it is actually optimum. You do not want to very low density because it will affect our buoyancy as well as if you will place below that height higher density will lead a drag and the temperature and solar irradiance. So, at that particular height this is optimum. So, these are the typical parameters you can see it is ground density is about how much density is ground at 1.2 to around that is 7.2 percent of that only. So, these are the typical values average wind speed is 25 kilometers 25 meter per second and solar irradiance is 500 and the actual solar irradiance without an emission and without any loss is around 1300, 1365 watt per meter square and after that loss it used to be around the typical value of 500, 400 it will depend upon location. So, these are the variations with height you can see in the is it very visible temperature variation wind you can see the minimum wind at that height and direction is changing the temperature is minus. So, move on. So, the temperature range is minus 60 to minus 40 degree and that will affect our envelope as well as it will affect the buoyancy it will affect the power output from solar cells humidity is there to at that height humidity is less. So, because the humidity creates always a problem it decrease the strength. So, the wind profile it is actual wind studies shows the variation of wind over the year and course I am maximum up to around 45 to 50 meter per second and average velocity of 25 and this actually the wind velocity and that it is direction is a major problem because when the direction changes you have to optimize the orientation of your ship to minimize the drag because same wind velocity and the airship is in longitudinal direction and in lateral direction the drive will be different. But whenever we will change the orientation of airship the power output will change because it will depend the relative position of earth's way that is the problem you have to take care. Wind direction will change at the some for some month in the year it will be in different direction for some month it will be in different direction. So, these are the challenges. So, you have to keep it for a longer period of time suppose you have to keep it for a year. So, you have to take care of the power availability as winter as well and the power availability will be lower at the winter and for the shorter duration of time and you have to store the power for a long duration because night will be longer that is another challenge power available is more in summer you know. So, the storing power the systems for restore that power will be lesser low I mean small but in winter you have to take care of that also otherwise at night it will fail to provide a power to the propulsion system as well as payload because power requirement will be for the basically for two systems for the payload we have what you have mounted like cameras or sensors or systems which will provide which will serve the purpose of the airship and other power requirement for the propulsion systems to overcome that drag which it is causing at that height.