Know unknown facts about satellites including Bangabandhu-1

The Dhaka Times Desk Many of us do not know about the benefits and benefits of Bangabandhu-1 satellite. Where is this satellite placed and will it orbit the Earth or remain stationary?

Bangabandhu-1 satellite flew into space a few days ago. It is a geostationary satellite. Many people call satellites “spacecraft” or “birds”. Not all satellites are geostationary. Geostationary satellites have two characteristics:
1. They are located just above the equator (may be one degree less/more).
2. As the Earth rotates around its axis once in 24 hours, these satellites also rotate around the Earth's axis once in 24 hours.

As a result of these two conditions, these satellites remain over a fixed area on the Earth's surface to keep up with the Earth's rotation, i.e. GEO (Earth or Geo) + Stationary (stationary). Fixed in name but not fixed in fact; Keeping up with the world is moving faster than a gunshot. But standing on earth, it will seem fixed.

If the sky is enlarged by drawing numerous lines along the equator from the center of the earth, the geostationary satellites will be above that line. But this distance is not infinite; According to the formula discovered hundreds of years ago by Newton and Kepler, we know that a geostationary satellite will be about 35,853 km from Earth. This is called geostationary orbit. Since science fiction writer Arthur C. Clarke first proposed the idea of a communication satellite, it is also called the Clarke Orbit after Clarke.

Permanent orbits have a special quality. It is a place where the motion of gravity and rotation collide, so that the object in that orbit i.e. our earth or the moon, whatever it is, rotates in the same way. Satellites also move in geostationary orbit in the same way. But how does it keep pace with the world? Indeed it is impossible to keep pace so neatly; Therefore, satellites contain gases that are periodically ejected at high pressure to fix their position like a rocket.

Why does it seem static?

Suppose you draw a circle of radius 5 inches, and draw another circle of radius 40 inches through the same center. If your circle drawing speed is the same, the larger circle will take longer to draw than the smaller circle. But if you increase the size of the big circle, then if it moves at a certain speed, it will be seen that the two circles are starting and ending at the same time, that is, the pencil of the small circle and the pencil of the big circle are moving in the same rhythm. Similarly, geostationary satellites appear to move faster than the Earth is fixed in one place.

Why not fly away or fall:

A plane or a rocket can fly in the sky by consuming fuel. But how does the satellite float without running the engine? First, the satellite is carried straight up by the rocket, then the rocket begins to move towards the Earth at a speed of about 11,000 km per hour, and at some point it intercepts the satellite. The released satellite also moves at the same speed due to inertia. For this speed, although the satellite falls down due to Earth's gravity, the amount of this descent is equal to the curvature of the orbit. So the distance from Earth remains the same. If this speed was low, it would fall at one time and if it was high, it would become elliptical. It is a little difficult to understand, so an example - suppose water is standing on the streets of Dhaka due to waterlogging. You are walking with a bag, the bag is 38 inches above the water. As you walk, the water deepens because of a hole somewhere, you lift the bag a little higher, so that the bag is 38 inches above the water. Similarly the satellite can also maintain the same altitude.
So the circumference of a circle with a radius of about 42,000 km is about 264,000 km (2πr). 264,000 satellites spaced one kilometer apart, right? On paper so, but not in reality.

What is Footprint?

Just as the light of a torch from a distance creates a luminous circle, the radio signal of a satellite is only available from a certain area. That area is called the satellite's footprint. Just as the sun falls behind the earth in the night sky, the geostationary satellite in America's sky is behind the earth for Bangladesh—Bangladesh is not in the footprint of that satellite and Bangladesh will have no business with that satellite. So for Bangladesh it is necessary to place the satellite in such a place, so that Bangladesh falls in its footprint. The places where satellites sit are called orbital slots, and the International Telecommunication Union (ITU) allocates slots to each country on a first-come, first-served basis. Here's the catch—all slots above or around Bangladesh are taken by some other country (list below). Bangladesh didn't want it before, so it didn't get it. Again, many countries do not need their own satellites, so they sold them with slots; For example, Tonga auctioned its five slots for $2 million a year in 1988.

There are many places above the sea in the southern hemisphere, where there is no land, no people. Slots are available in that footprint, but what about it? It's almost as if you live in Dhaka, and you can buy sea property 2,000 miles away if you want. But you need to build a home; What to do with the possession of sea water? So now you have to buy the land in Dhaka from others for a price. It's also important for satellites to stay in that footprint – we can't buy seawater. So Bangladesh has done just that, leasing a slot at 119.1 degrees longitude for 15 years from the Russians for $28 million, in whose footprint Bangladesh falls.

If you want to build a house, first you need to fix the land, after that you need to understand the plan, that plan needs to be passed from Rajuk, same for satellite. ITU assigns frequencies by first calculating what satellites are in the vicinity of the land (slot), what frequencies they use, so that there is no conflict with them. Then satellites need to be made. Bangladesh got the land, the plan was passed, and finally the satellite was built and flew into space.

Optimum Time of Launch:

SpaceX's Falcon 9 rocket aborted the launch at the last minute even after its first flight. But as soon as the problem is solved, why is it not launched again? Because it is a calculation of exactly when the launch will reach the satellite at the lowest cost. So when it was a little late, it had to wait for that specific time instead of launching again after a while. Have you ever hit something moving? The target moves as your rock approaches; So by calculating the speed of the target and the rock, the rock is hit in front of the target. Same here; The slot needs to be calculated and launched because the earth is rotating. Another thing is, less fuel is required when the launch pad is in a level orbit. It depends on where the slot is. Sending something into space costs a lot; The shipping cost per kg is around $25,000 or Tk 20 lakh. So sending extra fuel also costs a lot. Therefore, keeping these two accounts in mind to reduce the cost, the time of the day when the launch will cost the least is called the launch window.

At night, many people in Bangladesh saw how our Bangabandhu 1 satellite separated from the rocket and drifted towards space. As many have heard in this thread, the rocket's stage-2 reached transfer_orbit (transfer orbit). Suppose, he landed at the country's airport from abroad by plane. Now you have to go by car to go home. The transfer orbit is such an intermediate point where the satellite separates from the rocket. The satellite will then reach its own slot using its own fuel. This will be done by Thales engineers; Space-X has no further role to play here. After a few trials, its commercial use will begin. The country's two satellite geostations will communicate with our own satellites instead of other satellites.

What will happen after 15 years?

The satellite does not stay in one place, it moves slowly. It sometimes needs to be brought back into place. When it's life is over, if nothing is done it will descend and enter the atmosphere at some point and burn up to ash. But because of the cost of the slot, maybe instead of letting it go down on its own, it will be bumped down (burning fuel) or bumped up another 200 km where the dead satellite continues to orbit. And the next satellite can take the same slot without waiting too long. Why only 15 years?

Like all electronics, satellite capacity is increasing day by day and prices are decreasing. It is possible to build a satellite that will last 50 years, but it will not be able to compete with new satellites after 10-15 years. So they are designed that way.

Can storms be predicted with this satellite?

Just as TV cannot be seen through radio, weather cannot be seen through communication satellites. This satellite has no meteorological instruments. Then weather forecast cannot be obtained with it.