and they will probably use these satellites to produce the holograms over the cities

To produce hologram of that size you need a difraction grating of that size. You can't create holographic image in thin air visible from any angle without it.

Shortly, Hologram is a special image on some 2D surface with resolution comarable with wavelength of visible light. It create a sophisticated difraction grating, that after interaction with light from some source restore a wavefront from the object hologram was made from. To display artificial hologram you have to calculate and somehow display enormous amount of pixels far beyond any modern hardware could do. Devices that could do it named SLM (Spatial Light Modulator) and exists only as small LCD displays or DLPs with very high resolution and very small size. You could use a DLP from picoprojector to play with artificial holograms, but you will be able to create only amplitude holograms, that needs laser light to view and will be monochromatic. There exists SLMs that could modulate phase of light, they are better, but have same sizes and mach more expensive. This devices could work under usual light and create color holograms. You will see holographic images like the SLM is a window you see object through. Object also could appear before SLM, but as you move you head aside, image would be cropped by edges of SLM. And if you need a moving image, you meet with the main problem. You need enormous computing power to calculate that difraction grating to show on SLM. Best GPU will allow you to display a 3D object in real time on a SLM of 1-2 inches size. To display something on 10 inches SLM (it will be something like 10 million pixels x 10 million pixels - many orders more pixels than on all that fancy 8k displays) you will need a decent GPU or ASIC farm, larger than most mining farms on earth. There are no enough computing power on whole Earth to create a real-time hologram with size of car.

So, holograms in no way could be used by humans to create fake images of alien spaceships over cities. We have no necessary technology to create suitable light modulator, compute difraction image and power source to provide energy to all that stuff, especially in size of satellite.

There are other techologies to create 3D images, but the thing you mentioned, does not do it, really.

edit. look at these links https://www.youtube.com/watch?v=4svt7_tFT6o this techno is public

Mirror pyramid for your smartphone costs few bucks on Aliexpress. Software is free from different sources and authors. Check it, it's look like total shit in real. No way this shit could be named 3D. You just see a 2D image in 4 mirrors. It looks good on videos because camera shoot 2D image. But humans, usually have 2 eyes to percieve 3D and that break the illusion completely.

Closest thing to somewhat could be named 3D display is that thing - https://www.youtube.com/watch?v=V0fX9XMDNPw or devices using same principle but with rotating helix screen. At least you see real 3D image with your eyes from any angle, unlike in that mirror pyramid hoax. And in no way it is hologram.

There are even no any traces of technology that could be a ancestor of Earth technology to create 3D images in thin air with size of alien spaceship. Sudden appearance of any complex technology without any previous works that could somehow lead to the development of that technology is a perfect sign of alien interference. I looking for an example of technology suddenly appeared from nowhere for a long time, but still didn't find anything serious.

Finally, to create an images of alien spaceships over Earth cities, you inevitable need an alien technology. :) The appearance of simulated alien spaceship images over the cities will be the definite proof of alien existence. So, what is the point to simulate aliens existence, using the technology that only aliens could provide?

and they will probably use these satellites to produce the holograms over the cities

To produce hologram of that size you need a difraction grating of that size. You can't create holographic image in thin air visible from any angle without it.

Shortly, Hologram is a special image on some 2D surface with resolution comarable with wavelength of visible light. It create a sophisticated difraction grating, that after interaction with light from some source restore a wavefront from the object hologram was made from. To display artificial hologram you have to calculate and somehow display enormous amount of pixels far beyond any modern hardware could do. Devices that could do it named SLM (Spatial Light Modulator) and exists only as small LCD displays or DLPs with very high resolution and very small size. You could use a DLP from picoprojector to play with artificial holograms, but you will be able to create only amplitude holograms, that needs laser light to view and will be monochromatic. There exists SLMs that could modulate phase of light, they are better, but have same sizes and mach more expensive. This devices could work under usual light and create color holograms. You will see holographic images like the SLM is a window you see object through. Object also could appear before SLM, but as you move you head aside, image would be cropped by edges of SLM. And if you need a moving image, you meet with the main problem. You need enormous computing power to calculate that difraction grating to show on SLM. Best GPU will allow you to display a 3D object in real time on a SLM of 1-2 inches size. To display something on 10 inches SLM (it will be something like 10 million pixels x 10 million pixels - many orders more pixels than on all that fancy 8k displays) you will need a decent GPU or ASIC farm, larger than most mining farms on earth. There are no enough computing power on whole Earth to create a real-time hologram with size of car.

So, holograms in no way could be used by humans to create fake images of alien spaceships over cities. We have no necessary technology to create suitable light modulator, compule difraction image and power source to provide energy to all that stuff, especially in size of satellite.

There are other techologies to create 3D images, but the thing you mentioned, does not do it, really.

edit. look at these links https://www.youtube.com/watch?v=4svt7_tFT6o this techno is public

Mirror pyramid for your smartphone costs few bucks on Aliexpress. Software is free from different sources and authors. Check it, it's look like total shit in real. No way this shit could be named 3D. You just see a 2D image in 4 mirrors. It looks good on videos because camera shoot 2D image. But humans, usually have 2 eyes to percieve 3D and that break the illusion completely.

Closest thing to somewhat could be named 3D display is that thing - https://www.youtube.com/watch?v=V0fX9XMDNPw or devices using same principle but with rotating helix screen. At least you see real 3D image with your eyes from any angle, unlike in that mirror pyramid hoax. And in no way it is hologram.

There are even no any traces of technology that could be a ancestor of Earth technology to create 3D images in thin air with size of alien spaceship. Sudden appearance of any complex technology without any previous works that could somehow lead to the development of that technology is a perfect sign of alien interference. I looking for an example of technology suddenly appeared from nowhere for a long time, but still didn't find anything serious.

Finally, to create an images of alien spaceships over Earth cities, you inevitable need an alien technology. :) The appearance of simulated alien spaceship images over the cities will be the definite proof of alien existence. So, what is the point to simulate aliens existence, using the technology that only aliens could provide?