Not feasible in the way you propose it.

**Color of the light should be white**: laser are monochromatic, with a few nm bandwidth. Below you can see a qualitative [comparison][1] between the spectrum of a laser and the spectrum of a LED. To make it appear white as perceived by the human eye, you would need to cover the whole visible spectrum, which makes for about 500, 1 nm wide bands. Even using 3 colors to emulate white, you would still need about 150 lasers. Good luck finding a laser for each wavelength with a tuning of 1 nm. I have seen PhD being made on tunable lasers, but not in the range of powers you are interested in. And I am not mentioning the difficulty of compensating for the different diffraction of each wavelength. 

[![enter image description here][2]][2]

**Beam can be slightly angled, but the closer to 90° the better.**: a satellite normally circles the whole planet in about 90 minutes. It covers one degree around the vertical of a given spot for 7 hundreds of a second. Spy satellites can get that sort of control, but they don't aim for an object the size of a watermelon (with all the due respect for your head), though they can resolve it in their images.

**equipped with a powerful laser**: last but not least, what makes you think that it is smart to stand under the shine of a laser powerful enough to shine through more than 100 km of atmosphere? Unless your goal is to impress the bystanders with the laser burns that you will get.


  [1]: https://www.thefoa.org/tech/ref/appln/transceiver.html
  [2]: https://i.sstatic.net/kgZ79.jpg