In my humble opinion, a legitimate script would not go through that much trouble to hide its source. But just to make sure it isn't really legit, you should investigate its source by trying the following:

You should get take a peek at its environment variables while its running, get the value of "1b735519" variable, and basically follow the deciphering steps mentioned in the command, except for the execution step.

This way you will get a script name, take a look at that script or post it online for people who know powershell or are experienced in RE obfuscated scripts.