Can I use Project Image and Ethereal to make an illusory, ethereal scout?

Question

Situation:
A spell caster casts Ethereal to enter the Border Ethereal, creates an illusory copy of herself by using project image while she is in the Border Ethereal, and then dismisses Ethereal.

Would the illusory copy remain in the ethereal plane after the caster has left, allowing the caster to still be able to perceive (using the senses of the illusory ethereal copy) as it moves around as an ethereal traveler?

The idea here is to use the illusory copy as a scout/spy/traveler in the ethereal plane while the original caster remains in another plane. Does this work, or does something in the game prevent this?

Answer 1

This appears to work

The rules for Etherealness and Project Image don't have any obvious interactions, and I don't know of any rules that keep a spell with an effect in one plane from functioning if a caster shifts to another. Furthermore range is not a factor - the caster must create the illusory double within range, but (from the Spellcasting rules):

Range

...Once a spell is cast, its effects aren’t limited by its range, unless the spell’s description says otherwise.

Projected Image contains no such provision, so it follows that once the spell is cast the double can be as far from the caster as desired without any ill effects.

It appears that the only potential problem is the caster breaking concentration if they are unfortunate enough to take damage from ending up inside a creature or solid object after shifting back to their plane-of-origin :)