You have a problem.
First, there are lots of little chunks of stuff that have helium in it. A huge number are very small, but close enough to out gas and show up in a low resolution version of your survey.
That's where the problem comes in. This planet is very far out. If it is in the far reaches of its orbit, very little sunlight is going to hit the planet. You're going to have to capture very high resolution images to even get a few photons from this object. And they will be hidden by the myriad of closer objects.