Quoted:
space blanket
I prefer USGI casualty blankets... OD green on one side, much sturdier, and they have grommets to tie into a shelter like a poncho. The important thing is not to let the space blanket or casualty blanket touch your body or it will heat up and emit a signature. A pane of glass will also work very well. Don't stay in place for long periods of time as your body heat will warm the ground and give you away.
A well trained operator who knows you are in the area will likely find you because the blanket doesn't match the temperature of the surrounding vegetation, But let's be honest-if you have helicopters in your area looking for you then your ass is flying high enough on radar that they will get you one way or another. If a helicopter is zipping overhead and isn't looking for you in particular, you may have a better chance.
What I am wondering is if an aluminized mylar blanket will show up on targeting radar of something like an Apache?