The bulk of the emission in this waveband is from dust particles and large hydrocarbon molecules, which can only survive outside of the ionized central region. There is also some emission from ionized atoms within the hot central region.
Planetary nebulae are large luminous shells of material ejected from dying stars.
The material of this particular PN was ejected about a thousand years ago and is currently about 100 times the size of our Solar System. There is some work remaining to enable reliable fast guiding while chopping which is required to deliver good image quality during long integrations. This implies that low, uniform telescope background and good thermal uniformity have been achieved.