Orbit / Navigation
For the JWST to be able to make precise infrared observations it is necessary that the telescope and its instruments are cooled so as not to emit their own infrared radiation that might interfere with signals from observed astronomical objects. This is one of the reasons why the JWST orbit will be far away from Earth. Sunlight reflected from the Earth's clouds and oceans creates enough heat to disturb observations.
The remote location of the JWST at L2 puts very strict limits on its physical specifications. To be able to fly all the way to L2 the JWST can't weigh more than around 6200 kilograms, and it will need powerful radio transmission equipment to 'beam' back data to Earth.