Final answer:
The dimensions of the reference lights for cargo aircraft are not provided in the given information.
Step-by-step explanation:
The dimensions of the reference lights that mark an additional touchdown point for cargo aircraft are not provided in the given information. The information provided only mentions the dimensions of the LightSail spacecraft and its sails, which are unrelated to the reference lights for cargo aircraft. Therefore, specific information about the dimensions of the reference lights for cargo aircraft needs to be obtained from a reliable source or reference manual.