Knowing the iss was passing overhead in the evening in question myself, my wife and my sister in law who was visiting stood outside our house to watch. i was tracking the iss on the tracking app available and mentioned to my wife that the iss was over darwin at the northern tip of australia and let's see how long it took to get to us. as the iss approached we watched as it came almost overhead when a red object slightly dimmer than than the iss moved at similar speed towers it (iss) from the east. at first i thought it was an aircraft bit quickly realised it wasn't a normal aircraft as the light was solid red with no flashing and there where no navigation nor anti-collision lights visible. it seemingly passed very close to the iss then from my perspective slowed or stopped as the iss passed before it moved away in a westerly direction. i thought it may be a drone but it was very high or out of the atmosphere. i immediately checked flight radar and there was no civilian aircraft near that part of the sky and there was also no sound. we regularly get f18 super hornets over my house at high level during the day and very occasionally at night but they are very loud. i served 22 years in the air force as both an engineer and observer/photographer and this wasn't a normal event in my opinion. even my wife agrees it was very unusual.