This ATV blog is in the process of being archived and going into retirement but great questions are still coming in that we feel obliged to answer. In response to our “ATV-made in USA” post Marcin asked:
What's the configuration of lights on an ATV? It's not clear from the video... all of them are white?
Each ATV had five lights, two at the front left and right, one at the bottom, one at the top, and one at the back. The lights were only turned on during the spacecraft’s approach to the International Space Station and shortly after undocking.
The lights were requested by the astronauts who understandably wanted to be able to check the 20-tonne spacecraft’s approach at long distances and without sunlight. The lights flashed with a similar blink rate to aircraft lights but each set of lights flashed with different frequencies so the astronauts could check the spacecraft’s attitude on approach.
Normal incandescent light bulbs were used to avoid unnecessary costs and shorten the ATV development time.
Interestingly the light at the back of ATV was never seen in space as it approached and left the Station pointing with its hatch forward at all times. The rear light was placed as a precaution but even when designing ATV the engineers knew that if all went well it would never be seen!