One of the most distinctive features of the billboard is its depiction of Earth as seen from the lunar surface. The original concept used an image of Earth largely covered by white clouds.
Professor Kazuto Saiki, Director of the Earth & Space Exploration Center (ESEC) at Ritsumeikan University and one of the faculty members scheduled to join FREX, recognized that the image appeared to show the Northern Hemisphere centered on the Arctic region, near Greenland. He pointed out that this would be an unnatural view of Earth from the region where future lunar development is expected to take place. "Because this billboard will likely be seen by many people in a place where they naturally gather, such as when meeting someone, there will inevitably be viewers who ask themselves, 'Which part of Earth is actually visible?' We wanted to create a view that would feel authentic even to space enthusiasts while also encouraging people to ask, 'Why does Earth look this way?'" For this reason, the image was adjusted so that the view of Earth would be both scientifically plausible and easy for viewers to recognize, with the Japanese archipelago visible from the chosen angle.

Further refinements were also made to the boundary between Earth's day and night (the terminator). In the original draft, there was a slight inconsistency between the position of the Sun implied by the terminator and the direction of the shadows cast on the lunar surface. To resolve this, the orientation of Earth was adjusted to ensure the two were consistent. "If the relationship between Earth's terminator and the shadows on the Moon doesn't match, the scene becomes astronomically impossible. Details like these have a significant impact on the overall realism of the billboard. We also paid close attention to how Earth appears. For those who know what to look for, it's possible to tell roughly where on the Moon this base is located. I'd be delighted if someone waiting to meet a friend looked up at the billboard and started thinking about that," said Professor Saiki with a smile.

The rover and other equipment depicted on the lunar surface also underwent careful review. In the original draft, the shadows were somewhat subdued and did not fully capture the intense lighting conditions characteristic of the Moon, where there is virtually no atmosphere. In addition, because the Sun is expected to remain relatively low above the horizon in the regions where future lunar development is anticipated, long shadows would naturally be cast across the surface. Therefore, the length and contrast of the shadows were adjusted to create a more authentic lunar landscape.
Professor Taizo Kobayashi, Deputy Director of ESEC and another researcher scheduled to join FREX, explained: "The length and intensity of shadows are key elements in conveying the unique appearance of the lunar surface. If they are too strong or too weak, the scene looks unnatural, so achieving the right balance is essential." The direction of the shadows was also checked to ensure it remained consistent with Earth's terminator.

The rover shown on the lunar surface was also reviewed from an engineering perspective.
In the original draft, the steering mechanism—which controls the rover's direction by turning its wheels—appeared to be mounted slightly off the tires' centerline. Touching on how this was adjusted to create a more realistic design, Professor Kobayashi said, "For those of us involved in rover development, even details like this tend to stand out."

Further refinements were also made to the structure connecting the rover's wheels to its body, drawing on designs used in actual lunar rovers. Another subtle enhancement was the depiction of the wheels sinking slightly into the Moon's fine surface dust, or regolith. Professor Kobayashi explained: "Even having the tires sink just slightly into the surface creates the impression that the rover is actually driving across the Moon."

Throughout the creation of this billboard, the goal was not only to produce a striking design, but also to ensure that it was astronomically plausible and looked right from an engineering perspective. As Professor Saiki observed, "The smaller the inconsistency, the more likely it is to be noticed by those who look carefully." By carefully eliminating these subtle inconsistencies, the team ultimately enhanced the credibility of the billboard as a whole.
Although the scene may appear to be a simple depiction of a lunar landscape, it embodies a wealth of expert knowledge and discussion. If you have the opportunity to visit Hankyu Osaka-Umeda Station, we hope you will stop and take a closer look—not only at the billboard itself, but also at the expert-driven attention to detail paid by the researchers scheduled to join FREX.

• Professor Kazuto Saiki
• Professor Taizo Kobayashi