How to use the moon trek API to make heatmaps(grayscale) for unity terrain generation?

So i have a project where i need to make a game, on the moon, and the player should be able to explore the moon surface. for the terrain i thought i wiil use this particular image heightmap, but it is so massive, my computer can not handle it. Then i saw the site by nasa, NASA MOON TREK this site also has an api to get images of the moon’s surface, on a scaled level but this api is the worst documented api i ever encountered with.

Can anyone help me finding these heatmaps so that i can complete my project? thanks!