The paper says it is a 'digital camera', a dark sky could imply an ultraviolet sensor - but on second look it appears to be just an inverted grayscale image, po

The paper says it is a 'digital camera', a dark sky could imply an ultraviolet sensor - but on second look it appears to be just an inverted grayscale image, possible near-infrared but I would assume the image modification is just for improved visibility/contrast rather than special recording techniques. Here is the image in non-inverted mode: https://imgur.com/FBsuos1 https://imgur.com/FBsuos1