A NASA example with three dates
NASA’s retrospective On This Day in 2015: An EPIC New View of Earth explicitly says the image was acquired on July 6, 2015 and originally published on July 21, 2015. The later retrospective is another publication event. Its current presence on a website does not turn the underlying observation into a new view of Earth.
This clear example gives a useful method: copy the acquisition information from the caption, rather than inferring it from the date displayed at the top of an article.
Check whether the image spans time
NASA’s Earth, Behind the Scenes account describes a global map assembled from thousands of scenes collected over a hundred days. Such a composite can be scientifically useful without representing a single simultaneous camera exposure. A seamless-looking globe does not establish that every visible place was observed at the same moment.
Read whether the product is a single acquisition, a mosaic or an average. Keep the stated observation interval when no single capture date applies.
Compare like with like
For a before-and-after sequence, record the acquisition dates of both images, not just the programme’s release year. Consider season, cloud cover, sensor and processing as identified in the source notes. A change in display colours or image crop can alter appearance independently of a change on the ground.
Do not calculate a trend from two attractive images without the underlying method. The sequence may be an illustration selected to explain a process rather than a complete measurement series.
Preserve the useful caption
Save the location, instrument, acquisition date or range, processing description and original source link. If a programme supplies only a credit, use it to find the image’s institutional page. State uncertainty where the acquisition information cannot be recovered. When sharing, a caption such as acquired in 2015 and republished in a later retrospective keeps the chronology clear. This prevents a newly encountered image from being described as a current observation simply because it has just appeared in your feed or programme guide.
Related questions
Does an article’s date prove when its image was captured?
No. Read the acquisition date in the caption or data description.
Can a globe image combine many days?
Yes. Some composites deliberately combine observations over an interval.
Sources and scope
Scope notes distinguish published documentation, supplied information and editorial methods. They do not report a hands-on service test.
- NASA: EPIC retrospective — Explicit acquisition and original-publication dates in a later retrospective.
- NASA: Earth behind the scenes — Explains a global map assembled from many scenes over a hundred days.
