So far, the EU's Copernicus program has sent three Sentinel satellites to observe Earth - 1A, 2A and 3A. But they're just the first halves. Enter Sentinel-1B, and the first mission becomes whole.
The European Union's Copernicus Earth Observation program takes a whole step this week with the launch of its Sentinel-1B satellite. With it, the first of six Sentinel missions becomes whole. Each of the missions consist of two halves - a satellite A and a satellite B.
But already the three satellites in orbit (1A, 2A, and 3A) have delivered realms of high-resolution images and other data that is helping scientists observe Earth, monitor our impact on the environment, and track the movement of vessels on busy waterways.
Sentinel-1A, for instance, has recently shown that the Mekong River Delta - one of the world's major rice-growing areas - has experienced a drop in productivity over the past year, possibly due to the El Niño phenomenon, with knock-on effects for food security.
The Sentinel-1B satellite is scheduled to launch from Europe's Spaceport in French Guiana on April 22 at 21:02 GMT (23:02 CEST).
This gallery features a mere handful of the many striking images captured by Sentinels 1A, 2A and 3A since 2014.
These images have been cropped, with permission. They can be viewed here in their full glory.