So the time the temperature is measured (ie when the satellite is above a particular location) is critical and orbits of satellites gradually decay. (climateaudit.org)
Some apparent problems with the predictions of climate models, for example, have actually turned out to be due to problems with real - world data caused by the failure to correct for factors such as the gradual changes in orbits of satellites. (newscientist.com)
(That's a little bit of an exaggeration, because it's really skinny little stripes where there orbit of the satellite is, so it's not a full map.) (climatechangenationalforum.org)