True Color with Aqua and Terra

    Satellite images are great. Really great. However they have one glaring drawback: they're color blind. Take a look at any geostationary satellite image (GOES, MTSAT, METSAT, etc) and you'll find that they're grayscale. Sure, some might seem to be in color, but that is typically just the gray being colorized to highlight features or a static color image of the Earth being inserted as a background. Luckily there are two satellites (now three) that can observe in brilliant true color: Aqua and Terra.

Aqua

Terra

    These two satellites launched in 1999 (Terra) and 2002 (Aqua), share many of the same instruments and are often referred to as "siblings". The instrument that is most important to this post, the one that see color, is called the Moderate Resolution Imaging Spectroradiometer, or MODIS.

MODIS

    The two platforms, Terra and Aqua, are polar orbiting sun-synchronous satellites. This means that they orbit close to the Earth while scanning a swath of data along their track that is about 2300km wide. The term "sun-synchronous" means that the crafts pass over any given spot on the ground at the same time each day. As far as the of MODIS packages are concerned, Terra is placed in an orbit such that it always passes over around 10:30am local time, while Aqua passes over around 1:30pm. In order for this sun-synchronous timing to occur, the orbit does not actually pass over the poles (despite what the name suggests), instead it is at a slight angle.
    The beauty of MODIS is that is that it observes in thirty-six different bands (groups of wavelengths), all at high resolutions. Two of these bands have a resolution of 250m, so features as small as lakes and individual mountains are easily discernible. One of these bands, when combined with two others, enables MODIS to "see" in true color. Thus the Earth and its weather can be viewed as if one were actually up in space and viewing with their own eyes.
    For those who want a quick look at this data, NASA's Earth Observing System Data and Information System (EOSDIS) have developed an application called Worldview that allows users to view MODIS images just a few hours after they were captured. This images are projected onto a map of the Earth that is updated as data becomes available. Users can also add overlays of over fifty different other types of data, including the other instruments on board Aqua and Terra. Finally, Worldview allows for the creation of snapshots at multiple resolutions.

Worldview

    Many interesting things can be seen with MODIS imagery, so I often snapshots of particularly notable features. So, from time to time I'll post these images, along with a caption providing some kind of explanation. These aren't intended to be hard science data analysis, just something neat to look at. After all, everyone likes to look at pretty pictures.