Orbit & Coverage

Orbit

The Aura satellite orbits 438 miles (705 km) from Earth's surface. Its inclination (the angle between the orbit plane and the equator plane) is 98.21°. The orbit is sun-synchronous with a 1:43 PM ascending node.

Target Size

One of the features of a Fourier Transform Spectrometer (FTS) is that it readily supports an imaging mode, which, in turn, improves collection efficiency compared with the more traditional spatially scanning systems. TES employs 1 X 16 linear arrays, each of whose individual field of view is 0.75 X 7.5 mrad (see plot below).

(click to enlarge)

At the trailing limb, some 3100 km distant, these values translate to spatial resolutions of 2.3 km vertically and 23 km horizontally. Since the same arrays are used in nadir (705-km range), the projections become 0.5 km in-track and 5 km cross-track at the Earth's surface.

(click to enlarge)

Nadir View

The nadir mode is able to look at an area approximately 5.3 km x 8.3 km (3.3 x 5.2 miles) with a spectral resolution of 0.1 cm^-1 (low-resolution mode). TES is a pointable instrument and can access any target within 45 degrees of the local vertical and produce regional transects up to 885 km in length without any gaps in coverage.

Limb View

The TES limb mode is able to look at an area approximately 26 km x 41.8 km (16.2 x 25.9 miles) with a spectral resolution of 0.025 cm^-1 (high resolution mode). In the limb mode, TES has a height resolution of 2.3 km, with coverage from 0 to 33 km.

The at-launch version of the global survey consisted of four ground locations, two co-located nadir targets and three limb tangents projected to the ground. On May 25, 2005 the global survey was modified to conserve instrument life. The three limb scans were eliminated from the sequences and replaced by an additional nadir scan.

TES Nadir Observation Footprint Examples

This plot (JPG, 653 KB) shows an example of ground targets for a TES global survey period of 16-orbit (~26 hours). Global surveys are about 180 km apart. Here also are examples of a special observation Step & Stare (JPG, 36 KB) footprint (these are about 45 km apart) and a Transect (JPG, 23 KB) observation (about 12 km apart). Visit the Global Survey and Special Observations pages for more information on TES operating modes.

Animated views of TES global survey 16-orbit target ground locations:

These two animations, a rectangle view (QuickTime, 95.66 MB) and a hemisphere view (QuickTime, 57.59 MB), illustrate the target locations for a TES global survey period of 16 orbits. To view them, you may need to download the free Apple QuickTime player.