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Thaichote / THailand Earth Observation Satellite (THEOS)

The THailand Earth Observation Satellite (THEOS) is the first operational earth observation satellite of Thailand. The THEOS program was developed by GISTDA, EADS Astrium, the prime contractor, initiated work on the satellite in 2004. Thaichote the first Earth observation satellite of Thailand, was successfully launched by Dnepr launcher from Yasny, Russian Federation, on Wednesday, October 1, 2008 at 06:37:16 UTC (Universal Time Coordinated) or 13:37:16 hours, Bangkok Time.

The Thaichote imagery product is available in a variety of product options. Thaichote multispectral products provide 15 meter resolution (at nadir) and 8 bits information depth. All four bands are delivered as one file. The output scene is a square scene of 90 km. x 90 km. Thaichote panchromatic products provide 2 meter resolution (at nadir) and 8 bits information depth. The output scene is a square scene of 22 km. x 22 km. . Thaichote imagery products are also available in a 4-band pan-sharpened product option. These products combine the visual information of 4 multispectral bands (blue, green, red, Near IR), with the spatial information of the panchromatic band. Pan-Sharpened products are available as product option for level 2A only. The output scene is a square scene of 22 km. x 22 km.

These product options use different spectral band combinations and imply differences in the pixel resolution of the final product. The PAN strip is 22 km width and theMS strip is about 90 km width at nadir. Scenes are defined as a square portion of the imaged strip. An image strip can be acquired continuously with a length of up to 10 minutes, which is an equivalent of approximately 4,000 km.

Thaichote oblique viewing capability allows for the imaging of any area within a 1000 kilometer swath (for 30° roll). Oblique viewing can be used to increasethe viewing frequency for a given point during a givencycle. The frequency varies with latitude: over Thailand, a given area can be imaged 9 times duringthe same 26-days orbital cycle. This means a yearly revisit of 126 times and an average of 3 days, with an interval ranging from a minimum of 1 day to a maximum of 5 days.

Stereo pair can be used for relief perception and elevation plotting (Digital Elevation Modelling). Thesestereo images can be acquired by Thaichote with 2 different methods: 1. The programming of two images of the same areaon the ground acquired at different roll viewing angles on successive satellite passes 2. The pitch agility allows acquiring a stereo pair in the same pass at less than 5 mn delay.