Arun K Saraf
The polar orbiting satellites have the advantage of daily global coverage of data, which are being used for land, ocean and atmospheric research. The Indian Institute of Technology Roorkee – Satellite Earth Station (IITR-SES), established (sponsored by Department of Science and Technology, Govt. of India, New Delhi) and operational since 24 October 2002, has been acquiring and archiving day and night time Advanced Very High Resolution Radiometer (AVHRR) data from the American National Oceanic and Atmospheric Administration (NOAA) series of satellites and the Multi-channel Visible and Infrared Scan Radiometer (MVISR) data from the Chinese Feng Yun (FY) series of satellites. The archival system has been developed by building three auto archival software modules as a further enhancement to the existing archival system. The data is being used in earthquake studies, along with other studies like fog studies, floods, drought monitoring and snow cover mapping in collaboration with other research organizations.
The National Oceanic and Atmospheric Administration (NOAA) K, L and M (NOAA 15, 16 and 17, respectively) and NOAA-18 series of American satellites were launched to introduce a new era of improved environmental monitoring, meteorology, hydrology, climate research, agriculture etc. NOAA polar satellite program evolved over many years of experiments and operational satellite programs after the launch of their first satellite TIROS-1 on 1 April 1960. The subsequent generations were enhanced further in terms of sensors and machines. They carried additional payloads, including independent search and rescue facilities ) and enhancement of channels in the sensors came into being. Later, in the year 1988, the People’s Republic of China launched their Feng Yun (FY) -1 series of meteorological satellites. The launch dates and frequencies of transmission of the NOAA and FY series of satellites are given in the table 1.
|NOAA-15 (K)||13 May 1998||HRPT-1702.5|
|NOAA-16 (L)||21 September 2000||HRPT-1702.5|
|NOAA-17 (M)||24 June 2002||HRPT-1707.0|
|NOAA-18||20 May 2005||HRPT-1698.0|
|FY-1C||10 May 1999||CHRPT-1700.5|
|FY-1D||15 May 2002||CHRPT-1700.5|
Table 1: Launch dates and transmission frequencies of NOAA- and FY-series of satellites.
Polar orbiting satellites provide daily global data for land, ocean and atmosphere studies. In a polar satellite, the number of orbits per day is not an integer (makes 14.1 orbits per day), therefore the sub-orbital tracks do not repeat on a daily basis, although the local solar time of each satellite’s pass remains the same for a particular place.
Each satellite in the NOAA series of polar orbiting, sun-synchronous satellites with a six-channeled radiometer, provide global data at least four times a day with a spatial resolution of 1.1 km. Similar to the NOAA series are the Feng Yun (FY) -1C and -1D series of satellites with a ten-channeled radiometer, with the same spatial resolution (table 2). A comparison between NOAA-AVHRR and FY-MVISR scenes is shown in figure 1.
Table 2: Specifications of the NOAA and FY series of satellites.
Figure 1: Comparison of NOAA-AVHRR and FY-MVISR data.
Table 3: NOAA-AVHRR and FY-MVISR channels specifications and comparison