GPS-Global Positioning System | Electronics Seminar Topic
GPS-Global Positioning System
The GPS (Global Positioning System) radio occultation
experiment onboard the German CHAMP (CHAllenging Micro satellite payload)
satellite was successfully started on February 11,2001. By the end of July 2001
about 16,000 occultations were recorded.
More than 80% of the measurements
could be processed to derive vertical profiles of atmospheric temperature and
specific humidity. Throughout the measurement period GPS anti-spoofing mode was
enabled. On average, about 230 globally distributed occultations per day were
recorded.
Their distribution shows a characteristic latitudinal
dependence with maximum occultation density at polar regions and minimum
density in the equatorial region.
A statistical comparison of dry temperature
profiles, derived from CHAMP measurements, and corresponding meteorological
analyses shows excellent agreement between 8 and 30 km altitude. For the
Northern hemisphere the mean deviation is <0.5 K with a standard deviation
of <1 K between 12 and 25 km.A single difference technique was applied to
the data analysis.
The temperature difference for an individual profile
compared to the corresponding data, retrieved by double differencing, is
<0.1K below 20 km and <0.5 K below 35 km altitude. Keywords. GPS radio
occultation, CHAMP,remote sensing, temperature profiles
