On 3 April, 1995, a low earth-orbiting (LEO) receiver was
successfully launched aboard the Micro-Lab 1 satellite. This
receiver, orbiting at an altitude of about 700 km, receives radio
signals from the constellation of 24 Global Positioning System
(GPS) satellites. These radio signals are refracted, or bent by the
Earth's atmosphere, and by measuring the Doppler shifted
frequency of the received radio signals, these measurements are
converted into vertical pressure and temperature profiles of the
Earth's atmosphere. Early results indicate that accuracies of about
1 to 2 K are being obtained between altitudes of about 5 km to
35 km. This new remote sensing technique promises to open up
new ways to monitor climate and climate change, and also to
provide substantially improved initial global data for weather
prediction.
The project is a joint program between the University Corporation
for Atmospheric Research (UCAR), the National Center for
Atmospheric Research (NCAR), the Jet Propulsion Laboratory
(JPL), Orbital Sciences Corporation (OSC), Allan Osborne
Associates, and The University of Arizona. The figure shows a
typical GPS/MET vertical temperature profile together with nearby
high resolution radiosonde soundings (CL), regular radiosondes
(RS), and interpolated NMC data.=1A
For further information, please contact Prof. Benjamin M. Herman.