TODAY'S TOPICS Status check, photo opportunity Course goal and course learning objectives Some comments on the research process The research“catechism” The 16.62x cycle (16.62x Syllabus) Our thoughts on progress and achievement

Network Development of Network First measurements made in July 1992; just after start of International GPS Serviceigs). Since then measurements each year and often multiple campaigns per year. -The current network has over 1000 sites, many of them being recovery marks for the main

Styles of kinematic GPS Kinematic GPS techniques go by a number of names with features that are often receiver specific Kinematic GPS: Early term which implies that there is no loss of lock while the receiver is moving. In survey mode, if loss of ock occurs the antenna must be returned to a point of know ocation

GPS Groups/Gs There are many international and national groups involved in the deployment of GPS The international organization is the International GPs Service(IGs)

Primary research programs Geophysical research GPS analysis packages GAMIT (GPS at MIT): Uses double differences GYPSY: Jet Propulsion Laboratory (JPL) processing packages: Uses one-way observables and explicitly estimates clocks Bernese: Developed at Astronomical Institute

Rank deficiencies Ranks deficiencies are combinations of parameters that can not be separately estimated In GPs. there are several rank deficiencies UTl, Longitudes of all the stations and the nodes of the satellite orbits, effectively can not be separated In theory, orbit perturbations by the moon/sun on the GPs

Mathematical models in GPS Review assignment dates (updated on class web page) Paper draft due Mon April 29 Homework 3 due Fri May 03 -Final class is Wed May 15. Oral presentations o papers. Each presentation should be 15-20 minutes, with additional time for questions. · Next three lectures:

Basic antenna operation Receiving and transmitting antennas are identical: Time just flows in opposite directions. Antenna problems are solved knowing the current distribution J(x') in the antenna and using a vector potential

Propagation: lonospheric delay Summary -Quick review/introduction to propagating waves -Effects of low density plasma Additional effects -Treatment of ionospheric delay in GPS processing -Examples of some results

Basic atmospheric structure mosphere Troposphere is 2 100 where the temperature stops decreasing in the tmosphere(10 km altitude)