Measurement and time biases of the Geos 3 tracking systems in the Atlantic calibration area were determined in relation to the Goddard lasers. In collocation tests the lasers agreed with each other to about 10 cm. Early RAMLAS laser data contained an apparent time bias of 647 μs. Later, in a laser collocation test, RAMLAS differed from MOBLAS 2 by +11.3 cm and -28 μs. An overlooked correction reduced the -28 μs to -8 μs. The geoceivers initially had R˚ biases of 3-6 m/s and T biases of several milliseconds. During the first month of Geos 3 operations the R˚ biases decreased monotonically by 2.5¿1.0 m/s. The C band radar biases relative to the lasers were usually within several meters and several tenths of milliseconds. The unified S band system relative biases were usually within ¿4 mm/s and ¿0.1 ms. The average and scatter of the altimeter biases recovered on 18 laser reference arcs was -5.3¿0.6 m.