Satellite altimeters make extremely precise and accurate measurements of the range to the sea surface. In order to achieve an altimeter's ultimate accuracy, many effects must be accounted for. One important effect is error in the range caused by differences between the waveform observed by the altimeter and the simplified model waveform used to design the range tracking algorithms. The difference between the observations and the mode[ is mainly a function of satellite attitude and significant waveheight (SWH). SWH is mea- sured by the altimeter as pan of the range tracking process. The apparent satellite attitude can be determined from the "tail" of the waveform (see Brown, 1977; Rodriguez, 1988; Chelton et al., 1989).
The excess antenna gain in the 0.7-0.2 ° area will result in excess waveform power in gates 54-128 1128 is the naaximum, i.e., the altimeter only uses the center of the antenna bcam), which will appear in telemetry waveform samples 43-64 (Hayne et al., 1994). Anglcs between -0.17 ° are used in the ahimeter AGC determination which sets the overall scalc for the waveform. Angles around 0.45 ° affect the wavelbrm signal used for attitude determination and lot pointing angle/sea state corrections to other measured quantities. The residuals here show typical differences of about 5-7% between the relative power in the 0-0.2 ° region and the 0.45 ° region. This is similar to other features reported by Hayne ct al. (1994). CNES altimeter (Poseidon) data are also consistent with the results reported hcrc (O.-Z. Zanifc, private communication).