Altimetric satellites have characteristic sampling patterns in both space and time based on their repeat period and orbit inclination. Aliased phenomena measured by altimetric measurements can appear as propagating waves with both wavelength and direction of propagation different from the underlying phenomena. All signals that contribute to the altimetric measurement can be aliased and produce such patterns, not just tidal signals. For example, mesoscale energy will be aliased as will unmodeled atmospheric variations. Past discussions of aliasing have only considered spatially homogeneous signals. This paper extends this work to phenomena with finite wavelengths and considers both the north‐south and east‐west components of the resulting aliases.

Calibration data for the TOPEX/Poseidon altimeter was collected at Texaco's Platform Harvest off the coast of southern California. The CU sea level system, containing two Paros depth sensors, was designed and installed at Platform Harvest to collect submerged pressure data. Corrections for instrument bias, water density, and atmospheric pressure were applied to each depth sensor and sea level obtained relative to an established benchmark on the platform. Estimates of H 1/3 were determined to characterize the sea state during the 2‐h period surrounding each overflight using classical theory. To test the validity of these assumptions, the ratio between spectra measurements from the upper and lower depth sensors was normalized by the expected theoretical ratio. The results differ from theory by ∼1% with a standard deviation of ∼2%. The weighted mean frequency as a function of H 1/3 was calculated during several overflight periods. Results indicate that the frequency content tends to be bimodal for H 1/3 values below 2.5 m.

The advantages of having Geosat Follow-On in a Geosat orbit flying simultaneously with Topex Follow-On in a Topex/Poseidon orbit are examined. The orbits are evaluated using two criteria. The first is the acute crossover angle. This angle should be at least 40 degrees in order to accurately resolve the slope of sea level at crossover locations. The second is tidal aliasing. In order to solve for tides, the largest constituents should not be aliased to a frequency lower than two cycles/year and should be at least one cycle discrete from one another and from exactly two cycles/year over the mission life. The results show that TFO and GFO in these orbits complement each other. Both satellites have large crossover angles over a wide latitude range. In addition, the Topex orbit has good aliasing characteristics for the M2 and P1 tides for which the Geosat orbit has difficulty.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 Can I now introduce the members of the Commission, and because they are facing away from me I might get this wrong. On my extreme right is Iain Robertson; on the left of Iain Robertson is Jean Couper; on my extreme left is Keith Geddes, and on his right is John Baillie. Bill Magee is Secretary to the Commission and we may refer to him for advice during the hearing. A note of the procedure which we will follow has been made available to witnesses and copies are available in the hall, and I notice quite a few have taken copies. We intend to hear in the first instance from the Controller of Audit and where appropriate the audit team. We will then ask representatives of the council to give evidence. In addition we have received a number of requests from individuals to make representations today. We have agreed to hear representations from the