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WESTPAC 1 (Western Pacific Laser Tracking Network) is a small, passive laser ranging satellite for geodetic measurements.

At the Western Pacific Laser Tracking Network (WPLTN) Executive meeting in Moscow on 2 December 1995, it was announced that Electro Optic Systems (EOS) had entered into a joint project with the Russian Space Agency (RSA) to construct and launch a new SLR satellite (WESTPAC-1, formely known as WPLTN-1) designed to overcome the limitations of all present targets in relation to millimeter geodesy. Initially, this satellite was referred to as WPLTN-1. It is currently designated WESTPAC-1 and very similar in design to GFZ-1.

Its main immediate purpose is to provide the best possible target for the WPLTN stations and, by implication, the Keystone Project constructed by Communications Research Laboratory (CRL) of the Japanese Ministry of Posts and Telecommunications.

The WESTPAC satellite is covered with recessed retroreflectors of the Russian Fizeau design to permit only one retroreflector to contribute to the return. On average, 0.7 corner cubes contribute to the return, and therefore the return signal fades in and out as different reflectors come into view. The satellite is well-suited for advanced two color ranging experiments.

WESTPAC is a passive satellite with the only instrumentation onboard is the retroreflector array. The WESTPAC retroreflector array is designed so that:

  • Only a single corner-cube will reflect on any shot
  • Its response will be optimized for 1.54 micron wavelength, to provide for fully eyesafe ranging at any power
  • The center-of-mass correction is accurate to 0.5 millimeters
  • To verify indisputably the existence or otherwise of the Fizeau effect.


Nation: Australia
Type / Application: Geodesy
Operator: Electro Optic Systems (EOS), Western Pacific Laser Tracking Network (WPLTN)
Contractors: Russian Institute for Space Device Engineering (RISDE)
Equipment: 60 prism corner cube retroreflectors
Configuration: 24.5 cm dia brass body
Propulsion: None
Power: None
Mass: 23.5 kg
Orbit: 835 km × 835 km, 98.68
Satellite COSPAR Date LS Launch Vehicle Remarks
WESTPAC 1 (ex WPLTN 1) 1998-043E 10.07.1998 Ba LC-45/1 Zenit-2 with Resurs-O1 2, Techsat 1B, FASat Bravo, TMSat 1, Safir 2


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