A NOVEL, RUGGED AND ROBUST LONGITUDINAL RANGE FINDING METHOD FOR FORMATION FLYING MISSIONS

摘要

An optical metrology measurement system is beingrndeveloped for the Proba-3 formation flying mission tornmeasure the longitudinal separation of the satellites.rnBased on current experimental breadboard performance,rnit is anticipated that the inter-satellite spacing will bernunambiguously determined to ≤10 microns resolution atrnranges from metres to hundred of metres and at updaternrates of at least 10 Hz, thus meeting or exceeding thernProba-3 optical metrology requirements. The metrologyrntechnique employed is believed to be unique in that it isrnbased on a variable frequency optical pulse source, withrnthe optical pulse repetition rate varied to find the exactrnparameters which provide a null in the phase differencernbetween a reference pulse train and the return pulsesrnfrom the outlying satellite. The unambiguousrnmeasurement range is limited only by the coherencernlength of the laser, and therefore the system will bernappropriate for future formation flying missionsrnrequiring longitudinal range measurements over manyrnkilometres. Range accuracies are limited only by thernstability of an electronic reference frequency whichrngoverns the repetition rate of the optical pulses. Everyrnsystem component of this new metrology systemrnalready exists as either a military or space qualifiedrnversion, allowing rapid prototyping of a mission readyrnsystem. An important system feature is its ability tornswitch between pulsed and continuous laser operation,rnthus enabling variations in the satellite formationrnspacing to be tracked with interferometric resolutionrnfollowing initial range determination.