The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part Bl. Beijing 2008
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be less than 0.1 times of the PRT for application of triggering
the data acquisition, <T r < 25us is required.
But for application of timestamping, the positioning error
resulted by cr T should be less than 0.1 times of the baseline
measurement error. We can know from formula (7) , cr T <
263ns is needed.
aT ~Yo a ‘ /V ” (7)
GPS absolute time synchronisation is qualified to precisely
timestamp and trigger the data acquisition events. For GPS
receivers the uncertainty in absolute time is in the order of
100ns, thus absolute time synchronization accuracy for DSS
can reach 200ns.
4. CONCLUSION
In this paper, we proposed a novel DSS using one passive
satellite with a dual receive antenna(DRA) flying in formation
with an already existing conventional SAR satellite. Based on
analyse and simulations, accuracy requirements for baseline
estimation and time & frequency synchronization are given. A
method based on dual frequency GPS is introduced. Baseline
estimation could be realized by dual frequency GPS receivers
with 8mm accuracy(three axis). Pulse-Timing synchronization
is realized by GPS PPS signal and frequency synchronization is
realized by the STALOs synchronized by GPS-receivers which
could provide good frequency accuracy and long term stability.
In this way the highest possible coherency between Distributed
SAR Satellites is ensured. The new method is simple and
practical and, most importantly, very effective. Future work
would include the impact of oscillator phase noise and practical
method of reduction of relative phase noise for DSS.
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F. Meyer, S. Hinz, The Feasibility of Traffic Monitoring with
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Matthias Weiß, Synchronisation of Bistatic Radar Systems,
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GFZ( Geo Forschungs-Zentrum Potsdam) , Technical Note ,
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