BS ISO 17809:2014 pdf free

BS ISO 17809:2014 pdf free.Space data and information transfer systems一Delta-differential one-way ranging (Delta-DOR) operations
For a spacecraft, the one-way range is determined for a single station by extracting the phases of two or more signals emitted by the spacecraft. The DOR tones are generated by modulating a sine wave or square wave onto the downlink carrier at S-band, X-band, or Ka-band. Either a pure waveform may be used, producing a spectrum of pure tones, or a modulated waveform may be used, producing a spectrum that more closely resembles the spectrum of a natural radio source. DOR observables are formed by subtracting the one-way range measurements generated at the two stations. While each one-way range measurement is affected by the unknown offset in the spacecraft clock, the station differencing eliminates this effect. However, DOR measurements are still biased by ground station clock offsets and instrumental delays.
For measuring the quasar, each station is configured to acquire data from it in frequency channels centered on the spacecraft tone frequencies. This receiver configuration choice ensures that the spacecraft-quasar differencing eliminates the effects of ground station clock offsets and instrumental delays. By selecting a quasar that is close in an angular sense to the spacecraft, and by observing the quasar at nearly the same time as the spacecraft, the effects of errors in the modeled station locations, Earth orientation, and transmission media delays are diminished.
In navigation processing, the delay or DOR observable is modeled for each scan of each radio source. The measured observable depends on both geomtric factors and on delays introduced by transmission media. Meteo data are provided from each tracking site so that,possibly in conjunction with other data such as GPS measurements, corrections can be computed to account for tropospheric and ionospheric path delays. The modeled or ‘computed’observable is based on geometric parameters and available calibrations for tropospheric and ionospheric delays. Residuals are formed by subtracting the computed observables from the measured time delay values. The ‘Delta’ between spacecraft and quasar observations is generated internal to the navigation processing by subtracting residual values of quasar observations from residual values of spacecraft observations.BS ISO 17809 pdf download.