Abstract
Microwave tracking, usually performed by on ground processing of the signals coming from a spacecraft, represents a crucial aspect in every deep-space mission. Various noise sources, including receiver noise, affect these signals, limiting the accuracy of the radiometric measurements obtained from the radio link. There are several methods used for spacecraft tracking, including the Delta-Differential One-Way Ranging ( Δ DOR) technique. In the past years, European Space Agency (ESA) missions relied on a narrowband Δ DOR system for navigation in the cruise phase. To limit the adverse effect of nonlinearities in the receiving chain, an innovative wideband approach to Δ DOR measurements has recently been proposed. This work presents the hardware implementation of a new version of the ESA X/Ka Deep Space Transponder based on the new tracking technique named Wideband Δ DOR (W- Δ DOR). The architecture of the new transponder guarantees backward compatibility with narrowband Δ DOR.
Highlights
This paper presents the hardware implementation and characterization of a novel Delta-Differential One-Way Ranging (∆DOR) technique based on spread-spectrum waveforms [1,2]
The Wideband ∆DOR (W-∆DOR) bread-board is composed of a 0.18 μm ATMEL Ka-band Transponder (KaT) ASIC (i.e., ATC18RHA family) integrated in the TAS digital transponder platform [12,15] and by an ALTERA FPGA Stratix II DSP
A floating point (FLP) to fixed point (FXP) optimization phase was performed to reduce the hardware complexity maintaining the specification of 50 dB of Dynamic
Summary
This paper presents the hardware implementation and characterization of a novel Delta-Differential One-Way Ranging (∆DOR) technique based on spread-spectrum waveforms [1,2]. SBI measurements to a network of landers on the moon would provide differential range at least an order of magnitude more precise, providing useful geophysical information on the lunar interior This level of accuracy can be obtained by means of two-way radio links in X or Ka band enabled by suitably designed digital transponders and spread spectrum radio links, as described in this paper. Thanks to the differential nature of the measurement, the difference between the spacecraft and quasar delays produces an observable that minimizes calibration errors due to instrument dispersion, especially the ones due to phase ripples in the acquisition filter, providing enhanced performances [10]. The recent advancements in the field of on-board microelectronics, e.g., Digital Signal Processing cores for space applications, are enabling factors to develop the newest ∆DOR paradigm based on broadband observables: Wideband ∆DOR
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