Delta Differential One-way Ranging (ADOR) is a powerful method used for navigation of interplanetary probes. It provides a direct measurement of the angular position of a spacecraft using interferometric techniques to obtain the difference in the arrival time of a spacecraft signal received at two ground stations, using an ICRF (International Celestial Reference Frame) quasar as a reference. In 2005, Sapienza University of Rome undertook the development of a ADOR correlator for the European Space Agency, expanding the tools available for the operation of European planetary and astrometric missions. Since its delivery, the correlator has been successfully used for the orbit determination of Venus Express and Rosetta. In a later release the correlator's capabilities were expanded to accept data acquired not only at ESA's ESTRACK stations, but also at VLBI and NASA's Deep Space Network antennae. In 2011 ESA and Sapienza University have undertaken further enhancements of the correlator, by expanding the accepted data formats, extending the total spanned bandwidth and enabling the correlation of very-low SNR signals. The new Raw Data Exchange Format, RDEF, established by the Consultative-Committee for Space Data Systems (CCSDS) in order to increase the ADOR interoperability between different agencies has been implemented in the correlator. This enhancement will allow the direct processing of data acquired by different agencies. The second additional functionality provided an improved determination of the quasar and spacecraft delay by increasing the spanned bandwidth of the recorded signal. Due to current hardware limitations, the bandwidth at ESTRACK stations is currently limited to 28 MHz. ESA is planning to use three LDC (L-band Down-Converter) to acquire different portion of the signal spectrum, and route the signal to up to three IFMS receivers (Intermediate Frequency Modulation System). With this configuration the total spanned bandwidth could be increased up to 220 MHz at Ka-band. The enhanced version of the correlator is capable of handling this new configuration and take advantage of the wider bandwidth. Finally, a third enhancement enabled the correlation of narrowband, low-SNR, spacecraft signals. Although the correlator can operate in several modes, the processing of the spacecraft signal is currently carried out by means of a master phase locked loop (PLL) on the carrier and slave PLLs on the telemetry harmonics. A new PLL-free algorithm for the spacecraft data correlation allows the processing of low-SNR signals (up to 1 dBHz). Such weak signals cannot be tracked by a standard PLL (hardware or software).

ESA ∆DOR enhancement: agencies interoperability, wideband and low-SNR functionality / Barbaglio, Francesco; Alessandro, Ardito; Iess, Luciano; R., Madde; M., Mercolino; M., Lanucara; Gabriele, Rapino. - ELETTRONICO. - 5:(2012), pp. 3569-3575. (Intervento presentato al convegno 63rd International Astronautical Congress 2012, IAC 2012 tenutosi a Naples; Italy nel 1 October 2012 through 5 October 2012).

ESA ∆DOR enhancement: agencies interoperability, wideband and low-SNR functionality

BARBAGLIO, FRANCESCO;IESS, Luciano;
2012

Abstract

Delta Differential One-way Ranging (ADOR) is a powerful method used for navigation of interplanetary probes. It provides a direct measurement of the angular position of a spacecraft using interferometric techniques to obtain the difference in the arrival time of a spacecraft signal received at two ground stations, using an ICRF (International Celestial Reference Frame) quasar as a reference. In 2005, Sapienza University of Rome undertook the development of a ADOR correlator for the European Space Agency, expanding the tools available for the operation of European planetary and astrometric missions. Since its delivery, the correlator has been successfully used for the orbit determination of Venus Express and Rosetta. In a later release the correlator's capabilities were expanded to accept data acquired not only at ESA's ESTRACK stations, but also at VLBI and NASA's Deep Space Network antennae. In 2011 ESA and Sapienza University have undertaken further enhancements of the correlator, by expanding the accepted data formats, extending the total spanned bandwidth and enabling the correlation of very-low SNR signals. The new Raw Data Exchange Format, RDEF, established by the Consultative-Committee for Space Data Systems (CCSDS) in order to increase the ADOR interoperability between different agencies has been implemented in the correlator. This enhancement will allow the direct processing of data acquired by different agencies. The second additional functionality provided an improved determination of the quasar and spacecraft delay by increasing the spanned bandwidth of the recorded signal. Due to current hardware limitations, the bandwidth at ESTRACK stations is currently limited to 28 MHz. ESA is planning to use three LDC (L-band Down-Converter) to acquire different portion of the signal spectrum, and route the signal to up to three IFMS receivers (Intermediate Frequency Modulation System). With this configuration the total spanned bandwidth could be increased up to 220 MHz at Ka-band. The enhanced version of the correlator is capable of handling this new configuration and take advantage of the wider bandwidth. Finally, a third enhancement enabled the correlation of narrowband, low-SNR, spacecraft signals. Although the correlator can operate in several modes, the processing of the spacecraft signal is currently carried out by means of a master phase locked loop (PLL) on the carrier and slave PLLs on the telemetry harmonics. A new PLL-free algorithm for the spacecraft data correlation allows the processing of low-SNR signals (up to 1 dBHz). Such weak signals cannot be tracked by a standard PLL (hardware or software).
2012
63rd International Astronautical Congress 2012, IAC 2012
Data exchange format; Differential one-way ranging; European Space Agency
04 Pubblicazione in atti di convegno::04b Atto di convegno in volume
ESA ∆DOR enhancement: agencies interoperability, wideband and low-SNR functionality / Barbaglio, Francesco; Alessandro, Ardito; Iess, Luciano; R., Madde; M., Mercolino; M., Lanucara; Gabriele, Rapino. - ELETTRONICO. - 5:(2012), pp. 3569-3575. (Intervento presentato al convegno 63rd International Astronautical Congress 2012, IAC 2012 tenutosi a Naples; Italy nel 1 October 2012 through 5 October 2012).
File allegati a questo prodotto
Non ci sono file associati a questo prodotto.

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11573/504021
 Attenzione

Attenzione! I dati visualizzati non sono stati sottoposti a validazione da parte dell'ateneo

Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 1
  • ???jsp.display-item.citation.isi??? ND
social impact