Deep space communication has its own features such as long propagation delays, heavy noise, asymmetric link rates, and intermittent connectivity in space, therefore TCP/IP protocol cannot perform as well as it does in terrestrial communications. Accordingly, the Consultative Committee for Space Data Systems (CCSDS) developed CCSDS File Delivery Protocol (CFDP), which sets standards of efficient file delivery service capable of transferring files to and from mass memory located in the space segment. In CFDP, four optional acknowledge modes are supported to make the communication more reliable. In this paper, we gave a general introduction of typical communication process in CFDP and analysis of its four Negative Acknowledgement (NAK) modes on the respect of file delivery delay and times of retransmission. We found out that despite the shortest file delivery delay, immediate NAK mode suffers from the problem that frequent retransmission may probably lead to network congestion. Thus, we proposed a new mode, the error counter-based NAK mode. By simulation of the case focused on the link between a deep space probe on Mars and a terrestrial station on Earth, we concluded that error counter-based NAK mode has successfully reduced the retransmission times at negligible cost of certain amount of file delivery delay.

We statistically investigate the spectral scalings of magnetic fluctuations at the upstream and downstream regions near the Venusian bow shock and perform a differentiation by shock geometry. Based on the Venus Express data, 115 quasi-parallel (Q ∥ ) bow shock crossings and 303 quasi-perpendicular (Q ⊥ ) bow shock crossings are selected. The statistical results suggest that the bow shock tends to modify the upstream spectra flatter to 1/f noise in the magnetohydrodynamics (MHD) regime and steeper to turbulence in the kinetic regime after the magnetic fluctuations crossing the bow shock, and this modification for the Q ∥ and Q ⊥ bow shock is basically consistent. While the upstream spectral scalings are associated with the shock geometry. The changes of the spectral scalings of magnetic fluctuations near the Q ∥ bow shocks are not as significant as near the Q ⊥ bow shock crossings. That might result from the fluctuations generated by the backstreaming ions which can escape across the Q ∥ bow shock into the foreshock. Our results suggest that the energy cascade and dissipation near Venus can be modified by the Venusian bow shock, and the Q ∥ bow shock plays an important role on the energy injection and dissipation in the solar wind interaction with Venus. The large dispersion of spectral scalings indicates that this fluctuation environment is complicated, and the shock geometry is not the only key factor in the fluctuations across the Venusian bow shock. Other possible factors in the shock modification to the upstream fluctuations will be explored in future.

We statistically investigate the spectral scalings of magnetic fluctuations at the upstream and downstream regions near the Venusian bow shock and perform a differentiation by shock geometry. Based on the Venus Express data, 115 quasi-parallel ( {Q}_{\parallel } ) bow shock crossings and 303 quasi-perpendicular ( {Q}_{\perp } ) bow shock crossings are selected. The statistical results suggest that the bow shock tends to modify the upstream spectra flatter to 1/f noise in the magnetohydrodynamics (MHD) regime and steeper to turbulence in the kinetic regime after the magnetic fluctuations crossing the bow shock, and this modification for the {Q}_{\parallel } and {Q}_{\perp } bow shock is basically consistent. While the upstream spectral scalings are associated with the shock geometry. The changes of the spectral scalings of magnetic fluctuations near the {Q}_{\parallel } bow shocks are not as significant as near the {Q}_{\perp } bow shock crossings. That might result from the fluctuations generated by the backstreaming ions which can escape across the {Q}_{\parallel } bow shock into the foreshock. Our results suggest that the energy cascade and dissipation near Venus can be modified by the Venusian bow shock, and the {Q}_{\parallel } bow shock plays an important role on the energy injection and dissipation in the solar wind interaction with Venus.

We statistically investigate the spectral scalings of magnetic fluctuations at the upstream and downstream regions near the Venusian bow shock and perform a differentiation by shock geometry. Based on the Venus Express data, 115 quasi-parallel (Q∥) bow shock crossings and 303 quasi-perpendicular (Q⊥) bow shock crossings are selected. The statistical results suggest that the bow shock tends to modify the upstream spectra flatter to 1/f noise in the magnetohydrodynamics (MHD) regime and steeper to turbulence in the kinetic regime after the magnetic fluctuations crossing the bow shock, and this modification for the Q∥ and Q⊥ bow shock is basically consistent. While the upstream spectral scalings are associated with the shock geometry. The changes of the spectral scalings of magnetic fluctuations near the Q∥ bow shocks are not as significant as near the Q⊥ bow shock crossings. That might result from the fluctuations generated by the backstreaming ions which can escape across the Q∥ bow shock into the foreshock. Our results suggest that the energy cascade and dissipation near Venus can be modified by the Venusian bow shock, and the Q∥ bow shock plays an important role on the energy injection and dissipation in the solar wind interaction with Venus. The large dispersion of spectral scalings indicates that this fluctuation environment is complicated, and the shock geometry is not the only key factor in the fluctuations across the Venusian bow shock. Other possible factors in the shock modification to the upstream fluctuations will be explored in future.