The Consultative Committee for Space Data Systems has recently updated its recommendation for uplink communication systems, to cope with new requirements for telecommand and modern profiles and applications. Two short Low-Density Parity-Check (LDPC) codes have been added to the Coding and Synchronization sublayer options, to improve the link performance. In this paper we focus on the real-time implementation of the transmitter for the Ground Station segment. We analyze the critical modules, in particular LDPC encoding, for which two efficient solutions based on a Shift Register Adder Accumulator and on Winograd convolution are considered. We then discuss the selection of a proper hardware or software platform, and we show that a Central Processing Unit-based solution is able to achieve the high data-rates required by the new uplink applications.

The main technical objectives of the ESA financed activity (ITT 9111 - ESA Contract No. 4000123441/18/NL/FE) currently underway at Thales Alenia Space Italia is the design, development of a breadboard of an integrated Payload Data Transmitter (PDT) and Telemetry, Tracking and Command (TT&C) equipment and its validation. The paper will describe major achievements, key technologies and specific issues of the future integrated communication unit (ICU): in a single very compact equipment both the transponder and high data rate payload data transmitter functionalities are integrated. The ICU under development in TAS-in-Italy is based on new design concepts as long as disruptive technologies aiming to face the emerging so called “NewSpace” market. Leveraging on the many years of experiences on transponder line (well consolidated Digital Signal Processing (DSP) building blocks are used) and developing new and very attractive architecture approach (direct synthesis as opposed to traditional conversion approaches) the paper will show how a very lightweight equipment with reduced components can be conceived. The equipment architecture description will be provided by highlighting key concepts and main components. A section is here devoted to EEE parts quality policy. As far as technology is concerned, the RF-on-PCB will be introduced as a key cornerstone to achieve driver requirements as required by constellation market, e.g., low cost, short lead time and high production rate.

Since their dawning, space communications have been among the strongest driving applications for the development of error correcting codes. Indeed, space-to-Earth telemetry (TM) links have extensively exploited advanced coding schemes, from convolutional codes to Reed-Solomon codes (also in concatenated form) and, more recently, from turbo codes to low-density parity-check (LDPC) codes. The efficiency of these schemes has been extensively proved in several papers and reports. The situation is a bit different for Earth-to-space telecommand (TC) links. Space TCs must reliably convey control information as well as software patches from Earth control centers to scientific payload instruments and engineering equipment onboard (O/B) spacecraft. The success of a mission may be compromised because of an error corrupting a TC message: a detected error causing no execution or, even worse, an undetected error causing a wrong execution. This imposes strict constraints on the maximum acceptable detected and undetected error rates.

NEXCODE is a project promoted by the European Space Agency, aimed at research, design, development, and demonstration of a receiver chain for telecommand links in space missions, including the presence of new short low-density parity-check codes for error correction. These codes have excellent performance from the error rate viewpoint but also put new challenges as regards synchronization issues and implementation. In this paper, after a short review of the results obtained through numerical simulations, we present an overview of the breadboard designed for practical testing and the test-plan proposed for the verification of the breadboard and the validation of the new codes and novel synchronization techniques under relevant operation conditions.

Thales Alenia Space - Italy (TAS-I) Radio Communication Equipment Group has developed in the last few years a very competitive Digital Platform for Satellite Secure Communications which has been largely used in Telemetry, Tracking and Command (TTC) link for military-oriented programs. The standard Direct Sequence Spread Spectrum Anti-Jamming performances are further enhanced by an Adaptive Digital Filtering to remove part of the interference energy before codes correlation, allowing to cope with a Jammer over Signal Power ration (J/S) up to 50dB. Moreover, PN codes with several years period increases furthermore Data Confidentiality and Transmission Secrecy. This paper offers a complete overview of the advanced Spread Spectrum Equipment for Satellite Secure Communications.

Next generation of On-Board Telemetry, Tracking and Command (TTC) equipment for Secure Communications, based on Spread Spectrum Systems, shall adopt very long Pseudo Noise (PN) Cryptographic Codes in order to increase the Secure Satellite link Confidentiality and Anti-Jamming performances. This paper presents a new On Board PN Codes Synchronizer Architecture based on the Generalized Zero Padding Algorithm (GZP) and frequency domain Doppler compensation scheme in order to acquire very long PN codes at low Signal to Noise Ratio, large Doppler and large Jammer over Signal Power Ratio (J/S). It is shown that by adjusting the zeros padded to the received signal, the non coherent integrations and the Doppler compensation strategy, the On-Board Code Synchronizer satisfies all different satellite mission scenarios (Geo Stationary Orbit, Low Earth Orbit, Medium Earth Orbit and Launch and Early Orbit phases) requirements for very long PN code synchronization, ensuring very low code acquisition time due to the high parallel searching capability.

This paper reports the main characteristics of the deep space transponder (DST) equipment that has been designed, developed and tested by Thales Alenia Space—Italy (TAS-I) for the European Space Agency (ESA) BepiColombo mission to Mercury.

The paper presents a digital waveform generator for spaceborne applications capable of synthesizing a wide band signal with a high spectral purity and a flexible configuration capability from pulse to pulse. A parallelized processing architecture is employed to overcome space qualified ASICs clock limits. The baseband generator synthesizes linear and non-linear chirps from DC to 500 MHz. Signal phase and amplitude digital compensation is allowed in both time and frequency domain. Finally the generator is provided with frequency hopping and PSK modulation capabilities.

Near future on-board telemetry, tracking and command (TT&C) equipment for secure communications will likely adopt frequency hopping (FH) instead of direct sequence (DS) spread spectrum (SS) techniques. As far as TT&C systems will have to cope with jammer-to-signal power ratios higher than 50 dB, classical DS approaches must be abandoned in favour of more robust FH solutions. In the following paper we present an overview of synchronization, channel coding and modulation issues for next generation anti-jamming TT&C transponder under study and design at Alcatel Alenia Space-Italy (AAS-I)

In this paper the implementation of a multirate QPSK modulator is presented. The modulator architecture has been optimized to reduce the hardware complexity and maximize the carrier frequency in order to meet the requirements of deep space and satellite applications. Finally, the performance has been evaluated by implementing the modulator on a Xilinx XC2V3000 FPGA

This paper presents the Koreasat 5 secure communication system that has been design and developed by Alcatel Alenia Space-Italy (AAS-I) for Agency for Defense Development-South Korea

Aim of this paper is to provide an overview of Alcatel Alenia Space-Italy (AAS-I) Spread-Spectrum Transponder platform placing emphasis on its advanced features for secure telemetry, tracking & command (TT&C) applications

Aim of the paper is to present a novel digital platform for the transmitting side (NDP-Tx) of a deep space transponder which has been developed by Alenia Spazio in the frame of the ESA study on "Digital Techniques for TT&C Transponder". The proposed design has unique features in terms of flexibility and interfacing with the spacecraft command data sub-system (CDS). The NDP-Tx supports standard telemetry modulation formats based on residual carrier and more advanced schemes aiming to improve the space-to-earth link performance. In fact, in case of limited available power, as for satellite transmitters, the power efficiency is maximised driving the power amplifier in saturation, i.e. in the non-linear region of its transfer characteristic. Using constant (i.e. GMSK) or quasi-constant (i.e. Square-Root Raised Cosine SRRC-Filtered OQPSK) envelope modulation allows the transmitter stage to operate in saturation without the drawback of the non-linear distortion (i.e. adjacent channel interference due to sidelobes spreading and regeneration).

Aim of this tutorial is to provide an overview on band-pass sampling approach for on-board processing applications. The paper will focus on the I/Q sampling of bandpass signals and their downconversion. The image problem and two methods for its rejection is presented.

The progress of digital design techniques and the improvement of the very large scale integration (VLSI) technologies allow the implementation of the signal processing core of telemetry, tracking and command (TTC) equipments in customized digital devices which support the complete set of communication functions as required by the most advanced space applications and recently issued standards. Accordingly a new digital platform, the TTC Modem, has been developed by Alenia Spazio in the frame of the ESTEC Contract 15902/01/NL/JA. The TTC Modem is partitioned in two main sections: the receiver side (NDP-Rx, Receiver Novel Digital Platform) and the transmitter side side (NDP-Tx, Transmitter Novel Digital Platform), which are respectively based on the Rx-FPGA and the Tx-FPGA. In particular, this paper focuses on the NDP-Rx, while the companion paper (Simone et al., 2004) offers an overview on the NDP-Tx.

Aim of this paper is to provide some background on X/X/Ka transponder design taking into account typical operational requirements such as acquisition performance, tracking range and demodulation loss for the receiver side and phase noise, short term frequency stability and frequency coherence for what concern the transmitter side. The paper includes system concepts and trade-offs.

Aim of this paper is to provide an overview of the on-board signal acquisition techniques suited for Deep Space Transponders addressing also mission aspects and implementation issues.

This paper presents the digital Deep Space Transponder developed for the ESA next missions (Rosetta, Mars Express) placing emphasis on the digital design, turnaround ranging and achieved performance.

The present paper aims to define viable strategies for implementing flexible and programmable fully digital modulators, able to cope with multiple symbol rates, signal bandwidths, and modulation schemes, using a single analog section (composed by filters and up-converters). This development is applicable both in the field of broadband multimedia communication payloads, as well as in telemetry tracking and command links and also in deep space communications, for which the topics that need to be addressed are essentially the same. However, when state-of-the-art performance is required, it might be needed to separate the developments on the basis of the specific application. An example of a GMSK modulator architecture is also given.