Advances in Deep-Space Transponder Technology

The paper offers an overview of the deep-space transponder (DST) equipment that has been developed by Thales Alenia Space-Italy over the last two decades in the framework of various European programs. It briefly describes major achievements, technologies, and characteristics relevant to the present class of DSTs operating in S- and X-band (Rosetta, Mars Express, and Venus Express missions). A complete overview of the novel DST equipment designed and developed for X- and Ka-band applications (BepiColombo mission) is provided.     

A Common Receiver Architecture for ESA Radio Science and Delta-DOR Support

The need to support radio science experiments and enhance navigation accuracy for the currently flying deep-space missions of the European Space Agency (ESA) has triggered the development of suitable tools in the agency's deep-space stations. This paper describes the modifications implemented in the ESA standard receiver, the Intermediate Frequency and Modem System (IFMS), for the above goals. These modifications were possible due to the highly flexible architecture of the IFMS. Results obtained in the area of radio science research and delta differential one-way ranging tracking are also presented.     

GMSK Demodulator Implementation for ESA Deep-Space Missions

This paper discusses a new implementation of a Gaussian minimum-shift keying (GMSK) modulator and demodulator on the European Space Agency (ESA)'s common deep-space receiver-the Intermediate Frequency Modem System (IFMS), which is a software radio based platform. The GMSK demodulator is needed for ESA's deep-space and near-Earth missions, starting with the Herschel-Planck satellites in 2008. The implementation requirements and hardware restrictions from the IFMS lead to the need for a significant simplification versus the optimum demodulation approach. In part, this can be achieved by using a demodulator based on the Laurent decomposition, yet further simplifications and changes to obtain a feasible implementation were necessary. The presented GMSK demodulator was directly implemented on the existing IFMS receiver without requiring any hardware changes. Measurements with the demodulator showed only a marginal technical degradation in the order of 0.1-0.3 dB for the chosen approach. Furthermore, for testing purposes, a GMSK modulator was implemented on the same platform.     

Ground antennas in NASA's deep space telecommunications

Ground antennas are the major visible components of NASA's Deep Space Network (DSN). The role, key characteristics, and performance of these antennas in deep-space telecommunications are described. The system analyses and tradeoffs to optimize the overall ground-to-spacecraft link and to define future missions are elaborated from an antenna perspective. Overall performance of receiving systems is compared using the widely accepted G/T figure-of-merit, i.e., net antenna gain divided by the operating system noise temperature. Performance of past, present, and future antennas and receiving systems is discussed, including the planned development of a world-wide network of 34-m diameter beam-waveguide antennas. The need for multifrequency operation, presently in the S- and X-bands, and in the future in the Ka-band, is discussed. The resulting requirements placed on antenna technology are highlighted. Beam-waveguide antenna performance to further improve performance and operational advantages is discussed     

A novel antenna concept for future solar sails: application of Fresnel antennas

Recent studies have shown that interplanetary missions may be made possible using inflatable solar sails that employ solar-flux power, providing thrust for spacecraft while reducing onboard fuel requirements. These sails require a large surface area (i.e., 100 m in diameter) to capture enough solar flux for spacecraft navigation. In this paper, a novel communication antenna concept is proposed for future solar-sail missions, taking advantage of the large sail surface area via application of Fresnel-zone (FZ) antennas. This study focuses on utilizing a design/analysis methodology using physical optics (PO) and method of moments (MoM) for Fresnel-type antennas applicable to the solar-sail missions. Extensive parametric studies of Fresnel-zone antenna radiation characteristics have been performed, and the analytical methodologies were verified using a series of measurements. Fresnel-zone antenna gain is studied under different antenna configurations. Furthermore, a Fresnel-zone antenna under surface deformation is investigated to characterize Fresnel-zone antenna performance in the reflective mode. In addition, a new bandwidth-enhancement technique is introduced for Fresnel-zone antennas, to accommodate the dual-band operation ( X band uplink and downlink) of the antenna for the deep space network (DSN).     

Conformal array antenna for observation platforms in low Earth orbit

A conformal array antenna can provide the flexibility that platforms in low Earth orbit need to download their data to ground stations. It does this by producing multiple beams for various ground stations. Even if only one ground station is used at a time, the higher gain of this antenna, compared to a fixed-beam antenna, allows the ground-station antennas to be down-sized, or, equivalently, the data rate to be increased. Moreover, missions on which disturbances in the platform attitude are critical can take advantage of a phased array with no moving parts. Although the demonstration model was targeted at a low-Earth-orbit mission, the concept is equally applicable to future interplanetary science missions.     

基于AOTF的成像光谱技术在深空探测中的应用

首先介绍了欧空局(ESA)火星快车(Mars Express)上装载的火星大气特征研究光谱 仪(Spectroscopy for Investigation of Characteristics of the Atmosphere of Mars, SPICAM)和红外矿物光谱制图 仪(Observatory of Mineralogy, Water, Ice and Activity or IR Mineralogical Mapper, OMEGA)以及美国火星勘测轨道飞行器(Mars Reconnaissance Orbiter, MRO) 上搭载的紧凑型火星勘测成像光谱仪(Compact Reconnaissance Imaging Spectrometer for Mars, CRISM)的特点指标 及其相关应用。然后介绍了新型分光器件——声光可调谐滤波器(Acousto-Optic Tunable Filter, AOTF) 的原理及特点,并对拟用于月球探测的基于该分光技术的CE-3红外成像光谱仪和CE-5月球矿物光谱分 析仪进行了简要介绍。最后介绍了其光谱定标、辐射定标以及在宽温度范围内工作时的温度特性分析与校正,为AOTF在 深空探测中的进一步应用提供了技术参考。     

Prospects for a Next-Generation Deep-Space Network

A next-generation deep-space network is currently under consideration by the National Aeronautics and Space Administration. Building upon its many past successes, this network will be required to meet the needs of current and planned missions. These will, no doubt, include the familiar suite of telemetry, command, tracking, and navigation services, with performance levels derived from analysis of the probable future mission set. Additionally, it will be expected to provide enabling capabilities for missions still on the drawing boards. Traditionally, the network serves the robotic deep-space exploration fleet. However, at this time, consideration of the special needs of planned future human lunar missions is appropriate, as well as the evolution to the eventual human exploration of Mars.     

Uplink Arrays for the Deep Space Network

Deep-space communication and navigation is faced with two challenges in the future: (1) the potential retirement of the largest antennas of NASA's Deep Space Network and (2) an anticipated need for increasing ground system capacity so as to support higher data rates to and from missions operating at remote locations in the solar system, as well as in anticipation of a larger number of simultaneously flying missions. In the transmitting, or uplink, direction, one approach to increasing the effective transmitted power is to array multiple antennas. This is attractive mainly because it promises a lower construction cost than equivalent (large) single antenna systems. In addition, it has the potential for increasing the reliability of the uplink and reducing maintenance costs. This paper introduces the concept of uplink arraying by examining technological challenges and possible solutions to them. Arraying principles are presented and error sources described. The main challenge is to maintain carrier phase alignment among the antennas, and this must be done by periodic calibration. Presently, two calibration methods are being developed at the Jet Propulsion Laboratory as part of an uplink arraying demonstration effort. These methods are briefly discussed.     

Japanese deep-space station with 64-m-diameter antenna fed throughbeam waveguides and its mission applications

The Usuda Deep Space Center of the Institute of Space and Astronautical Science is a Japanese spacecraft tracking station constructed in October 1984. The station is equipped with a 64-m diameter antenna and associated electronics to support deep-space missions. The paper describes the 3-year development process of the station. The beam-waveguide configuration is described in detail to demonstrate its flexibility to modifications in order to adapt to subsequent missions. System configuration and operation examples are also given for several missions     

Deep space communications

Discusses communications with spacecraft in deep space from the point of view of: signal strength, the role of the DSN (Deep Space Network), the various missions, and the work of ESA/ESOC (European Space Operations Centre)     

Ruby masers for maximum G/Top

The Deep-Space Network (DSN) includes world-wide networks of 26-, 34- and 70-m antennas in Australia, Spain, and the USA. Ruby masers are used on the 34and 70-m antennas to maximize the system operating noise temperature and thereby maximize the DSN receiving system figure of merit, antenna gain divided by system operating noise temperature. These systems are used for deep-space telecommunications, solar system radar, and radio astronomy. Cavity, traveling-wave, and reflected-wave maser designs and performance characteristics from 960 MHz to 34 GHz are summarized. Effective noise temperatures of ruby masers are addressed with emphasis on a 33.68-GHz maser where quantum noise is a major source of noise     

Delay-Tolerant Network Technologies Coming Together

The Delay-Tolerant Network Research Group is a working group of the Internet Research Task Force, the research sister of the Internet Engineering Task Force standards body. DTNRG originated in discussions surrounding the inadequacies of TCP/IP for deep-space and interplanetary communications, but it has become a focal point for standardizing overlay technologies that address disconnected network environments on Earth as well.     

A phase-control approach for a large-element coherent microwavepower uplink system

Signal combining efficiencies of 98% have been achieved on low-Earth orbiting (LEO) debris with phase-locking of time-overlapped radar pulses from a two-element phased-array consisting of two 34-m beam waveguide steerable paraboloid antennas separated by 204 m. The uplink arraying at 7.19 GHz has been achieved for tracks from about 10° elevation at signal rise to 4° elevation at signal set under varying weather conditions (e.g., hail failing on one antenna). The typical root mean square (RMS) phase error for two coherent 100-μs 50-Hz 5-kW peak pulses reflected from LEO debris with signal-to-noise ratio (SNR) >23 dB is less than 4°. The phase-control system design, methods of calibration, and details of the design control table of phasing error contributors are presented and discussed. Based upon the measured performance, we predict that transmitting antennas for the Deep Space Network (DSN) could be coherently arrayed for up to hours at a time given static phase error calibrations on exo-atmospheric debris. Applications for this technique include low-cost implementation of high-power microwave transmitters for deep-space communication and radars for exploration of other planets and as part of a defense against comets and asteroids     

Power requirements for deep-space telecommunication links

The signal-to-noise ratio in a given equivalent bandwidth must be maintained above a minimum value during a deep-space mission in order to provide predictable performance, and in order to maintain effective telemetry communications with spacecraft at interplanetary distances it is necessary for earth stations to use maximum antenna gain. One solution is to extend telecommand range by reducing system noise temperature in the spacecraft receiver and reducing the bandwidth of the receiver's phase-lock loop. Low-noise preamplifiers have not yet been applied in planetary spacecraft in order to maintain simplicity and reliability. An answer to the problem seems to be high-power transmitters (earth-based) with outputs in the 1000-GW range.     

Power Flexible Ka-band Traveling Wave Tube Amplifiers of Up to 250-W RF for Space Communications

The latest model Ka-band helix traveling wave tube (TWT) amplifier designed and manufactured for onboard space satellite-communications systems at L-3 Communications Electron Technologies, Inc. is significantly improved over previous generations. This present-generation (model 999HA) TWT has demonstrated over 250-W RF output power over the 31.8- to 32.3-GHz deep-space frequency band with an overall efficiency exceeding 61% Robbins (Proc. IEEE Int. Vacuum Electron, 2006). In addition, the 999HA has low distortion and has demonstrated over 100-W RF output with 9-GHz instantaneous bandwidth. This TWT is expected to have application as a single unit or in power-combined systems so that deep-space missions can achieve a total RF output power of as much as 1 kW Wintucky (Proc. IEEE Int. Vacuum Electron, 2006). The 999HA can be mated to either 7-kV electronic power conditioners (EPCs) for low-power applications or to a recently developed 14-kV EPC (model 1693HC) to support higher power applications     

Space/ground systems as cooperating agents

Within NASA and the European Space Agency (ESA), it is agreed that autonomy is an important goal for the design of future spacecraft, and that this requires on-board artificial intelligence. NASA emphasises deep space and planetary rover missions, while ESA considers on-board autonomy as an enabling technology for missions that must cope with imperfect communications. ESA's attention is on the space/ground system. A major issue is the optimal distribution of intelligent functions within the space/ground system. This article describes the multi-agent architecture for space/ground systems (MAASGS). A MAASGS agent may model a complete spacecraft, a spacecraft subsystem or payload, a ground segment, a spacecraft control system, a human operator, or an environment. The MAASGS architecture has evolved through a series of prototypes. This study recommends that the MAASGS architecture should be implemented in the operational Dutch Utilisation Centre.     

Optimal horn antenna design to excite high-order Gaussian beammodes from TE0m smooth circular waveguide modes

The availability of medium-power gyrotron tubes (10-30 kW, CW) at millimeter-wave frequencies (30-100 GHz) allows applications such as advanced ceramic sintering, surface coating, radar, remote sensing, deep-space communications, etc. The concept of high-order Gaussian beam modes, which, under some conditions, can be assumed to be free-space modes, is applied to transport efficiently the power generated by a gyrotron for technological applications. A family of optimized nonlinear horn antennas is investigated in order to get the maximum coupling between the guided output mode of the gyrotron and the Gaussian beam modes. The numerical simulations show very favorable coupling with a conversion efficiency of about 99.8%     

Quasi-periodic radio frequency fluctuations in the circumsolar plasma observed during radio sounding experiments

Experimental radio sounding data of the circumsolar plasma, recorded with the help of the Ulysses, Mars Express, Venus Express, and Rosetta spacecraft, have been systematically analyzed. These data were processed via spectral and correlation methods with the aim of detecting quasi-periodic frequency fluctuations. Integral wavelet spectra have been constructed for the purpose of identifying periodic radio frequency fluctuations at different periods. Comparative analysis of the methods for detecting the quasi-periodic disturbances of the radio frequency in the circumsolar plasma has been carried out. It is demonstrated that frequency fluctuations with periods of 1–80 min are observed regularly in radio sounding experiments of the solar wind plasma.