Evolution of the Lunar Network

The National Aeronautics and Space Administration has conducted a comprehensive study to identify the most appropriate and efficient modulation, coding, multiple access and link protocol options for future space communication links supported by NASA's Ground Network, space network, deep space network, and earth-based ground terminals and in-situ relay satellites envisioned for Constellation Program mission support at the Moon and Mars. This paper briefly describes the study process and summarizes the multiple access recommendations for future NASA space communications.

The aggregate EIRP of an N-element antenna array is proportional to N 2 . This observation illustrates an effecti ve approach for providing deep space networks with very powerful uplinks. The increased aggregate EIRP can be employed in a number of ways, including improved emergency communications, reaching farther into deep space, increased uplink data rates, and the flexibility of simultaneously providing more than one uplink beam with the array. Furthermore, potential for cost savings also exists since the array can be formed using small apertures. I. Introduction plink arraying is a fundamentally new concept that promises to dramatically increase NASA's future deep - space communication s capabilities. The requirement to command spacecraft after launch and during encounter, and to provide two -way communication and two -way ranging as well as in -flight reconfiguration t o accommodate changes to mission objectives, is an integral part of every deep -space mission. The use of antenna arrays enables greater data -rates, greater effective operating distance, and cost -effective scaling for more demanding future missions through a highly flexible design philosophy, via the inherently parallel architecture of antenna arrays. Currently, uplink command and telemetry functions are carried out by 34 and 70 meter antennas in the deep -space network (DSN). The newer 34 meter antennas are used for routine uplink operations, whereas the older 70 meter antennas are employed when greater range or data rates are required. However, the 70 meter antennas may soon be decommissioned due to age and increasing maintenance costs. Instead of building new 70 meter or larger aperture antennas, current plans call for the construction of arrays of smaller antennas together with the required signal processing to maintain and eventually surpass NASA's current long -range and high data -rate communications capa bilities. This paper presents the uplink array technology program 's effort at JPL , with the goal of enabling NASA's deep space network to better serve planetary missions. Array calibration options will be discussed and a summary of error sources will be provided. Presently, three 70 -m and s ix 34 -m antennas constitute NASA's deep space network. If the array technology proves successful, ultimately, the large 70 -m and 34 -m antennas could be retired in favor of smaller size antennas.

The importance of the development of laser telemetry for reception of scientific data from space is pointed out by J. Bland-Hawthorn et al. in their Policy Forum “Laser telemetry from space” (26 July, p. 523). The authors consider the limitations to data communication in the microwave range due to spectrum allocations, but they do not consider the fundamental limitations for both radio and optical communications due to the signal-to-noise average power ratio as expressed by Shannon ([1][1], [2][2]). The spectrum allocation limit is relevant for near-Earth applications, but for the important case of communication at distances of 0.1 astronomical units (AU) and beyond, the signal-to-noise limit is dominant. At large distances, the radio and optical communication rates feasible in the next 15 years are comparable. This situation is illustrated in the figure, which plots data rate as a function of distance for three cases: (i) NASA's current radio Deep Space Network (DSN), (ii) optical technology expected to be available by 2010, and (iii) a future large radio array, such as discussed recently in Science (“Tuning in the radio sky,” R. Irion, 3 May 2002, p. [830][3]). ![Figure][4] Comparison of current and future radio and optical communication rates at astronomical distances. Data rate ( 3 ) versus distance for DSN (blue), expected optical technology (purple), and a future large radio array (red). The leveling off of the radio data rate at distances less than 0.2 AU (about 30 million km) is due to spectrum allocations of 50 MHz for the current DSN at 8.4 GHz and 500 MHz at 32 GHz for a future large array. The data rate in bits/second can exceed the bandwidth in hertz by using multilevel coding but has a flat logarithmic dependence on signal-to-noise ratio and, hence, distance. At the distance of Jupiter, the current radio data rate is limited by signal-to-noise ratio on the order of 50 kbits/s, which is three orders of magnitude lower than the spectrum allocation. An important goal is video data rates from the outer planets, which requires on the order of 5000 kbits/s. This rate is feasible with SKA-class large radio arrays that are under development for radio astronomy and are under consideration by NASA for space communications. Other factors such as the proven reliability of current spacecraft radio transmitters, sensitivity to location of the sun, spacecraft vibration and pointing requirements, and availability due to weather conditions (clouds) all need to be considered. Radio spectrum allocations of several GHz in the 100-GHz frequency range have yet to be explored. Both optical and radio communications need to be developed for future space communications of scientific data. 1. 1.[↵][5]1. C. Shannon , Bell System Tech. J. 27, 379 (1948)623. [OpenUrl][6][CrossRef][7][Web of Science][8] 2. 2.[↵][9]The Shannon limit is given by C = B .log2 (1 + S / N ), where C is the data rate in bits/s, B is the channel bandwidth in Hz, and S and N are the average signal and noise powers. It is important to note that N is proportional to B and refers to additive noise due to background sources and detectors and not the fluctuations due to the Poisson distribution of signal photons. 3. 3.The data rates in the figure are all for 50 W of DC power consumption and similar communication equipment mass of 18 kg at the spacecraft and assume 9 dB of link margin to account for atmospheric variations, error-correction coding efficiency, and component degradations. The 2010 optical link assumes a 10-m receiving antenna on Earth, a 0.3-m-diameter transmit antenna, a background noise level (daytime) of 10 quanta, and a data rate increase of of 1/ln 2 = 1.442 allowed by the Shannon limit for an optimum bandwidth much greater than data rate. The current radio link assumes a 70-m DSN antenna, 1.5-m-diameter transmit antenna, and total system noise of 54 quanta ( T sys = 22 K at 8.4 GHz). The future large array assumes 3600-by 12-m-diameter antennas, 1.5-m transmit antenna, and total system noise of 26 quanta ( T sys = 40K at 32 GHz). # Response {#article-title-2} Radio communication technology has been around for a very long time and is now so nearly optimized that little improvement can be anticipated unless increasingly large and correspondingly costly antenna arrays are constructed. Optical/near-infrared communications are still in their infancy. But, in many applications, the high inherent bandwidth of optical frequencies should ultimately make them far more powerful than radio waves. Our Policy Forum anticipated that near-infrared telemetry techniques would take the lead in communication across space sometime in the next decade. Weinreb correctly points out the importance of Shannon's limit on data transmission rates in telemetry across vast stretches of space. Our Policy Forum took this limit into full account, albeit without specific mention. For transmission from the astronomically important Lagrangian point L2 at 0.01 AU, Weinreb's plot clearly illustrates the large advantage that optical telemetry has even over the most ambitious currently projected radio techniques. Over greater interplanetary distances, Weinreb's plot shows the future radio array winning out at radio frequencies, but this is only because he compares laser transmission with a relatively small 0.3-m transmitting antenna to radio transmission with a 1.5-m-diameter antenna. With comparable transmitting dishes, the two systems would perform equally well. For regular access from space, ground receiving stations need to be distributed around the globe to assure communication at all times of day. The anticipated ground stations for near-infrared telemetry are expected to be affordable and more easily installed at widely distributed sites. The billion-dollar Square Kilometer Array will be a wonderfully powerful astronomical instrument, but it should, and most probably will, be used primarily for exquisitely sensitive radio astronomical observations rather than for spacecraft telemetry. [1]: #ref-1 [2]: #ref-2 [3]: /lookup/doi/10.1126/science.296.5569.830 [4]: pending:yes [5]: #xref-ref-1-1 View reference 1. in text [6]: {openurl}?query=rft.jtitle%253DBell%2BSystem%2BTech.%2BJ.%26rft.volume%253D27%26rft.spage%253D379%26rft_id%253Dinfo%253Adoi%252F10.1002%252Fj.1538-7305.1948.tb01338.x%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [7]: /lookup/external-ref?access_num=10.1002/j.1538-7305.1948.tb01338.x&link_type=DOI [8]: /lookup/external-ref?access_num=A1948UH03900001&link_type=ISI [9]: #xref-ref-2-1 View reference 2. in text

Communications with satellites exploring other planets and objects far from Earth is provided by NASA's Deep Space Network (DSN). Deep space by its nature places a limit on return data rates. This adds to mission cost through extended contact time. Methods that increase mission data rates can substantially reduce the number of required ground contacts and overall cost; or, alternatively, they can increase science data return for a fixed amount of contact time. This paper reports on the first in-flight results of using polarization diversity combining in deep space communications to nearly double the downlink data rate. The DSN and the satellite microwave telecommunications systems are detailed, along with a model of the DSN combining gain. Test results from Mars Odyssey and the New Horizons Mission to Pluto are described, including operational constraints and potential improvements. The significant impact and benefits of this new capability are discussed.

The Cassini Mission is in the final years of its second extension, the Cassini Solstice Mission (CSM). Nine months prior to the end-of-mission, the spacecraft will embark on its final mission phase, the F-ring and Proximal Orbits (FRPO). These orbits will bring the spacecraft closer to Saturn than ever before, allowing for the collection of some of the most unprecedented, imperative, and profuse science of the entire mission. A key challenge during this phase is identifying viable spacecraft downlink opportunities given the reduced orbital period and the temporal ‘balancing act’ that must be maintained between science data acquisition, orbit trim maneuvers (OTMs), orbital geometry, other missions' events, and Deep Space Network (DSN) downtimes. This paper describes the development of the DSN straw-man for the FRPO phase of the Cassini mission, starting with the constraints identified from the above sources, then the process followed to select DSN passes given those constraints, and finally the products produced to summarize the selected passes and verify their compliance with the constraints. Ultimately, the DSN straw-man included 286 selected passes, of which only 44 had conflicts with constraints.

Over the past two decades, radar and radio observations of planets and spacecraft have been made by stations of the Deep Space Network (DSN), which by the unprecedented nature of their accuracy have produced the most accurate tests of general relativity available. We review the history of the instrumentation and data analysis of the first spacecraft test, the three percent determination of the effect of solar gravity on radio signals between DSN stations and the two spacecraft, Mariner 6 and Mariner 7 (Anderson et al., 1975), as well as later more accurate tests using the Mariner 9 spacecraft anchored to Mars (Reasenberg and Shapiro, 1977; Anderson et al., 1978) and the Viking orbiters and landers (Shapiro et al., 1977; Hellings, 1985). We also review tests of the metric nature of gravity using radar, optical observations, and radio astrometry of the planets (Anderson et al., 1978; Reasenberg, 1985; Hellings, 1985) and the limits placed on the variability of the gravitational constant G (Hellings et al., 1983). Finally, we discuss the prospects for improved accuracy through ongoing upgrades of DSN instrumentation and show the results of covariance analyses for a possible future NASA mission to the Sun (Solar Probe) in the mid 1990's (Mease et al., 1984) and the next NASA mission to Mars, the Mars Observer mission planned for launch in late 1990.

In this paper, we discuss a novel intelligent channel sensing based secure cross layer cognitive networking architecture for resilient space communication. A cognitive network can accurately, autonomously, intelligently, and rapidly adapt to a continuously/dynamically changing communication environment. We propose to develop a new cognitive networking architecture in the context of space communication for various NASA applications such as SCaN (space communication and navigation) system. Specifically, an intelligent channel sensing engine will sense space communication channel information and interferences including signal and interference detection, RF parameter estimation, signal identification via advanced signal processing techniques such as cyclostationary analysis. Next, artificial intelligence techniques such as neural network and support vector machine are exploited to learn and predict the channel dynamics from past channel sensing data. Such characterization enables optimizing waveforms through combinations of coding, encryption, and modulation before the short communication window becomes available, thereby saving valuable resources (e.g. time). Furthermore, a cross-layer cognitive networking algorithm will be developed to dynamically select and reconfigure network protocols at several layers in varying degrees. Finally, algorithms, instrumentation, methods, and software being used by the cognitive network in decision-making will be protected via i) intelligent malicious behavior detection/prevention and ii) secure hardware where applicable.

In deep space data transmission systems, deep space networks can be constructed on different orbits, and the data from each orbit are always associated with the different reliability requirements. In this study, a novel UEP (unequal error protection) transmission scheme based on distributed LT codes is proposed in order to ensure that all the data can be transmitted according to their own reliability requirements and obtain high transmission efficiency property. In the proposed scheme, the sub-codes on each node (orbits) were performed by a classic LT encoding process. By assigning different degree distributions to the sub-codes, all types of data can be transmitted with better transmission efficiency in comparison to the traditional scheme, and can be recovered at the destination with their own reliability requirements. Moreover, the design of the proposed scheme is much easier than that of the traditional scheme, and is also suitable to the strictly limited processing capacity property of deep space networks. By carrying out asymptotic analysis on the proposed scheme, and by obtaining the numerical and simulation results, it can be seen that the proposed scheme can approximately achieve the same UEP property and much better transmission efficiency than the traditional scheme. Additionally, the results demonstrate that the proposed scheme is much more suitable to deep space network data transmission, in comparison to the traditional scheme.

Transmitters of the JPL/NASA Deep Space Network (DSN) typically operate at power levels in excess of 100 kW. This causes heat dissipation and loss problems even in the conventional DSN transmit frequencies of the S and X bands. These problems are compounded by operation in continuous mode, rather than in pulsed operation where the average power is low. In an effort to avoid the heat dissipation, waveguide loss, and arcing problems aggravated by high average power, the DSN has helped pioneer the development of beam waveguide antennas. These beam waveguide antennas use quasi-optical techniques to confine the fields, eliminating waveguide usage and their associated losses. The development of quasi-optical, non-reciprocal devices is natural to the beam waveguide environment. The present paper discusses the use of a ferrite circulator in this context.

Accurately recognizing rice seed varieties poses significant challenges due to their diverse morphological characteristics and complex classification requirements. Traditional image recognition methods often struggle with both accuracy and efficiency in this context. To address these limitations, this study proposes the Deep Space and Channel Residual Network with Double Attention Mechanism (RSCD-Net) to enhance the recognition accuracy of 36 rice seed varieties. The core innovation of RSCD-Net is the introduction of the Space and Channel Feature Extraction Residual Block (SCR-Block), which improves inter-class differentiation while minimizing redundant features, thereby optimizing computational efficiency. The RSCD-Net architecture consists of 16 layers of SCR-Blocks, structured into four convolutional stages with 3, 4, 6, and 3 units, respectively. Additionally, a Double Attention Mechanism (A2Net) is incorporated to enhance the network's global receptive field, improving its capacity to distinguish subtle variations among seed types. Experimental results on a self-collected dataset demonstrate that RSCD-Net achieves an average accuracy of 81.94%, surpassing the baseline model by 4.16%. Compared with state-of-the-art models such as InceptionResNetV2, ConvNeXt, MobileNetV3, and Swin Transformer, RSCD Net has improved by 1.17%, 3%, 24.72%, and 13.22%, respectively, showcasing its superior performance. These findings confirm that RSCD-Net provides an effective and efficient solution for rice seed classification, offering a promising reference for addressing similar fine-grained recognition challenges in agricultural applications.

The integration of optical communication links into space networks via Disruption Tolerant Networking (DTN) is a largely unexplored area of research. Building on successful foundational work accomplished at JPL, we discuss a multi-hop multi-path network featuring optical links. The experimental test bed is constructed at the NASA Glenn Research Center featuring multiple Ethernet-to-fiber converters coupled with free space optical (FSO) communication channels. The test bed architecture models communication paths from deployed Mars assets to the deep space network (DSN) and finally to the mission operations center (MOC). Reliable versus unreliable communication methods are investigated and discussed; including reliable transport protocols, custody transfer, and fragmentation. Potential commercial applications may include an optical communications infrastructure deployment to support developing nations and remote areas, which are unburdened with supporting an existing heritage means of telecommunications. Narrow laser beam widths and control of polarization states offer inherent physical layer security benefits with optical communications over RF solutions. This paper explores whether or not DTN is appropriate for space-based optical networks, optimal payload sizes, reliability, and a discussion on security.

With the increase in the demand of space exploration in recent years and the increase in the amount of communication data between the earth and spacecrafts, the development of deep space communication is undoubtedly a great support for space exploration. Deep Space Network (DSN) is an important organization that helps people to get in touch with spacecrafts. This paper introduces the communication technology and achievements of the DSN and the problems that are still facing by it, and look forward to the future development trend of deep space communication and exploration technologies, so as to promote the development of Deep Space Network.

The effects of CW interference on a phase-locked loop (PLL) have been examined in many papers. None of these included the effects of a bandpass limiter (BPL) preceding the phase-locked loop. This paper extends some of those analyses to include the effects of a BPL and applies the results to the carrier tracking loop of a Deep Space Network (DSN) receiver, which employs a second-order phase-locked loop preceded by a BPL. The DSN receiver is used for deep space communications and is often subject to potential interference. Experimental data and computer simulation results are presented.

The end of the space shuttle program did not imply the end of NASA activities and research. The International Space Station continues to have an on-board crew who live and work in space with part of the station supporting various laboratory activities. As you can see from our front and back cover, we have an interesting article in this issue on NASA's Space Communications and Navigation (SCAN) Test Bed which was launched in 2012 and is externally mounted on the International Space Station. It will operationally test communications, networks, and navigation capabilities in space. An interesting point to note is that this capability is available for experimentation not only by government agencies but by academia and industry as well in order to aid in technology assessments and standards advancements. This article is just one of many we hope will peak your interest and draw you in to read further. We also include information from Darin Dunham, our book review editor, in this issue that will help guide you if you are considering reading and reviewing a book for the magazine. Finally, please take a look at our call for nominations for the Pioneer Award. Next month we will have a piece dedicated to discussing the award and its history.

This study presents the application of machine learning (ML) to a space-to-ground communication link, showing how ML can be used to detect the presence of detrimental channel fading. Using this channel state information, the communication link can be used more efficiently by reducing the amount of lost data during fading. The motivation for this work is based on channel fading observed during on-orbit operations with NASA's Space Communication and Navigation (SCaN) testbed on the International Space Station (ISS). This paper presents the process to extract a target concept (fading and not-fading) from the raw data. The preprocessing and data exploration effort is explained in detail, with a list of assumptions made for parsing and labelling the dataset. The model selection process is explained, specifically emphasizing the benefits of using an ensemble of algorithms with majority voting for binary classification of the channel state. Experimental results are shown, highlighting how an end-to-end communication system can utilize knowledge of the channel fading status to identity fading and take appropriate action. With a laboratory testbed to emulate channel fading, the overall performance is compared to standard adaptive methods without fading knowledge, such as adaptive coding and modulation.