Thomas C. Jedrey

An aeronautical-mobile satellite experiment

The authors describe the results of a recently completed joint US NASA/US FAA/International Maritime Satellite (INMARSAT) satellite experiment using a land-mobile satellite communication terminal developed by the Jet Propulsion Lab. The experiment was performed in two parts during 1989. The first segment of the experiment consisted of establishing a full duplex 4800-b/s digital data and voice communication link through the INMARSAT Marecs B2 satellite between Atlantic City, NJ, and Southway, CT. The second segment consisted of establishing the same communication link between Southbury and an aircraft flying along the East Coast of the US. During both segments, a series of tests was performed to characterize the terminal performance over the links. The experimental setup and the results of the speech and data experiments are presented. Any differences in performance between theory/simulation laboratory, and field operation are emphasized and analyzed. >

Relay support for the Mars Science Laboratory mission

The Mars Science Laboratory (MSL) mission landed the Curiosity Rover on the surface of Mars on August 6, 2012, beginning a one-Martian-year primary science mission. An international network of Mars relay orbiters, including NASAs 2001 Mars Odyssey Orbiter (ODY) and Mars Reconnaissance Orbiter (MRO), and ESAs Mars Express Orbiter (MEX), were positioned to provide critical event coverage of MSLs Entry, Descent, and Landing (EDL). The EDL communication plan took advantage of unique and complementary capabilities of each orbiter to provide robust information capture during this critical event while also providing low-latency information during the landing. Once on the surface, ODY and MRO have provided effectively all of Curiositys data return from the Martian surface. The link from Curiosity to MRO incorporates a number of new features enabled by the Electra and Electra-Lite software-defined radios on MRO and Curiosity, respectively. Specifically, the Curiosity-MRO link has for the first time on Mars relay links utilized frequency-agile operations, data rates up to 2.048 Mb/s, suppressed carrier modulation, and a new Adaptive Data Rate algorithm in which the return link data rate is optimally varied throughout the relay pass based on the actual observed link channel characteristics. In addition to the baseline surface relay support by ODY and MRO, the MEX relay service has been verified in several successful surface relay passes, and MEX now stands ready to provide backup relay support should NASAs orbiters become unavailable for some period of time.

The ACTS Mobile Terminal (AMT)

This article presents an overview of a proof of concept K/Ka-band mobile-satellite terminal under development by NASA at JPL. This terminal is intended to demonstrate the system techniques and high risk technologies to accelerate the commercial utilization of K/Ka-band. The terminal will be demonstrated with NASAs Advanced Communications Technologies Satellite (ACTS) and is therefore called the ACTS Mobile Terminal (AMT).

A FREQUENCY OFFSET ESTIMATION AND COMPENSATION ALGORITHM FOR K/Ka‐BAND COMMUNICATIONS

This paper presents a new open-loop technique for estimating and correcting Doppler frequency shift in K/Ka-band communication systems with special reference to the advanced communications technology satellite (ACTS) mobile terminal (AMT) modem, which utilizes square-wave pulse-shaped, binary differential phase shift-keyed (DPSK) modulation. The novelty of this estimation scheme is that it exploits the Doppler-induced phase shift over a fraction of a symbol interval to provide an estimate of the Doppler offset, without requiring symbol synchronization. Furthermore, by utilizing time-differential detection (delay-and-multiply), the proposed technique can tolerate much larger frequency offsets than existing open- or closed-loop techniques. Analytical results are provided for the variance of the above estimator and the error probability performance of the AMT is evaluated in the presence of the Doppler correction. Practical design considerations are also discussed, including a method for modifying the front end, digital bandlimiting filter in such a way that Doppler bias effects in the new estimator are eliminated. Simulation results reveal that, in general, performance improves with increasing data rates, i.e., the new frequency offset estimation/compensation algorithm induces a degradation from ideal of approximately 1 dB at a 6 dB energy per data symbol (bit) and a 2.4 kbps data rate. However, there is no appreciable degradation when the data rate is increased to 9.6 or 19.2 kbps.

The Universal Space Transponder: A next generation software defined radio

The Universal Space Transponder (UST) is a next generation transponder developed at the Jet Propulsion Laboratory to meet a large variety of telecom, navigation, and radio science needs for future deep-space and near-Earth missions. This paper details the UST software defined radio design and describes how the combination of a modular hardware architecture and in-flight reprogrammability enables a new level of flexibility and expandability for a space transponder. The UST uses common power and digital processing assemblies that can be integrated with a variety of RF modules and is capable of simultaneous, multiband operations with data rates up to 37.5 Mbps RX and 300 Mbps TX. This allows a single radio to support all the direct-to-Earth and relay communication requirements for even complex mission scenarios, reducing the total cost, mass, and power. The discussion includes a description of the current UST engineering models that have been built and tested, as well as details about the next generation capabilities supported by UST, including advanced link coding and modulation, radiometric techniques, and in-radio protocol handling. Details are also presented on RF modules and digital processing in development for radio science and astronomy purposes, including a bistatic radar receiver and broadband planetary emissions receiver. These will demonstrate the ability to integrate low-cost science instruments into the UST architecture, further expanding the versatility of the UST.

The MSAT-X MARECS B2 satellite experiment: ground segment results

The results of a recently completed satellite experiment employing the JPL MSAT-X developed land-mobile satellite communication terminal are described. In this experiment, a full duplex 4800-b/s digital data and voice communication link was established through the INMARSAT MARECS B2 satellite between Atlantic City, New Jersey, and Southbury, Connecticut. A series of experiments was performed to characterize the terminal performance over this link. The basic experimental setup and the preliminary results of the speech and data experiments are presented. The satellite environment proved to be near to what was expected, and as a result the experimental results were very close to theory/simulation/laboratory experiments. It was found that the ground-to-ground communication links were more benign links than the ground-to-air and air-to-ground links, and this is reflected in the improved margins for the ground-to-ground links (approximately 5 dB versus 3.2 dB for the aeronautical links.<<ETX>>