Miles K. Sue

Lessons Learned During Implementation and Early Operations of the DS1 Beacon Monitor Experiment

A new approach to mission operations will be flight validated on NASA’s New Millennium Program Deep Space One (DS1) mission which launched in October 1998. The Beacon Monitor Operations Technology is aimed at decreasing the total volume of downlinked engineering telemetry by reducing the frequency of downlink and the volume of data received per pass. Cost savings are achieved by reducing the amount of routine telemetry processing and analysis performed by ground staff. The technology is required for upcoming NASA missions to Pluto, Europa, and possibly some other missions. With beacon monitoring, the spacecraft will assess its own health and will transmit one of four beacon messages each representing a unique frequency tone to inform the ground how urgent it is to track the spacecraft for telemetry. If all conditions are nominal, the tone provides periodic assurance to ground personnel that the mission is proceeding as planned without having to receive and analyze downlinked telemetry. If there is a problem, the tone will indicate that tracking is required and the resulting telemetry will contain a concise summary of what has occurred since the last telemetry pass. The primary components of the technology are a tone monitoring technology, Al-based software for onboard engineering data summarization, and a ground response system. In addition, there is a ground visualization system for telemetry summaries. This paper includes a description of the Beacon monitor concept, the trade-offs with adapting that concept as a technology experiment, the current state of the resulting implementation on DS1, and our lessons learned during the initial checkout phase of the mission. Applicability to future missions is also included.

Ground antennas in NASA's deep space telecommunications

Ground antennas are the major visible components of NASAs 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 20/30 GHz personal access satellite system design

A strawman design for a personal access satellite system (PASS) to provide low-bit-rate voice and data services to users in the contiguous United States (CONUS) in the early 2000s using the 20/30 GHz band is presented. As currently envisaged, the PASS system links suppliers throughput CONUS with users in 142 fixed spot beams of 0.35 degrees beamwidth in one satellite hop; user-to-user communication requires two satellite hops. Through the use of time-division multiple access (TDMA) on the forward link and frequency-division multiple access (FDMA) on the return link, this system will support 2000 duplex voice channels at 4.8 kb/s with a satellite of moderate size and weight. For the user terminal, four antenna designs that trade-off compact size, cost, and electrical performance are described. Last, an experimentation plan taking advantage of planned Ka-band satellite capabilities is outlined.<<ETX>>

Lessons from implementation of beacon spacecraft operations on Deep Space One

A new approach to mission operations has been flight validated on NASAs Deep Space One (DS1) mission that launched in October 1998. The beacon monitor operations technology is aimed at decreasing the total volume of downlinked engineering telemetry by reducing the frequency of downlink and the volume of data received per pass. Cost savings are achieved by reducing the amount of routine telemetry processing and analysis performed by ground staff. With beacon monitoring, the spacecraft will assess its own health and will transmit one of four subcarrier frequency tones to inform the ground how urgent it is to track the spacecraft for telemetry. If all conditions are nominal, the tone provides periodic assurance to ground personnel that the mission is proceeding as planned without having to receive and analyze downlinked telemetry. If there is a problem, the tone will indicate that tracking is required and the resulting telemetry will contain a concise summary of what has occurred since the last telemetry pass. The beacon technology has been proven successful on DS1 through a series of tone tests and data summarization experiments. This collection of experiments was called the DS1 Beacon Monitor Experiment or BMOX. There are important lessons still to be learned from this experiment that can be applied to future spacecraft missions.

ACTS aeronautical experiments

A description of the two aeronautical mobile satellite experiments utilizing NASAs Advanced Communications Technology Satellite (ACTS) is presented. The low bit rate experiment is principally a Ka-band technology demonstration of a prototype 4.8 Kbps aeronautic mobile terminal employing three experimental active electronically steered arrays. The high bit rate experiment can demonstrate a 64 Kbps to 384 Kbps satellite link between a ground terminal and an aircraft.

A 20/30 GHz personal access satellite system study

The potential and feasibility of a personal access satellite system which will offer the user freedom and mobility are being explored. The authors define the system concept and applications, present a strawman design, and identify the enabling technologies. The system as currently conceived could provide voice and data services to users in the contiguous US in the late 1990s to the early 2000s using the 20/30 GHz bands.<<ETX>>

Effects of CW Interference on the Carrier Tracking Loop of the 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.

A high-capacity aeronautical mobile satellite system

This paper describes a conceptual system design for a satellite-based aeronautical safety communications system capable of serving both general aviation (GA) aircraft and commercial aviation (CA) aircraft in the contiguous U.S. (CONUS) in the mid-1990s. Serving such a large number of aircraft requires a large system capacity. This paper describes how a large capacity can be obtained using a 15-m deployable antenna on board a high-power commercial communications satellite expected to be available in the mid- 1990 time frame.

Interference estimate around Canberra DSN station at 2.04 GHz during Huygens release phase

During the descent phase of the Huygens Probe released from the Cassini spacecraft and inserted at Titan, the Deep Space Network (DSN) Canberra Deep Space Station (DSS) 43 (with its 70-m antenna) is being considered as a backup station to directly receive the Huygens Probe data being transmitted at 2.04 GHz. This study provides an assessment on the interference level from the major nearby transmitters operating in this frequency band. The minimum trans-horizon attenuations are calculated using terrain topographic data and the Trans-Horizon Interference Propagation Loss (THIPL) Computing Program recently developed based on ITU-R P.452, and the calculations take into account all propagation modes under a 0.1% of time exceeded. We find that there are five terrestrial transmitters within 100 km of DSS 43. Transmitter 1 is the closest to DSS 43, and needs to be coordinated to avoid interference. The rest of the four transmitters will not interfere with DSS 43. The interference levels from these transmitters are all below the DSN protection criteria of 99.9% of time