Deep Space Transponder Research Articles

A test of general relativity with ESA’s JUICE mission

The ESA’s JUICE mission is planned for launch in April 2023. After a 8.3-year interplanetary cruise it will reach the Jovian system in mid 2031. The mission is devoted to the study of Jupiter and three of the Galilean moons (Europa, Callisto and Ganymede). The 3GM (Geodesy and Geophysics of Jupiter and the Galilean Moons) radio-science package onboard the spacecraft comprises a Ka-band Transponder (KaT) that will enable a highly stable two-way coherent Ka/Ka link to study the gravity fields of the three Jovian satellites and their internal structure, and an Ultra Stable Oscillator (USO) to probe the atmosphere of Jupiter and the ionospheres of the three moons. The KaT can be used together with the onboard Deep Space Transponder (DST), enabling a full multi-frequency radio link system capable to suppress the dispersive noise, due to solar plasma and ionospheric effects, at nearly all solar elongation angles. The cruise phase of the mission provides three opportunities to perform classical tests of general relativity by measuring the relativistic time-delay and the frequency shift experienced by radio signals during superior solar conjunctions. A similar experiment, performed by Cassini in 2002, provided the most accurate measurement of the post-Newtonian parameter γ so far, with an accuracy of 2.3×10-5. The MORE experiment onboard the ESA/JAXA BepiColombo mission to Mercury is expected to improve the result obtained by Cassini up to a factor of 10 while orbiting the planet. Less significant improvements are expected in the cruise phase. The advanced radio-tracking system of JUICE and the favorable dynamical environment experienced in the outer solar system make a repetition of the Cassini and BepiColombo cruise experiments quite significant. In this work, we show the results of numerical simulations of JUICE superior conjunction experiments. We have found that 3GM can estimate γ with an accuracy at the level of 4.8×10-7, which represents a constraint on the value of γ 50 times tighter than the one obtained by Cassini and about four times better than the expected result from BepiColombo at the end of the mission.

The Iris Deep-Space Transponder for the SLS EM-1 Secondary Payloads

The Jet Propulsion Laboratory (JPL) is supporting several deep-space CubeSat missions selected as secondary payloads on the Space Launch System Exploration Mission One (SLS EM-1) launch of the Orion spacecraft. Seven secondary payload CubeSat missions (Lunar Flashlight, Near-Earth Asteroid Scout, BioSentinel, Lunar IceCube, CubeSat for Solar Particles, Lunar Polar Hydrogen Mapper, and ArgoMoon) have baselined the Iris deep space transponder as the main telecommunications and navigation transponder for their missions. Iris, first developed for JPL's interplanetary nanospacecraft pathfinder in relevant environment mission, and further developed for JPL's Mars Cube One mission, is a software-defined radio based on various JPL flight heritage designs. The transponder operates at X-band frequencies (7.2-GHz uplink, 8.4-GHz downlink) for compatibility with NASA's Deep Space Network, but the modular hardware design allows for further expanded capabilities into other frequency bands such as UHF, S-, and Ka-band. The transponder has a maximum power consumption of 35 W at 4-W radio frequency output, with uplink sensitivities down to −150 dBm. Various encoding schemes are available for the user to choose, from traditional convolutional coding with Reed Solomon concatenation to Turbo codes, and support for low-density parity-check coding is in the plan for future support. This paper will discuss the current capabilities and specifications of the Iris deep space transponder, as well as current hardware, firmware, and software implementations, and provide a short overview of future capabilities currently in the works.

Hardware Prototyping and Validation of a W-ΔDOR Digital Signal Processor

Microwave tracking, usually performed by on ground processing of the signals coming from a spacecraft, represents a crucial aspect in every deep-space mission. Various noise sources, including receiver noise, affect these signals, limiting the accuracy of the radiometric measurements obtained from the radio link. There are several methods used for spacecraft tracking, including the Delta-Differential One-Way Ranging ( Δ DOR) technique. In the past years, European Space Agency (ESA) missions relied on a narrowband Δ DOR system for navigation in the cruise phase. To limit the adverse effect of nonlinearities in the receiving chain, an innovative wideband approach to Δ DOR measurements has recently been proposed. This work presents the hardware implementation of a new version of the ESA X/Ka Deep Space Transponder based on the new tracking technique named Wideband Δ DOR (W- Δ DOR). The architecture of the new transponder guarantees backward compatibility with narrowband Δ DOR.

The X/X/KA-band deep space transponder for the BepiColombo mission to mercury

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.

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.

Communication "Tones" and Their Use as Reliability Assessment Tools in High Risk Aerospace Maneuvers

he success of the Mars Exploratory Rovers, Spirit and Opportunity, has pleased many in the scientific community. The findings concerning the past and present Mars environment and geology continue to impress scientists of many professional backgrounds. For engineers however, the success of these two spacecraft is more related to the fact that they were able to survive all the perils in these missions. It also confirms the need for a lot of hard work, such as establishing reliability assessment tools that allow us to measure, quantitatively and qualitatively, the health of the spacecraft. One such assessment tool is the design and development of hardware and software functionalities, within the spacecraft telecommunication subsystem, which will transmit “tones” upon the successful completion of each of the many high-risk maneuvers in the last ten minutes of the flight (descent and landing). It is known from past experience, that most U.S. missions to Mars have failed in the last ten minutes of the flight. This timeframe is known as the “ten minutes of terror,” and accounts for all the descent and landing maneuvers the spacecraft needs to make for a successful landing. A single failure in any of these maneuvers (more than 20 which are fully automated) would be catastrophic. In 1999 the Mars Polar Lander, a three-legged spacecraft, rather than a rover, failed in its attempt to land on Mars’ south pole. The mission was going well until the last ten minutes —the start of the descent and landing phase of the mission. In the last ten minutes of the flight, the spacecraft rotates into its attitude for entry into the Mars atmosphere. The fiery descent is the start of the ten minutes of terror. We never knew for certain what maneuver failed during the descent and landing of the Mars Polar Lander. A later failure investigation determined that a software error cut off the descent engines prematurely during the last maneuver and caused the spacecraft to crash land during the last 500 m. However, it is also possible that the failure occurred earlier, but we will never know. From an engineering point of view it is necessary to understand the failure mechanisms during these critical mission events in order to improve the reliability of subsequent spacecraft. Therefore, it is important to know when a failure occurs (i.e. which critical maneuver and at what time), and how did it occur. During the last ten minutes there is no spacecraft telemetry, the spacecraft transponder is switched to a carrier-only mode. Sometimes major events can be detected during the descent through a Doppler shift in the carrier frequency (e.g. during the descent the spacecraft velocity is reduced from 30,000+ miles/hour to about 7000 miles/hour). However, many small events will go undetected. Any failure in these small events could be catastrophic. How can we assure ourselves that a particular event, small or large, was completed successfully? Or from a failure analysis point of view, if a failure occurred, in a particular maneuver, can we associate that maneuver with a given event in the descent and landing timeline? If so, we will know with some confidence the hardware or software responsible for a given failure and how to improve its reliability the next time around. (Notice that Spirit and Opportunity spacecraft were launched within 24 days of each other). The spacecraft deep space transponders were designed to accommodate the additional feature of a tone mode. The X-band transponder will transmit a tone every time a successful event is accomplished. The very weak tones will be captured by the very large diameter dish antennas of the deep space network, located in New Mexico, Spain, and Australia. The failure to transmit or receive a tone will indicate that the particular maneuver or event may have failed. Fault management software is synchronized with the flight software such that failures, or lack of failures, detected by fault management software will translate into executable commands by the flight software to activate the tone mode feature in the X-band deep space transponder. A hardware interface was developed in the deep space transponder to accommodate this particular type of command from the flight software.

SMART-1: key technologies and autonomy implementations

SMART-1 is the first of the Small Missions for Advanced Research in Technology of the ESA Horizons 2000 Science Plan. The main mission objective of SMART-1 is to demonstrate innovative and key technologies for scientific deep-space missions. One of the key technologies is the solar electric propulsion used as primary propulsion. The electric propulsion will be using 1400 W to transfer the 350 kg spacecraft from an Ariane 5 standard GTO to an elliptic Moon polar orbit, 10000×300 km . The total mission time is 24 months including a maximum of 18 months transfer time. The spacecraft development entered the detailed design and implementation phase in October 1999, under the responsibility of the Swedish Space Cooperation as prime contractor, and the flight acceptance is targeted for the 3rd quarter of 2002. The committed total life cost budget is 84 million Euro. Apart from the in-orbit demonstration of electric propulsion as primary propulsion, SMART-1 is implementing many other enabling technologies for deep-space missions such as • deep-space transponder with communication in X-band for uplink and in X- and Ka-band for downlink, • highly integrated and radiation tolerant microprocessors, FPGAs and memories, • high on-board autonomy driven by ground communication only once per 4 days, • maximum available power to electric propulsion by centralised and software-controlled power management, • minimum propellant consumption through innovative angular momentum management. In addition, the spacecraft avionics design is tailored to the low-cost philosophy by enabling flexible integration of commercial off the shelf (COTS) equipment. The scientific instruments, five in total, support characterisation of the electric propulsion thrust environment during the long transfer phase and detailed imaging and spectroscopy of the lunar surface in visible, infrared and X-ray during the Moon orbiting phase. Several of the instruments implement new enabling technologies, e.g. swept charge devices for the X-ray spectrometer and quarts gratings for the near-infrared reflectance spectrometer. The paper summarises the baseline mission design, the projected scientific and technology output, and describe the spacecraft bus design. The main part of the paper highlights and elaborate on a number of spacecraft bus technologies; the on-board autonomy, the avionics design, and the X/Ka-band transponder.

2.4.3 Deep Space One Spacecraft System Engineering Techniques and the Application of Heuristic Reasoning

ABSTRACTThe Deep Space One Project is part of the National Aeronautics and Space Administration's (NASA's) New Millennium Program. The team is chartered with the design, development, and in‐flight validation of new technologies. The knowledge gained in flight will be instrumental in the success of future projects as they strive to build “faster, better, cheaper” spacecraft for NASA, the nation, and the world. There are a total of twelve new technologies planned to fly as part of the first deep space mission, many of which were either selected by the program and/or project manager independently or some that were coupled un‐conditionally with one another. These technologies include the miniature imaging camera and spectrometer, autonomous on‐board optical navigation, and the small deep space transponder. However, the most striking of these are arguably the ion propulsion system and advanced solar concentrator array, the combination of which will result in a ten fold or order of magnitude increase in impulse (ratio of force over the propellant mass) over a conventional chemical system. At the time of this writing, the Deep Space One Project is nearing completion of the thirty‐three month development life cycle and is being mechanically and electrically integrated and tested at the Jet Propulsion Laboratory in Pasadena, California. This paper discusses the system engineering techniques used to date, especially the application of heuristic reasoning, in the design, development, and test of the Deep Space One spacecraft.

An X-band spacecraft transponder for deep space applications-design concepts and breadboard performance

The design concepts and measured performance characteristics of an X-band breadboard deep-space transponder (DST) for future spacecraft applications are summarized. The DST consists of a double-conversion, superheterodyne, automatic phase tracking receiver, and an X-band exciter to drive redundant downlink power amplifiers. The receiver acquires and coherently phase tracks the modulated or unmodulated X-band uplink carrier signal. The exciter phase modulates the X-band downlink signal with composite telemetry and ranging signals. The measured tracking threshold, automatic gain control (AGC), static phase error, and phase jitter characteristics of the breadboard DST are in good agreement with the expected performance. The measured results show a receiver tracking threshold of -158 dBm and a dynamic signal range of 88 dB.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>