NASA Office of Logic Design

NASA Office of Logic Design

A scientific study of the problems of digital engineering for space flight systems,
with a view to their practical solution.


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General Aerospace

Title, Authors, Reference Abstract

A GPS Receiver Upgrade For The Space Shuttle – Rationale And Considerations

John L. Goodman
United Space Alliance LLC
40th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, Fort Lauderdale, FL, July 11-14, 2004.

In the mid 1990s, a 5 channel Global Positioning System (GPS) receiver was integrated into the Space Shuttle avionics system due to the anticipated start of Tactical Air Control and Navigation (TACAN) phase-out in the year 2000. While the early 1990s technology level receiver adds redundancy and flexibility to the navigation process, and improves safety at emergency landing sites, new capabilities in modern GPS receivers would further enhance Shuttle navigation. All-in-view satellite tracking, new GPS signals and ground and space based augmentation systems would provide a more robust GPS navigation solution for the orbiters, particularly if future missions call for automated landings, or on-board precision orbit determination.

Electrical Systems in Missiles and Space Vehicles

H. J. Fichtner
Astrionics Division
George C. Marshall Space Flight Center
National Aeronautics and Space Administration
Huntsville, Alabama

Commemorating the Fiftieth Birthday of Wernher von Braun, March 23, 1962
Edited by: Ernst Stuhlinger, Frederick I. Ordway, III, Jerry C. McCall, and George C. Bucher

Introduction (excerpt)
     Now that space operations have become a reality, it is appropriate to review the accomplishments of the past and to discuss what must be done in the future to insure the operational readiness of our large carrier vehicle systems. Well-planned overall systems engineering is the key to this task, with electrical systems engineering playing a major subsidiary role.
     When missiles were introduced on a relatively large scale some 25 years ago overall electrical systems engineering did not exist as such, although with theV2 missile the systems approach was being utilized for the first time. In those days the designers of the propulsion system provided for the system's electrical needs by maintaining the required start and cutoff sequence. The designers of the guidance and control system worked their own electrical system and took care of the electrical equipment needed for the checkout and launch operations.

Special Instrumentation for Apollo Developmental Spacecraft

Alfred B. Eickmeier
NASA Manned Spacecraft Center, Houston Texas
Aerospace Instrumentation, Volume 4
Proceedings of the Fourth International Aerospace Symposium, 1966, Edited by M.A. Perry

Introduction (excerpt):
The recent advent of space exploration and manned space flight has provided aerospace technologists and engineers with many challenging problems in instrumentation development and application  Capabilities for accurate determination of inflight spacecraft performance and external environmental parameters have steadily increased from early missile flights, which required only a few relatively simple measurements, to present-day programs such as Apollo, which require in excess of several hundred independent and individual measurements.

AIRBUS A320/A330/A340 Electrical Flight Controls: A Family of Fault-Tolerant Systems

Domique Briere, Pascal Traverse

This paper deals with the digital electrical flight control system of the Airbus A320/A330/A340. The A320 was the first civil aircraft equipped with such a system. It was certified and entered into service in the first quarter of 1988. The A330 and A340 have identical systems, closely related to the A320 system.
     These systems are built to very stringent dependability requirements both in terms of safety (the systems must not output erroneous signals) and availability. The basic building blocks are fail-safe control and monitoring computers. The control channel performs the function allocated to the computer (control of a control surface for example). The monitoring channel ensures that the control channel operates correctly.
    A high level of redundancy is built into the system. Special attention has been paid to possible external aggressions. The system is built to tolerate both hardware and software design faults. The A320 system is described together with the significant differences between the A320 and the A330/A340, and A320 in service experience.

Triple-Triple Redundant 777 Primary Flight Computer

Yeh, Y.C.;
Aerospace Applications Conference, 1996. Proceedings., 1996 IEEE , Volume: 1 , 3-10 Feb. 1996, pp. 293 -307 vol.1


The flight control system for the Boeing 777 airplane is a Fly-By-Wire (FBW) system. The FBW system must meet extremely high levels of functional integrity and availability. The heart of the FBW concept is the use of triple redundancy for all hardware resources: computing system, airplane electrical power, hydraulic power and communication path. The Primary Flight Computer (PFC) is the central computation element of the FBW system. The triple modular redundancy (TMR) concept also applies to the PFC architectural design. Further, the N-version dissimilarity issue is integrated to the TMR concept. The PFCs consist of three similar channels (of the same part number), and each channel contains three dissimilar computation lanes. The 777 program design is to select the ARINC 629 bus as the communication media for the FBW

The Reentry Breakup Recorder: A “Black Box for Space Hardware"

Vinod B. Kapoor and Dr. William H. Ailor
The Aerospace Corporation
Paper: SSC03-VIII-3
17th Annual AIAA/USC Conference on Small Satellites, 2003.

Abstract (excerpt)
Unless specifically designed to survive, space hardware reentering the Earth’s atmosphere will break up due to aerodynamic heating and loads. Some materials will survive this severe environment and impact the earth, posing a hazard to people and property on the ground. At present, there is very little data that can be used to calibrate reentry breakup and hazard prediction models, yet these same models are used to predict risk and determine when satellite owners must plan for deorbiting into ocean areas— increasing mission cost and limiting payload mass. Occasionally, reentered debris is recovered on the Earth’s surface, but as a rule, little information is available on the reentry environment experienced by those objects, so information from this source is limited.

The Aerospace Corporation is developing a "Reentry Breakup Recorder" (REBR) to fill this void.

Avionics Data Buses: An Overview

J-G Zhang, A. Pervez, and A.B. Sharma
IEEE AESS Systems Magazine
February 2003, pp. 18-22


An overview of military avionics data buses and their applications, with the emphasis on optical fiber networking techniques.  The evolution of military avionics data buses is discussed.  The development trend actually reflects an increasing demand on such data buses, which requires the change from low-speed to high-speed transmissions, from single-rate to dual-rate operations, and from centralized control to distributed control.  Recent progress in military avionics networks is described.

The Problem with Aviation COTS

Lionel D. Alford, Jr. USAF
IEEE AESS Systems Magazine
February 2001, pp. 33-37


Commercial Off the Shelf (COTS) has become a byword for acquisition reform, but there are significant risks associated with the use of COTS products in military systems.  This paper explains how COTS can negatively affect military acquisitions and gives ideas on how to plan and resolve COTS caused problems.

The Evolution of the Mission Control Center"

Michael W. Kearney, III
NASA Lyndon B. Johnson Space Center

Proceedings of the IEEE
Vol. 75, No. 3, March 1987, pp. 399 - 416


The Space Station holds promise of being a showcase user and driver of advanced automation and robotics technology.  The author addresses the advances in automation and robotics from the Space Shuttle - with its high-reliability redundancy management and fault-tolerance design and its remote manipulator system - to the projected knowledge-based systems for monitoring, control; fault diagnosis, planning, and scheduling, and the telerobotic systems of the future Space Station.

Data Systems for the Space Station and Beyond

John R. Garman
Johnson Space Center

AIAA/ACM/NASA/IEEE Computers in Aerospace V Conference; A Collection of Technical Papers
Long Beach, California
October 21-23, 1985



This paper addresses the use of data systems within the Space Station Program both as management and engineering tools as well as operational components, flight and ground, of the overall Space Station system and the effects that we can project across the Agency back into Shuttle operations and forward into future development and operational programs.

In sum, this paper discusses the changing nature of software architectures and the growing leverage of software and computers on the success of a major program like the Space Station. It contrasts the characteristics of the flight and ground support systems for the Space station to those of the Shuttle and prior programs, and pleads the case for an end to unique project support systems and architectures in the name of cost, evolution, and technology transparency. It examines the JSC strategy toward data systems and the application of that macroarchitecture and approach toward data systems development and utilization on the Space station Program.

On-Board Autonomy for a Low Cost Lunar Mission

N.D Monekosso
Surrey Satellite Technology Ltd, Centre for Satellite Engineering Research, University of Surrey

10th Annual AIAA/ Utah State University Conference on Small Satellites


The lunar mission is to be Surrey Satellite Technology first step to interplanetary travel. SSTL has designed, built and launched twelve low cost microsatellites into LEO, starting in 1981 with UoSAT-1. Design of the next generation of low cost spacecraft, (250-400 Kg) is well underway, with UoSAT-12. This spacecraft is the first in a series of missions planned to qualify SSTL’s minisatellite technology and to pave the way for the low cost lunar orbiter. The primary objective of this technology demonstration exercise is to show that low cost interplanetary missions are possible and to validate the minisatellite bus. In keeping with the low cost approach, it is intended that the lunar mission project cost including launch shall not exceed $15M. This paper discusses how we intend to meet the cost challenge by applying our current low cost practices augmented with autonomy. Spacecraft autonomy will be described specifically in relation to the orbit determination and control sub-system.

A Beacon Monitoring System for Automatic Management Operations

Michael A. Swartwout and Christopher A. Kitts
Faculty Advisor - Professor Robert J. Twiggs
Space Systems Development Laboratory
Department of Aeronautics and Astronautics
Stanford University

10th Annual AIAA/ Utah State University Conference on Small Satellites


Stanford's Space Systems Development Laboratory (SSDL) has initiated a new space system technology initiative in order to develop, demonstrate, and validate a beacon monitoring system for spacecraft. This system consists of automated fault detection on board a spacecraft, a state of health beacon signal broadcast by the spacecraft, a ground based monitoring network, and a mission control center capable of efficiently integrating this health assessment strategy into its operating architecture. SSDL is investigating this technique by identifying fundamental design drivers, developing a system responsive to these drivers, and deploying the resulting system on microspacecraft and within SSDL's developing, global, automated space operations network. This paper reviews the beacon monitoring concept, describes the design criteria for such an operations strategy, and presents the current development of the SSDL beacon system.

A Radiation-Hardened, Computer for Satellite Applications

John I. Gaona Jr.
Sandia National Laboratories, Embedded Processor Subsystems Department

10th Annual AIAA/ Utah State University Conference on Small Satellites


This paper describes high reliability radiation hardened computers built by Sandia for application aboard Department Of Energy (DOE) Satellite programs requiring 32-bit processing. The computers highlight a radiation hardened (1 Mrad(Si)) R3000 executing up to 10 Million Reduced Instruction Set Instructions (RISC) Per Second (MIPS), a dual purpose module control bus used for real-time fault and power management which allows for extended mission operation on as little as 1.2 watts, and a Local Area Network capable of 480 Megabits per second. The Central Processing Unit (CPU) is the NASA Goddard R3000 nicknamed the "Mongoose or Mongoose 1". The Sandia Satellite Computer (SSC) uses Rational’s Ada compiler, debugger, operating system kernel, and Enhanced Floating Point Emulation Library targeted at the Mongoose.

The SSC gives Sandia the capability of processing complex types of spacecraft attitude determination and control algorithms and of modifying programmed control laws via ground command. And in general, SSC offers end users the ability to process data onboard the spacecraft that would normally have been sent to the ground which allows reconsideration of traditional space-ground partitioning options.

The NEAR Discovery Mission: Lessons Learned

R. H. Maurer and A. G. Santo

10th Annual AIAA/ Utah State University Conference on Small Satellites


Under a contract from NASA The Johns Hopkins University Applied Physics Laboratory built and launched a spacecraft that will rendezvous and orbit the near earth asteroid 433 Eros. The Near Earth Asteroid Rendezvous (NEAR) spacecraft is the first under NASA’s Discovery Program, which is a series of low cost solar system missions. While in orbit around Eros the spacecraft will measure the bulk, surface, and internal properties of the asteroid for 10 months. This paper describes the lessons learned from design, test, and fabrication that are appropriate to other programs in quick development, or of an interplanetary nature.

Miniaturized Data Processing Unit for Use on Small Satellites

Bernd Gerlach and Fritz O. Gliem
Institut für Datenverarbeitungsanlagen/IDA
Technische Universität Braunschweig

12th AIAA/USU Conference on Small Satellites



High density packaging of non rad-hard commercial of the shelf (COTS) components combined with mission specific tailored shielding, error correcting codes and latchup current breakers provides a significant reduction in mass, volume, power and cost compared to the traditional approach using rad. hard components. A prototype development of a miniaturized Data Processing Unit (DPU) exhibits the potential of the approach. The traditional approach for the ROSETTA-OSIRIS DPU is taken as reference.

Spacecraft Computers on the SeaStar Satellite

Sawat Tantiphanwadi
Orbital Sciences Corporation

13th AIAA/USU Conference on Small Satellites


The SeaStar spacecraft requires a high performance computer system to handle its various requirements. It must process not only the high-rate data from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) instrument, but also the spacecraft ground interface system and the attitude control system data. This paper will describe the spacecraft computer architecture and its hardware. With minimum peripheral changes, the same computer can be configured to perform the payload, or the ground interface, or the attitude control functions. Each flight computer consists of three computer slices and a power module. There are two main flight computers on the SeaStar satellite; the second unit is used as a back-up. To date, the satellite has not required the service of the back-up computer.

[Note: This uses a modified 68302 processor]

A Remote I/O (RIO) Smart Sensor Analog-Digital Chip for Next Generation Spacecraft

Dr. Nick Paschalidis

12th AIAA/USU Conference on Small Satellites


The RIO Smart Sensor chip is APL’s analog-digital, radiation-hardened, low-power, data acquisition device suitable for spacecraft and instrument data collection. The chip communicates over a standard serial I2C bus or a standard parallel bus. RIO, in its complete version, will measure temperatures using external thermistors, total ionizing dose using external radFETs, and voltages and currents. Its sensing capability can extend to other physical quantities such as photons, vibration, etc. A first version of this chip, is focusing on temperature measurements only (TRIO chip). TRIO measures 16 temperature channels using external platinum resistance thermometers (PRTs). It can also measure voltages only, using an external voltage reference. The TRIO chip contains all of the front-end analog conditioning circuitry, the analog multiplexer (MUX), a 10-bit analog-digital converter (ADC), memory, and both a serial I2C and standard parallel interface. TRIO can operate in a fixed mode, where only a particular sensor is addressed, digitized, and read out, or in a scanning mode where all 16 sensors are sequentially and continuously scanned, digitized, and stored into self-contained memory. This single chip system will be a valuable enabling technology for next-generation small spacecraft.



Advanced Avionics Systems for Dependable Computing in Future Space Exploration

Leon Alkalai, Savio Chau, Ann Tai

Center for Integrated Space Microsystems
Jet Propulsion Laboratory, California Institute of Technology

GOMAC – 2002, March 12th, 2002

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