4: it W::: 050-7 ~AS ACR-/3017s B ORBITING SOLAR OBSERVATORY FINAL REPORT N C) U2a ~ 0mU 4~~~~~~~~~~~~~~~~~~~~~~~~~~~~~-4' W 10 ~~~~~~ -7 Ol C",.1-a -9- ---- o ' ocl '.-l Q) o QU2i~WL4cO 1-a . ), 3xr N~~~~~~~~~~~~~~~. .~ tjir~ V I ed F7. 3 wUii rH1 _.1- ~~z,~~OULECORD r~ BALBOTESRSERHCRPRTO o~~~~~USDAY FBL OPRTO BOULDER, COLRAD I~ ~..... LDER-'COLOR.DO '-01 OSO-7 ORBITING SOLAR OBSERVATORY PROGRAM FINAL REPORT F72-01 December 31, 1972 PREPARED BY APPROVED BY OSO Program Staff J. O. Simpson Director, OSO Programs BALL BROTHERS RESEARCH CORPORATION SUBSIDIARY OF BALL CORPORATION BOULDER, COLORADO F72-01 PREFACE During the 1950's rapid progress was made in solar physics and in instrument and space hardware technology, using rocket and balloon flights that, although of brief duration, provided a view of the sun free from the obscuring atmosphere. The significance of data from these flights confirmed the often-asserted value of long-term observations from a spacecraft in advancing our knowledge of the sun's behavior. Thus, the first of NASA's space platforms designed for long-term observations of the universe from above the atmosphere was planned, and the Orbiting Solar Observatory program started in 1959. Solar physics data return began with the launch of OSO-1 in March of 1962. OSO-2 and OSO-3 were launched in 1965, OSO-4 and OS0-5 in 1967, OSO-6 in 1969, and the most recent, OSO-7/, was launched on September 29, 1971. All seven OSO's have been highly successful both in scientific data return and in per- formance of the engineering systems. The gain to date in scientific knowledge amply justifies the foresight of the early planners. OSO lifetimes have been several years, allowing long-term observations of solar and other galactic and extra-galactic events as planned. This report describes OSO-7, the seventh of the continuing series of Orbiting Solar Observatories. iii/iv F72-01 CONTENTS Section Page PREFACE iii 1 PROGRAM SUMMARY 1-1 1.1 Overall Orbiting Solar Observatory Program Objectives 1-1 1.2 OSO-7 Program Activity Summary 1-2 1.3 Observatory Description 1-6 1.4 Mission Performance 1-15 2 HARDWARE PERFORMANCE 2-1 2.1 In-Orbit Performance 2-1 2.2 Launch Phase Performance 2-14 3 DESIGN, INTEGRATION, AND TEST PROGRAM SUMMARY 3-1 3.1 Subassembly Qualification 3-1 3.2 Observatory Qualification Model Testing 3-1 3.3 Flight Model Test History 3-2 4 DYNAMICS 4-1 4.1 Rotational Dynamics of OSO 4-1 4.2. Ballasting for Proper Moment of Inertia 4-10 4.3 Stability and Dynamics During Initial Acquisition 4-11 5 OBSERVATORY ASPECT MONITORS 5-1 5.1 General Description 5-1 5.2 Fine Pitch Monitor 5-2 5.3 Large-Angle Pitch Monitor 5-4 5.4 Coarse Aspect Monitor (SORE) 5-7 5.5 Fine Aspect Monitor (ASA) 5-13 6 CONTROL SYSTEMS 6-1 6.1 Introduction 6-1 6.2 Pneumatic Pitch-Attitude Control 6-2 6.3 Pneumatic Roll-Attitude Control 6-5 6.4 Pneumatic Spin-Rate Control 6-5 6.5 Magnetic Roll, Pitch and Spin Control 6-12 6.6 Pointing Control 6-14 6.7 Launch-Sequence Control 6-45 6.8 Nutation Control 6-50 7 POWER SYSTEM 7-1 7.1 General Description 7-1 7.2 Observatory Power Budget 7-1 7.3 Power Source 7-3 7.4 Energy Storage 7-7 7.5 Power Control 7-9 7.6 Power Distribution 7-12 8 TELEMETRY SYSTEM 8-1 8.1 Introduction 8-1 8.2 Data Handling Subsystem 8-4 8.3 Spacecraft Housekeeping Data Acquisition 8-32 8.4 RF Subsystem 8-33 8.5 Telemetry Link Analysis 8-42 v F72-01 CONTENTS (Cont.) Section Page 9 COMMAND SYSTEM 9-1 9.1 General Description 9-1 9.2 Command and Address Formats 9-4 9.3 Decoder Description 9-6 9.4 Command Receivers 9-17 9.5 System Performance Requirements 9-18 10 STRUCTURAL, PNEUMATIC AND THERMAL CONTROL DESCRIPTION 10-1 10.1 Development History of OSO-7 10-1 10.2 Observatory Structure 10-5 10.3 Pneumatic Systems 10-9 10.4 Structural Analysis Summary 10-10 10.5 Mass Properties 10-16 10.6 OSO-7 Thermal System Description 10-19 Appendix Page A SORE AND ASA SOFTWARE AND ASPECT COORDINATE SYSTEMS A-1 B THERMAL ANALYSIS METHODS B-1 vi F72-01 ILLUSTRATIONS Figure Page 1-1 OSO-7 Program Activities Summary 1-7 1-2 OS0-7 Configuration 1-8 1-3 OSO-7 Dimensions 1-9 1-4 Spacecraft Structural Breakdown 1-10 1-5 Azimuth Drive Assembly 1-11 1-6 Pointing Modes 1-12 2-1 Attitude History, Spacecraft Spin Axis 2-2 2-2 Wheel Spin Rate and Spin Gas Pressure History 2-2 2-3 Pitch Attitude, Pitch Coil Status, and Pitch Gas Pressure History 2-3 2-4 Spacecraft Bus Voltage, Load Current, and Solar Array Current History 2-3 2-5 Solar Array Energy Developed During Orbit Revolution Nos. 225, 274, 665, 892, 1905 2-4 2-6 Elevation and Azimuth Motor Torque History 2-5 2-7 Solar Array Temperature History 2-5 2-8 Spin-Axis (Pitch) Motion After Dawn Acquisition (Gyro Control During Night-Orbit Revolution No. 968) 2-6 2-9 Pitch Motion During Changes in Pointing Modes - Orbit Revolution No. 846 2-7 2-10 Pointing Control Performance Read-Out Sensor. Output - Orbit Revolution No. 75 2-8 2-11 Typical Gyro Azimuth Drift (Orbit Revolution No. 225) Measured Relative to Stars Observed by Star Scanner 2-9 2-12 Star Scanner Sensitivity 2-10 2-13 Star Sensor Performance During Orbit Revolution No. 271. Comparison of Results Using Original and Improved Data Reduction 2-11 2-14 Power System Parameters - Normal Profiles (Pars 318) and Overcharge Condition (Pars 76) 2-12 2-15 Wheel Experiment Temperature, Orbit Revolution 77 2-15 2-16 OSO-7 Wheel Temperatures, Orbit Revolution 77 2-16 2-17 OSO-7 Pointed Experiment Temperature, Orbit Revolution 77 2-17 2-18 OSO-7 Sail Temperatures, Orbit Revolution 77 2-18 2-19 Nominal and Actual OSO-7 Launch Sequence 2-20 2-20 Pitch Attitude and Spin Rate Data 2-22 2-21 Pitch Attitude Sensor Geometry 2-23 2-22 Permissible Pitch Attitude Readout-Momentum Vector 19 Degrees from Line of Sight to Sun 2-23 2-23 Telemetry Data, Modes, and Corrective Commands - OSO-7 Recovery 2-24 3-1 Qualification Model Test History 3-3 3-2 Spacecraft Test History 3-5 3-3 Observatory Test History 3-7 4-1 Motion of R and S During Pitch Precession 4-3 4-2 Residual Nutation of S After Constant Torquing Stops 4-6 4-3 Dusk Transient 4-7 4-4 Dawn Transient 4-8 4-5 Time Required to Enter Dynamically Stable Region During Launch Sequence 4-13 4-6 Worst Case Expected Nutation Decay During First Solar Acquisition 4-14 vii F72-01 ILLUSTRATIONS (Cont.) Figure Page 5-1 Location of Aspect Sensors and Reference Axes 5-3 5-2 Diagram of Pitch Readout Sensor 5-4 5-3 Pitch Readout Sensor Output Curve 5-5 5-4 Principle of Large-Angle Pitch Monitor 5-6 5-5 Flux-Gate Magnetometer 5-8 5-6 Azimuth Encoder (Blipper) Operation 5-9 5-7 SORE Functional Block Diagram 5-10 5-8 Aspect Sensor Assembly 5-14 5-9 ASA Optics 5-15 5-10 ASA Data Words 5-16 5-11 ASA Timing Relationships 5-17 6-1 Pneumatic Pitch Control Block Diagram 6-3 6-2 Pitch Control Sensors 6-4 6-3 Typical Pitch Control Sensor Response 6-4 6-4 Pneumatic Spin Control Block Diagram 6-6 6-5 Spin-Down-Loop Timing Diagram 6-8 6-6 Spin-Up Loop Timing Diagram 6-9 6-7 Day/Night Sensing and Timing 6-11 6-8 Pitch and Roll Coils Functional Diagram 6-13 6-9 Servo Loops Functional Interfacing 6-15 6-10 OSO-7 Pointing Control Block Diagram 6-18 6-11 Coarse Sensor Assemblies 6-19 6-12 Coarse Sensor Signal 6-20 6-13 Rate Signal Compensation 6-21 6-14 Net Despin Drive Efficiency 6-23 6-15 Coarse-Azimuth Preamp/AC Amplifier Response 6-24 6-16 Typical PWM/Power Switch Response 6-25 6-17 Fine Control Eyes and Response Curve 6-28 6-18 Offset-Mode Patterns 6-32 6-19 Offset Mode Block Diagram 6-33 6-20 OIRU Configuration and Dimensions 6-36 6-21 Night-Pointing Control Functional Diagram 6-39 6-22 Rate-Integrating Gyro 6-44 6-23 Launch Sequence Control Block Diagram 6-47 6-24 Time-Delay Relay Driver 6-49 6-25 Nutation Damper 6-51 6-26 Nutation Damper Effectiveness 6-54 7-1 Simplified OSO-7 Power System Schematic 7-2 7-2 OSO-7 Power Load Tree 7-4 7-3 OSO-7 Solar Panel Layout and Module Dimensions 7-6 7-4 Solar Cell and Interconnect 7-7 7-5 OSO-7 Seven-Cell Battery Pack 7-8 7-6 Dummy Load System Simplified Schematic 7-10 7-7 Dummy Load Locations 7-11 viii F72-01 ILLUSTRATIONS (Cont.) Figure Page 7-8 Simplified Power Distribution 7-13 7-9 Flex Cable 7-13 7-10 Flex Cable Mounting Configuration 7-14 8-1 Telemetry System Block Diagram 8-2 8-2 Data-Handling System Functional Block Diagram 8-9 8-3 Digital Multiplexer and Encoder Logic Diagram 8-11 8-4 DME Timing Chart 8-14 8-5 ASC Functional Block Diagram 8-17 8-6 Analog Subcommutator Logic Diagram 8-18 8-7 ASC Timing Chart 8-19 8-8 ASC Block Diagram 8-21 8-9 PCM Junction Box Functional Block Diagram 8-23 8-10 PCM Junction Box Power Switching 8-24 8-11 Frame Counter and Digital Submultiplexer Functional Block Diagram 8-25 8-12 Tape Recorder Block Diagram 8-27 8-13 Tape Recorder Switching Diagram 8-30 8-14 Tape Recorder Timer 8-31 8-15 ASSC Synchronization Circuit 8-33 8-16 Telemetry System (PSK-600A) Block Diagram 8-34 8-17 Turnstile Slot Antenna 8-36 8-18 Progressive Phase Feed Layout 8-37 8-19 Progressive Phase Feed Block Diagram 8-38 8-20 Feed Network Schematic 8-39 8-21 Telemetry Frequency Radiation Pattern (RHC Polarized) 8-40 8-22 Telemetry Frequency Radiation Pattern (LHC Polarized) 8-40 8-23 Telemetry Frequency Radiation Pattern (Combined RHC and LHC) 8-41 8-24 Vehicle/Antenna Coordinate System 8-42 8-25 Command Frequency Radiation Pattern (RHC Polarized) 8-43 9-1 OSO-7 Command System Block Diagram 9-1 9-2 Command and Address Word Format 9-5 9-3 Command Frame Timing Formats 9-7 9-4 Command Decoder Functional Diagram 9-11 9-5 Decoder Timing Diagram 9-14 9-6 Output Switch Configuration 9-17 9-7 VHF Command Receiver Block