Info

Distribution, mathematical model of 263

Identification 706

Identification techniques 239-266

Instrumental magnitudes of 238

Magnitudes 144-143

Position modeling 143-130 State (in differential correction or "state"

estimation) 439

State estimation 436-483

Advantages relative to deterministic 437-438

Need for 407-408

Operational limits on accuracy 476

Subroutine for (DC) 691

Use in CTS attitude system 702 State estimators—

Analytic basis 447-470

Operational use of 471-484

Prelaunch evaluation 471-473 Subsystem in attitude software system 697-698

Unresolved analytic problems 722-723

State noise «»variance matrix 463

State plane trajectory 637

Examples of 638

For HEAO-1 607

State space 637

State transition matrix 430 State vector 436, 438-443

Choice of elements to be solved for 476-483

Construction of 438-443

Need for 407-408

Subroutine for updating (RECUR) 692 State vector elements—

Choice of 439-443

Observability of 443

—Limitations 476-483

State weight matrix 449 STDN (See Spaceflight Tracking and Data Network)

Steady state (in Kalman filters) 467

Steady-state error, in control systems 393

Steady-state system response 770

Steady-state trajectory 608 Steepest descent, method of (differential correction tecKiique) 455

Steering law 604

Stellar parallax 31

Stepsfze, in numerical integration 560

STEREOSAT, use of AEM spacecraft 720

Stictlon 272 Stiffness matrix (for flexible spacecraft) 553 STORMSAT—

Disturbance torques 580

Use of MMS spacecraft 720

Strapdown torque rebalanced gyroscope 199

Stratopause 107

Stratosphere 107

Subcommutated data 293-294

Subsatellite, Apollo 15, nutation of 495-497

Subsatellite point (See also Nadir) 22

Alternative definitions 83

Local mean time of 68

Longitude of 805

Subsotar point 84

Summing point, in control system 589 Sun— (See also Solar) Analytic ephemeris subroutines

Approach by spacecraft 60 As attitude determination reference source 17 Definitive ephemeris subroutines

(SUNRD, RJPLT) 693 Effect on acceleration of Earth satellite 127

Effect on geomagnetic activity 120-123

Energy flux from 130

Expression for mean motion 141

Interference with horizon sensors 169 Multipurpose ephemeris subroutine

(EPHEMX) 693

Properties of 818 Solar wind 120, 129-132

Symbol for 50 Sun angle measurement 11,23,344

Density of 347

For nutating spacecraft 539-548

Information content 480 Sun angle/nadir angle single-axis attitude solutions 368

Singularities in 406-407

Sun cone 12

Use in attitude determination 364 Sun presence detector 156,159-161

Sun sensor 11,13

Analysis of SIRIO vs. SMS design 717-718 Calculation of coverage of celestial sphere 34-35

Calibration constants 230 Combination Sun/Earth horizon sensor 178-179

Data validation 329-330

Example of use in attitude control 14-16 Example of use in attitude determination 10-14

Field of view 225-226

Hardware 155-166

List of spacecraft by Sun sensor type 797

Mathematical models 218-230 Model of azimuth biases relative to horizon sensor 239-242

Nutation monitoring with 539-548

Simple vs. complex 716-718

Two axis, accuracy analysis 355-357

Use for single-axis attitude 362-409

Use for three-axis attitude 426 Sun sensor/horizon sensor rotation angle measurement 357-359

Information content 480-482

Models 237-242 Use in attitude determination 364-365,369

Son shade (for star sensor,) 186

Sun-synchronoUs orbit 68

Sundials 800

SUNRD (subroutine) 140, 693

SUN1X (subroutine) 693

Analytic basis 141

Supereommutated data 293-294

Superior conjunction 49-50

Superior planet 49

Surface spherical harmonics 775

Surveyor (spacecraft), attitude reference system 189

Switching, Conferencing, and Monitoring

Arrangement (SCAMA) 291.

Switching One (component of control system) 657

Symbols, astronomical 50

Symmetric mass distribution, principal axis of 489

Symmetric matrix 750

Symmetric spacecraft 524

SYMPHONIE (French/German communications satellite)— Attitude system of 794-795

Horizon sensors 180

Synch speed, of reaction wheel 270

Synchronization pattern, quality flag for 314 Synchronization signal, role in telemetry 293 Synchronization word, in NASCOM data format 291

Synchronous satellite 55

Of various planets, table 825

Syndrome vector 296

Synodic month 52

Synodic period 50

System gain— Of a control system 590

Role in root locus diagram 597-600

Selection of for attitude control 622,624 System mass matrix (for flexible spacecraft) 553 Systematic error, in attitude measurements 402 Effect on deterministic solution behavior 404 Syzygy 49

Tachometers, for measuring wheel speed 202 Tangent height 93

Tangent plane coordinates (See Local langenI coordinates) TCON20 (subroutine) 692

TCON40 (subroutine) 692

TDRSS (See Tracking and Data Relay

Satellite System) Teflon—

Use in gas jets 206

Use in momentum wheel bearings 202

Telemetry 293-298

Generation and transmission of 278-298 Time tagging 298-304

Telemetry antennas 284-288

Telemetry data errors (See also Data errors) 310-311

Table of representative examples 311

Telemetry formats 279,293-295

Telemetry On-Line Processing System

(TELOPS) 292

Telemetry processor 304-308

In attitude software systems 696-697

Of CTS attitude system 701

Telemetry word 293

Tell-tale (data flag) 313-315

TELOPS (Telemetry On-Line Processing

System) 292

Temperature— Of Earth's atmosphere 107

Units and conversion factors 812

Tensor 519

Terminator 84,86-90

Identification of 331-334

Tessera! harmonic coefficients, explanation of 777-778 Testing—

Of attitude software 686

Of state estimators 471-473

Thermal radiation (See Infrared radiation)

Definition of 83

Thermistor, as energy detector for horizon sensor 171,178

Thermopile, as energy detector for horizon sensor I7I>180

Thermosphere 107

Third-body interactions, effect on orbit

63,69-71

Three-axis attitude 343,359-361

Three axis attitude determination—

Accuracy 429-434

Example of least-squares estimator 456-459 Methods 410-434,420-428

Three-axis stabilized spacecraft 3

Thrust profile (of gas jet) 207, 272-175

Thnisters (See Gas jets) Time-

Local mean time of subsatellite point 68 Measurement and broadcast facilities

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