Momentum wheels (See also Dual-spin spacecraft; Reaction wheels) As part of horizon sensor system 176-178 Attitude control systems using 503, 507-508 Dynamic equations of motion for spacecraft with 522-523

Effect on spacecraft nutation 536-539

Eider's equations for 559

Hardware description 201-203

List of spacecraft using 787,796

Torque model 656

Use in attitude acquisition sequence 667-669 Use in attitude stabilization 600-603

Use in inertial guidance maneuvers 655-661 Monopropellant gas jet 206


Types of 52

—Numerical values for 822

Analytic ephemeris subroutine (SMPOS) 693 Dark angle 88

Definitive ephemeris subroutines


Effect on acceleration of Earth satellite 127 Effect on Earth satellite orbit 63,70-71 Identification of from RAE-2 data 335 Lagrange points with Earth 55

Located horizon dependent on temperature 168

Magnitude and phase law of, table 823 Multipurpose ephemeris subroutine

(EPHEMX) 693

Numerical values of different types 822 Orbit of 139,141-143

Parallax of 142-143

Properties of 822-823

Properties of orbit 51-52

Shadow cone of 75

Types of 52

Moon-centered coordinates (See Selena-

centric coordinates) Moving arc filter 322

Moving edge tracker (Earth sensor) 179-180 Multimlsslon software 686,721-722

Multiplexor 280

Multlstep Integrators 561

Nadir 22,83

Nadr angle 12,23

Error due to unmodeled oblateness 105

Nadir angle measurement 344

Density of 348

Information content 482

Nadir angle/Sun angle measurement, information content 480-482

Nadir angle/Sun angle single-axis attitude solutions 368

Singularities of 406-407

Nadir cone 12

Use in attitude determination 365

Nadir vector 12

Nadir vector projection model, for horizon sensors 232-233

Napfer, John 34

Napier's Rules 34

For quadrantal spherical triangles 731

For right spherical triangles 730,731

NASA Communications Network 291

NASA Monograph atmosphere model 110

NASA Standard Spacecraft Computers

NASCOM (See NASA Communications Network)

National Bureau of Standards, timekeeping system 299

Natural frequency, of control system 591

NAVSTAR (See Global positioning system)

Near-real-time attitude determination requirements 681

Network Operations Control Center 284

Neumann normalization, of Legendre polynomials 776

Neutral sheet, geomagnetic field 121

Newcomb, Simon 802

Newton, Issac 36-38

Nimbus (meteorology satellite)— Attitude system of 792-793

Digital Sun sensor 157,162

Horizon sensors 176-178

Momentum and reaction wheels 601

Momentum wheel 202

State vector for bias determination 441-442 Telemetry data errors 311

Yaw reaction wheel 270

Nineteen Fifty (1950) Coordinates 27

Node, of an orbit 44

Motion of (See Regression of nodes) Nodical month 52

Noise, White vs. colored 269

Noise correlation, a« criteria for observation model selfinn 444-445 Nongravitational forces, effect on orbit 63-65 Nonlntersecting loci, use of in attitude solutions 370

Nonreturn to zero level pulse generation 281 Nonreturn to zero mark pulse generation 281 Nonspherical mass distribution, effect on orbit 63,65-69

Nonspinnlng Earth Sensor Assembly

169, 175-176

Normal matrix 731

Notation— For attitude angles Use in this book NSSC (See NASA Standard Spacecraft

Computers) Null (attitude geometry parameter)

Use of in evaluating correlation angles Null (optical center line of a sensor) Notation— Astronomical Description from spacecraft frame

494, 499-501

Effect on sensor data 534-548

Effect on spin period measurement 544-548 Effect on Sun angle data Equation for, in spacecraft frame Example of Apollo 15 subsateDite Measurement of Monitoring via Sun angle data Physical description Nyquist criterion, for system stability

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