L 

NASA Technical Memorandum 107032 

Compendium of Information for Interpreting 

the Microgravity Environment of 

the Orbiter Spacecraft 

Richard DeLombard 

Lewis Research Center 

Cleveland, Ohio 

August 1996 

National Aeronautics and 

Space Administration 

l 

L 

NASA Technical Memorandum 107032 

Compendium of Information for Interpreting 

the Microgravity Environment of 

the Orbiter Spacecraft 

Richard DeLombard 

Lewis Research Center 

Cleveland, Ohio 

August 1996 

National Aeronautics and 

Space Administration 

l 
CONTENTS 

SUMMARy ................................................ . ....... . ... ... .......... 1 

INTRODUCTION . ........... .. . .... .... .. ... . . ........ .................. ..... ....... 1 

NASA's Microgravity Science Program . ..... . . .... . . ... . . ... ....... . . .... ......... . . .. . 1 

What is Weightlessness? ................. . .... . . ... .. .. ....... .... ........ .. . ..... .. . 2 

ACCELERATION ENVIRONMENT . .................................................... 2 

Acceleration Categories ....... . ......... . . . . ...... . ... . . . . .... ........... ... ...... . .. 2 

Quasi-Steady Accelerations ...... .. . . . . .. .. . ...... . .. . . .. ........................... 2 

Oscillatory Accelerations .... . ................ .... . ... ......... ... .................. 2 

Transient Accelerations . . ...... ..... .. . . ......... . ................................. 3 

Vehicle Response ................. . .. . ... . . ... . ................................. .. .. 3 

MEASUREMENT ..................... . ........ . .... . .... . ... ..... ....... . .... . . ... .. 3 

Acceleration Sensors .. . ..... ... .... .. . .............................................. 3 

Frame of Reference ...... ... . . . . ... ......................... . ...... . ........ . .. .. ... 4 

Accelerometer Systems ........................ . ..................................... 4 

Fluid Experiment System (FES) Accelerometer ... ..... . ... ... . .. . ... .. . ................ 4 

High Resolution Accelerometer Package (HiRAP) ... . ....... . .. . ... . .. .. . ... .......... . . 4 

Honeywell In-Space Accelerometer (HISA) ...... . . .. . . ............ . ........ . .......... 4 

Microgravity Measurement Assembly (MMA) ............ .. .............. . ...... . ...... 4 

Microgravity Measuring Device (MMD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 5 

Orbital Acceleration Research Experiment (OARE) ... ...... .. .. . .. ...................... 5 

Passive Accelerometer System (PAS) .. . ........ . .... . . . . . ......... . ...... . ........... 5 

Quasi-Steady Acceleration Measurement (QSAM) System .. . ................... .... ...... 5 

Space Acceleration Measurement System (SAMS) ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 5 

Three-Dimensional Microgravity Accelerometer (3DMA) .. . .. .. ......... ... ........ .. .... 5 

COORDINATE SySTEMS ................ . ...... .. .................................... 5 

Orbiter Center of Mass (CM) (On Orbit) . . ...................... .. ......... .... ..... . .. .. 6 

Orbiter Body Coordinate System ... ........ . .. . .. ... ....... . ..... . ................ . .... 6 

Orbiter Structural Coordinate System .. . ................... . . . ... . ..... ... ........ . ..... 6 

Orbit Local VerticallLocal Horizontal Coordinate System ... ..... ......... . .......... ... .... 6 

Sensor Head Coordinate System .. . ...................... . ............................. 6 

Coordinate Systems Conversion ... . . ................................................... 6 

Sensor Head Location ... ... . .............................. . ........... .. .... ....... 6 

Sensor Head Orientation .................. . .. . .. .. .. . . .... ... ....................... 7 

Orbiter Attitudes ....... . ... . ..... .. ..... . ............ ....... ... . ... .............. . .. 7 

DATA PROCESSING ......... ....... . ... ...... . . . . . .. . ............................... 7 

Data Processes ........ ......................... . . . . ................................ 7 

Vector Versus Single Axe . . .... . . . .. . . ............................................. 7 

Acceleration Versus Time .. . . .. .. .... .. ....... ....... .. . ...... . ............ . ....... 8 

Arithmetic Mean and Root-Mean-Square (rms) Versus Time .. . ... .. ................... .... 8 

Arithmetic Mean Calculation .................... . . . . ...... . .. . .... . ............... 8 

Root Mean Square (rms) Calculation ................................................ 8 

Acceleration Power Spectral Density Versus Frequency ... .. . ............... . ........ . .... 8 

Acceleration Power Spectral Density Versus Time Versus Frequency . . ..... .... ......... . ... 8 

Data Access . ..... .... . . . . ... ... . .. ..... ...... . .................................... 8 

Standard Services ......... . . . .. ..... . ... .... . . . . ....... ... ... . ..... ...... ..... .... . . 9 

DATA INTERPRETATION . ..... ... . .. ...... .. . .. . .. . . .... ................. .. .. ..... .. 9 

Acceleration Events Characteristics ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 9 

Thrusters .... ....... ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 9 

Crew Exercise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 9 

Life Science Experiments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 10 

Shuttle Maneuvers ... . ... . ....... . . . . . ... ..... . ......... .. . . .. ......... ... ....... 10 

Shuttle Equipment .... . ....... .. . . . . . .. ... ..... ... ... ................ .. ......... . 10 

.-- ------ --

CONTENTS 

SUMMARy ................................................ . ....... . ... ... .......... 1 

INTRODUCTION . ........... .. . .... .... .. ... . . ........ .................. ..... ....... 1 

NASA's Microgravity Science Program . ..... . . .... . . ... . . ... ....... . . .... ......... . . .. . 1 

What is Weightlessness? ................. . .... . . ... .. .. ....... .... ........ .. . ..... .. . 2 

ACCELERATION ENVIRONMENT . .................................................... 2 

Acceleration Categories ....... . ......... . . . . ...... . ... . . . . .... ........... ... ...... . .. 2 

Quasi-Steady Accelerations ...... .. . . . . .. .. . ...... . .. . . .. ........................... 2 

Oscillatory Accelerations .... . ................ .... . ... ......... ... .................. 2 

Transient Accelerations . . ...... ..... .. . . ......... . ................................. 3 

Vehicle Response ................. . .. . ... . . ... . ................................. .. .. 3 

MEASUREMENT ..................... . ........ . .... . .... . ... ..... ....... . .... . . ... .. 3 

Acceleration Sensors .. . ..... ... .... .. . .............................................. 3 

Frame of Reference ...... ... . . . . ... ......................... . ...... . ........ . .. .. ... 4 

Accelerometer Systems ........................ . ..................................... 4 

Fluid Experiment System (FES) Accelerometer ... ..... . ... ... . .. . ... .. . ................ 4 

High Resolution Accelerometer Package (HiRAP) ... . ....... . .. . ... . .. .. . ... .......... . . 4 

Honeywell In-Space Accelerometer (HISA) ...... . . .. . . ............ . ........ . .......... 4 

Microgravity Measurement Assembly (MMA) ............ .. .............. . ...... . ...... 4 

Microgravity Measuring Device (MMD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 5 

Orbital Acceleration Research Experiment (OARE) ... ...... .. .. . .. ...................... 5 

Passive Accelerometer System (PAS) .. . ........ . .... . . . . . ......... . ...... . ........... 5 

Quasi-Steady Acceleration Measurement (QSAM) System .. . ................... .... ...... 5 

Space Acceleration Measurement System (SAMS) ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 5 

Three-Dimensional Microgravity Accelerometer (3DMA) .. . .. .. ......... ... ........ .. .... 5 

COORDINATE SySTEMS ................ . ...... .. .................................... 5 

Orbiter Center of Mass (CM) (On Orbit) . . ...................... .. ......... .... ..... . .. .. 6 

Orbiter Body Coordinate System ... ........ . .. . .. ... ....... . ..... . ................ . .... 6 

Orbiter Structural Coordinate System .. . ................... . . . ... . ..... ... ........ . ..... 6 

Orbit Local VerticallLocal Horizontal Coordinate System ... ..... ......... . .......... ... .... 6 

Sensor Head Coordinate System .. . ...................... . ............................. 6 

Coordinate Systems Conversion ... . . ................................................... 6 

Sensor Head Location ... ... . .............................. . ........... .. .... ....... 6 

Sensor Head Orientation .................. . .. . .. .. .. . . .... ... ....................... 7 

Orbiter Attitudes ....... . ... . ..... .. ..... . ............ ....... ... . ... .............. . .. 7 

DATA PROCESSING ......... ....... . ... ...... . . . . . .. . ............................... 7 

Data Processes ........ ......................... . . . . ................................ 7 

Vector Versus Single Axe . . .... . . . .. . . ............................................. 7 

Acceleration Versus Time .. . . .. .. .... .. ....... ....... .. . ...... . ............ . ....... 8 

Arithmetic Mean and Root-Mean-Square (rms) Versus Time .. . ... .. ................... .... 8 

Arithmetic Mean Calculation .................... . . . . ...... . .. . .... . ............... 8 

Root Mean Square (rms) Calculation ................................................ 8 

Acceleration Power Spectral Density Versus Frequency ... .. . ............... . ........ . .... 8 

Acceleration Power Spectral Density Versus Time Versus Frequency . . ..... .... ......... . ... 8 

Data Access . ..... .... . . . . ... ... . .. ..... ...... . .................................... 8 

Standard Services ......... . . . .. ..... . ... .... . . . . ....... ... ... . ..... ...... ..... .... . . 9 

DATA INTERPRETATION . ..... ... . .. ...... .. . .. . .. . . .... ................. .. .. ..... .. 9 

Acceleration Events Characteristics ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 9 

Thrusters .... ....... ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 9 

Crew Exercise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 9 

Life Science Experiments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 10 

Shuttle Maneuvers ... . ... . ....... . . . . . ... ..... . ......... .. . . .. ......... ... ....... 10 

Shuttle Equipment .... . ....... .. . . . . . .. ... ..... ... ... ................ .. ......... . 10 

.-- ------ --
Atmospheric Drag ...... . ...... ... ........... .. ... .. ...... .... . . . .. . . ..... . . . .... 10 

Vehicle Location . . .. ... ....... . .... . .... . . . . .. .. . . .......... . ...... . . .. ... ... . . . 10 

Satellite Launches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 

CONCLUDING REMARKS .... ... ... . . . . ... .. . . . . . . .. . ........ . ........ .. . .. . .. . . . . . . 11 

ACKNOWLEDGMENTS ........... . . . .... . ...... .. .................. .. . ...... ... . .. . 11 

APPENDIX A-ACRONYMS . . . . ..... .... . .... . . . .. . . . . ..... . . ........ .... .. . . . .... . . 30 

APPENDIX B-DEFINITIONS .. ... ...... . .... . ....... .... ......... . ...... ........ . .. . 32 

APPENDIX C-ACCESSING SAMS DATA FILES VIA INTERNET .. . .. . . ... . ....... . ... . .. 33 

APPENDIX D-RCS AND OMS ENGINES DESCRIPTION ..... . .. . ..... .. . . .. . .. ......... 34 

Reaction Control System (RCS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 

Orbital Maneuvering System (OMS) . ..... .. . . ....... . ............ ... ... . .............. 34 

REFERENCES ... . ... .. . . . . . . .. .. ............ . .. .. ... . .. . ..................... .. .... 38 

BIBLIOGRAPHY ..... ..... . ... .. ... . . ... ....... . ... . ... ... . .. ............... . ..... . 39 

Microgravity Environment ... . ....... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 39 

Mission Microgravity Environment Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 

Instrumentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 40 

Science Impacts . . .... . . ... ..... . . . .. . . . ............. .. ........... . . .. . ......... .. . 40 

ii 

~------------------------------ ---------

Atmospheric Drag ...... . ...... ... ........... .. ... .. ...... .... . . . .. . . ..... . . . .... 10 

Vehicle Location . . .. ... ....... . .... . .... . . . . .. .. . . .......... . ...... . . .. ... ... . . . 10 

Satellite Launches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 

CONCLUDING REMARKS .... ... ... . . . . ... .. . . . . . . .. . ........ . ........ .. . .. . .. . . . . . . 11 

ACKNOWLEDGMENTS ........... . . . .... . ...... .. .................. .. . ...... ... . .. . 11 

APPENDIX A-ACRONYMS . . . . ..... .... . .... . . . .. . . . . ..... . . ........ .... .. . . . .... . . 30 

APPENDIX B-DEFINITIONS .. ... ...... . .... . ....... .... ......... . ...... ........ . .. . 32 

APPENDIX C-ACCESSING SAMS DATA FILES VIA INTERNET .. . .. . . ... . ....... . ... . .. 33 

APPENDIX D-RCS AND OMS ENGINES DESCRIPTION ..... . .. . ..... .. . . .. . .. ......... 34 

Reaction Control System (RCS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 

Orbital Maneuvering System (OMS) . ..... .. . . ....... . ............ ... ... . .............. 34 

REFERENCES ... . ... .. . . . . . . .. .. ............ . .. .. ... . .. . ..................... .. .... 38 

BIBLIOGRAPHY ..... ..... . ... .. ... . . ... ....... . ... . ... ... . .. ............... . ..... . 39 

Microgravity Environment ... . ....... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 39 

Mission Microgravity Environment Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 

Instrumentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 40 

Science Impacts . . .... . . ... ..... . . . .. . . . ............. .. ........... . . .. . ......... .. . 40 

ii 

~------------------------------ ---------
COMPENDIUM OF INFORMATION FOR INTERPRETING THE 

MICROGRAVITY ENVIRONMENT OF THE 

ORBITER SPACECRAFT 

Richard DeLombard 

National Aeronautics and Space Administration 

Lewis Research Center 

Cleveland, Ohio 44135 

SUMMARY 

Science experiments are routinely conducted on the NASA shuttle Orbiter vehicles. Primarily, these experiments 

are operated on such missions to take advantage of the microgravity (low-level acceleration) environment conditions 

during on-orbit operations. 

Supporting accelerometer instruments are operated with the experiments to measure the microgravity acceleration 

environment in which the science experiments were operated. The Principal Investigator Microgravity Services 

(PIMS) Project at NASA Lewis Research Center interprets these microgravity acceleration data and prepares mission summary reports to aid the principal investigators of the scientific experiments in understanding the 

microgravity environment. 

Much of the information about the Orbiter vehicle and the micro gravity environment remains the same for each 

mission. Rather than repeat that information in each mission summary report, reference information is presented in 

this report to assist users in understanding the micro gravity acceleration data. 

The characteristics of the microgravity acceleration environment are first presented. The methods of measurement 

and common instruments used on Orbiter missions are described. The coordinate systems utilized in the Orbiter and 

accelerometers are described. Some of the Orbiter attitudes utilized in micro gravity-related missions are illustrated. 

Methods of data processing are described and illustrated. The interpretation of the microgravity acceleration data is 

included with an explanation of common disturbance sources. 

Instructions to access some of the acceleration data and a description of the Orbiter thrusters are explained in the 

appendixes. A micro gravity environment bibliography is also included. 

INTRODUCTION 

NASA's Microgravity Science Program 

The Microgravity Science and Applications Division (MSAD) of the NASA Headquarters Office of Life and 

Microgravity Sciences and Applications sponsors Principal Investigators (PI's) to fly science experiments in 

microgravity conditions on the NASA shuttle Orbiters, Russia's Mir space station, and the International Space Station. There are several Orbiter missions which have, as their primary payloads, laboratories containing many 

microgravity science experiments and are operated by the crew and/or by the PI's in ground control stations. 

Many of the science experiments flown on the shuttle, and to be flown on the Mir and the International Space 

Station, require a knowledge of the microgravity environment for the analysis of the experimental data. The 

Microgravity Measurement and Analysis Project (MMAP) at NASA Lewis Research Center has responsibility for 

measuring the microgravity environment for the science experiment PI's and providing expertise in microgravity 

environment assessment. 

This document presents information to assist the principal investigators in planning the acquisition and utilization 

of the microgravity environment data. This document includes a description of the microgravity environment, a brief 

description of microgravity acceleration measurement, types of common data processing techniques, and an overview of acceleration data analysis. 

Acronyms and definitions used in this report are listed and defined in appendixes A and B, respectively. 

COMPENDIUM OF INFORMATION FOR INTERPRETING THE 

MICROGRAVITY ENVIRONMENT OF THE 

ORBITER SPACECRAFT 

Richard DeLombard 

National Aeronautics and Space Administration 

Lewis Research Center 

Cleveland, Ohio 44135 

SUMMARY 

Science experiments are routinely conducted on the NASA shuttle Orbiter vehicles. Primarily, these experiments 

are operated on such missions to take advantage of the microgravity (low-level acceleration) environment conditions 

during on-orbit operations. 

Supporting accelerometer instruments are operated with the experiments to measure the microgravity acceleration 

environment in which the science experiments were operated. The Principal Investigator Microgravity Services 

(PIMS) Project at NASA Lewis Research Center interprets these microgravity acceleration data and prepares mission summary reports to aid the principal investigators of the scientific experiments in understanding the 

microgravity environment. 

Much of the information about the Orbiter vehicle and the micro gravity environment remains the same for each 

mission. Rather than repeat that information in each mission summary report, reference information is presented in 

this report to assist users in understanding the micro gravity acceleration data. 

The characteristics of the microgravity acceleration environment are first presented. The methods of measurement 

and common instruments used on Orbiter missions are described. The coordinate systems utilized in the Orbiter and 

accelerometers are described. Some of the Orbiter attitudes utilized in micro gravity-related missions are illustrated. 

Methods of data processing are described and illustrated. The interpretation of the microgravity acceleration data is 

included with an explanation of common disturbance sources. 

Instructions to access some of the acceleration data and a description of the Orbiter thrusters are explained in the 

appendixes. A micro gravity environment bibliography is also included. 

INTRODUCTION 

NASA's Microgravity Science Program 

The Microgravity Science and Applications Division (MSAD) of the NASA Headquarters Office of Life and 

Microgravity Sciences and Applications sponsors Principal Investigators (PI's) to fly science experiments in 

microgravity conditions on the NASA shuttle Orbiters, Russia's Mir space station, and the International Space Station. There are several Orbiter missions which have, as their primary payloads, laboratories containing many 

microgravity science experiments and are operated by the crew and/or by the PI's in ground control stations. 

Many of the science experiments flown on the shuttle, and to be flown on the Mir and the International Space 

Station, require a knowledge of the microgravity environment for the analysis of the experimental data. The 

Microgravity Measurement and Analysis Project (MMAP) at NASA Lewis Research Center has responsibility for 

measuring the microgravity environment for the science experiment PI's and providing expertise in microgravity 

environment assessment. 

This document presents information to assist the principal investigators in planning the acquisition and utilization 

of the microgravity environment data. This document includes a description of the microgravity environment, a brief 

description of microgravity acceleration measurement, types of common data processing techniques, and an overview of acceleration data analysis. 

Acronyms and definitions used in this report are listed and defined in appendixes A and B, respectively. 
What is Weightlessness? 

On Earth, the force of gravity manifests itself by accelerating an object toward the Earth. A second object, such as 

a hand, a floor, or a table, which restrains the fIrst object from falling exerts a force on the object which produces the 

sensation of an object's weight. It has been shown that, in the absence of air resistance, two articles will free-fall 

toward the Earth with the same acceleration rate, nominally 9.8 mlsec2. There are no restraining forces on these 

articles during their free-fall, so they are weightless. 

If enough horizontal velocity is imparted to a free-falling article, it can be made to orbit the Earth. To illustrate 

this, consider a hypothetical cannon on a mountain top (fig. 1). It is fIred horizontally with 5 kg of gunpOWder. The 

cannon ball falls to Earth 1 km from the cannon. The cannon is reloaded and fired with 10 Ian of gunpowder and the 

cannon ball falls to Earth 2 km away. The amount of gunpowder (in this hypothetical cannon) is increased until the 

cannon ball lands beyond the horizon. The cannon ball is starting to fall around the Earth. If more gunpowder is 

used, the cannon ball will fall beyond the horizon far enough as to not contact the Earth; it is then in orbit. Reference 1 provides a good background of gravity, microgravity , orbital flight, and microgravity sciences. 

A major feature of an orbiting spacecraft is the apparent lack of gravity that is due to the free-fall condition of 

orbit. On a spacecraft in orbit, any freely floating particle has no weight because there are no restraining forces 

imparted to it and the particle is in free-fail like the spacecraft. For any free-floating particle not colocated with the 

spacecraft center of mass, the particle is in a different orbit than the spacecraft and has a relative acceleration with 

respect to the spacecraft. This relative acceleration situation is disturbed by other acceleration effects which are 

present in a spacecraft, such as aerodynamic drag, spacecraft motion, rotating machinery, transient equipment, and 

crew actions. 

Weightlessness is a nebulous term in this situation because there are accelerations involved in the spacecraft environment. The term microgravity has become the common descriptive term for the low-level acceleration and vibration environment experienced onboard the spacecraft during orbital flight. 

ACCELERATION ENVIRONMENT 

The on-orbit acceleration environment is classifIed into three major categories of disturbances: quasi-steady, 

oscillatory, and transient. 

Acceleration Categories 

Quasi-Steady Accelerations.-Quasi-steady accelerations are those that vary little over long periods of time, typically with periods longer than a minute. These are also referred to as residual accelerations. The major contributors 

to the quasi-steady acceleration environment are aerodynamic drag, gravity-gradient effects, and Orbiter rotational 

accelerations. Aerodynamic drag effects are primarily functions of the Orbiter attitude, the Orbiter altitude, and the 

atmospheric density. For most microgravity science missions, the Orbiter attitude is determined by the integrated 

science requirements of the primary payload(s). Atmospheric density varies with the 11-yr solar cycle, Orbiter altitude, time of year, and position within an orbit. Gravity-gradient accelerations result from an object being displaced 

from the flight path of the vehicle center of mass. Rotational accelerations acting on a body within the Orbiter are 

comprised of radial and tangential accelerations (from vehicle rotational motion). For a descri ption of quasi-steady 

accelerations in an orbiting spacecraft, see reference 2. 

Oscillatory Accelerations .-Oscillatory accelerations are those that are harmonic and periodic in nature with a 

characteristic frequency. Characteristic frequencies on orbiting space laboratories are in the sub-Hertz to hundreds of 

Hertz range. Typical examples of oscillatory disturbances are rotating or reciprocating pumps, communication 

antenna dither motion, and Orbiter structural oscillation. A standard Orbiter refrigerator/freezer has a pump which 

causes vibrations at 22 Hz. The Orbiter Ku-band antenna has a strong 17-Hz dither which is evident during most of a 

mission when this antenna is utilized. There are several Orbiter structural modes in the 1- to IO-Hz frequency regime 

which are often excited by transient acceleration events or by other oscillatory accelerations. These structural mode 

frequencies vary slightly among the different Orbiter vehicles and payloads. 

2 

What is Weightlessness? 

On Earth, the force of gravity manifests itself by accelerating an object toward the Earth. A second object, such as 

a hand, a floor, or a table, which restrains the fIrst object from falling exerts a force on the object which produces the 

sensation of an object's weight. It has been shown that, in the absence of air resistance, two articles will free-fall 

toward the Earth with the same acceleration rate, nominally 9.8 mlsec2. There are no restraining forces on these 

articles during their free-fall, so they are weightless. 

If enough horizontal velocity is imparted to a free-falling article, it can be made to orbit the Earth. To illustrate 

this, consider a hypothetical cannon on a mountain top (fig. 1). It is fIred horizontally with 5 kg of gunpOWder. The 

cannon ball falls to Earth 1 km from the cannon. The cannon is reloaded and fired with 10 Ian of gunpowder and the 

cannon ball falls to Earth 2 km away. The amount of gunpowder (in this hypothetical cannon) is increased until the 

cannon ball lands beyond the horizon. The cannon ball is starting to fall around the Earth. If more gunpowder is 

used, the cannon ball will fall beyond the horizon far enough as to not contact the Earth; it is then in orbit. Reference 1 provides a good background of gravity, microgravity , orbital flight, and microgravity sciences. 

A major feature of an orbiting spacecraft is the apparent lack of gravity that is due to the free-fall condition of 

orbit. On a spacecraft in orbit, any freely floating particle has no weight because there are no restraining forces 

imparted to it and the particle is in free-fail like the spacecraft. For any free-floating particle not colocated with the 

spacecraft center of mass, the particle is in a different orbit than the spacecraft and has a relative acceleration with 

respect to the spacecraft. This relative acceleration situation is disturbed by other acceleration effects which are 

present in a spacecraft, such as aerodynamic drag, spacecraft motion, rotating machinery, transient equipment, and 

crew actions. 

Weightlessness is a nebulous term in this situation because there are accelerations involved in the spacecraft environment. The term microgravity has become the common descriptive term for the low-level acceleration and vibration environment experienced onboard the spacecraft during orbital flight. 

ACCELERATION ENVIRONMENT 

The on-orbit acceleration environment is classifIed into three major categories of disturbances: quasi-steady, 

oscillatory, and transient. 

Acceleration Categories 

Quasi-Steady Accelerations.-Quasi-steady accelerations are those that vary little over long periods of time, typically with periods longer than a minute. These are also referred to as residual accelerations. The major contributors 

to the quasi-steady acceleration environment are aerodynamic drag, gravity-gradient effects, and Orbiter rotational 

accelerations. Aerodynamic drag effects are primarily functions of the Orbiter attitude, the Orbiter altitude, and the 

atmospheric density. For most microgravity science missions, the Orbiter attitude is determined by the integrated 

science requirements of the primary payload(s). Atmospheric density varies with the 11-yr solar cycle, Orbiter altitude, time of year, and position within an orbit. Gravity-gradient accelerations result from an object being displaced 

from the flight path of the vehicle center of mass. Rotational accelerations acting on a body within the Orbiter are 

comprised of radial and tangential accelerations (from vehicle rotational motion). For a descri ption of quasi-steady 

accelerations in an orbiting spacecraft, see reference 2. 

Oscillatory Accelerations .-Oscillatory accelerations are those that are harmonic and periodic in nature with a 

characteristic frequency. Characteristic frequencies on orbiting space laboratories are in the sub-Hertz to hundreds of 

Hertz range. Typical examples of oscillatory disturbances are rotating or reciprocating pumps, communication 

antenna dither motion, and Orbiter structural oscillation. A standard Orbiter refrigerator/freezer has a pump which 

causes vibrations at 22 Hz. The Orbiter Ku-band antenna has a strong 17-Hz dither which is evident during most of a 

mission when this antenna is utilized. There are several Orbiter structural modes in the 1- to IO-Hz frequency regime 

which are often excited by transient acceleration events or by other oscillatory accelerations. These structural mode 

frequencies vary slightly among the different Orbiter vehicles and payloads. 

2 
Transient Accelerations.-Transient accelerations are those that are nonperiodic in nature and typically have a 

duration of less than 1 sec. The energy in the disturbance is typically spread across the frequency range from the 

sub-Hertz to hundred of Hertz range. These broad-band disturbances may excite oscillations of the Orbiter, experiment carrier, subsystems, or experiment structural modes. There are several Orbiter structural modes in the 1- to 

lO-Hz region which are typically excited by transient disturbances. 

Common sources of transient disturbances are Orbiter thruster operations, some Orbiter Remote Manipulator System (RMS) operations, satellite launches, and some crew actions. Some of these sources may be inhibited or controlled to minimize the impact on microgravity science experiments. 

Vehicle Respon e 

The Orbiter vibrational respon e to the previously described acceleration environment is extremely complex and, 

in general, difficult to characterize by a single measurement, taken over a single discrete period of time, at a single 

location. The various disturbance sources described previously do not occur simultaneously but instead occur in a 

random fashion. Furthermore, there are multiple structural paths between the disturbances at anyone time and the 

location of a particular microgravity experiment. The acceleration inputs to an experiment and its vibratory response 

constitute a highly complex multiple-source, multiple-path dynamic system. 

The quasi-steady accelerations at frequencies below the vehicle's structural mode frequencies are experienced 

throughout the vehicle because the vehicle is a rigid body in this frequency range. The magnitude of some 

quasi-steady accelerations (generated by Orbiter rotational motions, for example) are dependent on the location 

within the vehicle and the motion of the vehicle. 

The accelerations at frequencies higher than the vehicle's lowest structural mode frequency, though, have a very 

localized magnitude and direction. The propagation of oscillatory accelerations throughout the vehicle and payload 

is dependent on the characteristics of the structural path through which the accelerations are transmitted. These characteristics may change based on changes in the vehicle and payload configuration such as those that occur after a 

satellite is launched. 

Transient accelerations quite often cause vehicle vibrations to occur across a wide-frequency band. This will also 

cause a "ringing" effect of the vehicle structure at the primary structural frequencies. 

The acceleration inputs to an experiment, consequently, constitute a highly complex multiple-source, multiplepath dynamic system. 

MEASUREMENT 

Acceleration Sensors 

Many acceleration sensors, which are commonly used for microgravity acceleration measurements, are designed 

to measure the acceleration of the sensor case (or mounting structure) relative to inertial space for navigation purposes. These sensors include pendulous mass sensors (fig. 2) and electrostatically suspended sensors (fig. 3). Pendulous 

mass sensors use an internal proof mass on a cantilever to sense the acceleration of the sensor case relative to inertial 

space. The electrostatically suspended proof mass sensor utilizes electrostatic forces to center a proof mass in a 

chamber. In either sensor, the position of the mass is detected and a restoring force (either magnetic or electrostatic) 

is applied to keep the mass centered. The output acceleration signal is then derived from the restoring force signal. 

Other types of acceleration sensors measure the movement of an inertial mass relative to the sensor case, such as a 

ball in a viscous fluid (fig. 4). The polarity of this type of sensor depends on the relative densities of the inertial 

mass and the fluid (fig. 5). This type of sensor is referred to here as a "fluidic suspended sensor." In these sensors, 

the movement of the inertial mass (the ball) is interpreted to indicate the acceleration of inertial space relative to the 

sensor structure. 

The polarity of a sensor (as reflected in the data) needs to be considered when analyzing any acceleration data, 

particularly in the quasi-steady acceleration regime. The frame of reference also needs to be considered in the process of correlating acceleration data with science results. 

3 

Transient Accelerations.-Transient accelerations are those that are nonperiodic in nature and typically have a 

duration of less than 1 sec. The energy in the disturbance is typically spread across the frequency range from the 

sub-Hertz to hundred of Hertz range. These broad-band disturbances may excite oscillations of the Orbiter, experiment carrier, subsystems, or experiment structural modes. There are several Orbiter structural modes in the 1- to 

lO-Hz region which are typically excited by transient disturbances. 

Common sources of transient disturbances are Orbiter thruster operations, some Orbiter Remote Manipulator System (RMS) operations, satellite launches, and some crew actions. Some of these sources may be inhibited or controlled to minimize the impact on microgravity science experiments. 

Vehicle Respon e 

The Orbiter vibrational respon e to the previously described acceleration environment is extremely complex and, 

in general, difficult to characterize by a single measurement, taken over a single discrete period of time, at a single 

location. The various disturbance sources described previously do not occur simultaneously but instead occur in a 

random fashion. Furthermore, there are multiple structural paths between the disturbances at anyone time and the 

location of a particular microgravity experiment. The acceleration inputs to an experiment and its vibratory response 

constitute a highly complex multiple-source, multiple-path dynamic system. 

The quasi-steady accelerations at frequencies below the vehicle's structural mode frequencies are experienced 

throughout the vehicle because the vehicle is a rigid body in this frequency range. The magnitude of some 

quasi-steady accelerations (generated by Orbiter rotational motions, for example) are dependent on the location 

within the vehicle and the motion of the vehicle. 

The accelerations at frequencies higher than the vehicle's lowest structural mode frequency, though, have a very 

localized magnitude and direction. The propagation of oscillatory accelerations throughout the vehicle and payload 

is dependent on the characteristics of the structural path through which the accelerations are transmitted. These characteristics may change based on changes in the vehicle and payload configuration such as those that occur after a 

satellite is launched. 

Transient accelerations quite often cause vehicle vibrations to occur across a wide-frequency band. This will also 

cause a "ringing" effect of the vehicle structure at the primary structural frequencies. 

The acceleration inputs to an experiment, consequently, constitute a highly complex multiple-source, multiplepath dynamic system. 

MEASUREMENT 

Acceleration Sensors 

Many acceleration sensors, which are commonly used for microgravity acceleration measurements, are designed 

to measure the acceleration of the sensor case (or mounting structure) relative to inertial space for navigation purposes. These sensors include pendulous mass sensors (fig. 2) and electrostatically suspended sensors (fig. 3). Pendulous 

mass sensors use an internal proof mass on a cantilever to sense the acceleration of the sensor case relative to inertial 

space. The electrostatically suspended proof mass sensor utilizes electrostatic forces to center a proof mass in a 

chamber. In either sensor, the position of the mass is detected and a restoring force (either magnetic or electrostatic) 

is applied to keep the mass centered. The output acceleration signal is then derived from the restoring force signal. 

Other types of acceleration sensors measure the movement of an inertial mass relative to the sensor case, such as a 

ball in a viscous fluid (fig. 4). The polarity of this type of sensor depends on the relative densities of the inertial 

mass and the fluid (fig. 5). This type of sensor is referred to here as a "fluidic suspended sensor." In these sensors, 

the movement of the inertial mass (the ball) is interpreted to indicate the acceleration of inertial space relative to the 

sensor structure. 

The polarity of a sensor (as reflected in the data) needs to be considered when analyzing any acceleration data, 

particularly in the quasi-steady acceleration regime. The frame of reference also needs to be considered in the process of correlating acceleration data with science results. 

3 
Frame of Reference 

An experiment chamber (as part of an experiment which is operated on the Orbiter) is exposed to an acceleration environment caused by the vehicle, the crew, other experiments, and the experiment apparatus itself. 

Ideally, the experiment chamber would free-float in inertial space to be totally free of outside acceleration 

disturbances. 

In general, an experiment chamber is composed of a portion fixed to the vehicle (e.g., fluid chamber walls, crystal 

growth ampoule) and a portion which is "free-floating" from the vehicle (e.g., bubble in fluid, molten liquid bridge). 

The acceleration disturbances coming from the vehicle have a direct effect on the fixed portion which causes a 

relative effect to the free-floating portion. As an illustration, a trace particle in a liquid (fig. 6) is not moving within a 

fluid. With an impulsive acceleration disturbance (e.g., thruster firing) in the +X direction, the Orbiter and fixed 

chamber walls move in the -X direction. Relative to the Orbiter and fixed chamber walls, the particle is subject to an 

acceleration in the +X direction. Because this acceleration is imparted to the Orbiter vehicle in the reverse direction 

by a forward-facing thruster, the vehicle body goes in the -X direction. This would be interpreted as a negative 

acceleration by a pendulous mass sensor or an electrostatically suspended sensor, but a fluidic suspended sensor 

would interpret this as a positive acceleration. 

A scientist typically utilizes the acceleration relative to a frame of reference fixed to the chamber wall or structure. The reported accelerations are those experienced by the free-floating experiment material (e.g., molten liquid 

bridge, flame body, or trace particles). 

Some acceleration measurement systems measure the accelerations of the mounting surface to which the triaxial 

sensor head is mounted, relative to inertial space. The axis polarity must be reversed for application to 

experiment-based observations of free-floating articles. 

On the other hand, the polarity of a fluidic suspended sensor (with the proof mass density higher than that 

of the fluid) would be the same as the experiment-based observations. The Passive Accelerometer System 

(PAS) utilizes a steel ball within a column filled with a buffered water solution to sense and display the 

low-frequency accelerations. 

Accelerometer Systems 

There are various accelerometer systems available for measuring the micro gravity conditions during experiment 

operations on orbit. The salient features of some of these accelerometer systems are summarized here and the missions flown by each system are shown in table I. 

Fluid Experiment System (FES) Accelerometer.-The FES accelerometer measures acceleration at the base of 

the rack in which the FES apparatus is mounted. The accelerometer is a three-axis device utilizing an electrostatic 

suspended proofmass sensor. A low-pass filter set for 50 Hz is applied to the data. Data are analyzed and reported in 

reference 3. 

The FES accelerometer was developed by Bell Aerospace under contract to NASA Marshall Space Flight Center 

(MSFC). 

High Resolution Accelerometer Package (HiRAP).-The HiRAP is a three-axis accelerometer utilizing pendulous accelerometer sensors. The data are passed through a 20-Hz low-pass filter prior to be digitized. 

The HiRAP instrument was developed by KMS Fusion, Incorporated which was under contract to NASA Johnson 

Space Center (JSC) to acquire data for shuttle aerodynamic research. 

Honeywell In-Space Accelerometer (HISA).-The HISA is a three-axis accelerometer utilizing pendulous accelerometer sensors. The data are passed through a 19.5 Hz low-pass filter prior to being digitized. The dc bias is electronically eliminated resulting in frequency response from 0.025 to 19.5 Hz. 

The HISA was developed by Honeywell Incorporated to monitor oscillatory and transient accelerations onboard 

the spacecraft. Further techillcal details on the operation of the HISA can be found in references 4 and 5. 

Microgravity Measurement Assembly (MMA).-This general purpose accelerometer was developed to measure 

the microgravity environment to support microgravity experiments in the Spacelab module. Data are available in 

near-real-time (NRT) in the Payload Operations Control Center (pOCC) or other operations control centers during a 

mission. The MMA utilizes pendulous mass sensors. An electrostatic suspended sensor is under development for 

future use by MMA. 

4 

- - -----------------------

Frame of Reference 

An experiment chamber (as part of an experiment which is operated on the Orbiter) is exposed to an acceleration environment caused by the vehicle, the crew, other experiments, and the experiment apparatus itself. 

Ideally, the experiment chamber would free-float in inertial space to be totally free of outside acceleration 

disturbances. 

In general, an experiment chamber is composed of a portion fixed to the vehicle (e.g., fluid chamber walls, crystal 

growth ampoule) and a portion which is "free-floating" from the vehicle (e.g., bubble in fluid, molten liquid bridge). 

The acceleration disturbances coming from the vehicle have a direct effect on the fixed portion which causes a 

relative effect to the free-floating portion. As an illustration, a trace particle in a liquid (fig. 6) is not moving within a 

fluid. With an impulsive acceleration disturbance (e.g., thruster firing) in the +X direction, the Orbiter and fixed 

chamber walls move in the -X direction. Relative to the Orbiter and fixed chamber walls, the particle is subject to an 

acceleration in the +X direction. Because this acceleration is imparted to the Orbiter vehicle in the reverse direction 

by a forward-facing thruster, the vehicle body goes in the -X direction. This would be interpreted as a negative 

acceleration by a pendulous mass sensor or an electrostatically suspended sensor, but a fluidic suspended sensor 

would interpret this as a positive acceleration. 

A scientist typically utilizes the acceleration relative to a frame of reference fixed to the chamber wall or structure. The reported accelerations are those experienced by the free-floating experiment material (e.g., molten liquid 

bridge, flame body, or trace particles). 

Some acceleration measurement systems measure the accelerations of the mounting surface to which the triaxial 

sensor head is mounted, relative to inertial space. The axis polarity must be reversed for application to 

experiment-based observations of free-floating articles. 

On the other hand, the polarity of a fluidic suspended sensor (with the proof mass density higher than that 

of the fluid) would be the same as the experiment-based observations. The Passive Accelerometer System 

(PAS) utilizes a steel ball within a column filled with a buffered water solution to sense and display the 

low-frequency accelerations. 

Accelerometer Systems 

There are various accelerometer systems available for measuring the micro gravity conditions during experiment 

operations on orbit. The salient features of some of these accelerometer systems are summarized here and the missions flown by each system are shown in table I. 

Fluid Experiment System (FES) Accelerometer.-The FES accelerometer measures acceleration at the base of 

the rack in which the FES apparatus is mounted. The accelerometer is a three-axis device utilizing an electrostatic 

suspended proofmass sensor. A low-pass filter set for 50 Hz is applied to the data. Data are analyzed and reported in 

reference 3. 

The FES accelerometer was developed by Bell Aerospace under contract to NASA Marshall Space Flight Center 

(MSFC). 

High Resolution Accelerometer Package (HiRAP).-The HiRAP is a three-axis accelerometer utilizing pendulous accelerometer sensors. The data are passed through a 20-Hz low-pass filter prior to be digitized. 

The HiRAP instrument was developed by KMS Fusion, Incorporated which was under contract to NASA Johnson 

Space Center (JSC) to acquire data for shuttle aerodynamic research. 

Honeywell In-Space Accelerometer (HISA).-The HISA is a three-axis accelerometer utilizing pendulous accelerometer sensors. The data are passed through a 19.5 Hz low-pass filter prior to being digitized. The dc bias is electronically eliminated resulting in frequency response from 0.025 to 19.5 Hz. 

The HISA was developed by Honeywell Incorporated to monitor oscillatory and transient accelerations onboard 

the spacecraft. Further techillcal details on the operation of the HISA can be found in references 4 and 5. 

Microgravity Measurement Assembly (MMA).-This general purpose accelerometer was developed to measure 

the microgravity environment to support microgravity experiments in the Spacelab module. Data are available in 

near-real-time (NRT) in the Payload Operations Control Center (pOCC) or other operations control centers during a 

mission. The MMA utilizes pendulous mass sensors. An electrostatic suspended sensor is under development for 

future use by MMA. 

4 

- - -----------------------
The MMA unit was developed by the European Space Research and Technology Center in The Netherlands. 

Microgravity Measuring Device (MMD).-The Microgravity Measuring Device was developed to characterize 

the micro gravity environment of the Wake Shield Facility (WSF) free flyer and the WSF carrier. The MMD was 

sponsored by the Space Vacuum Epitaxy Center of the University of Houston in support of the JSc. Data are 

recorded at 25 samples/sec for each of three axes. Data are downlinked to the JSC control center during a mission. 

The MMD utilizes pendulous proofmass sensors. 

The MMD was subsequently used in the Orbiter middeck in support of crew exercise disturbance studies by JSC. 

The MMD unit was developed by JSc. 

Orbital Acceleration Research Experiment (OARE).-The OARE is a three-axis accelerometer utilizing an electrostatically suspended proofmass sensor which measures low-frequency (lower than 0.1 Hz) accelerations of the 

Orbiter vehicle. The OARE instrument is mounted on the cargo bay floor, very close to the center of mass of the 

vehicle. Raw data are recorded on the payload tape recorder and downlinked. The data are also processed with a 

trimmed mean filter and recorded on OARE internal memory for access after the mission. Compensated data are 

available on a file server after the mission. 

The OARE instrument was developed by KMS Fusion, Incorporated (currently Canopus Systems, Inc.) under 

contract to JSC to acquire data for shuttle aerodynamic research. The OARE instrument is presently managed by 

LeRC and is currently used to support microgravity science experiments. 

Passive Accelerometer System (PAS).-The PAS was developed at the Center for Microgravity and Materials 

Research at the University of Alabama in Huntsville (UAH) to estimate the magnitude of quasi-steady accelerations 

related to atmospheric drag and gravity-gradient effects (ref. 6). PAS operations are based on a simple method used 

to measure viscosity. The instrument is composed of a steel spherical mass in a tube filled with a buffered water 

solution. The time it takes the mass to drift along a known distance in the fluid is used to calculate the velocity of the 

mass, and from that the acceleration is calculated. 

Quasi-Steady Acceleration Measurement (QSAM) System.-The QSAM system measures the quasi-steady and 

vibration-acceleration environment experienced in the Spacelab module. The QSAM instrument has dual two-axis 

invertible sensors for low-frequency acceleration measurements and a triaxial sensor head (TSH) for high-frequency 

measurements. The QSAM utilizes pendulous proofmass sensors. 

The QSAM unit was developed by Deutsche Forschungsanstalt fur Luft und Raumfahrt (DLR) in Germany. 

Space Acceleration Measurement System (SAMS).-A SAMS unit measures acceleration at up to three experiment locations simultaneously and records the raw data in digital format on optical disks. The SAMS units were 

developed by LeRC for use in multiple locations on the Orbiter in support of multiple microgravity missions. There 

are two configurations of SAMS units, one for the Orbiter middeck, Spacelab module or SPACEHAB module and 

one for the Spacelab MPESS carrier in the Orbiter cargo bay. For SAMS units mounted on the Spacelab MPESS 

experiment carriers, some ofthe data are downlinked to the POCC for access in near-real-time by PI's. The SAMS 

TSH's heads utilize pendulou proofmass sensors. 

After the mission, the recorded data are processed to result in engineering units. CD-ROM's are then produced 

containing these data for distribution to users. The downlink data are processed in NRT in the POCC for display and 

analysis during the mission and are also distributed via CD-ROM. The processed data are also available from an 

Internet-connected file server. 

The SAMS units are managed by LeRC. One SAMS unit has also been installed on the Russian Mir Space 

Station. Further information on SAMS may be found in the literature (refs. 7 to 9). 

Three-Dimensional Microgravity Accelerometer (3DMA).-The 3DMA includes three remote TSH's and three 

single-axis invertible sensors for on-orbit measurement of low-frequency accelerations. The 3DMA utilizes pendulous proofmass sensors. All of the data are recorded on the 3DMA instrument, and some of the data may be 

down linked to the POCC during a mission. 

The 3DMA was developed at the Center for Materials Development in Space at UAH. 

COORDINATE SYSTEMS 

There are several coordinate systems which need to be considered when analyzing acceleration data. Care must be 

exercised when dealing with data (whether acceleration environment, Orbiter operations, or experimental data) to 

refer to the proper coordinate system. 

5 

The MMA unit was developed by the European Space Research and Technology Center in The Netherlands. 

Microgravity Measuring Device (MMD).-The Microgravity Measuring Device was developed to characterize 

the micro gravity environment of the Wake Shield Facility (WSF) free flyer and the WSF carrier. The MMD was 

sponsored by the Space Vacuum Epitaxy Center of the University of Houston in support of the JSc. Data are 

recorded at 25 samples/sec for each of three axes. Data are downlinked to the JSC control center during a mission. 

The MMD utilizes pendulous proofmass sensors. 

The MMD was subsequently used in the Orbiter middeck in support of crew exercise disturbance studies by JSC. 

The MMD unit was developed by JSc. 

Orbital Acceleration Research Experiment (OARE).-The OARE is a three-axis accelerometer utilizing an electrostatically suspended proofmass sensor which measures low-frequency (lower than 0.1 Hz) accelerations of the 

Orbiter vehicle. The OARE instrument is mounted on the cargo bay floor, very close to the center of mass of the 

vehicle. Raw data are recorded on the payload tape recorder and downlinked. The data are also processed with a 

trimmed mean filter and recorded on OARE internal memory for access after the mission. Compensated data are 

available on a file server after the mission. 

The OARE instrument was developed by KMS Fusion, Incorporated (currently Canopus Systems, Inc.) under 

contract to JSC to acquire data for shuttle aerodynamic research. The OARE instrument is presently managed by 

LeRC and is currently used to support microgravity science experiments. 

Passive Accelerometer System (PAS).-The PAS was developed at the Center for Microgravity and Materials 

Research at the University of Alabama in Huntsville (UAH) to estimate the magnitude of quasi-steady accelerations 

related to atmospheric drag and gravity-gradient effects (ref. 6). PAS operations are based on a simple method used 

to measure viscosity. The instrument is composed of a steel spherical mass in a tube filled with a buffered water 

solution. The time it takes the mass to drift along a known distance in the fluid is used to calculate the velocity of the 

mass, and from that the acceleration is calculated. 

Quasi-Steady Acceleration Measurement (QSAM) System.-The QSAM system measures the quasi-steady and 

vibration-acceleration environment experienced in the Spacelab module. The QSAM instrument has dual two-axis 

invertible sensors for low-frequency acceleration measurements and a triaxial sensor head (TSH) for high-frequency 

measurements. The QSAM utilizes pendulous proofmass sensors. 

The QSAM unit was developed by Deutsche Forschungsanstalt fur Luft und Raumfahrt (DLR) in Germany. 

Space Acceleration Measurement System (SAMS).-A SAMS unit measures acceleration at up to three experiment locations simultaneously and records the raw data in digital format on optical disks. The SAMS units were 

developed by LeRC for use in multiple locations on the Orbiter in support of multiple microgravity missions. There 

are two configurations of SAMS units, one for the Orbiter middeck, Spacelab module or SPACEHAB module and 

one for the Spacelab MPESS carrier in the Orbiter cargo bay. For SAMS units mounted on the Spacelab MPESS 

experiment carriers, some ofthe data are downlinked to the POCC for access in near-real-time by PI's. The SAMS 

TSH's heads utilize pendulou proofmass sensors. 

After the mission, the recorded data are processed to result in engineering units. CD-ROM's are then produced 

containing these data for distribution to users. The downlink data are processed in NRT in the POCC for display and 

analysis during the mission and are also distributed via CD-ROM. The processed data are also available from an 

Internet-connected file server. 

The SAMS units are managed by LeRC. One SAMS unit has also been installed on the Russian Mir Space 

Station. Further information on SAMS may be found in the literature (refs. 7 to 9). 

Three-Dimensional Microgravity Accelerometer (3DMA).-The 3DMA includes three remote TSH's and three 

single-axis invertible sensors for on-orbit measurement of low-frequency accelerations. The 3DMA utilizes pendulous proofmass sensors. All of the data are recorded on the 3DMA instrument, and some of the data may be 

down linked to the POCC during a mission. 

The 3DMA was developed at the Center for Materials Development in Space at UAH. 

COORDINATE SYSTEMS 

There are several coordinate systems which need to be considered when analyzing acceleration data. Care must be 

exercised when dealing with data (whether acceleration environment, Orbiter operations, or experimental data) to 

refer to the proper coordinate system. 

5 
Orbiter Center of Mass (CM) (On Orbit) 

The Orbiter vehicle center of mass is generally controlled to be within a small volume with the largest dimension 

being 0.8 m in the Orbiter structural X-axis direction. Structural coordinate system dimensions for a typical location 

of the CM are given in table II. 

Orbiter Body Coordinate System 

The body coordinate system of the Orbiter is illustrated in figure 7. The Orbiter body coordinate system (Xb, Y b' 

21,) is defined as a right-handed, orthogonal coordinate system with the +Xb axis extending forward (through the 

Orbiter nose) and the +21, axis extending downward through the Orbiter belly. The + Y b axis completes the righthanded system and extends to starboard (ref. 10). The origin of this coordinate system is located at the CM of the 

vehicle. 

Orbiter operational data, such as attitude rates, are typically given in the Orbiter body coordinate system. 

Orbiter Structural Coordinate System 

The structural coordinate system (Xo' Yo' Zo) of the Orbiter is illustrated in figure 8. The Orbiter structural coordinate system is defined as a right-handed, orthogonal coordinate system with the +Xo axis extending aft (through 

the Orbiter tail) and the +Zo axis extending upward out of the Orbiter payload bay. The + Y 0 axis extends to starboard (ref. 11). The origin of this coordinate system is at the tip of the shuttle external fuel tanle 

The physical location of equipment within the Orbiter is usually specified in terms of this system. 

Orbit Local VerticallLocal Horizontal Coordinate System 

The orbit local vertical (L V)/local horizontal (LH) coordinate system (XLVLH' Y LVLH' ZLVLH) is illustrated in 

figure 9. This coordinate system is based on the Orbiter direction of motion and the center of the Earth. It is independent of the vehicle's attitude. The +XLVLH axis (LH direction) is in the orbital plane and colinear to the Orbiter 

velocity vector (VV). The +ZLVLH axis (LV direction) is toward the center of the Earth. The + Y LVLH axis completes the right-handed coordinate system. The origin of this coordinate system is the vehicle CM (ref. 12). 

The Orbiter orbital attitude is quite often given in reference to LV and the velocity vector (LH) (see the section 

Orbiter Attitudes). 

Sensor Head Coordinate System 

Another axis system is that of the accelerometer sensor head. Sensor heads may be of one, two, or three axes with 

an inherent orthogonal axis system. The SAMS TSH coordinate system is shown as an example in figure 10. This 

sensor head coordinate system is related to a shuttle coordinate system by the orientation of the sensor head as 

mounted to the shuttle. In applying the acceleration data to an experiment, the relationship of the sensor head polarity and orientation relative to the experiment chamber must be determined. 

Coordinate Systems Conversion 

Sensor Head Location.-To convert a sensor head location from the structural coordinate system to the body 

coordinate system, the following method is used. 

The vehicle center of gravity (CG) location in structural coordinates is (XOCG' Y OCG' ZOCG)' The location of a 

sensor head in structural coordinates is (XOSH' Y OSH' ZOSH)' The position vector from the CG to the sensor head in 

structural coordinates is given by 

6 

Orbiter Center of Mass (CM) (On Orbit) 

The Orbiter vehicle center of mass is generally controlled to be within a small volume with the largest dimension 

being 0.8 m in the Orbiter structural X-axis direction. Structural coordinate system dimensions for a typical location 

of the CM are given in table II. 

Orbiter Body Coordinate System 

The body coordinate system of the Orbiter is illustrated in figure 7. The Orbiter body coordinate system (Xb, Y b' 

21,) is defined as a right-handed, orthogonal coordinate system with the +Xb axis extending forward (through the 

Orbiter nose) and the +21, axis extending downward through the Orbiter belly. The + Y b axis completes the righthanded system and extends to starboard (ref. 10). The origin of this coordinate system is located at the CM of the 

vehicle. 

Orbiter operational data, such as attitude rates, are typically given in the Orbiter body coordinate system. 

Orbiter Structural Coordinate System 

The structural coordinate system (Xo' Yo' Zo) of the Orbiter is illustrated in figure 8. The Orbiter structural coordinate system is defined as a right-handed, orthogonal coordinate system with the +Xo axis extending aft (through 

the Orbiter tail) and the +Zo axis extending upward out of the Orbiter payload bay. The + Y 0 axis extends to starboard (ref. 11). The origin of this coordinate system is at the tip of the shuttle external fuel tanle 

The physical location of equipment within the Orbiter is usually specified in terms of this system. 

Orbit Local VerticallLocal Horizontal Coordinate System 

The orbit local vertical (L V)/local horizontal (LH) coordinate system (XLVLH' Y LVLH' ZLVLH) is illustrated in 

figure 9. This coordinate system is based on the Orbiter direction of motion and the center of the Earth. It is independent of the vehicle's attitude. The +XLVLH axis (LH direction) is in the orbital plane and colinear to the Orbiter 

velocity vector (VV). The +ZLVLH axis (LV direction) is toward the center of the Earth. The + Y LVLH axis completes the right-handed coordinate system. The origin of this coordinate system is the vehicle CM (ref. 12). 

The Orbiter orbital attitude is quite often given in reference to LV and the velocity vector (LH) (see the section 

Orbiter Attitudes). 

Sensor Head Coordinate System 

Another axis system is that of the accelerometer sensor head. Sensor heads may be of one, two, or three axes with 

an inherent orthogonal axis system. The SAMS TSH coordinate system is shown as an example in figure 10. This 

sensor head coordinate system is related to a shuttle coordinate system by the orientation of the sensor head as 

mounted to the shuttle. In applying the acceleration data to an experiment, the relationship of the sensor head polarity and orientation relative to the experiment chamber must be determined. 

Coordinate Systems Conversion 

Sensor Head Location.-To convert a sensor head location from the structural coordinate system to the body 

coordinate system, the following method is used. 

The vehicle center of gravity (CG) location in structural coordinates is (XOCG' Y OCG' ZOCG)' The location of a 

sensor head in structural coordinates is (XOSH' Y OSH' ZOSH)' The position vector from the CG to the sensor head in 

structural coordinates is given by 

6 
Because X Body = -XStructural (i.e., X B = -Xo), Y B = Yo' and ~ = -Zo, and because the body coordinate system's 

origin lies at the CG, the location of the sensor head in body coordinates is given by 

This conversion method can be used for any object of known location in the Orbiter. 

Sensor Head Orientation.--Conversion of acceleration data from one axis system to another, such as from 

Orbiter structural axes to experiment-based axes, requires the knowledge of the relative orientations of the two axis 

systems. Given the parameters in table ill where A.u 'u = cos <1> , for <1> the angle between the u'-axis and the u-axis, the 

equations for a simple rotation transformation are 

Orbiter Attitudes 

The Orbiter is flown in attitudes determined by the requirements of the payload(s) being flown . Some attitudes are 

based on a need for a specific orientation of the payload bay relative to the Earth, the Sun, or some other point in 

inertial space. Some attitudes are based on operational constraints such as minimal number of thruster firings or 

specific orientation of the quasi-steady acceleration vector. 

The attitudes selected for a mission are quite often a compromise among the requirements of the various payloads 

and the attitude changes during a mission based on the requirements of the active payloads. 

The typical Earth-oriented attitudes are illustrated in figure 11. The attitude names are based on the Orbiter body 

axis orientation relative to local vertical and the velocity vector (ref. 12). The attitude at the upper left is referred to 

as -ZL V /-XVV which indicates that the Orbiter - Z body axis is toward the Earth (local vertical) and -x body axis 

is in the direction of flight (velocity vector). 

The Orbiter attitude determines major features of the microgravity environment due to the frequency and intensity 

of the required thruster firi ngs, rotational effects, atmospheric drag and the resultant magnitude, and the direction of 

the quasi-steady residual acceleration vector at the experiment site within the vehicle. 

DATA PROCESSING 

Data Processe 

Various methods may be applied to the sampled data set produced by accelerometer systems. The method or 

methods applied to the data are determined by the nature of information desired from the analysis. Common processes applied to acceleration data are described here with the basic information which is typically extracted from 

each method. 

Vector Versus Single Axes.- In some cases, an experiment may be interested in acceleration data from individual 

axes. There may be a high degree of symmetry in the experimental apparatus that makes a single axis acceleration 

predominate in its effect on the science apparatus. 

The common method of processing to be applied to multidimensional (either two or three axes) accelerometer 

data is to combine the individual orthogonal axis data into a vector magnitude. The vector magnitude of an individual data point is derived by the following equation: 

7 

Because X Body = -XStructural (i.e., X B = -Xo), Y B = Yo' and ~ = -Zo, and because the body coordinate system's 

origin lies at the CG, the location of the sensor head in body coordinates is given by 

This conversion method can be used for any object of known location in the Orbiter. 

Sensor Head Orientation.--Conversion of acceleration data from one axis system to another, such as from 

Orbiter structural axes to experiment-based axes, requires the knowledge of the relative orientations of the two axis 

systems. Given the parameters in table ill where A.u 'u = cos <1> , for <1> the angle between the u'-axis and the u-axis, the 

equations for a simple rotation transformation are 

Orbiter Attitudes 

The Orbiter is flown in attitudes determined by the requirements of the payload(s) being flown . Some attitudes are 

based on a need for a specific orientation of the payload bay relative to the Earth, the Sun, or some other point in 

inertial space. Some attitudes are based on operational constraints such as minimal number of thruster firings or 

specific orientation of the quasi-steady acceleration vector. 

The attitudes selected for a mission are quite often a compromise among the requirements of the various payloads 

and the attitude changes during a mission based on the requirements of the active payloads. 

The typical Earth-oriented attitudes are illustrated in figure 11. The attitude names are based on the Orbiter body 

axis orientation relative to local vertical and the velocity vector (ref. 12). The attitude at the upper left is referred to 

as -ZL V /-XVV which indicates that the Orbiter - Z body axis is toward the Earth (local vertical) and -x body axis 

is in the direction of flight (velocity vector). 

The Orbiter attitude determines major features of the microgravity environment due to the frequency and intensity 

of the required thruster firi ngs, rotational effects, atmospheric drag and the resultant magnitude, and the direction of 

the quasi-steady residual acceleration vector at the experiment site within the vehicle. 

DATA PROCESSING 

Data Processe 

Various methods may be applied to the sampled data set produced by accelerometer systems. The method or 

methods applied to the data are determined by the nature of information desired from the analysis. Common processes applied to acceleration data are described here with the basic information which is typically extracted from 

each method. 

Vector Versus Single Axes.- In some cases, an experiment may be interested in acceleration data from individual 

axes. There may be a high degree of symmetry in the experimental apparatus that makes a single axis acceleration 

predominate in its effect on the science apparatus. 

The common method of processing to be applied to multidimensional (either two or three axes) accelerometer 

data is to combine the individual orthogonal axis data into a vector magnitude. The vector magnitude of an individual data point is derived by the following equation: 

7 
Acceleration Versus Time.-This data plot illustrated in figure 12 plots the acceleration data points as acquired in 

time. Individual axis data, vector magnitude, or statistical representations may be chosen. 

A peak acceleration function displays the peak acceleration in successive interval of time. An average acceleration function displays the average acceleration in successive intervals of time. 

Arithmetic Mean and Root-Mean-Square (rms) Versus Time .-By choosing a small interval of time relative to 

the sampling rate and the total time of the acceleration data, several processes (such as an arithmetic mean and rms) 

may be applied to each interval. Typically, this interval can range from tens of seconds to minutes, depending on the 

sample rate of the data and/or the needs of the PI. 

Arithmetic Mean Calculation: Applying an arithmetic mean to the data within the interval results in a total set of 

data with a frequency response less than the inverse of the time interval. An average plot may be produced by calculating an interval average of each axis and then combining the results into a vector magnitude repre entation. 

Root Mean Square (rms) Calculation: By applying an rms calculation to the interval of data, information relative 

to the periodic content of the data is apparent. A rms plot may be produced by calculating the rms of an interval of 

data for each axis and then combining the results into a vector magnitude representation. 

Acceleration Power Spectral Density Versus Frequency.-This data plot, illustrated in figure 13, plots the acceleration power spectral density (PSD) against frequency. This data plot may use vector magnitude or individual axis 

data. 

Applying a fast-Fourier-transform (FFT) routine to a window of data transforms the time-sampled data into the 

frequency domain. The data in figure 13 is the same as that in figure 12. The obvious oscillation occurring with a 

period of about 3 sec in figure 12 appears as the peak at 0.3 Hz in figure 13. 

The power spectral density illu trates where the energy content of the total vibration resides. This is useful for 

examining the data for its effects on specific experiments. 

Acceleration Power Spectral Density Versus Time Versus Frequency .--Calculating successive acceleration 

power spectral density and appending them in time results in a three-dimensional plot of the acceleration data 

(fig. 14). 

Activities which contain distinct frequencies are apparent by horizontal bands or bars in the plot. The vehicle 

vibration modes are in the range between 3 and 10 Hz, the Ku-band antenna operates at 17 Hz and a refrigerator/ 

freezer compressor operates at 22 Hz. Short time-based events (such as a thruster firing) are manifested by narrow 

vertical lines. 

This type of data plot allows several types of information to be extracted. Some experiments are sensitive to 

vibrations in a certain frequency region, whereas others are sensitive to impulsive types of disturbances with energy 

spread across the entire frequency spectrum. 

Data Access 

Access to acceleration data is desired as soon as possible during or after experiment operation . In some cases, 

knowledge of the acceleration environment is needed in preparation for future experiment operations. 

Most accelerometer systems record data by means of magnetic tape storage, optical disk storage, or magnetic hard 

disk. The data are returned to Earth, processed into engineering units, and then made available for analysis. The time 

delay for this may range from days to months after the experiment operations. Final data products are available in a 

variety of formats ranging from survey reports describing the mission to acceleration data in engineering units on 

floppy disks, CD-ROM's, and network accessible files. 

In some accelerometer systems, data are available in NRT during the mission for conversion to engineering units 

and availability for analysis. 

For accelerometer systems with downlinked data available in the POCC, standard processes and data display techniques are utilized. In some cases, the raw data are also available for experiment teams to process and analyze 

directly on their ground support equipment. 

SAMS and OARE acceleration data are available on a file server for access over the Internet. The files are primarily for PI's funded by MSAD but other organizations with a demonstrated need may also acce the data. In the 

future, it is planned that the mission summary reports will also be available over the Internet. The file server Internet 

name is beech . 1 ere . nasa . gOY and the data are in a directory entitled pub. Appendix C-Accessing SAMS Data 

Files Via Internet contains further instructions on utilizing this file server. 

8 

Acceleration Versus Time.-This data plot illustrated in figure 12 plots the acceleration data points as acquired in 

time. Individual axis data, vector magnitude, or statistical representations may be chosen. 

A peak acceleration function displays the peak acceleration in successive interval of time. An average acceleration function displays the average acceleration in successive intervals of time. 

Arithmetic Mean and Root-Mean-Square (rms) Versus Time .-By choosing a small interval of time relative to 

the sampling rate and the total time of the acceleration data, several processes (such as an arithmetic mean and rms) 

may be applied to each interval. Typically, this interval can range from tens of seconds to minutes, depending on the 

sample rate of the data and/or the needs of the PI. 

Arithmetic Mean Calculation: Applying an arithmetic mean to the data within the interval results in a total set of 

data with a frequency response less than the inverse of the time interval. An average plot may be produced by calculating an interval average of each axis and then combining the results into a vector magnitude repre entation. 

Root Mean Square (rms) Calculation: By applying an rms calculation to the interval of data, information relative 

to the periodic content of the data is apparent. A rms plot may be produced by calculating the rms of an interval of 

data for each axis and then combining the results into a vector magnitude representation. 

Acceleration Power Spectral Density Versus Frequency.-This data plot, illustrated in figure 13, plots the acceleration power spectral density (PSD) against frequency. This data plot may use vector magnitude or individual axis 

data. 

Applying a fast-Fourier-transform (FFT) routine to a window of data transforms the time-sampled data into the 

frequency domain. The data in figure 13 is the same as that in figure 12. The obvious oscillation occurring with a 

period of about 3 sec in figure 12 appears as the peak at 0.3 Hz in figure 13. 

The power spectral density illu trates where the energy content of the total vibration resides. This is useful for 

examining the data for its effects on specific experiments. 

Acceleration Power Spectral Density Versus Time Versus Frequency .--Calculating successive acceleration 

power spectral density and appending them in time results in a three-dimensional plot of the acceleration data 

(fig. 14). 

Activities which contain distinct frequencies are apparent by horizontal bands or bars in the plot. The vehicle 

vibration modes are in the range between 3 and 10 Hz, the Ku-band antenna operates at 17 Hz and a refrigerator/ 

freezer compressor operates at 22 Hz. Short time-based events (such as a thruster firing) are manifested by narrow 

vertical lines. 

This type of data plot allows several types of information to be extracted. Some experiments are sensitive to 

vibrations in a certain frequency region, whereas others are sensitive to impulsive types of disturbances with energy 

spread across the entire frequency spectrum. 

Data Access 

Access to acceleration data is desired as soon as possible during or after experiment operation . In some cases, 

knowledge of the acceleration environment is needed in preparation for future experiment operations. 

Most accelerometer systems record data by means of magnetic tape storage, optical disk storage, or magnetic hard 

disk. The data are returned to Earth, processed into engineering units, and then made available for analysis. The time 

delay for this may range from days to months after the experiment operations. Final data products are available in a 

variety of formats ranging from survey reports describing the mission to acceleration data in engineering units on 

floppy disks, CD-ROM's, and network accessible files. 

In some accelerometer systems, data are available in NRT during the mission for conversion to engineering units 

and availability for analysis. 

For accelerometer systems with downlinked data available in the POCC, standard processes and data display techniques are utilized. In some cases, the raw data are also available for experiment teams to process and analyze 

directly on their ground support equipment. 

SAMS and OARE acceleration data are available on a file server for access over the Internet. The files are primarily for PI's funded by MSAD but other organizations with a demonstrated need may also acce the data. In the 

future, it is planned that the mission summary reports will also be available over the Internet. The file server Internet 

name is beech . 1 ere . nasa . gOY and the data are in a directory entitled pub. Appendix C-Accessing SAMS Data 

Files Via Internet contains further instructions on utilizing this file server. 

8 
For questions about access to this data, contact 

Richard DeLombard 

PIMS Project Manager 

e-mail: pims@lerc .nasa . gOY 

Telephone: 216-433-5285 

Facsimile: 216-433-8660 

Standard Services 

Standard reports are prepared after each MSAD science mission with an accelerometer system. The reports 

describe the accelerometer systems flown on the mission and summarize the data acquired by the SAMS and OARE 

accelerometer ystems. Other accelerometer systems are summarized when they have been used to support MSAD 

PI's. Reports which have been prepared for previous missions are listed in the bibliography. 

For the SAMS data acquired from missions, CD-ROM's are prepared and are available for distribution. For the 

SAMS and OARE data acquired from missions, the processed data is available on an Internet-connected fil e server 

for access by users. 

Specialized data processing is also available for MSAD-sponsored PI's. 

DATA INTERPRETATION 

Acceleration Events Characteristics 

Many events onboard the shuttle may be characterized by their acceleration signature. Whereas each occurrence is 

essentially unique, there are distinguishing patterns for similar types of events. The following sections are a summary of what is currently known about these types of events. The characterization will continue to be refined in the 

future. 

Thrusters.-There are three basic types of thrusters on the Orbiter which are used during on-orbit operations (see 

Appendix D-RCS and OMS Engines Description). Vernier Reaction Control System (VRCS) thrusters, which 

provide about 24 Ib of thrust, are used for fine attitude control. A thruster of this type will cause a disturbance at or 

below 10-4 g. 

Primary Reaction Control System (PRCS) thrusters, which provide about 870 Ib of thrust, are used for attitude 

changes. A thruster of this type will cause a disturbance at or below 10-2 g. 

Orbital Maneuvering System (OMS) thrusters, which provide about 6,000 lb of thrust, are used for orbit insertion, 

orbit changes and de-orbit. The OMS are not typically used during Spacelab module operations. 

These three thruster types have similar signatures (figs. 15, 16, and 17), but are differentiated by acceleration 

magnitude and duration. The stars in figures 15 and 16 indicate the time that thrusters were fired. The vernier and 

primary thrusters are typically fired for a very short event (typically 80 msec to 1 sec). The OMS thrusters operations can occur from seconds to minutes in length. 

A thruster action is an impulse action and contributes energy across a wide frequency band. Figure 18 (see color 

plate 1) illustrates four thruster events which occurred in a I min time frame on STS-62 and were approximately 

15 sec apart. The coar eness of the data plot is due to the short time interval included in the plot. These same thrusters are shown in figure 16, starting at 150 sec. 

Crew Exercise.-Disturbances from crew exercise are dependent on the type of exercise device utilized, the particular crew member's physical characteristics, and the robustness of the exercise. The method (if any) of vibration 

isolation or control incorporated in the exercise device has a direct effect on the microgravity environment. Experimental investigations are ongoing to find the optimal method of crew exercise and vibration isolation for the 

devices. Exercise remains necessary for the health and well-being of the crew members. 

The disturbance from a treadmill shown in figure 19 typifies crew exercise-induced disturbances. The basic 

frequency of 2.3 Hz originates with the foot fall frequency of the crew member. One-half of that frequency is the 

stride rate with the disturbance caused by the side-to-side motion of the crew member's body. With a fundamental 

9 

For questions about access to this data, contact 

Richard DeLombard 

PIMS Project Manager 

e-mail: pims@lerc .nasa . gOY 

Telephone: 216-433-5285 

Facsimile: 216-433-8660 

Standard Services 

Standard reports are prepared after each MSAD science mission with an accelerometer system. The reports 

describe the accelerometer systems flown on the mission and summarize the data acquired by the SAMS and OARE 

accelerometer ystems. Other accelerometer systems are summarized when they have been used to support MSAD 

PI's. Reports which have been prepared for previous missions are listed in the bibliography. 

For the SAMS data acquired from missions, CD-ROM's are prepared and are available for distribution. For the 

SAMS and OARE data acquired from missions, the processed data is available on an Internet-connected fil e server 

for access by users. 

Specialized data processing is also available for MSAD-sponsored PI's. 

DATA INTERPRETATION 

Acceleration Events Characteristics 

Many events onboard the shuttle may be characterized by their acceleration signature. Whereas each occurrence is 

essentially unique, there are distinguishing patterns for similar types of events. The following sections are a summary of what is currently known about these types of events. The characterization will continue to be refined in the 

future. 

Thrusters.-There are three basic types of thrusters on the Orbiter which are used during on-orbit operations (see 

Appendix D-RCS and OMS Engines Description). Vernier Reaction Control System (VRCS) thrusters, which 

provide about 24 Ib of thrust, are used for fine attitude control. A thruster of this type will cause a disturbance at or 

below 10-4 g. 

Primary Reaction Control System (PRCS) thrusters, which provide about 870 Ib of thrust, are used for attitude 

changes. A thruster of this type will cause a disturbance at or below 10-2 g. 

Orbital Maneuvering System (OMS) thrusters, which provide about 6,000 lb of thrust, are used for orbit insertion, 

orbit changes and de-orbit. The OMS are not typically used during Spacelab module operations. 

These three thruster types have similar signatures (figs. 15, 16, and 17), but are differentiated by acceleration 

magnitude and duration. The stars in figures 15 and 16 indicate the time that thrusters were fired. The vernier and 

primary thrusters are typically fired for a very short event (typically 80 msec to 1 sec). The OMS thrusters operations can occur from seconds to minutes in length. 

A thruster action is an impulse action and contributes energy across a wide frequency band. Figure 18 (see color 

plate 1) illustrates four thruster events which occurred in a I min time frame on STS-62 and were approximately 

15 sec apart. The coar eness of the data plot is due to the short time interval included in the plot. These same thrusters are shown in figure 16, starting at 150 sec. 

Crew Exercise.-Disturbances from crew exercise are dependent on the type of exercise device utilized, the particular crew member's physical characteristics, and the robustness of the exercise. The method (if any) of vibration 

isolation or control incorporated in the exercise device has a direct effect on the microgravity environment. Experimental investigations are ongoing to find the optimal method of crew exercise and vibration isolation for the 

devices. Exercise remains necessary for the health and well-being of the crew members. 

The disturbance from a treadmill shown in figure 19 typifies crew exercise-induced disturbances. The basic 

frequency of 2.3 Hz originates with the foot fall frequency of the crew member. One-half of that frequency is the 

stride rate with the disturbance caused by the side-to-side motion of the crew member's body. With a fundamental 

9 
vibration mode of the Orbiter at 4.7 Hz, a significant amount of acceleration is observed at this frequency. The crew 

exercise activities usually last for 20 to 30 min for each crew member daily during a mission. 

Disturbances caused by crew exercise on a bicycle ergometer are similar in nature. 

Life Science Experiments .-Some life sciences experiments employ devices such as rotating chairs for crew 

members and centrifuges for plants and animals. The data shown in figures 12 and 13 were acquired during an 

experiment in which one crew member was seated in a chair while another crew member manua]]y rotated the chair. 

The chair rotation rate was approximately one revolution every 3 sec. 

Shuttle Maneuvers.-Maneuvers to change the shuttle attitude can be significant sources of disturbance. 

During a typical mission, attitude maneuvers may be performed for a variety of reasons, such as navigation, communications, and Orbiter thermal requirements. The disturbances created are a combination of thruster firing disturbances (described in the previous section) together with rotational and translational accelerations as the vehicle is 

reoriented. 

The quasi-steady acceleration level changes between attitudes is illustrated in figure 20 from OARB data on STS62. The Orbiter was reoriented from the -XL V /-ZVV attitude to the -XL V /+ZVV attitude. The Z-axis acceleration 

can be seen to change sign since the Orbiter reversed direction in the Z-axis. The high-level acceleration which 

occurred during the maneuver is due to the rotational and translational accelerations during the maneuvers. 

Shuttle Equipment.-Some equipment on the shuttle, such as the Ku-band antenna and refrigerators, operate 

almost continuously during on-orbit operations. 

The Ku-band antenna has a 17-Hz dither frequency for the pointing control system. This signature (figs. 14, 18, 

21 , and 22) is quite often found in the acceleration environment of the Orbiter and can be quite significant compared 

with the background environment. 

Notice the relative strengths of the first and second harmonics of this disturbance at 34 and 51 Hz. Note that the 

data in figure 22 were acquired during a crew sleep period and were filtered by the SAMS instrument with an eight 

pole filter at 25 Hz. 

The refrigerators commonly used in the Spacelab module and in the Orbiter middeck have a characteristic frequency of 22 Hz and harmonics (figs. 13 and 14) and a typical cycle time of 3 min on and 9 min off. A different 

refrigerator used in the SPACEHAB module on the SH-2 mission operates with a frequency of 60 Hz. 

Other Orbiter equipment, which does not contribute significantly to microgravity disturbances, has been investigated. The movements of the cargo bay cameras and the Ku-band antenna (apart from the dither mentioned earlier) 

do not appear to significantly affect the environment. 

Atmospheric Drag.-The shuttle experiences atmospheric drag due to the slight atmosphere which exists at 

orbital altitudes. The magnitude of this atmospheric drag depends on many variables, such as altitude, attitude, 

orbital inclination, time of year, day/night portion of the orbit, etc. Atmospheric drag is characterized by its variation 

with an orbital period (typically 90 min). The orientation of the drag is opposite the velocity vector. 

The variation in the quasi-steady acceleration in the ~-axis of the shuttle in a-XL V/-ZVV attitude during 

STS-62 is shown in figure 23. During this time, the shuttle was in a near-circular orbit with an altitude which varied 

between 161 and 163 n mi. 

The variation in the quasi-steady acceleration in the Y b axis of the shuttle in a -ZLV/+ YVV attitude during STS62 is shown in figure 24. In this figure, this attitude was maintained from hour 320 into hour 328. During this time, 

the shuttle was in an elliptical orbit with apogee and perigee altitudes of 138 and 105 n mi, respectively. This difference in altitudes accentuated the variation in drag accelerations compared to those occurring in a more circular orbit. 

This is due to the difference in atmospheric density experienced at the different altitudes during one orbit. In this 

attitude, the majority of the drag is aligned with the Orbiter Y b -axis since that axis is in the direction of flight. 

Vehicle Location.-There are variations in the quasi-steady acceleration levels depending on the location within 

an orbital vehicle. These variations are due to the effects of the gravity gradient and rotational accelerations (see the 

section Quasi-Steady Accelerations and ref. 13). Figures 25 and 26 illustrate the difference between OARB data as 

acquired at the OARB location (fig. 25) and at an experiment location (fig. 26) almost 5 m away. 

Satellite Launches.-Some MSAD science experiment payloads are manifested on missions which include satellite launches from the cargo bay of the shuttle. One such mission, the USMP-1 on STS- 52, included the launch of 

the LAGEOS satellite on the first day of the mission. This event is shown in figure 27 and is characterized by the 

shuttle maneuvers prior to and after the launch and the short discrete high-level disturbance when the satellite was 

actually launched. 

10 

vibration mode of the Orbiter at 4.7 Hz, a significant amount of acceleration is observed at this frequency. The crew 

exercise activities usually last for 20 to 30 min for each crew member daily during a mission. 

Disturbances caused by crew exercise on a bicycle ergometer are similar in nature. 

Life Science Experiments .-Some life sciences experiments employ devices such as rotating chairs for crew 

members and centrifuges for plants and animals. The data shown in figures 12 and 13 were acquired during an 

experiment in which one crew member was seated in a chair while another crew member manua]]y rotated the chair. 

The chair rotation rate was approximately one revolution every 3 sec. 

Shuttle Maneuvers.-Maneuvers to change the shuttle attitude can be significant sources of disturbance. 

During a typical mission, attitude maneuvers may be performed for a variety of reasons, such as navigation, communications, and Orbiter thermal requirements. The disturbances created are a combination of thruster firing disturbances (described in the previous section) together with rotational and translational accelerations as the vehicle is 

reoriented. 

The quasi-steady acceleration level changes between attitudes is illustrated in figure 20 from OARB data on STS62. The Orbiter was reoriented from the -XL V /-ZVV attitude to the -XL V /+ZVV attitude. The Z-axis acceleration 

can be seen to change sign since the Orbiter reversed direction in the Z-axis. The high-level acceleration which 

occurred during the maneuver is due to the rotational and translational accelerations during the maneuvers. 

Shuttle Equipment.-Some equipment on the shuttle, such as the Ku-band antenna and refrigerators, operate 

almost continuously during on-orbit operations. 

The Ku-band antenna has a 17-Hz dither frequency for the pointing control system. This signature (figs. 14, 18, 

21 , and 22) is quite often found in the acceleration environment of the Orbiter and can be quite significant compared 

with the background environment. 

Notice the relative strengths of the first and second harmonics of this disturbance at 34 and 51 Hz. Note that the 

data in figure 22 were acquired during a crew sleep period and were filtered by the SAMS instrument with an eight 

pole filter at 25 Hz. 

The refrigerators commonly used in the Spacelab module and in the Orbiter middeck have a characteristic frequency of 22 Hz and harmonics (figs. 13 and 14) and a typical cycle time of 3 min on and 9 min off. A different 

refrigerator used in the SPACEHAB module on the SH-2 mission operates with a frequency of 60 Hz. 

Other Orbiter equipment, which does not contribute significantly to microgravity disturbances, has been investigated. The movements of the cargo bay cameras and the Ku-band antenna (apart from the dither mentioned earlier) 

do not appear to significantly affect the environment. 

Atmospheric Drag.-The shuttle experiences atmospheric drag due to the slight atmosphere which exists at 

orbital altitudes. The magnitude of this atmospheric drag depends on many variables, such as altitude, attitude, 

orbital inclination, time of year, day/night portion of the orbit, etc. Atmospheric drag is characterized by its variation 

with an orbital period (typically 90 min). The orientation of the drag is opposite the velocity vector. 

The variation in the quasi-steady acceleration in the ~-axis of the shuttle in a-XL V/-ZVV attitude during 

STS-62 is shown in figure 23. During this time, the shuttle was in a near-circular orbit with an altitude which varied 

between 161 and 163 n mi. 

The variation in the quasi-steady acceleration in the Y b axis of the shuttle in a -ZLV/+ YVV attitude during STS62 is shown in figure 24. In this figure, this attitude was maintained from hour 320 into hour 328. During this time, 

the shuttle was in an elliptical orbit with apogee and perigee altitudes of 138 and 105 n mi, respectively. This difference in altitudes accentuated the variation in drag accelerations compared to those occurring in a more circular orbit. 

This is due to the difference in atmospheric density experienced at the different altitudes during one orbit. In this 

attitude, the majority of the drag is aligned with the Orbiter Y b -axis since that axis is in the direction of flight. 

Vehicle Location.-There are variations in the quasi-steady acceleration levels depending on the location within 

an orbital vehicle. These variations are due to the effects of the gravity gradient and rotational accelerations (see the 

section Quasi-Steady Accelerations and ref. 13). Figures 25 and 26 illustrate the difference between OARB data as 

acquired at the OARB location (fig. 25) and at an experiment location (fig. 26) almost 5 m away. 

Satellite Launches.-Some MSAD science experiment payloads are manifested on missions which include satellite launches from the cargo bay of the shuttle. One such mission, the USMP-1 on STS- 52, included the launch of 

the LAGEOS satellite on the first day of the mission. This event is shown in figure 27 and is characterized by the 

shuttle maneuvers prior to and after the launch and the short discrete high-level disturbance when the satellite was 

actually launched. 

10 
CONCLUDING REMARKS 

The microgravity acceleration environment is typically measured during micro gravity science missions on the 

Orbiter. These acceleration data are processed and presented to the scientists to aid in the analysis of their scientific 

data. 

This document includes information which is common to different missions and complements the contents of the 

Mission Summary Reports produced by the PIMS Project at NASA LeRC. It is anticipated that this compendium of 

information will be expanded in the future when additional information is available. 

With the information in this document, scientists will be better able to apply the acceleration data to their scientific data. 

ACKNOWLEDGMENTS 

The author wishes to thank several people for their contributions to this report. The data were extracted from 

work done by four members of the PI Microgravity Services project at NASA LeRC. Melissa J.B. Rogers, Kim 

Destro-Sidik, Ken Hrovat, and Doug Deutsch, all employees of Tal-Cut Company, have spent many hours deciphering and interpreting the acceleration environment data. Brian Matisak, Teledyne Brown Engineering, Huntsville, 

Alabama has spent many hours reviewing and explaining the orbital aspects of the acceleration environment for the 

author. 

11 

CONCLUDING REMARKS 

The microgravity acceleration environment is typically measured during micro gravity science missions on the 

Orbiter. These acceleration data are processed and presented to the scientists to aid in the analysis of their scientific 

data. 

This document includes information which is common to different missions and complements the contents of the 

Mission Summary Reports produced by the PIMS Project at NASA LeRC. It is anticipated that this compendium of 

information will be expanded in the future when additional information is available. 

With the information in this document, scientists will be better able to apply the acceleration data to their scientific data. 

ACKNOWLEDGMENTS 

The author wishes to thank several people for their contributions to this report. The data were extracted from 

work done by four members of the PI Microgravity Services project at NASA LeRC. Melissa J.B. Rogers, Kim 

Destro-Sidik, Ken Hrovat, and Doug Deutsch, all employees of Tal-Cut Company, have spent many hours deciphering and interpreting the acceleration environment data. Brian Matisak, Teledyne Brown Engineering, Huntsville, 

Alabama has spent many hours reviewing and explaining the orbital aspects of the acceleration environment for the 

author. 

11 
TABLE I.-ACCELEROMETER SYSTEMS BY FLIGHT 

Mission Microgravity Launch FES Hi RAP 

payload 

STS-6, 7, 8, 9, 11, 13, 24, 26, 30, 35 X 

STS- 17 

(51-B) 

STS- 32 

STS-40 

STS-43 

STS-42 

STS- 50 

STS-47 

STS- 52 

STS- 55 

STS-57 

STS- 58 

STS-60 

STS-62 

STS-65 

STS-66 

STS-63 

Spacelab 4/85 X 

3 

1190 X 

SLS-l 6/91 X 

8/91 

IML-l 1192 X 

USML-l 6/92 X 

SL-J 9/92 

USMP-I 10/92 X 

SL-D2 4/93 X 

SH-I 6/93 

SLS-2 10/93 X 

SH-2 2194 

USMP-2 3/94 X 

IML-2 7/94 X 

PCG 11194 

SH-3 2195 

TABLE n .-ORBITER CENTER OF 

MASS (CM) LOCATION (TYPICAL) 

Orbiter structural Orbiter structural 

axi location, 

in. 

X 1096 

Y 0.38 

Z 377 

HISA MMA 

X 

X 

12 

MMD OARB PAS QSAM SAMS 

X X 

X 

X 

X X X 

X 

X 

X 

X 

X X X 

X X X 

X X X X 

X 

X 

TABLE ill.-DIRECI'IO COSINE 

TABLE 

New coorclinate Old coordinate system 

system x y z 

x' "'x'x "'x'Y "'x·z 

y' "'Y'x "'Y'y "'y'Z 

Z' "'z'x "'z'y "'z'z 

3DMA 

X 

X 

X 

TABLE I.-ACCELEROMETER SYSTEMS BY FLIGHT 

Mission Microgravity Launch FES Hi RAP 

payload 

STS-6, 7, 8, 9, 11, 13, 24, 26, 30, 35 X 

STS- 17 

(51-B) 

STS- 32 

STS-40 

STS-43 

STS-42 

STS- 50 

STS-47 

STS- 52 

STS- 55 

STS-57 

STS- 58 

STS-60 

STS-62 

STS-65 

STS-66 

STS-63 

Spacelab 4/85 X 

3 

1190 X 

SLS-l 6/91 X 

8/91 

IML-l 1192 X 

USML-l 6/92 X 

SL-J 9/92 

USMP-I 10/92 X 

SL-D2 4/93 X 

SH-I 6/93 

SLS-2 10/93 X 

SH-2 2194 

USMP-2 3/94 X 

IML-2 7/94 X 

PCG 11194 

SH-3 2195 

TABLE n .-ORBITER CENTER OF 

MASS (CM) LOCATION (TYPICAL) 

Orbiter structural Orbiter structural 

axi location, 

in. 

X 1096 

Y 0.38 

Z 377 

HISA MMA 

X 

X 

12 

MMD OARB PAS QSAM SAMS 

X X 

X 

X 

X X X 

X 

X 

X 

X 

X X X 

X X X 

X X X X 

X 

X 

TABLE ill.-DIRECI'IO COSINE 

TABLE 

New coorclinate Old coordinate system 

system x y z 

x' "'x'x "'x'Y "'x·z 

y' "'Y'x "'Y'y "'y'Z 

Z' "'z'x "'z'y "'z'z 

3DMA 

X 

X 

X 
Position 

sensor -, 

Proof 

mass --

Position 

sensor --

/~ Rebalance 

force coil 

__ ~ Pendulum 

'~ Rebalance 

force coil 

Figure 1.-0rbital cannonball concept. Figure 2.-Pendulous mass acceleration sensor (single axis). 

Position sensors ..... ............... """ "' . "" "'" ' .... "', ... ............ " ....... ............ ". 

and electrostatic 

''''. rebalance - ' '''.::-,:- ....... 

, .::::: ---

Proof mass 

Position 

sensors and 

electrostatic 

....... 

....... 

.....•. -- '", 

rebalance --- .. ~ 

", 

Position 

sensors and 

electrostatic 

rebalance 

Figure 3.-Electrostatically suspended acceleration sensor (three axes.) 

Fluid 

Supended 

mass ---

Figure 4.-Fluid suspended mass sensor. 

13 

Position 

sensor -, 

Proof 

mass --

Position 

sensor --

/~ Rebalance 

force coil 

__ ~ Pendulum 

'~ Rebalance 

force coil 

Figure 1.-0rbital cannonball concept. Figure 2.-Pendulous mass acceleration sensor (single axis). 

Position sensors ..... ............... """ "' . "" "'" ' .... "', ... ............ " ....... ............ ". 

and electrostatic 

''''. rebalance - ' '''.::-,:- ....... 

, .::::: ---

Proof mass 

Position 

sensors and 

electrostatic 

....... 

....... 

.....•. -- '", 

rebalance --- .. ~ 

", 

Position 

sensors and 

electrostatic 

rebalance 

Figure 3.-Electrostatically suspended acceleration sensor (three axes.) 

Fluid 

Supended 

mass ---

Figure 4.-Fluid suspended mass sensor. 

13 
Silicone 

oil fluid ~-_ 

Steel ball ----

-------~.-. -----

Silicone 

oil fluid ~-- __ 

----

Cork ball ---

Figure 5.-Forward and reverse polarity fluidic sensor. 

Vernier thruster 

exhaust direction 

[;

Xb 

Orbiter 

body axes 

Direction of ball motion relative 

to container 

Zb 

Direction of apparent 

motion relative to 

inertial space 

Silicone 

oil fluid ~ 

Steel ball 

Figure 6.-Mobile tracer particle in fluid. 

14 

--1 

I 

Silicone 

oil fluid ~-_ 

Steel ball ----

-------~.-. -----

Silicone 

oil fluid ~-- __ 

----

Cork ball ---

Figure 5.-Forward and reverse polarity fluidic sensor. 

Vernier thruster 

exhaust direction 

[;

Xb 

Orbiter 

body axes 

Direction of ball motion relative 

to container 

Zb 

Direction of apparent 

motion relative to 

inertial space 

Silicone 

oil fluid ~ 

Steel ball 

Figure 6.-Mobile tracer particle in fluid. 

14 

--1 

I 
+Yo 

(Starboard) 

Figure 7.-Orbiter body coordinate system. 

", 

", 

", 

", 

", 

", 

", 

", 

-Yo (Port) 

", 

.,,- ", 

", 

", 

", 

", 

Figure 8.-Orbiter structural coordinate system. 

15 

Vehicle center of mass 

<t Payload bay 

___ I 

+Yo 

(Starboard) 

Figure 7.-Orbiter body coordinate system. 

", 

", 

", 

", 

", 

", 

", 

", 

-Yo (Port) 

", 

.,,- ", 

", 

", 

", 

", 

Figure 8.-Orbiter structural coordinate system. 

15 

Vehicle center of mass 

<t Payload bay 

___ I 
LV - Local vertical 

LH - Local horizontal 

W - Velocity vector 

Direction of motion 

Vehicle 

orbital , 

plane ----' 

Center of Earth 

Orbiting 

vehicle body 

Figure 9.-Orbiter local vertical/local horizontal coordinate system. 

NASA-Lewis 

Research Center: 

eM 

2 

Figure 1 O.--5AMS triaxial sensor head coordinate system. 

16 

VV 

LV - Local vertical 

LH - Local horizontal 

W - Velocity vector 

Direction of motion 

Vehicle 

orbital , 

plane ----' 

Center of Earth 

Orbiting 

vehicle body 

Figure 9.-Orbiter local vertical/local horizontal coordinate system. 

NASA-Lewis 

Research Center: 

eM 

2 

Figure 1 O.--5AMS triaxial sensor head coordinate system. 

16 

VV 
-

-.) 

-

Orbiter standard attitudes 

n- ,1J# 17 

-ZLV 

-XW 

T 

-"r- -I i i" ; 

-ZLV 

-I+YW 

-ZLV 

+XW 

Preferred ______________ _ 

atitude 

-I+YLV 

+ZW 

Reduced desirability 

+XLV 

+ZW 

-XLV 

+zw 

Orbiter moving to left of page, 

Earth to bottom of page. 

X, Y, Z Orbiter body axes 

VV..-, 

LV' 

p 

, !! ! :)' . 

• t·-r ic i1 

+ZLV 

+XW 

-I+YLV 

-XW 

+XLV 

-I+YW 

-XLV 

-/+YW 

. ',C: I, . 

m 

q 

-I+YLV 

+XW 

Reduced desirability 

+XLV 

-zw 

Figure 11.-Orbiter local verticai/local horizontal attitudes. 

ll; , 

+Z LV 

-XW 

-XLV 

-ZW 

1)' j.g .. , . .,. L 

-ZLV 

-xw 

T 

T 

-ZLV 

-I+YW 

. J 

-it , , 

-ZLV 

+xw 

Orbiter standard attitudes 

'<t 

-I+YLV 

+zw 

+XLV 

+zw 

-XLV 

+zw 

+Z LV 

-XW 

Preferred _____________ _ Reduced desirability atitude 

+ZLV 

+XW 

-I+YLV 

-XW 

Orbiter moving to left of page, 

Earth to bottom of page. 

X, Y, Z Orbiter body axes 

VV..-, 

LV' 

I . 

·

.t: 

m 

+XLV 

-I+YW 

-XLV 

-/+YW 

Reduced desirability 

-I+YLV 

+XW 

+XLV 

-zw 

-XLV 

-ZW 

_____________ 

Figure 11.-Orbiter local verticai/local horizontal attitudes. 
0> 

co 

2x1Q-4 

~ Q) 0 

Q) 

u 

~ 

- 1 

L------L------L------L------L------L---- L------L----~ 

o 5 10 15 20 25 30 35 40 

Time, sec 

Figure 12.-Acceleration magnitude versus time. ST5-40, TSH-A, X-axis, SET 003/03:18:50. 

10.

4 

10.

5 

N 

10.

6 I 

NO> 

6 

en 10.

7 c.. 

i-

·iii 

c: 10.

8 Q) 

"0 

(ij 

... 

-

u 10.

9 Q) 

a. 

fI) 

... 

Q) 

:: 

0 

c.. 

10.

11 

10.

12 

0 2 3 4 5 

Frequency, Hz 

Figure 13.-Acceleration vector magnitude versus frequency. STS-40, TSH-A, X-axis, SET 003/03:18:50, 40 sec. 

18 

0> 

co 

2x1Q-4 

~ Q) 0 

Q) 

u 

~ 

- 1 

L------L------L------L------L------L---- L------L----~ 

o 5 10 15 20 25 30 35 40 

Time, sec 

Figure 12.-Acceleration magnitude versus time. ST5-40, TSH-A, X-axis, SET 003/03:18:50. 

10.

4 

10.

5 

N 

10.

6 I 

NO> 

6 

en 10.

7 c.. 

i-

·iii 

c: 10.

8 Q) 

"0 

(ij 

... 

-

u 10.

9 Q) 

a. 

fI) 

... 

Q) 

:: 

0 

c.. 

10.

11 

10.

12 

0 2 3 4 5 

Frequency, Hz 

Figure 13.-Acceleration vector magnitude versus frequency. STS-40, TSH-A, X-axis, SET 003/03:18:50, 40 sec. 

18 
c----- ----- - - --- - - ---------------- .--... - ---------------. 

120 

100 

80 

N 

I 

~ u 

c 60 (l) 

::l 

cr 

(l) 

U: 

40 

20 

600 1200 1800 

Time, sec 

2400 

10-1 

10- 2 

~ rJl 

.0 10-3 Ol 

~ c· 0 0 ~ :;:; Ol <1l .2 '-

(l) 

Qi 

u 10-4 u 

<I: 

10-5 

10-6 

3000 3600 

Figure 14.-Acceleration magnitude versus time verse frequency. STS-47, TSH-A, MET 000/23:00:00, 1 hr, fc = 50 Hz; 250 sis. 

10-5 

10-6 

10-7 

§ 

rJl 10-8 .0 Ol 

~ c· 0 0 

Oi :;:; 

<1l .2 10-9 '-

(l) 

Qi 

u 

u 

<I: 

10-10 

10-11 

10-12 

o 10 20 30 40 50 60 

Time, sec 

Figure 18.- Thruster disturbance over wide-frequency band. STS-62, TSH-B, MET 010/17:14:20, 66 sec, fc = 25 Hz; 250 sis. 

19 

c----- ----- - - --- - - ---------------- .--... - ---------------. 

120 

100 

80 

N 

I 

~ u 

c 60 (l) 

::l 

cr 

(l) 

U: 

40 

20 

600 1200 1800 

Time, sec 

2400 

10-1 

10- 2 

~ rJl 

.0 10-3 Ol 

~ c· 0 0 ~ :;:; Ol <1l .2 '-

(l) 

Qi 

u 10-4 u 

<I: 

10-5 

10-6 

3000 3600 

Figure 14.-Acceleration magnitude versus time verse frequency. STS-47, TSH-A, MET 000/23:00:00, 1 hr, fc = 50 Hz; 250 sis. 

10-5 

10-6 

10-7 

§ 

rJl 10-8 .0 Ol 

~ c· 0 0 

Oi :;:; 

<1l .2 10-9 '-

(l) 

Qi 

u 

u 

<I: 

10-10 

10-11 

10-12 

o 10 20 30 40 50 60 

Time, sec 

Figure 18.- Thruster disturbance over wide-frequency band. STS-62, TSH-B, MET 010/17:14:20, 66 sec, fc = 25 Hz; 250 sis. 

19 
1.0x10-3 

I * * -.II:lIr **-

OJ 0.5 

C 

0 

III 

.... 0.0 

Q) 

Qi 

0 0 

« -0.5 

-1.0 

0 20 40 60 80 100 120 140 

Time, sec 

1.0x10-3 

I * * -.II:lIr **. 

OJ 

0.5 

C 

0 

:;::; 

III 

.... 0.0 

Q) 

Qi 

0 

N 0 

0 « -0.5 

-1.0 

0 20 40 60 80 100 120 140 

Time, sec 

0.5 

OJ 

co 

0.0 Q) 

Qi 

0 0 

« -05

b (c) 

40 

-1.0 0 

20 60 80 100 120 140 

Time, sec 

Figure 15.-Vemier Reaction Control System thruster acceleration signature. STs-65, TSH-A, MET 006/10:08:40. (a) X-axis. (

1.0x10-3 

* * -.II:lIr **-

OJ 0.5 

C 

0 

III 

.... 0.0 

Q) 

Qi 

0 0 

« -0.5 

(a) 

-1.0 

0 20 40 60 80 100 120 140 

Time, sec 

1.0x10-3 

* * -.II:lIr **. 

OJ 

0.5 

C 

0 

:;::; 

III 

.... 0.0 

Q) 

Qi 

0 

tv 0 

0 « -0.5 

(b) 

-1.0 

0 20 40 60 80 100 120 140 

Time, sec 

0.5 

OJ 

co 

0.0 Q) 

Qi 

0 0 

« -0.5 

(c) 

-1.0 

0 20 40 60 80 100 120 140 

Time, sec 

Figure 15.-Vemier Reaction Control System thruster acceleration signature. STs-65, TSH-A, MET 006/10:08:40. (a) X-axis. (
0.10 

I * * * * * * * * * * * * * * 

Cl 0.05 

c" 

0 

Q) 0.0 

Q) 

() 

() 

<t 

-D.05 

-0.10 

0 50 100 150 200 

Time, sec 

0.10 

I * * * * * * * * * * * * * * 

Cl 0.05 

c" 

0 

Q) 0.0 

Q) 

() 

IV () 

...... <t 

-0.05 

-0.10 

0 50 100 150 200 

Time, sec 

0.10 

I * * * * * * * * * * * * * * 

Cl 0.05 

C 

0 

... 

Q) 0.0 

Q) 

() () 

<t 

-0.05 

- 0.10 

0 50 100 150 200 

Time, sec 

Figure 16.-Primary Reaction Control System thruster acceleration signature. STS-62, TSH-B, MET 010/17:12:00. (a) X-axis. 

0.10 

* * * * * * * * * * * * * * 

OJ 0.05 

C 

0 

Q) 0.0 

Qi 

() () 

« 

-0.05 

(a) 

-0.10 

0 50 100 150 200 

Time, sec 

0.1 0 

* * * * * * * * * * * * * * 

OJ 0.05 

C 

0 

Q) 0.0 

Qi 

() 

IV () 

.... « 

- 0.05 

-0.10 

(b) 

0 50 100 150 200 

Time, sec 

0.10 

* * * * * * * * * * * * * * 

OJ 0.05 

C 

0 

.... 

Q) 0.0 

Qi 

() 

() 

« 

-0.05 

- 0.10 (c) 

0 50 100 150 200 

Time, sec 

Figure 16.- Primary Reaction Control System thruster acceleration signature. STS- 62, TSH-B, MET 010/17:12:00. (a) X-axis. 

----------------

- -_. 

-------

. 

__ 

.. _._----
01

OJ 0.05 1 <------- OMS on -------> 

Co 

:;::: 

Q) 0.0 I l r Qi 0 

0 

ex: 

-0.05 r 

- 0.10 

I (a) 

0 20 40 60 80 100 

Time, sec 

0.10 

OJ 0.05 

Co 

Q) 0.0 

Qi 

0 0 N ex: N -0.05 

-0.10 

0 20 40 60 80 100 

Time, sec 

0.10 

OJ 0.05 

Co 

Q) 0.0 

Qi 

0 0 

ex: 

-0.05 

-0.10 b 

0 20 40 60 80 100 

Time, sec 

Figure 17.-0rbital Maneuvering System (OMS) thruster acceleration signature. STS-62, TSH-B, MET 009/17:09:00. (a) X-axis

---

- ---

0.10 -

Cl 0.05 - <------- OMS on -------> 

C 

0 

Q) 0.0 r Cii 0 

0 « 

- 0.05 -

(a) I I I I I 

- 0.10 

0 20 40 60 80 100 

Time, sec 

0.10 

Cl 0.05 

C 

0 

Q) 0.0 

Cii 

0 0 

tv « tv -0.05 

-0.10 (b) 

0 20 40 60 80 100 

Time, sec 

0.10 

Cl 0.05 

C 

0 

Q) 0.0 

Cii 

0 0 « 

-0.05 

-0.10 

(c) 

0 20 40 60 80 100 

Time, sec 

Figure 17.-0rbital Maneuvering System (OMS) thruster acceleration signature. STS-62, TSH-B, MET 009/17:09:00. (a) X-axis

--
10-1 

Structural mode frequencies 

10-2 2.3 Hz 

N 

J: 

c\t 10-3 Ol 

c:i 

en 

a. 

i- 10-4 4.7 Hz ·iii 

c 

Q) 

"C 1.15 Hz "iii 

.... 10-5 

"0 

Q) 

a. 

III 

.... 

Q) 10--6 :: 

0 

a. 

10-7 

10-8 

0 2 3 4 5 6 7 8 9 10 

Frequency, Hz 

Figure 19.-Crew exercise on treadmill. STS-43, TSH-A, MET 001/07:17:10, 66 sec. 

Orbiter body axes I Attitude transition I 2~--------~--------~----~~==~===-----------~ 

1 

Ol 

::l. 

Qi 

> 

~ 

c 

0 0 :;:; 

!II 

.... 

Q) 

Qi 

() 

() 

<I: 

-XLV / -ZVV -XLV / +ZVV 

191 .35 191.70 192.04 192.39 192.74 193.08 193.43 

Mission elapsed time, hr 

Figure 20.-Quasi-steady acceleration before, during, and after Orbiter maneuver. 

23 

10-1 

Structural mode frequencies 

10-2 2.3 Hz 

N 

J: 

c\t 10-3 Ol 

c:i 

en 

a. 

i- 10-4 4.7 Hz ·iii 

c 

Q) 

"C 1.15 Hz "iii 

.... 10-5 

"0 

Q) 

a. 

III 

.... 

Q) 10--6 :: 

0 

a. 

10-7 

10-8 

0 2 3 4 5 6 7 8 9 10 

Frequency, Hz 

Figure 19.-Crew exercise on treadmill. STS-43, TSH-A, MET 001/07:17:10, 66 sec. 

Orbiter body axes I Attitude transition I 2~--------~--------~----~~==~===-----------~ 

1 

Ol 

::l. 

Qi 

> 

~ 

c 

0 0 :;:; 

!II 

.... 

Q) 

Qi 

() 

() 

<I: 

-XLV / -ZVV -XLV / +ZVV 

191 .35 191.70 192.04 192.39 192.74 193.08 193.43 

Mission elapsed time, hr 

Figure 20.-Quasi-steady acceleration before, during, and after Orbiter maneuver. 

23 
10-2 

44 Hz 

17 Hz 22 Hz 

10-3 

N 

J: 

N0) 10-4 

0" Structural mode 

en frequencies 0.. 

i- 10- 5 4,8 Hz 

'iii 

c 

Q) 

'tl 

~ 10-6 -

u 

Q) 

a. 

(f) 

'-

Q) 10-7 3: 

0 

0.. 

10--8 

10-9 

0 5 10 15 20 25 30 35 40 45 50 

Frequency, Hz 

Figure 21 .-Antenna and refrigerator/freezer operating frequencies. ST8-47, TSH-A, MET 000/23:28:04, 66 sec. 

10-4 

10-5 

N 

J: 10-6 NO) 

0" 

en 10-7 0.. 

i-'iii 

c 

Q) 10--8 'tl 

iii 

'--

u 

Q) 10-9 a. 

(f) 

Gi 

3: 

0 10-10 0.. 

10-11 

10-12 

0 10 20 30 40 50 60 

Frequency, Hz 

Figure 22.-Antenna dither frequency with first and second harmonic frequencies. 

STS-£2, TSH-8, MET 008/09:53:1 6, 8 min 44 sec, fc = 25 Hz, 125 sis. 

24 

------ ---

10-2 

44 Hz 

17 Hz 22 Hz 

10-3 

N 

J: 

N0) 10-4 

0" Structural mode 

en frequencies 0.. 

i- 10- 5 4,8 Hz 

'iii 

c 

Q) 

'tl 

~ 10-6 -

u 

Q) 

a. 

(f) 

'-

Q) 10-7 3: 

0 

0.. 

10--8 

10-9 

0 5 10 15 20 25 30 35 40 45 50 

Frequency, Hz 

Figure 21 .-Antenna and refrigerator/freezer operating frequencies. ST8-47, TSH-A, MET 000/23:28:04, 66 sec. 

10-4 

10-5 

N 

J: 10-6 NO) 

0" 

en 10-7 0.. 

i-'iii 

c 

Q) 10--8 'tl 

iii 

'--

u 

Q) 10-9 a. 

(f) 

Gi 

3: 

0 10-10 0.. 

10-11 

10-12 

0 10 20 30 40 50 60 

Frequency, Hz 

Figure 22.-Antenna dither frequency with first and second harmonic frequencies. 

STS-£2, TSH-8, MET 008/09:53:1 6, 8 min 44 sec, fc = 25 Hz, 125 sis. 

24 

------ ---
1.5 

1.0 Cl 

:::l. 

C 

0 

+:: 

... 

C1I 0.5 Q) 

Qi 

0 

0 

~ 

0.0 

-0.5 (a) 

174 176 178 180 182 184 

Mission elapsed time, hr 

1.5 

1.0 Cl 

:::l. 

C 

0 

~ ... 0.5 Q) 

Qi 

0 

0 

~ 

0.0 

-O.5~------------~----------~~------------~------------~----------~~ 

174 176 178 180 182 184 

Mission elapsed time, hr 

1.5 

1.0 Cl 

:::l. 

c;-

0 

~ ... 0.5 Q) 

Qi 

0 

0 

~ 

0.0 

(c) 

-0.5 

174 176 178 180 182 184 

Mission elapsed time, hr 

Figure 23.-Acceleration magnitude variation at orbital period with near-circular orbit. (a) X-axis. (b) V-axis. (c) Z-axis. 

25 

1.5 

1.0 Cl 

:::l. 

C 

0 

+:: 

... 

C1I 0.5 Q) 

Qi 

0 

0 

~ 

0.0 

-0.5 (a) 

174 176 178 180 182 184 

Mission elapsed time, hr 

1.5 

1.0 Cl 

:::l. 

C 

0 

~ ... 0.5 Q) 

Qi 

0 

0 

~ 

0.0 

-O.5~------------~----------~~------------~------------~----------~~ 

174 176 178 180 182 184 

Mission elapsed time, hr 

1.5 

1.0 Cl 

:::l. 

c;-

0 

~ ... 0.5 Q) 

Qi 

0 

0 

~ 

0.0 

(c) 

-0.5 

174 176 178 180 182 184 

Mission elapsed time, hr 

Figure 23.-Acceleration magnitude variation at orbital period with near-circular orbit. (a) X-axis. (b) V-axis. (c) Z-axis. 

25 
5 

C> 

~ 

r;; 

0 

+:: 0 

I'Cl 

.... 

Q) 

Qi 

(,) 

(,) 

« 

-5 

(a) 

0 322 324 326 328 330 

Mission elapsed time, hr 

5 

C> 

~ 

r;; 

0 

+:: 0 ~ Q) 

Qi 

0 

0 « 

(b) 

- 5 

0 322 324 326 328 330 

Mission elapsed time, hr 

5 

C> 

~ 

r;; 

0 

+:: 0 

~ f'h' ~ Q) 

Qi 

0 

(,) 

« 

(c) 

-5 

0 322 324 326 328 330 

Mission elapsed time, hr 

Figure 24.-Acceleration magnitude variation at orbital period with elliptical orbit. (a) X-axis. (b) Y-axis. (c) Z-axis. 

26 

5 

C> 

~ 

r;; 

0 

+:: 0 

I'Cl 

.... 

Q) 

Qi 

(,) 

(,) 

« 

-5 

(a) 

0 322 324 326 328 330 

Mission elapsed time, hr 

5 

C> 

~ 

r;; 

0 

+:: 0 ~ Q) 

Qi 

0 

0 « 

(b) 

- 5 

0 322 324 326 328 330 

Mission elapsed time, hr 

5 

C> 

~ 

r;; 

0 

+:: 0 

~ f'h' ~ Q) 

Qi 

0 

(,) 

« 

(c) 

-5 

0 322 324 326 328 330 

Mission elapsed time, hr 

Figure 24.-Acceleration magnitude variation at orbital period with elliptical orbit. (a) X-axis. (b) Y-axis. (c) Z-axis. 

26 
!j 

Cl 

::l. 

C o 

Q) 

Qi 

0.2 0.0 

tl -02 ex: • 

- 0.4 ______________ ________________ -L ________________ ________________ __________

M 

Cl 

::l. 

0.2 

C 0.0 o 

Q) 

Qi 

(,) -0.2 

- 0.4 Jb) 

82 

Cl 

::l. 

-0.4 

c: -0.6 

.Q 

.... 

Q) 

Qi 

(,) -0.8 

(cl 

Mission elapsed time, hr 

83 84 85 86 

Mission elapsed time, hr 

-1.0 L! ____________________ -L ____________________ -L ____________________ ____________________ ___________

82 83 84 85 86 

Mission elapsed time, hr 

Figure 25.-Acceleration magnitude at DARE location. (a) X-axis. (b) Y-axis. (el Z-axis. 

Cl 

::l. 

C o 

Q) 

Qi 

0.2 

0.0 

u - 0.2 

- 0.4 ______________ -L ________________ L-______________ -L ________________ L-_______

M 

Cl 

::l. 

0.2 

C 0.0 o 

Q) 

Qi 

8 -0.2 

« 

(b) 

- 0.4 

Cl 

::l. 

-0.4 

c: - 0.6 

o 

:;:: 

Q) 

Qi 

g - 0.8 « 

82 

(c) 

Mission elapsed time, hr 

83 84 85 86 

Mission elapsed time, hr 

-1 .0 L-________________ J-________________ ________________ ________________ _________

82 83 84 85 86 

Mission elapsed time, hr 

Figure 25.- Acceleration magnitude at DARE location. (a) X-axis. (b) Y-axis. (el Z-axis. 
N 

00 

CJ) 

:::l. 

C" 

o 

Q) 

Cii 

u 

0.6 

0.4 

0.2 

0.0 ________________ ________________ -L ________________ __________________ ______

CJ) 

:::l. 

0.2 

C 0.0 

.2 

Q) 

Cii 

u -0.2 

M M 

Mission elapsed time, hr 

-0.4 ! L ____________________ L-__________________ -L ____________________ L-__________________ ________

CJ) 

:::l. 

C 

o 

Q) 

Cii 

u 

82 83 84 85 86 

Mission elapsed time, hr 

0.8 

0.6 

0.4 

0.2 (c) ,L-__________________ -L ____________________ L-__________________ -L ____________________ L-_______

M M 

Mission elapsed time, hr 

Figure 26.-Acceleration magnitude at IDGE location. (a) X-axis. (b) Y-axis. (c) Z-axis. 

N 

00 

Cl 

:::l. 

C o 

Q) 

Qi 

() 

() « 

0.6 

0.4 

0.2 

0.0 ______________ -L ________________ L-______________ -L ________________ L-_____

Cl 

:::l. 

0.2 

C 0.0 o 

Q) 

Qi 

g -0.2 « 

M M 

Mission elapsed time, hr 

(b) -0.4 L_ ________________ ________________ _L ________________ ________________ ______

Cl 

:::l. 

0.8 

C 0.6 

o 

Q) 

Qi 

g 0.4 « 

82 

(c) 

83 84 85 86 

Mission elapsed time, hr 

0.2 L-______________ ________________ ________________ _L ________________ _L ______

82 83 84 85 86 

Mission elapsed time, hr 

Figure 26.-Acceleration magnitude at IDGE location. (a) X-axis. (b) V-axis. (c) Z-axis. 
OJ 

c:" 

0 

~ L. 

Q) 

Qi 

() 

() 

~ 

10-1 

10-2 

1Q-3 

10--4 

10-5 

Satellite 

deploy 

OMS burns 

for separation 

1~ L-____ -L ______ i-____ ~ ______ _L ______ l_ ____ ~ ______ ~ 

o 200 400 600 800 1000 1200 1400 

Time, sec 

Figure 27.-LAGEOS satellite launch. STS-52, TSH-B, vector magnitude, MET 000/20:36:00. 

29 

OJ 

c:" 

0 

~ L. 

Q) 

Qi 

() 

() 

~ 

10-1 

10-2 

1Q-3 

10--4 

10-5 

Satellite 

deploy 

OMS burns 

for separation 

1~ L-____ -L ______ i-____ ~ ______ _L ______ l_ ____ ~ ______ ~ 

o 200 400 600 800 1000 1200 1400 

Time, sec 

Figure 27.-LAGEOS satellite launch. STS-52, TSH-B, vector magnitude, MET 000/20:36:00. 

29 
APPENDIX A-ACRONYMS 

3DMA Three-Dimensional Microgravity Accelerometer 

CD-ROM compact clisk read only memory 

CG center of gravity 

CM center of mass 

DLR Deutsche Forschungsanstalt fur Luft und Raumfahrt 

FES Fluid Experiment System 

FFT fast Fourier transform 

HiRAP High Resolution Accelerometer Package 

HISA Honeywell In-Space Accelerometer 

IML International Microgravity Laboratory mission series 

JSC Johnson Space Center 

LeRC Lewis Research Center 

LH local horizontal 

LV local vertical 

MMA Microgravity Measurement Assembly 

MMAP Microgravity Measurement and Analysis Project 

MMD Microgravity Measuring Device 

MPESS Mission Peculiar Equipment Support Structure 

MSAD Microgravity Science and Applications Division 

MSFC Marshall Space Flight Center 

NRT near-real-time 

OARE Orbital Acceleration Research Experiment 

OMS Orbital Maneuvering System 

PAS Passive Accelerometer System 

PI Principal Investigator 

PIMS Principal Investigator Microgravity Services 

30 

APPENDIX A-ACRONYMS 

3DMA Three-Dimensional Microgravity Accelerometer 

CD-ROM compact clisk read only memory 

CG center of gravity 

CM center of mass 

DLR Deutsche Forschungsanstalt fur Luft und Raumfahrt 

FES Fluid Experiment System 

FFT fast Fourier transform 

HiRAP High Resolution Accelerometer Package 

HISA Honeywell In-Space Accelerometer 

IML International Microgravity Laboratory mission series 

JSC Johnson Space Center 

LeRC Lewis Research Center 

LH local horizontal 

LV local vertical 

MMA Microgravity Measurement Assembly 

MMAP Microgravity Measurement and Analysis Project 

MMD Microgravity Measuring Device 

MPESS Mission Peculiar Equipment Support Structure 

MSAD Microgravity Science and Applications Division 

MSFC Marshall Space Flight Center 

NRT near-real-time 

OARE Orbital Acceleration Research Experiment 

OMS Orbital Maneuvering System 

PAS Passive Accelerometer System 

PI Principal Investigator 

PIMS Principal Investigator Microgravity Services 

30 
POCC 

PRCS 

PSD 

QSAM 

RCS 

RMS 

rms 

SAMS 

SL-D-2 

SL-J 

SLS 

STS 

TSH 

UAH 

USML 

USMP 

VRCS 

VV 

WSF 

Payload Operations Control Center 

Primary Reaction Control System 

power spectral density 

Quasi-Steady Acceleration Measurement 

Reaction Control System 

Remote Manipulator System 

root mean square 

Space Acceleration Measurement System 

Second German Spacelab mission 

Spacelab J mission 

Spacelab Life Sciences mission series 

Space Transportation System 

triaxial sensor head 

University of Alabama in Huntsville 

United States Microgravity Laboratory mission series 

United States Microgravity Payload mission series 

Vernier Reaction Control System 

velocity vector 

Wake Shield Facility 

31 

POCC 

PRCS 

PSD 

QSAM 

RCS 

RMS 

rms 

SAMS 

SL-D-2 

SL-J 

SLS 

STS 

TSH 

UAH 

USML 

USMP 

VRCS 

VV 

WSF 

Payload Operations Control Center 

Primary Reaction Control System 

power spectral density 

Quasi-Steady Acceleration Measurement 

Reaction Control System 

Remote Manipulator System 

root mean square 

Space Acceleration Measurement System 

Second German Spacelab mission 

Spacelab J mission 

Spacelab Life Sciences mission series 

Space Transportation System 

triaxial sensor head 

University of Alabama in Huntsville 

United States Microgravity Laboratory mission series 

United States Microgravity Payload mission series 

Vernier Reaction Control System 

velocity vector 

Wake Shield Facility 

31 
APPENDIX B-DEFINITIONS 

The meaning of the following terms is necessary for an understanding of this document: 

mg or milli-g 

flg or micro-g 

an acceleration equal to the normal Earth's gravitational acceleration at sea level 

(nominally 9.8 m/sec2). 

an acceleration equal to one thousandth of the normal Earth's gravitational acceleration at sea level (goX Io-3) 

an acceleration equal to one millionth of the normal Earth's gravitational acceleration at sea level (goXlO--6) 

specific impulse 

components of the Orbiter body coordinate system 

XLVLH' Y LVLH' ~VLH components of the local verticalJlocal horizontal coordinate system 

components of the Orbiter structural coordinate system 

density of a ball 

Pfluid fluid density 

Pmass density of a mass 

32 

APPENDIX B-DEFINITIONS 

The meaning of the following terms is necessary for an understanding of this document: 

mg or milli-g 

flg or micro-g 

an acceleration equal to the normal Earth's gravitational acceleration at sea level 

(nominally 9.8 m/sec2). 

an acceleration equal to one thousandth of the normal Earth's gravitational acceleration at sea level (goX Io-3) 

an acceleration equal to one millionth of the normal Earth's gravitational acceleration at sea level (goXlO--6) 

specific impulse 

components of the Orbiter body coordinate system 

XLVLH' Y LVLH' ~VLH components of the local verticalJlocal horizontal coordinate system 

components of the Orbiter structural coordinate system 

density of a ball 

Pfluid fluid density 

Pmass density of a mass 

32 
APPENDIX C-ACCESSING SAMS DATA FILES VIA INTERNET 

SAMS data are ctistributed on CD-ROM mectia and are available on a computer file server. In both cases, files of 

SAMS data are organized in a treelike structure as illustrated in figure Cl. Data acquired from a mission are categorized by sensor head, mission day, and type of data. Data files are stored at the highest level in the tree, and the file 

name reflects the contents of the file. For example, the file named axmOOl 02 . 15r contains data for sensor head 

A, the X-axis, the time base was Mission Elapsed Time, day 001, hour 02, 1 of 5 files for that hour, and it contains 

reduced data. The file readme.doc provides a comprehensive description and guide to the data. 

Also available from the file server are some data access tools for ctifferent computer platforms. 

SAMS data files may be accessed from a file server at NASA LeRC. The NASA LeRC file server 

beeeh . 1 ere . nasa . gOY can be accessed via anonymous file transfer protocol (ftp), as follows: 

(1) Establish ftp connection to the beech file server. 

(2) Login: anonymous 

(3) Password: gues t 

(4) Change the ctirectory to: pub 

(5) List the files and directories in the pub directory. 

(6) Change the directory to the mission of interest, for example: usml-l 

(7) List files and directories for the specific mission chosen in previous step. 

(8) Use the data file structure shown in the figure to find the files of interest. 

(9) Transfer the data files of interest. 

If you encounter ctifficulty in accessing the data using the file server, please send an electronic mail message to 

the following Internet address: pims@lere. nasa. gOY. Please describe the nature of the ctifficulty and a description of the hardware and software you are using to access the file server. 

Figure C1 .-SAMS data file structure. 

33 

APPENDIX C-ACCESSING SAMS DATA FILES VIA INTERNET 

SAMS data are ctistributed on CD-ROM mectia and are available on a computer file server. In both cases, files of 

SAMS data are organized in a treelike structure as illustrated in figure Cl. Data acquired from a mission are categorized by sensor head, mission day, and type of data. Data files are stored at the highest level in the tree, and the file 

name reflects the contents of the file. For example, the file named axmOOl 02 . 15r contains data for sensor head 

A, the X-axis, the time base was Mission Elapsed Time, day 001, hour 02, 1 of 5 files for that hour, and it contains 

reduced data. The file readme.doc provides a comprehensive description and guide to the data. 

Also available from the file server are some data access tools for ctifferent computer platforms. 

SAMS data files may be accessed from a file server at NASA LeRC. The NASA LeRC file server 

beeeh . 1 ere . nasa . gOY can be accessed via anonymous file transfer protocol (ftp), as follows: 

(1) Establish ftp connection to the beech file server. 

(2) Login: anonymous 

(3) Password: gues t 

(4) Change the ctirectory to: pub 

(5) List the files and directories in the pub directory. 

(6) Change the directory to the mission of interest, for example: usml-l 

(7) List files and directories for the specific mission chosen in previous step. 

(8) Use the data file structure shown in the figure to find the files of interest. 

(9) Transfer the data files of interest. 

If you encounter ctifficulty in accessing the data using the file server, please send an electronic mail message to 

the following Internet address: pims@lere. nasa. gOY. Please describe the nature of the ctifficulty and a description of the hardware and software you are using to access the file server. 

Figure C1 .-SAMS data file structure. 

33 
APPENDIX D-RCS AND OMS ENGINES DESCRIPTION I 

Reaction Control System (RCS) 

The reaction control system (RCS) consists of 44 individual thrusters located in three separate modules in the 

Orbiter (forward, aft-left, and aft-right). There are 38 primary jets and 6 vernier jets. Each primary jet is rated at 

870 lb of thrust, and each vernier jet is rated at 24 lb of thrust. The primary jets are u ed to control the motion of 

the space shuttle vehicle through a combination of translation andlor rotational movement. The vernier jets are used 

on orbit for fine attitude control. The locations of the RCS thrusters in relationship to the Orbiter are shown in figure Dl, and details of the jet locations and plume directions are shown in figure D2. While most thrusters are 

aligned with the Orbiter body axes, it should be noted that many of the thrusters in the forward module are off-axis. 

This is further illustrated in figure D3. The 6 vernier thrusters are shown in figure D2 as FSR, FSL, LSL, LSD, RSR, 

and RSD. 

Orbital Maneuvering System (OMS) 

The OMS engines provide propulsion for the space shuttle vehicle during the orbit phase of flight. They are used 

for orbital insertion maneuvers after the main propulsion ystem has shut down. They are also the primary propulsion system for orbital transfer maneuvers and the de-orbit maneuver. 

There are two OMS engines per Orbiter. Each OMS engine produces 6000 lb of thrust. The locations of the OMS 

engines in relationship to the Orbiter are shown in figure Dl. The OMS engines are canted IS.8° upward and 6.So 

outboard with respect to the Orbiter body axes. The OMS engines can be pivoted up and down (±6°) and from side 

to side (±7°) from their null position. 

'Reprinted from Appendix B of NASA TP- 3141 (ref. 4). 

34 

-------- -- -

APPENDIX D-RCS AND OMS ENGINES DESCRIPTION I 

Reaction Control System (RCS) 

The reaction control system (RCS) consists of 44 individual thrusters located in three separate modules in the 

Orbiter (forward, aft-left, and aft-right). There are 38 primary jets and 6 vernier jets. Each primary jet is rated at 

870 lb of thrust, and each vernier jet is rated at 24 lb of thrust. The primary jets are u ed to control the motion of 

the space shuttle vehicle through a combination of translation andlor rotational movement. The vernier jets are used 

on orbit for fine attitude control. The locations of the RCS thrusters in relationship to the Orbiter are shown in figure Dl, and details of the jet locations and plume directions are shown in figure D2. While most thrusters are 

aligned with the Orbiter body axes, it should be noted that many of the thrusters in the forward module are off-axis. 

This is further illustrated in figure D3. The 6 vernier thrusters are shown in figure D2 as FSR, FSL, LSL, LSD, RSR, 

and RSD. 

Orbital Maneuvering System (OMS) 

The OMS engines provide propulsion for the space shuttle vehicle during the orbit phase of flight. They are used 

for orbital insertion maneuvers after the main propulsion ystem has shut down. They are also the primary propulsion system for orbital transfer maneuvers and the de-orbit maneuver. 

There are two OMS engines per Orbiter. Each OMS engine produces 6000 lb of thrust. The locations of the OMS 

engines in relationship to the Orbiter are shown in figure Dl. The OMS engines are canted IS.8° upward and 6.So 

outboard with respect to the Orbiter body axes. The OMS engines can be pivoted up and down (±6°) and from side 

to side (±7°) from their null position. 

'Reprinted from Appendix B of NASA TP- 3141 (ref. 4). 

34 

-------- -- -
w 

1Il 

panel 

Electrical disconnect bracket 

Access 

cover 

RCS only 

1 Forward RSC module, 2 aft RCS su

38 Main thrusters (14 forward, 12 pe

Thrust level = 870 Ib (vacuum) 

6 Vemier thrusters (2 forward and 4 

Thrust level = 24 Ib each; Isp = 

Propellants: Oxidizer 

RCS prope

manifold va

OMS 

OMS propellant ta

RCS pressurization components 

OMS/RCS arcs pod 

Figure D1.-Reaction Control System (RCS) thruster locations. 

panel 

Vernier 

thrusters (2) 

Electrical disconnect bracket 

Access 

cover 

RCS only 

1 Forward RSC module, 2 aft RCS su

38 Main thrusters (14 forward, 12 pe

Thrust level = 870 Ib (vacuum) 

6 Vemier thrusters (2 forward and 4 

Thrust level = 24 Ib each; Isp = 

Propellants: Oxidizer 

N<P4 

RCS prope

manifold va

OMS 

RCS pressurization components 

OMS/RCS arcs pod 

Figure D1.-Reaction Control System (RCS) thruster locations. 
 

__ 

w 

C'I 

+Pitch 

-Pitch 

 ________ . _____ _ 

+Pitch 

-z 

-Yaw 

R4R 

R4U 

+IS 

RlU +X R2U 

R3A RtA 

Figure D2.-Reaction Control System (RCS) jet locations and plume axes. 

LlU 

L2U 

L2D 

L4D 

t Direc

vehic

t Direc

thrus

 

L 

- ------ -- -- 

+Pitch 

- Pitch 

+Pitch 

-z 

-Yaw 

+ZB 

RlU +X R2U 

R4U R3A RIA 

Figure D2.-Reaction Control System (RCS) jet locations and plume axes. 

---- - - -

----

- ._._.- --- -

- -- -- ------

L1U 

L2U 

L4D 

t Direc

vehic

t Direc

thrus
.v. 

@ 

o 

-as 

I:: 

~ 

~ 

'C 'n; 

Q) 

:g. 

(/) 

(1) 

~ (1) w E 

::J 

0. 

'C 

I:: 

111 

(/) 

I:: 

0 

:;::; ..J ..J 

~ 

111 

:.. () 

.Q -,~ 

fii 

() 

QU :I:====::;:~ t:. ';;:;:== =~otJ QU au 

ff. 

E 

(1) -(/) 

?i 

'0 

.... -I:: 

0 

() 

I:: 

0 

:;::; 

() 

ntJ 111 

(1) 

a: 

I 

M 

0 

nu 

(1) 

.... 

::J 

Ol 

~ 

37 

.v. 

@ 

o 

-as 

I:: 

~ 

~ 

'C 'n; 

Q) 

:g. 

(/) 

(1) 

~ (1) w E 

::J 

0. 

'C 

I:: 

111 

(/) 

I:: 

0 

:;::; ..J ..J 

~ 

111 

:.. () 

.Q -,~ 

fii 

() 

QU :I:====::;:~ t:. ';;:;:== =~otJ QU au 

ff. 

E 

(1) -(/) 

?i 

'0 

.... -I:: 

0 

() 

I:: 

0 

:;::; 

() 

ntJ 111 

(1) 

a: 

I 

M 

0 

nu 

(1) 

.... 

::J 

Ol 

~ 

37 
REFERENCES 

1. Vogt, G.L.; Wargo, MJ.: Microgravity: A Teacher's Guide with Activities, Secondary Level. NASA EP-280, 

July 1992. (Available WWWMicrogravity Home Page at http://microgravity.msad.hq.nasa.gov). 

2. Hamacher, H.: Spacecraft Low-Frequency Residual Acceleration. Spac. Rock. vol. 32, no. 2, pp. 324-327, 

1995. 

3. Rogers, M.J.B.; and Alexander, J.I.D.: Analysis of Spacelab 3 Residual Acceleration Data. J. Spac. Rock., 

vol. 28,1991, pp. 707-712. 

4. Dunbar, B.J.; Giesecke, R.L.; and Thomas, D.A.: The Microgravity Environment of the Space Shuttle Columbia Payload Bay During STS-32. ASA TP-3141,1991. 

5. Dunbar, B.J.; Thomas, D.A.; and Schoess, J.N.: The Microgravity Environment ofthe Space Shuttle Columbia 

Middeck During STS-32. NASA TP-341O, 1991. 

6. Matisak, B.P. ; Rogers, MJ.B.; and Alexander, J.I.D.: Analysis of the Passive Accelerometer System (PAS) 

Measurements During USML-1. AIAA Paper 94-0434, 1994. 

7. DeLombard, R.; Finley, B.D.; and Baugher, c.R.: Development of and Flight Results From the Space Acceleration Measurement System (SAMS). NASA TM-105652 (AIAA Paper 92-0354),1992. 

8. DeLombard, R.; and Finley, B.D.: Space Acceleration Measurement System Description and Operations on the 

First Spacelab Life Sciences Mission. NASA TM-I05301, 1991. 

9. Rogers, M.J.B., et a1 .: Low Gravity Environment On-Board Columbia During STS-40. AIAA Paper 93-0833, 

1993. 

10. NASA Johnson Space Center: Shuttle Orbiter/Cargo Standard Interfaces Document. ICD 2-19001, 

fig. 3.1.1.4-1, 1991. 

11. NASA Johnson Space Center: Shuttle Orbiter/Cargo Standard Interfaces Document. ICD 2-19001 , 

fig. 3.1.1.1-1, 1991. 

12. NASA Johnson Space Center: Attitude and Pointing Handbook. JSC-105U , rev. B, 1988. 

13. Blanchard, R.c.; Nicholson, J.Y.; and Ritter, J.R.: Preliminary DARE Absolute Acceleration Measurements on 

STS-50. NASA TM-107724, 1993. 

38 

REFERENCES 

1. Vogt, G.L.; Wargo, MJ.: Microgravity: A Teacher's Guide with Activities, Secondary Level. NASA EP-280, 

July 1992. (Available WWWMicrogravity Home Page at http://microgravity.msad.hq.nasa.gov). 

2. Hamacher, H.: Spacecraft Low-Frequency Residual Acceleration. Spac. Rock. vol. 32, no. 2, pp. 324-327, 

1995. 

3. Rogers, M.J.B.; and Alexander, J.I.D.: Analysis of Spacelab 3 Residual Acceleration Data. J. Spac. Rock., 

vol. 28,1991, pp. 707-712. 

4. Dunbar, B.J.; Giesecke, R.L.; and Thomas, D.A.: The Microgravity Environment of the Space Shuttle Columbia Payload Bay During STS-32. ASA TP-3141,1991. 

5. Dunbar, B.J.; Thomas, D.A.; and Schoess, J.N.: The Microgravity Environment ofthe Space Shuttle Columbia 

Middeck During STS-32. NASA TP-341O, 1991. 

6. Matisak, B.P. ; Rogers, MJ.B.; and Alexander, J.I.D.: Analysis of the Passive Accelerometer System (PAS) 

Measurements During USML-1. AIAA Paper 94-0434, 1994. 

7. DeLombard, R.; Finley, B.D.; and Baugher, c.R.: Development of and Flight Results From the Space Acceleration Measurement System (SAMS). NASA TM-105652 (AIAA Paper 92-0354),1992. 

8. DeLombard, R.; and Finley, B.D.: Space Acceleration Measurement System Description and Operations on the 

First Spacelab Life Sciences Mission. NASA TM-I05301, 1991. 

9. Rogers, M.J.B., et a1 .: Low Gravity Environment On-Board Columbia During STS-40. AIAA Paper 93-0833, 

1993. 

10. NASA Johnson Space Center: Shuttle Orbiter/Cargo Standard Interfaces Document. ICD 2-19001, 

fig. 3.1.1.4-1, 1991. 

11. NASA Johnson Space Center: Shuttle Orbiter/Cargo Standard Interfaces Document. ICD 2-19001 , 

fig. 3.1.1.1-1, 1991. 

12. NASA Johnson Space Center: Attitude and Pointing Handbook. JSC-105U , rev. B, 1988. 

13. Blanchard, R.c.; Nicholson, J.Y.; and Ritter, J.R.: Preliminary DARE Absolute Acceleration Measurements on 

STS-50. NASA TM-107724, 1993. 

38 
BIBLIOGRAPHY 

Microgravity Environment 

1. Rogers, M.J.B.; Matisak, B.P.; and Alexandar, J.I.D.: Venting Force Contributions- Quasi-Steady Acceleration on STS-50. Microgravity Science and Technology, vol. VII, no. 4, Feb. 1994, pp. 293- 298. 

2. Dunbar, BJ.; Thomas, D.A.; and Schoess, J.N.: The Microgravity Environment of the Space Shuttle Columbia 

Middeck During STS- 32. NASA TP-3140, 1991. 

3. Baugher, C.R.; Martin, G.L. ; and DeLombard, R.: Review of the Shuttle Vibration Environment. AIAA 

Paper 93-0832, 1993. 

4. Baugher, c.R.; Martin, G.L.; and DeLombard, R.: Low-Frequency Vibration Environment for Five Shuttle 

Missions. NASA TM- 106059, 1993. 

5. Rogers, M.J.B., et. al.: Low Gravity Environment On-Board Columbia During STS-40. AIAA Paper 93-0833, 

1993. 

6. Rogers, M.J.B., et. al.: A Comparison of Low-Gravity Measurements On-Board Columbia During STS-40. 

Microgravity Science and Technology, vol. VI, no. 3, Sept. 1993, pp. 207- 216. 

7. Blanchard, R.C.; Hinson, E.W.; and Nicholson, J.Y.: Shuttle High Resolution Accelerometer Package Experiment Results: Atmospheric Density Measurements Between 60 and 160 km. J. Spac. Rock., vol. 26, 1989, 

pp. 173-180. 

8. Dunbar, B.J.; Giesecke, R.L.; and Thomas, D.A.: The Microgravity Environment of the Space Shuttle Columbia Payload Bay During STS-32. NASA TP-3141 , 1991. 

Mission Microgravity Environment Summary 

1. Baugher, c.R.; and Henderson, FH.: Early Summary Report of Mission Acceleration Measurements From 

STS-40. ACAP Project Report, Sept. 9, 1991. 

2. Baugher, c.R. ; and Henderson, F.H.: Early Summary Report of Mission Acceleration Measurements From 

STS-43. ACAP Project Report, March 2,1992. 

3. Baugher, C.R.; and Henderson, FH.: Early Summary Report of Mission Acceleration Measurements From 

STS-42. ACAP Project Report, Aug. 7, 1992. 

4. Baugher, C.R.; and Henderson, FH.: Summary Report of Mission Acceleration Measurements From STS-47. 

ACAP Project Report, March 31, 1993. 

5. Baugher, C.R.; and Henderson, FH.: Summary Report of Mission Acceleration Measurements From STS- 50. 

ACAP Project Report, Nov. 9, 1992. 

6. Baugher, C.R.; and Henderson, FH.: STS-52 Mission Acceleration Measurements Summary-Sensor Report. 

ACAP Project Report, Sept. 7, 1993. 

7. Finley, B.D., Grodsinksy, c.; and DeLombard, R.: Summary Report of Mission Acceleration Measurements for 

Spacehab-Ol, STS- 57. NASA TM-106514, 1994. 

8. Rogers, MJ.B.; and DeLombard, R.: Summary Report of Mission Acceleration Measurements for STS-62. 

NASA TM-I06773, 1994. 

9. Rogers, MJ.B.; and DeLombard, R.: Summary Report of Mission Acceleration Measurements for STS-60, 

SPACEHAB-2. NASA TM-106797, 1994. 

10. Rogers, M.J.B.; and DeLombard, R.: Summary Report of Mission Acceleration Measurements for STS-65. 

NASA TM-106871 , 1995. 

11. DeLombard, R.; and Rogers, M.J.B.: Quick Look Report of Acceleration Measurements on Mir Space Station 

During Mir-16. NASA TM-I06835, 1995. 

12. Rogers, MJ.B.; and DeLombard, R.: Summary Report of Mission Acceleration Measurements for STS-66. 

NASA TM-106914, 1995. 

39 

BIBLIOGRAPHY 

Microgravity Environment 

1. Rogers, M.J.B.; Matisak, B.P.; and Alexandar, J.I.D.: Venting Force Contributions- Quasi-Steady Acceleration on STS-50. Microgravity Science and Technology, vol. VII, no. 4, Feb. 1994, pp. 293- 298. 

2. Dunbar, BJ.; Thomas, D.A.; and Schoess, J.N.: The Microgravity Environment of the Space Shuttle Columbia 

Middeck During STS- 32. NASA TP-3140, 1991. 

3. Baugher, C.R.; Martin, G.L. ; and DeLombard, R.: Review of the Shuttle Vibration Environment. AIAA 

Paper 93-0832, 1993. 

4. Baugher, c.R.; Martin, G.L.; and DeLombard, R.: Low-Frequency Vibration Environment for Five Shuttle 

Missions. NASA TM- 106059, 1993. 

5. Rogers, M.J.B., et. al.: Low Gravity Environment On-Board Columbia During STS-40. AIAA Paper 93-0833, 

1993. 

6. Rogers, M.J.B., et. al.: A Comparison of Low-Gravity Measurements On-Board Columbia During STS-40. 

Microgravity Science and Technology, vol. VI, no. 3, Sept. 1993, pp. 207- 216. 

7. Blanchard, R.C.; Hinson, E.W.; and Nicholson, J.Y.: Shuttle High Resolution Accelerometer Package Experiment Results: Atmospheric Density Measurements Between 60 and 160 km. J. Spac. Rock., vol. 26, 1989, 

pp. 173-180. 

8. Dunbar, B.J.; Giesecke, R.L.; and Thomas, D.A.: The Microgravity Environment of the Space Shuttle Columbia Payload Bay During STS-32. NASA TP-3141 , 1991. 

Mission Microgravity Environment Summary 

1. Baugher, c.R.; and Henderson, FH.: Early Summary Report of Mission Acceleration Measurements From 

STS-40. ACAP Project Report, Sept. 9, 1991. 

2. Baugher, c.R. ; and Henderson, F.H.: Early Summary Report of Mission Acceleration Measurements From 

STS-43. ACAP Project Report, March 2,1992. 

3. Baugher, C.R.; and Henderson, FH.: Early Summary Report of Mission Acceleration Measurements From 

STS-42. ACAP Project Report, Aug. 7, 1992. 

4. Baugher, C.R.; and Henderson, FH.: Summary Report of Mission Acceleration Measurements From STS-47. 

ACAP Project Report, March 31, 1993. 

5. Baugher, C.R.; and Henderson, FH.: Summary Report of Mission Acceleration Measurements From STS- 50. 

ACAP Project Report, Nov. 9, 1992. 

6. Baugher, C.R.; and Henderson, FH.: STS-52 Mission Acceleration Measurements Summary-Sensor Report. 

ACAP Project Report, Sept. 7, 1993. 

7. Finley, B.D., Grodsinksy, c.; and DeLombard, R.: Summary Report of Mission Acceleration Measurements for 

Spacehab-Ol, STS- 57. NASA TM-106514, 1994. 

8. Rogers, MJ.B.; and DeLombard, R.: Summary Report of Mission Acceleration Measurements for STS-62. 

NASA TM-I06773, 1994. 

9. Rogers, MJ.B.; and DeLombard, R.: Summary Report of Mission Acceleration Measurements for STS-60, 

SPACEHAB-2. NASA TM-106797, 1994. 

10. Rogers, M.J.B.; and DeLombard, R.: Summary Report of Mission Acceleration Measurements for STS-65. 

NASA TM-106871 , 1995. 

11. DeLombard, R.; and Rogers, M.J.B.: Quick Look Report of Acceleration Measurements on Mir Space Station 

During Mir-16. NASA TM-I06835, 1995. 

12. Rogers, MJ.B.; and DeLombard, R.: Summary Report of Mission Acceleration Measurements for STS-66. 

NASA TM-106914, 1995. 

39 
Instrumentation 

1. Rogers, MJ.B.; Alexander, lI.D.; and Snyder, R.: Analysis Techniques for Residual Acceleration Data NASA 

TM-I03507,1990. 

2. Arrott, A.: Making Acceleration Data More Accessible and Useful to Microgravity Investigators. Presented at 

the 1988 TMS-AIME Annual Meeting (Phoenix, AZ), Jan. 1988. 

3. Shyr, c.K.: COPS Transformation Algorithms for Ephemeris and Attitude Parameters. NASA GSFC 560-

731.1, rev. 2,1992. 

4. Martin, G.L.; Baugher, c.R.; and DeLombard, R. : Vibration Environment: Acceleration Mapping Strategy and 

Microgravity Requirements for Spacelab and Space Station. lAP Paper 90-350, 1990. 

5. DeLombard, R.: Proposed Ground-Based Control of Accelerometer on Space Station Freedom. NASA 

TM-I05960, 1993. 

6. DeLombard, R.; Finley, B. D. ; and Baugher, C. R.: Development Of and Flight Results From the Space Acceleration Measurement System (SAMS). AlAA Paper 92- 0354 (NASA TM-105652), 1992. 

7. DeLombard, R.; and Finley, B. D.: Space Acceleration Measurement System Description and Operations on the 

First Spacelab Life Sciences Mission. NASA TM-I05301, 1991. 

8. DeLombard, R.: Early Mission Science Support: Space Acceleration Measurement System (SAMS). International Workshop on Vibration Isolation Technology for Microgravity Science Applications, NASA 

CP-10094, 1992. 

9. Blanchard, R.c., et al.: Orbital Acceleration Research Experiment. J. Spac. Rock., vol. 24,1986, pp. 504-511. 

10. Cooke, M.P.: STS-60 Wake Shield Facility Payload Microgravity Measuring Device Quick-Look Report. 

JSC-26620,1994. 

11. Rogers, M.J.B.; Alexander, J.I.D.; and Schoess, J.: Detailed Analysis of Honeywell In-Space Accelerometer 

Data - STS-32-Crystal Microstructure Response to Different Types of Residual Acceleration. Microgravity 

Science and Technology, vol. VI, 1993, pp. 28-33. 

Science Impacts 

1. Alexander, ll.D: Low-Gravity Experiment Sensitivity to Residual Acceleration: A Review. Microgravity Science and Technology, vol. 3, Sept. 1990, pp. 52-68. 

2. de Groh ill, H.C.; and Nelson, E.S.: On Residual Acceleration During Space Experiments. Heat Transfer in 

Microgravity Systems, S.S. Sadhal; and A. Gopinath, ed., HTD-Vol. 290, ASME, New York, 1994, 

pp.23-33. 

3. Favier, J.J., et al.: Mass Transport Phenomena During Solidification in Microgravity: Preliminary Results of the 

First MEPHISTO Flight Experiment. J Cryst. Growth, vol. 140, no. 1-2, June 1994, pp. 237-243. 

4. Ramachandran, N.; and Winter, c.A.: Effects of g-jitter and Marangoni Convection on Float Zones. J Spac. 

Rock., vol. 29, no. 4, July-Aug. 1992, pp. 514-522. 

5. Arnold, W.A., et al. : Three-Dimensional Flow Transport Modes in Directional Solidification During Space 

Processing. l Spac. Rock., vol. 28, Mar-Apr. 1991, pp. 238-243. 

6. Nelson, E.S.: An Examination of Anticipated g-jitter on Space Station and Its Effects on Materials Processes. 

NASA TM-I03775, 1994. 

40 

Instrumentation 

1. Rogers, MJ.B.; Alexander, lI.D.; and Snyder, R.: Analysis Techniques for Residual Acceleration Data NASA 

TM-I03507,1990. 

2. Arrott, A.: Making Acceleration Data More Accessible and Useful to Microgravity Investigators. Presented at 

the 1988 TMS-AIME Annual Meeting (Phoenix, AZ), Jan. 1988. 

3. Shyr, c.K.: COPS Transformation Algorithms for Ephemeris and Attitude Parameters. NASA GSFC 560-

731.1, rev. 2,1992. 

4. Martin, G.L.; Baugher, c.R.; and DeLombard, R. : Vibration Environment: Acceleration Mapping Strategy and 

Microgravity Requirements for Spacelab and Space Station. lAP Paper 90-350, 1990. 

5. DeLombard, R.: Proposed Ground-Based Control of Accelerometer on Space Station Freedom. NASA 

TM-I05960, 1993. 

6. DeLombard, R.; Finley, B. D. ; and Baugher, C. R.: Development Of and Flight Results From the Space Acceleration Measurement System (SAMS). AlAA Paper 92- 0354 (NASA TM-105652), 1992. 

7. DeLombard, R.; and Finley, B. D.: Space Acceleration Measurement System Description and Operations on the 

First Spacelab Life Sciences Mission. NASA TM-I05301, 1991. 

8. DeLombard, R.: Early Mission Science Support: Space Acceleration Measurement System (SAMS). International Workshop on Vibration Isolation Technology for Microgravity Science Applications, NASA 

CP-10094, 1992. 

9. Blanchard, R.c., et al.: Orbital Acceleration Research Experiment. J. Spac. Rock., vol. 24,1986, pp. 504-511. 

10. Cooke, M.P.: STS-60 Wake Shield Facility Payload Microgravity Measuring Device Quick-Look Report. 

JSC-26620,1994. 

11. Rogers, M.J.B.; Alexander, J.I.D.; and Schoess, J.: Detailed Analysis of Honeywell In-Space Accelerometer 

Data - STS-32-Crystal Microstructure Response to Different Types of Residual Acceleration. Microgravity 

Science and Technology, vol. VI, 1993, pp. 28-33. 

Science Impacts 

1. Alexander, ll.D: Low-Gravity Experiment Sensitivity to Residual Acceleration: A Review. Microgravity Science and Technology, vol. 3, Sept. 1990, pp. 52-68. 

2. de Groh ill, H.C.; and Nelson, E.S.: On Residual Acceleration During Space Experiments. Heat Transfer in 

Microgravity Systems, S.S. Sadhal; and A. Gopinath, ed., HTD-Vol. 290, ASME, New York, 1994, 

pp.23-33. 

3. Favier, J.J., et al.: Mass Transport Phenomena During Solidification in Microgravity: Preliminary Results of the 

First MEPHISTO Flight Experiment. J Cryst. Growth, vol. 140, no. 1-2, June 1994, pp. 237-243. 

4. Ramachandran, N.; and Winter, c.A.: Effects of g-jitter and Marangoni Convection on Float Zones. J Spac. 

Rock., vol. 29, no. 4, July-Aug. 1992, pp. 514-522. 

5. Arnold, W.A., et al. : Three-Dimensional Flow Transport Modes in Directional Solidification During Space 

Processing. l Spac. Rock., vol. 28, Mar-Apr. 1991, pp. 238-243. 

6. Nelson, E.S.: An Examination of Anticipated g-jitter on Space Station and Its Effects on Materials Processes. 

NASA TM-I03775, 1994. 

40 
REPORT DOCUMENTATION PAGE 

Form Approved 

OMB No. 0704-0188 

Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, 

gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this 

collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson 

Davis Highway, Suite 1204, AMington, VA 22202-4302, and to the Office of Management and Budget, Paperwork Reduction Project (0704-0188), Washington, DC 20503. 

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1

2

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REPORT DATE r' REPORT TYPE AND DATES COVERED 

August 1996 Technical Memorandum 

4. TITLE A ND SUBTITLE 5 . FUNDING NUMBERS 

Compendium of Information for Interpreting the Microgravity 

Environment of the Orbiter Spacecraft 

6. A UTHOR(S) WU - 963-60-0D 

Richard DeLombard 

7 . PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8 . PERFORMING ORGANIZAT ION 

REPORT NUMBER 

National Aeronautics and Space Administration 

Lewis Research Center E-9851 

Cleveland, Ohio 44135-3191 

9. SPONSORINGIMONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSORINGIMONITORING 

AGENCY REPORT NUMBER 

National Aeronautics and Space Administration 

Washington, D.C. 20546-0001 NASA TM-I07032 

11. SUPPLEMENTARY NOTES 

Responsi ble person, Richard DeLombard, organization code 6743, (216) 433-5285. 

1 2a. DISTRIBUTION/AVAILABILITY STATEMENT 1 2b. DISTRIBUTION CODE 

Unclassified -Unlimited 

Subject Categories 20, 35, and 18 

This publication is available from the NASA Center for Aerospace Information, (301) 621-0390. 

13. A BSTRA CT (Maximum 200 words) 

Science experiments are routinely conducted on the NASA shuttle Orbiter vehicles. Primarily, these experiments are operated on such 

missions to take advantage of the microgravity (low-level acceleration) environment conditions during on-orbit operations. Supporting 

accelerometer instruments are operated with the experiments to measure the microgravity acceleration environment in which the 

science experiments were operated. The Principal Investigator Microgravity Services (pIMS) Project at NASA Lewis Research Center 

interprets these micro gravity acceleration data and prepares mission summary reports to aid the principal investigators of the scientific 

experiments in understanding the micro gravity environment. Much of the information about the Orbiter vehicle and the microgravity 

environment remains the same for each mission. Rather than repeat that information in each mission summary report, reference 

information is presented in this report to assist users in understanding the microgravity-acceleration data. The characteristics of the 

micro gravity acceleration environment are first presented. The methods of measurement and common instruments used on Orbiter 

missions are described. The coordinate systems utilized in the Orbiter and accelerometers are described. Some of the Orbiter attitudes 

utilized in microgravity related missions are illustrated. Methods of data processing are described and illustrated. The interpretation of 

the microgravity acceleration data is included with an explanation of common disturbance sources. Instructions to access some of the 

acceleration data and a description of the Orbiter thrusters are explained in the appendixes. A microgravity environment bibliography is 

also incl uded. 

14. SUBJECT TERMS 15. NUMBER OF PAGES 

Microgravity environment; Acceleration; Orbiter; Acceleration analysis; 44 

Microgravity disturbances 16. PRICE CODE 

A03 

17. SECURITY CLASSIFICATION 18. SECURITY CLASSIFICATION 19. SECURITY CLASSIFICATION 20. LIMITATION OF ABSTRACT 

OF REPORT OF THIS PAGE OF ABSTRACT 

Unclassified Unclassified Unclassified 

NSN 7540-01-280-5500 Standard Form 2 98 (Rev. 2-89) 

Prescribed by ANSI Std. Z39-18 

298-102 

REPORT DOCUMENTATION PAGE 

Form Approved 

OMB No. 0704-0188 

Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, 

gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this 

collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson 

Davis Highway, Suite 1204, AMington, VA 22202-4302, and to the Office of Management and Budget, Paperwork Reduction Project (0704-0188), Washington, DC 20503. 

1 . AGENCY USE ONLY (Leave blanK) 

1

2

. 

REPORT DATE r' REPORT TYPE AND DATES COVERED 

August 1996 Technical Memorandum 

4. TITLE A ND SUBTITLE 5 . FUNDING NUMBERS 

Compendium of Information for Interpreting the Microgravity 

Environment of the Orbiter Spacecraft 

6. A UTHOR(S) WU - 963-60-0D 

Richard DeLombard 

7 . PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8 . PERFORMING ORGANIZAT ION 

REPORT NUMBER 

National Aeronautics and Space Administration 

Lewis Research Center E-9851 

Cleveland, Ohio 44135-3191 

9. SPONSORINGIMONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSORINGIMONITORING 

AGENCY REPORT NUMBER 

National Aeronautics and Space Administration 

Washington, D.C. 20546-0001 NASA TM-I07032 

11. SUPPLEMENTARY NOTES 

Responsi ble person, Richard DeLombard, organization code 6743, (216) 433-5285. 

1 2a. DISTRIBUTION/AVAILABILITY STATEMENT 1 2b. DISTRIBUTION CODE 

Unclassified -Unlimited 

Subject Categories 20, 35, and 18 

This publication is available from the NASA Center for Aerospace Information, (301) 621-0390. 

13. A BSTRA CT (Maximum 200 words) 

Science experiments are routinely conducted on the NASA shuttle Orbiter vehicles. Primarily, these experiments are operated on such 

missions to take advantage of the microgravity (low-level acceleration) environment conditions during on-orbit operations. Supporting 

accelerometer instruments are operated with the experiments to measure the microgravity acceleration environment in which the 

science experiments were operated. The Principal Investigator Microgravity Services (pIMS) Project at NASA Lewis Research Center 

interprets these micro gravity acceleration data and prepares mission summary reports to aid the principal investigators of the scientific 

experiments in understanding the micro gravity environment. Much of the information about the Orbiter vehicle and the microgravity 

environment remains the same for each mission. Rather than repeat that information in each mission summary report, reference 

information is presented in this report to assist users in understanding the microgravity-acceleration data. The characteristics of the 

micro gravity acceleration environment are first presented. The methods of measurement and common instruments used on Orbiter 

missions are described. The coordinate systems utilized in the Orbiter and accelerometers are described. Some of the Orbiter attitudes 

utilized in microgravity related missions are illustrated. Methods of data processing are described and illustrated. The interpretation of 

the microgravity acceleration data is included with an explanation of common disturbance sources. Instructions to access some of the 

acceleration data and a description of the Orbiter thrusters are explained in the appendixes. A microgravity environment bibliography is 

also incl uded. 

14. SUBJECT TERMS 15. NUMBER OF PAGES 

Microgravity environment; Acceleration; Orbiter; Acceleration analysis; 44 

Microgravity disturbances 16. PRICE CODE 

A03 

17. SECURITY CLASSIFICATION 18. SECURITY CLASSIFICATION 19. SECURITY CLASSIFICATION 20. LIMITATION OF ABSTRACT 

OF REPORT OF THIS PAGE OF ABSTRACT 

Unclassified Unclassified Unclassified 

NSN 7540-01-280-5500 Standard Form 2 98 (Rev. 2-89) 

Prescribed by ANSI Std. Z39-18 

298-102