SCIENTIFIC AND TECHNICAL AEROSPACE REPORTS

A Biweekly Publication of the National Aeronautics and Space Administration
VOLUME 44, ISSUE 10 - MAY 19, 2006

18 SPACECRAFT DESIGN, TESTING AND PERFORMANCE
Includes satellites; space platforms; space stations; spacecraft systems and components such as thermal and environmental controls; and spacecraft control and stability characteristics.

For life support systems see 54 Man/System Technology and Life Support.

For related information see also 05 Aircraft Design, Testing and Performance; 39 Structural Mechanics; and 16 Space Transportation and Safety.

20060012257 NASA Glenn Research Center, Cleveland, OH, USA

International Space Station Increment-6/8 Microgravity Environment Summary Report November 2002 to April 2004

Jules, Kenol; Hrovat, Kenneth; Kelly, Eric; Reckart, Timothy; January 2006; 186 pp.; In English; Original contains color and black and white illustrations Contract(s)/Grant(s): WBS 22-400-35-40-05 Report No.(s): NASA/TM-2006-213896; E-15267; Copyright; Avail.: CASI: A09, Hardcopy

This summary report presents the analysis results of some of the processed acceleration data measured aboard the International Space Station during the period of November 2002 to April 2004. Two accelerometer systems were used to measure the acceleration levels for the activities that took place during Increment-6/8. However, not all of the activities during that period were analyzed in order to keep the size of the report manageable.

The National Aeronautics and Space Administration sponsors the Microgravity Acceleration Measurement System and the Space Acceleration Measurement System to support microgravity science experiments that require microgravity acceleration measurements. On April 19, 2001, both the Microgravity Acceleration Measurement System and the Space Acceleration Measurement System units were launched on STS-100 from the Kennedy Space Center for installation on the International Space Station. The Microgravity Acceleration Measurement System unit was flown to the station in support of science experiments requiring quasi-steady acceleration measurements, while the Space Acceleration Measurement System unit was flown to support experiments requiring vibratory acceleration measurement. Both acceleration systems are also used in support of the vehicle microgravity requirements verification as well as in support of the International Space Station support cadre.

The International Space Station Increment-6/8 reduced gravity environment analysis presented in this report uses acceleration data collected by both sets of accelerometer systems: 1. The Microgravity Acceleration Measurement System, which consists of two sensors: the Orbital Acceleration Research Experiment Sensor Subsystem, a low frequency range sensor (up to 1 Hz), is used to characterize the quasi-steady environment for payloads and vehicle, and the High Resolution Accelerometer Package, which is used to characterize the vibratory environment up to 100 Hz. 2. The Space Acceleration Measurement System measures vibratory acceleration data in the range of 0.01 to 400 Hz.

This summary report presents analysis of some selected quasi-steady and vibratory activities measured by these accelerometers during Increment-6/8 from November 2002 to April 2004. Author

Microgravity; International Space Station; Acceleration Measurement; Vibration; Gravitational Effects; Space Transportation System; Frequency Ranges

20060012308 NASA Goddard Space Flight Center, Greenbelt, MD, USA

On the Extraction of Angular Velocity from Attitude Measurements

Bar-Itzhack, I. Y.; Harman, Richard R.; Thienel, Julie K.; [2006]; 29 pp.; In English; 46th Israel Annual Conference on Aerospace Sciences, 1-2 Mar. 2006, Haifa, Israel; Copyright; Avail.: CASI: A03, Hardcopy

In this paper we research the extraction of the angular rate vector from attitude information without differentiation, in particular from quaternion measurements. We show that instead of using a Kalman filter of some kind, it is possible to obtain good rate estimates, suitable for spacecraft attitude control loop damping, using simple feedback loops, thereby eliminating the need for recurrent covariance computation performed when a Kalman filter is used. This considerably simplifies the computations required for rate estimation in gyro-less spacecraft. Some interesting qualities of the Kalman filter gain are explored, proven and utilized. We examine two kinds of feedback loops, one with varying gain that is proportional to the well known Q matrix, which is computed using the measured quaternion, and the other type of feedback loop is one with constant coefficients. The latter type includes two kinds; namely, a proportional feedback loop, and a proportional-integral feedback loop. The various schemes are examined through simulations and their performance is compared. It is shown that all schemes are adequate for extracting the angular velocity at an accuracy suitable for control loop damping. Author

Angular Velocity; Attitude Control; Velocity Measurement; Spacecraft Control; Loops; Feedback; Damping; Kalman Filters; Quaternions

Source: NASA