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Proceedings Paper

Testing the inertial pseudo-star reference unit
Author(s): Michael F. Luniewicz; J. Murphy; Edward O'Neil; Dale T. Woodbury; Marcus R. Schulthess
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Paper Abstract

IPSRU (Inertial Pseudo Star Reference Unit) is an inertial line- of-sight pointing reference that has an ultralow jitter of less than 40 nrad rms from 0.4 to 312 Hz. IPSRU emits a collimated optical reference beam from a stabilized, sterrable two degree of freedom platform, and this reference beam is used to stabilize a payload's line-of-sight against vehicle vibrations. IPSRU's three critical performance parameters are isolation of host vehicle vibration from the reference beam, the intrinsic reference beam jitter due to self-generated platform noise, and open-loop inertial pointing accuracy of the reference beam. IPSRU, developed at Draper, is in final performance testing before delivery to Phillips Laboratory for the high-altitude balloon experiment (HABE). The challenges of measuring and validating IPSRU's performance, including a total beam jitter of less than 40 nrad, a base isolation transfer function that ranges from -93 dB at 1 Hz to -55 dB at 100 Hz, and an open-loop pointing accuracy of 21 ppm, are met with a specially designed pointing scoring facility that includes state of the art instrumentation and a quiet reference pier. Beam jitter and base motion isolation are measured with a Draper-enhanced quad-type detector with an rms noise of 6 nrad from 0.4 to 312 Hz and a field of view of 8 (mu) rad. Open-loop pointing maneuvers are measured with an enhanced-resolution laser interferometer (LI) (6.8 nrad per bit) with a 4 deg field of view. Additionally, IPSRU is scored in a thermal vacuum chamber that simulates the HABE environment or a satellite environment.

Paper Details

Date Published: 5 July 1994
PDF: 12 pages
Proc. SPIE 2221, Acquisition, Tracking, and Pointing VIII, (5 July 1994); doi: 10.1117/12.178969
Show Author Affiliations
Michael F. Luniewicz, Charles Stark Draper Lab., Inc. (United States)
J. Murphy, Charles Stark Draper Lab., Inc. (United States)
Edward O'Neil, Charles Stark Draper Lab., Inc. (United States)
Dale T. Woodbury, Charles Stark Draper Lab., Inc. (United States)
Marcus R. Schulthess, Air Force Phillips Lab. (United States)

Published in SPIE Proceedings Vol. 2221:
Acquisition, Tracking, and Pointing VIII
Michael K. Masten; Larry A. Stockum; Morris M. Birnbaum; George E. Sevaston, Editor(s)

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