In this paper, we discuss the effects of atmospheric fluctuations on PFF performance, steps taken to reduce the strength of these fluctuations, and simulations showing how part of the PFF error maybe filtered out with the use of a Kalman filter.

interferometry astropherics real-time control test↗

NASA NTRS2002

Dim star fringe stabilization on the SIM Test-Bed 3 using pathlength feed-forward of the 'guide' interferometer optical path variation

Explore the source record for details and available documents.

interferometry SIM real-time control testbed attit↗

NASA NTRS2002

On path feed forward performance of an astrometric 3-BL Interferometer Test Bed (STB-3): mitigating atmospheric effects

Explore the source record for details and available documents.

interferometry atmospherics real-time control test↗

NASA NTRS2002

SIM testbed 3 real-time control software

SIM System Testbed 3 (STB3) features three optical interferometers sharing a common baseline, as a dynamic representation of the SIM instrument. An artificial star feeding the interferometers is installed on a separate optics bench. All three interferometers use photons captured by avalanche photo diodes (APDs) to measure the position and quality of fringes, and additional pointing precision is achieved by fast steering mirrors (FSMs) that keep the star images centered on the beam combining optics using a CCD camera. Each interferometer uses internal metrology to measure changes in its optical pathlength. External metrology beams measure changes in the baseline vector. This system acquires and tracks white light fringes with one interferometer, while the other two acquire and track laser light fringes representing the bright guide stars that will be used by SIM. The white light source represents a dim star that cannot supply enough photons for the Science interferometer to lock onto fringes in closed-loop mode; instead it operates open-loop, using pathlength corrections fed to it from the two guide interferometers and the external metrology subsystem to reject disturbances and maintain the fringes. This tracking mode is known as Pathlength Feed Forward (PFF). The precise real-time behavior required to achieve this result is implemented by a complex set of interacting software control loops. This paper describes how these loops take advantage of the benefits of the RTC Core architecture, and how they work together to accomplish STB3's objectives.

interferometry↗

NASA NTRS2002

Dim star fringe stabilization demonstration using pathlength feed-forward on the SIM Test-Bed 3 (STB3)

This paper describes the STB3 setup, the pathlength feed-forward architecture, implementation issues and data collected with the system.

Space↗