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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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NASA NTRS1981

Development of a Shuttle Infrared Telescope Facility /SIRTF/ fine guidance sensor

Fine guidance technology development for the Shuttle Infrared Telescope Facility (SIRTF) centers upon the use of a single multiple-star-tracking sensor to provide the position information necessary to produce three-axis attitude control signals for precision payload pointing. The effort described in this paper is concerned with the development of a fine guidance sensor that employs a high-density charge-coupled imaging device for producing position information signals by using star fields. Multiple star position information produces three-axis position error signals that are used to update inertial reference gyros. The sensor employs advanced position interpolation algorithms to enhance field-of-view resolution and to correct for optical aberrations inherent in spatially chopped star images resulting from the telescope's movable secondary mirror. Operation of the sensor is under the control of a high-performance microcomputer that provides both autonomy and flexibility in a guidance application.

Salomon, P. M.↗
NASA NTRS1992

An analysis of the Hubble Space Telescope fine guidance sensor Fine Lock mode

There are two guiding modes of the Hubble Space Telescope used for the acquisition of astronomical data by one of its six scientific instruments. The more precise one is called Fine Lock. Command and control problems in the on-board electronics, compounded by the aberrations in the main optics, has limited routinely successful Fine Lock to brighter stars, V less than 13.0 mag, instead of fulfilling its prelaunch goal of V = 14.5 mag. Consequently, the less precise guiding mode of Coarse Track (about 25 milliarcsecond in practice) has to be used fairly frequently. Indeed, almost half of the celestial hemisphere has stars too faint to support guidance in the Fine Lock mode. Hence, some of the scientific observations to have been made with the Hubble Space Telescope will be compromised. In this paper a report on the only realistic or extensive simulations of the Fine Lock guidance mode is presented. The theoretical analysis underlying the Monte Carlo experiments and the numerical computations show that the control electronics have significant limitations and how to adjust the various control parameters in an attempt to extend Fine Lock guiding performance back to V - 14.0 mag.

Taff, L. G.↗
NASA NTRS1991

An analysis of the Hubble Space Telescope fine guidance sensor fine lock mode

There are two guiding modes of the Hubble Space Telescope (HST) used for the acquisition of astronomical data by one of its six scientific instruments. The more precise one is called Fine Lock. Command and control problems in the onboard electronics has limited Fine Lock to brighter stars, V less than 13.0 mag, instead of fulfilling its goal of V = 14.5 mag. Consequently, the less precise guiding mode of Coarse Track (approximately 40 milli-arc seconds) has to be used fairly frequently. Indeed, almost half of the scientific observations to have been made with the HST will be compromised. The only realistic or extensive simulations of the Fine Lock guidance mode are reported. The theoretical analysis underlying the Monte Carlo experiments and the numerical computations clearly show both that the control electronics are severely under-engineered and how to adjust the various control parameters to successfully extend Fine Lock guiding performance back to V = 14.0 mag and sometimes beyond.

Taff, L. G.↗
NASA NTRS1991

Scientific results from the Hubble Space Telescope Fine Guidance Sensors

The Fine Guidance Sensors of the Hubble Space Telescope have two roles to play. They are the ultimate pointing and control instruments onboard the spacecraft and they are the primary astrometric instruments of the observatory. Because they are used for every scientific observation with the Hubble Space Telescope, independently of the ultimate scientific instrument being utilized, there is much more experience with them than with any of the other scientific devices. The Fine Guidance Sensors have already serendipitously discovered their first binary star from the Hubble Space Telescope Guide Star Catalog, have been exercised in most of their observing modes, and are able to fulfill their pointing and control functions up to their original specifications (in the absence of external influences). In addition, the imperfections in the primary mirror have minimally affected the performance of the Fine Guidance Sensors. An up-to-date summary of FGS engineering and science will be presented.

Taff, L. G.↗
NASA NTRS1992

Acquisition, pointing and tracking performance of the Hubble Space Telescope fine guidance sensors

The three fine guidance sensors (FGSs) on board the HST have been operated extensively since the observatory was launched in April, 1990. The FGSs, each capable of measuring angles as small as 0.003 arcsec, provide required fine pointing information to the HST's pointing control system and are intended to serve as astrometry instruments. On-orbit data have shown that the acquisition, pointing and tracking performance of the FGSs in most cases meets, and of these sometimes exceeds, requirements. The versatility of the FGS digital control electronics to adapt to the unexpected conditions imposed on the sensors by the telescope spherical aberration and by solar panel jitter is discussed. There is encouragement from both on-orbit tests and analytical studies that the FGSs can accommodate the current telescope characteristics. Improvements to guide star acquisitions within the FGSs and to target acquisitions within science instruments have been accomplished with the internal distortion calibration of each FGS and with the alignment calibration between sensors. Techniques used in the calibration process and the resulting improvements in acquisitions are presented.

Eaton, David J.↗
NASA NTRS1975

Design constraints of the LST fine guidance sensor

The LST Fine Guidance Sensor design is shaped by the rate of occurrence of suitable guide stars, the competition for telescope focal plane space with the Science Instruments, and the sensitivity of candidate image motion sensors. The relationship between these parameters is presented, and sensitivity to faint stars is shown to be of prime importance. An interferometric technique of image motion sensing is shown to have improved sensitivity and, therefore, a reduced focal plane area requirement in comparison with other candidate techniques (image-splitting prism and image dissector tube techniques). Another design requirement is speed in acquiring the guide star in order to maximize the time available for science observations. The design constraints are shown parametrically, and modelling results are presented.

Wissinger, A. B.↗
NASA NTRS1992

Astrometric performance characteristics of the Hubble Space Telescope fine guidance sensors

Each of the three fine guidance sensors for the Hubble Space Telescope constitutes a sixth science instrument to be used for astrometry. We detail the tests and results used in choosing one of the three sensors to be the prime astrometer. The Astrometry Science Team has chosen Fine Guidance Sensor (FGS) 3. FGS 3 produces position measurements on a star with V = 17 with a peraxis precision of 0.003 arcsec. The interferometer response function should permit double-star astrometry at least down to V = 16 for the central region of FGS 3. In a 10-h test of the stability of POS-mode astrometric measurements made in FGS 3, we found no scale or orientation variations greater than two parts in 100,000. During this same time period, we found no statistically significant systematic guide-star radial separation changes. Spacecraft jitter is found to be the prime determinant of astrometry success or failure.

Benedict, G. F.↗
NASA NTRS1990

Hubble Space Telescope: Fine guidance sensors instrument handbook. Version 2.1

The Fine Guidance Sensors (FGS) are a system of photomultiplier tubes and white light amplitude interferometers (Koester's prism) which are used for the fine guidance of the Hubble Space Telescope (HST). The purpose of the handbook is to provide information to a potential user of the FGS so that he may explore the feasibility of performing various observations. A brief overview is given of how the FGS works, along with an explanation of the instrument in some detail. The procedure for estimating exposure times is explained. The observing modes are described. Some details needed to specify the exposures and observation requirements on the proposal forms are explained. Data reduction procedures are outlined.

Taff, Larry↗
NASA NTRS1991

The in-flight calibration of the Hubble Space Telescope fine guidance sensors

The Hubble Space Telescope (HST) fine guidance sensors are unique in the precision and performance levels being attempted; spacecraft control and astrometric research at the near milliarcsecond level are the ultimate goals. The inflight calibration of the sensors is presented, describing both the algorithms being used as well as the results achieved to date. The calibration items of principal interest are optical distortion, sensor magnification, and relative alignments. Calibration accuracies at the 20 milliarcsecond level have been achieved for specific data sets for optical distortion parameters. Unexpected variations occurring from Dec. 1990 - May 1991 in the magnification and alignment parameters are currently under investigation. Plans are being developed for new data acquisitions and reductions that should substantially improve HST pointing performance.

Welter, G. L.↗
NASA NTRS1989

Hubble Space Telescope fine guidance sensor control system

The fine pointing information required for the extraordinary pointing stability of the Hubble Space Telescope (HST) is provided by the fine guidance sensor (FGS), which is capable of measuring extremely small pointing errors, of the order of 3 milliarcseconds. The FGS provides this fine pointing information over a relatively large, continuous range of angles of guide stars relative to the optical axis of the telescope. The FGS accomplishes this task by a judicious design involving the following: a two-axis high precision star selector servo system; an optical deflection system that provides high reduction from shaft angle to optical angle; a unique interferometer using Koester prisms and extremely sensitive photomultiplier tubes that enable the FGS to lock onto guide stars whose magnitude may be any value over a wide range of brightness (including 14.5 Mv and fainter); and the use the large aperture of the telescope itself to advantage. This paper describes the FGS control systems involved in achieving this performance, supported by test data.

Nurre, Gerald S.↗
NASA NTRS1993

On-orbit performance of the Hubble Space Telescope fine guidance sensors

The observed and measured on-orbit performance of various aspects of the fine guidance sensors is presented and discussed in the light of the original requirements and predictions. The fine guidance sensors are shown to meet or exceed the original requirements concerning dynamic pointing errors, photometric repeatability, and moving-target tracking capability. Calibration accuracy has been sufficient for observations to date, and fine-lock acquisitions are approaching a 100 percent success rate. Improvements to the fine-guidance-sensor tolerance of telescope spherical aberration, the South Atlantic anomaly, and solar-panel vibrations have been made, and further improvements are expected.

Eaton, David J.↗
NASA NTRS2019

Fine Guidance Sensor Data

The Kepler and K2 missions collected Fine Guidance Sensor (FGS) data in addition to the science data, as discussed in the Kepler Instrument Handbook (KIH, Van Cleve and Caldwell 2016). The FGS CCDs areframe transfer devices located in the corners of the Kepler focal plane, which are read out 10 times every second. The FGS data are being made available to the user community for scientific analysis as flux and centroid time series, along with a limited number of FGS full frame images which may be useful for constructing a World Coordinate System (WCS) or otherwise putting the time series data in context. This document will describe the data content and file format, and give example MATLAB scripts to read the time series.

FGS↗
NASA NTRS2017

Kepler Fine Guidance Sensor Data

The Kepler and K2 missions collected Fine Guidance Sensor (FGS) data in addition to the science data, as discussed in the Kepler Instrument Handbook (KIH, Van Cleve and Caldwell 2016). The FGS CCDs are frame transfer devices (KIH Table 7) located in the corners of the Kepler focal plane (KIH Figure 24), which are read out 10 times every second. The FGS data are being made available to the user community for scientific analysis as flux and centroid time series, along with a limited number of FGS full frame images which may be useful for constructing a World Coordinate System (WCS) or otherwise putting the time series data in context. This document will describe the data content and file format, and give example MATLAB scripts to read the time series. There are three file types delivered as the FGS data.1. Flux and Centroid (FLC) data: time series of star signal and centroid data. 2. Ancillary FGS Reference (AFR) data: catalog of information about the observed stars in the FLC data. 3. FGS Full-Frame Image (FGI) data: full-frame image snapshots of the FGS CCDs.

Kepler↗
NASA NTRS1991

Astrometry using the Hubble Space Telescope fine guidance sensors

Plans for the use of the three fine guidance sensors (FGSs) of the NASA Hubble Space Telescope for direct astrometric observations are reviewed. Topics addressed include the optical elements and detectors of the FGSs, the basic and astrometric operating modes of the FGSs, spacecraft pointing control during astrometric observations, and the astrometric data-reduction software provided to HST users. Particular attention is given to the calibration procedures for optical-field angle distortion, the plate scale, filter-wedge errors, lateral color effects, secular changes, velocity aberration, and transfer function. Also discussed are the steps being taken to verify the HST orbit. It is pointed out that the performance of the interferometric FGSs should not be affected by the focusing problems of the main HST instrument.

Duncombe, Raynor L.↗
NASA NTRS1994

Hubble Space Telescope Fine Guidance Sensors Instrument Handbook, version 4.0

This is a revised version of the Hubble Space Telescope Fine Guidance Sensor Instrument Handbook. The main goal of this edition is to help the potential General Observer (GO) learn how to most efficiently use the Fine Guidance Sensors (FGS's). First, the actual performance of the FGS's as scientific instruments is reviewed. Next, each of the available operating modes of the FGS's are reviewed in turn. The status and findings of pertinent calibrations, including Orbital Verification, Science Verification, and Instrument Scientist Calibrations are included as well as the relevant data reduction software.

Holfeltz, S. T.↗
NASA NTRS1994

The photometric properties of the HST astrometer Fine Guidance Sensor

This paper presents the results of the photometric calibration of the F583W filter in the astrometer Fine Guidance Sensor on the Hubble Space Telescope. Dozens of observations of the 9.58 mag Fine Guidance Sensor (FGS) transfer mode reference star Upgren 69 (in the cluster NGC 188) have been utilized to verify the consistency and demonstrate the temporal stability of the photomultipliers. The measurements which provided the material for a transformation from the FGS instrumental system to the Johnson V magnitude consisted of the extensive position mode observations performed during the Optical Field Angle Distortion calibration. A total of 588 measurements of 92 stars in the galactic cluster M35 were performed. Johnson V band photometry with a precision (i.e., random errors) of plus or minus 0.05 mag is available with an accuracy (i.e., systematic errors) of 0.05 mag over 2 yr.

Bucciarelli, B.↗