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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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At least 109 records · Page 6
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NASA NTRS1991

Initial refinement of minor planet orbits for pointing and observation with the Hubble Space Telescope

Refinements of the orbital elements for 24 minor planets that will be observed with the Fine Guidance Sensors (FGSs) on the Hubble Space Telescope (HST) are presented. The accuracy of these orbits is discussed in the context of the ephemeris requirements for target acquisition with the FGSs. Comparisons with standard catalog orbits are made to evaluate the suitability of the use of the catalog orbits for HST pointing. It is found that the orbits published in the most recent Minor Planet Circulars are capable of positional predictions that are accurate at the 1-arcsec level. However, there are still many orbits that have not been revised in the last 10 yr and these should not be used for critical pointing ephemerides. In many cases, the orbital elements will have to be refined using recent ground-based observations before a minor planet can be reliably observed by HST.

Whipple, Arthur L.↗
NASA NTRS1991

Space astronomical telescopes and instruments; Proceedings of the Meeting, Orlando, FL, Apr. 1-4, 1991

The present volume on space astronomical telescopes and instruments discusses lessons from the HST, telescopes on the moon, future space missions, and mirror fabrication and active control. Attention is given to the in-flight performance of the Goddard high-resolution spectrograph of the HST, the initial performance of the high-speed photometer, results from HST fine-guidance sensors, and reconstruction of the HST mirror figure from out-of-focus stellar images. Topics addressed include system concepts for a large UV/optical/IR telescope on the moon, optical design considerations for next-generation space and lunar telescopes, the implications of lunar dust for astronomical observatories, and lunar liquid-mirror telescopes. Also discussed are space design considerations for the Space Infrared Telescope Facility, the Hubble extrasolar planet interferometer, Si:Ga focal-plane arrays for satellite and ground-based telescopes, microchannel-plate detectors for space-based astronomy, and a method for making ultralight primary mirrors.

Bely, Pierre Y.↗
NASA NTRS1992

A deconvolution technique for Hubble Space Telescope FGS fringe analysis

A technique has been developed for directly transforming interferometer fringe visibility functions ('S curves') from the Hubble Space Telescope (HST) fine guidance sensors (FGSs) into intensity profiles of the program object. In a process analogous to Fourier transform image deconvolution, an S curve from a double star yields a pair of narrow profiles containing information on the separation (in one coordinate), and relative brightness of the two stars. The procedure has yielded high internal precision for the separation and relative brightness in tests with HST data. Simulations indicate that it can also deconvolve S curves from multiple stars or continuous intensity distributions such as resolvable stellar or extragalactic objects. Similar deconvolution analyses may be useful in other types of interferometry.

Hershey, John L.↗
NASA NTRS1993

Pointing and figure control system for a space-based far-IR segmented telescope

A pointing and figure control system for two space-based far-IR telescopes, the 10-20 m Large Deployable Reflector and the 3.6 m Submillimeter Intermediate Mission, is described. The figure maintenance control system is designed to counter the optical elements translational and rotational changes induced by long-term thermal drifts that the support structure may experience. The pointing system applies optical truss to telescope pointing; a laser metrology system is used to transfer pointing informaton from an external fine guidance sensor to the telescope optical boresight, defined by the primary mirror, secondary mirror, and focal plane assembly.

Lau, Kenneth↗
NASA NTRS1993

Periodic low-amplitude variations in the brightness of Proxima Centauri

Using data acquired with Fine Guidance Sensor No. 3 on board the Hubble Space Telescope we find that the brightness of Proxima Centauri varies with an amplitude of 0.01 mag and a period P = 41.6 +/- 0.6 days. We interpret this variation as rotational modulation of star spots or bright regions in the photosphere of Proxima Cen. In a total of 89.36 min of monitoring over 212 days, we detected one major flare and three post-flare brightenings.

Benedict, G. F.↗
NASA NTRS1993

Design and simulation of EVA tools for first servicing mission of HST

The Hubble Space Telescope (HST) was launched into near-earth orbit by the space shuttle Discovery on April 24, 1990. The payload of two cameras, two spectrographs, and a high-speed photometer is supplemented by three fine-guidance sensors that can be used for astronomy as well as for star tracking. A widely reported spherical aberration in the primary mirror causes HST to produce images of much lower quality than intended. A space shuttle repair mission in late 1993 will install small corrective mirrors that will restore the full intended optical capability of the HST. The first servicing mission (FSM) will involve considerable extravehicular activity (EVA). It is proposed to design special EVA tools for the FSM. This report includes details of the data acquisition system being developed to test the performance of the various EVA tools in ambient as well as simulated space environment.

Naik, Dipak↗
NASA NTRS1994

Design and simulation of EVA tools for first servicing mission of HST

The Hubble Space Telescope (HST) was launched into near-earth orbit by the Space Shuttle Discovery on April 24, 1990. The payload of two cameras, two spectrographs, and a high-speed photometer is supplemented by three fine-guidance sensors that can be used for astronomy as well as for star tracking. A widely reported spherical aberration in the primary mirror causes HST to produce images of much lower quality than intended. A Space Shuttle repair mission in January 1994 installed small corrective mirrors that restored the full intended optical capability of the HST. The First Servicing Mission (FSM) involved considerable Extra Vehicular Activity (EVA). Special EVA tools for the FSM were designed and developed for this specific purpose. In an earlier report, the details of the Data Acquisition System developed to test the performance of the various EVA tools in ambient as well as simulated space environment were presented. The general schematic of the test setup is reproduced in this report for continuity. Although the data acquisition system was used extensively to test a number of fasteners, only the results of one test each carried on various fasteners and the Power Ratchet Tool are included in this report.

Naik, Dipak↗
NASA NTRS1992

A dual purpose optical truss laser metrology system for a space-based far-IR segmented telescope: Figure maintenance and pointing control

To obtain imaging performance as for monolithic mirrors, large segmented reflectors used for astronomy must be actively aligned and pointed to extreme levels of precision. A system concept for a dual purpose optical truss laser metrology system is described which is used for both figure and alignment maintenance and telescope pointing. A two-stage figure active control approach was developed for several proposed spaceborne far infrared segmented telescopes, one of which is the 10-20 meters Large Deployable Reflector (LDR). The first active control stage, the figure initialization control system, aligns the optical elements (i.e., the primary segments, secondary and focal plane assembly) based on images obtained. The second stage, the figure maintenance control system, maintains the alignment between re-initializations using measurements provided by laser interferometers arranged in an optical truss configuration. It measures the relative positions and alignments of the telescope segments so that a controller can reposition them appropriately. The application of this optical truss for figure maintenance control is the subject of the first part of this paper. The second portion of this paper discusses the application of the optical truss to telescope pointing. Here, the laser metrology system is used to transfer pointing information from an external fine guidance sensor (FGS) to the telescope optical boresight as defined by the primary mirror, secondary mirror, and focal plane assembly. Thus, any alignment variations between the two boresights can be observed and accounted for.

Lau, Kenneth↗
NASA NTRS1993

Determination and characterization of the Hubble Space Telescope pointing stability

The Hubble Space Telescope (HST) was designed to maintian a pointing stability (jitter) of 0.007 arc seconds rms throughout every observing period, which can last from a few seconds to several orbits. On-orbit measurements indicate that the hardware excitation induced by the reaction wheels. gyros, high gain antennae, science instrument mechanisms and tape recorders are well within specifications. Unexpectedly, the solar arrays because the dominant source of jitter. Every passage through an orbital terminator produces vibrations which emanate from the solar arrays due to thermal effects, which affect the relative positional stability. Broadband frequencies centered about 0.11 and 0.65 Hz were detected in the frequency content of the vehicle jitter. On-board modifications to the control law have attenuated the disturbance torques and reduced the vehicle jitter close to specification. Replacement of the solar arrays in December, 1993, should eliminate the torque distubances. Astrometric science observations are extremely susceptible to corruption from vehicle jitter. The removal of vehicle jitter from astrometric Transfer function scans of binary stars is explained in detail. A binary star separation of 16 milli-seconds of arc has been achieved, a separation resolution of 10 to 12 milli-seconds of arc appears feasible, with a binary star magnitude of 9 m(sub V). The achievement of this resolution is in part due to vehicle jitter removal. Comparison of vehicle jitter measurements from the position path of the vehicle control law, or from the guiding Fine Guidance Sensors (FGS), are shown to be equivalent to approximately 0.001 arc second.

Bradley, A. J.↗
NASA NTRS1995

Design and simulation of EVA tools and robot end effectors for servicing missions of the HST

The Hubble Space Telescope (HST) was launched into near-earth orbit by the Space Shuttle Discovery on April 24, 1990. The payload of two cameras, two spectrographs, and a high-speed photometer is supplemented by three fine-guidance sensors that can be used for astronomy as well as for star tracking. A widely reported spherical aberration in the primary mirror causes HST to produce images of much lower quality than intended. A Space Shuttle repair mission in January 1994 installed small corrective mirrors that restored the full intended optical capability of the HST. A Second Servicing Mission (SM2) scheduled in 1997 will involve considerable Extra Vehicular Activity (EVA). To reduce EVA time, the addition of robotic capability in the remaining servicing missions has been proposed. Toward that end, two concept designs for a general purpose end effector for robots are presented in this report.

Naik, Dipak↗
NASA NTRS1997

An investigation into the milliarcsecond attitude control errors of Hubble Space Telescope

An analysis of the fine pointing errors of the Hubble Space Telescope (HST), in the range from 1 to 15 milliarcsecs, is reported on. The emphasis is on the study of the performance characteristics of the pointing control system, fine guidance sensors and the optical telescope assembly, which produce relative attitude and astrometric measurement errors. Since the first servicing mission in December 1993, the HST relative short term position stability is of the order of 3 milliarcsecs RMS when averaged over 1 min intervals. At this level of accuracy, longer term systematic attitude errors in this range can have a noticeable impact on the telescope's observations. The various error sources are described, including: internal temperature effects; spacecraft structure temperature effects; calibration procedures, and computational inaccuracies.

Bradley, A. J.↗
NASA NTRS1997

The 1997 HST Calibration Workshop with a New Generation of Instruments

The Second Servicing mission in early 1997 has brought major changes to the Hubble Space Telescope (HST). Two of the original instruments, Faint Object Spectrograph (FOS) and Goddard High Resolution Spectrograph (GHRS), were taken out, and replaced by completely new instruments, the Space Telescope Imaging Spectrograph (STIS) and the Near Infrared Camera Multi-Object Spectrograph (NICMOS). Two new types of detectors were installed, and for the first time, HST gained infrared capabilities. A new Fine Guidance Sensor (FGS) was installed, with an alignment mechanism that could improve substantially both guiding and astrometric capabilities. With all these changes come new challenges. The characterization of the new instruments has required a major effort, both by their respective Investigation Definition Teams and at the Space Telescope Science Institute. All necessary final calibrations for the retired spectrographs needed to be carried out, and their properties definitively characterized. At the same time, work has continued to improve our understanding of the instruments that have remained on board. The results of these activities were discussed in the 1997 HST (Hubble Space Telescope) Calibration Workshop. The main focus of the Workshop was to provide users with the tools and the understanding they need to use HST's instruments and archival data to the best of their possibilities. This book contains the written record of the Workshop. As such, it should provide a valuable tool to all interested in using existing HST data or in proposing for new observations.

Casertano, S.↗
NASA NTRS1999

STS-103 Crew Training

The Hubble Space Telescope (HST) team is preparing for NASA's third scheduled service call to Hubble. This mission, STS-103, will launch from Kennedy Space Center aboard the Space Shuttle Discovery. The seven flight crew members are Commander Curtis L. Brown, Pilot Scott J. Kelly, European Space Agency (ESA) astronaut Jean-Francois Clervoy who will join space walkers Steven L. Smith, C. Michael Foale, John M. Grunsfeld, and ESA astronaut Claude Nicollier. The objectives of the HST Third Servicing Mission (SM3A) are to replace the telescope's six gyroscopes, a Fine-Guidance Sensor, an S-Band Single Access Transmitter, a spare solid-state recorder and a high-voltage/temperature kit for protecting the batteries from overheating. In addition, the crew plans to install an advanced computer that is 20 times faster and has six times the memory of the current Hubble Space Telescope computer. To prepare for these extravehicular activities (EVAs), the SM3A astronauts participated in Crew Familiarization sessions with the actual SM3A flight hardware. During these sessions the crew spent long hours rehearsing their space walks in the Guidance Navigation Simulator and NBL (Neutral Buoyancy Laboratory). Using space gloves, flight Space Support Equipment (SSE), and Crew Aids and Tools (CATs), the astronauts trained with and verified flight orbital replacement unit (ORU) hardware. The crew worked with a number of trainers and simulators, such as the High Fidelity Mechanical Simulator, Guidance Navigation Simulator, System Engineering Simulator, the Aft Shroud Door Trainer, the Forward Shell/Light Shield Simulator, and the Support Systems Module Bay Doors Simulator. They also trained and verified the flight Orbital Replacement Unit Carrier (ORUC) and its ancillary hardware. Discovery's planned 10-day flight is scheduled to end with a night landing at Kennedy.

Source record↗
NASA NTRS1999

Hubble Space Telescope Servicing Mission 3A

The Hubble Space Telescope's purpose is to spend 20 years probing the farthest and faintest reaches of the cosmos. Crucial to fulfilling this objective is a series of on-orbit servicing missions. Hubble was placed in orbit on April 25, 1990, by the shuttle Discovery and subsequent servicing followed in December 1993 and February 1997. The third in the series of planned servicing missions for the Hubble Space Telescope was scheduled for June 2000. This third Servicing Mission has been separated into two flights. The first of these flights, Servicing Mission 3A, is scheduled for December 1999, and the second, Servicing Mission 3B, is scheduled for 2001. The fourth Servicing Mission is scheduled for 2003 with a "close-out" Mission in 2010. Three instruments are currently in active scientific use on Hubble - the Wide Field and Planetary Camera 2, the Space Telescope Imaging Spectrograph, and Fine Guidance Sensor I R, which has been designated as the prime FGS for astrometric science. Other instrument bays are occupied by the Near Infrared Camera and Multi-Object Spectrometer (NICMOS), which is now dormant due to the depletion of its solid nitrogen cryogen, the Faint Object Camera, which has been decommissioned, and the corrective optical device called COSTAR, which is no longer needed.

Source record↗
NASA NTRS2003

The James Webb Telescope Instrument Suite Layout: Optical System Engineering Considerations for a Large, Deployable Space Telescope

The James Webb Space Telescope (JWST) is a space-based, infrared observatory designed to study the early stages of galaxy formation in the Universe. The telescope will be launched into an elliptical orbit about the second Lagrange point and passively cooled to 30-50 K to enable astronomical observations from 0.6 to 28 microns. A group from the NASA Goddard Space Flight Center and the Northrop Grumman Space Technology prime contractor team has developed an optical and mechanical layout for the science instruments within the JWST field of view that satisfies the telescope s high-level performance requirements. Four instruments required accommodation within the telescope's field of view: a Near-Infrared Camera (NIRCam) provided by the University of Arizona; a Near-Mared Spectrometer (NIRSpec) provided by the European Space Agency; a Mid-Infrared Instrument (MIRI) provided by the Jet Propulsion Laboratory and a European consortium; and a Fine Guidance Sensor (FGS) with a tunable filter module provided by the Canadian Space Agency. The size and position of each instrument's field of view allocation were developed through an iterative, concurrent engineering process involving the key observatory stakeholders. While some of the system design considerations were those typically encountered during the development of an infrared observatory, others were unique to the deployable and controllable nature of JWST. This paper describes the optical and mechanical issues considered during the field of view layout development, as well as the supporting modeling and analysis activities.

Bos, Brent↗
NASA NTRS1997

Astrometric Detection of Planets

Astrometry is undergoing a rebirth. From modern photoelectric instruments on telescopes to the fine guidance sensors on HST to the Hipparcos mission, astrometric instruments have significantly increased in accuracy in the recent past.

Detection of Planets Astrometry photoelectric inst↗
NASA NTRS2008

James Webb Space Telescope Project (JWST) Overview

This presentation provides an overview of the James Webb Space Telescope (JWST) Project. The JWST is an infrared telescope designed to collect data in the cosmic dark zone. Specifically, the mission of the JWST is to study the origin and evolution of galaxies, stars and planetary systems. It is a deployable telescope with a 6.5 m diameter, segmented, adjustable primary mirror. outfitted with cryogenic temperature telescope and instruments for infrared performance. The JWST is several times more sensitive than previous telescope and other photographic and electronic detection methods. It hosts a near infrared camera, near infrared spectrometer, mid-infrared instrument and a fine guidance sensor. The JWST mission objection and architecture, integrated science payload, instrument overview, and operational orbit are described.

Dutta, Mitra↗
NASA NTRS2008

James Webb Space Telescope (JWST) Project Status for the AIAA Working Group on Space Simulation

This brief presentation discusses developments in the design of the James Webb Space Telescope (JWST). The JWST master schedule is provided and its system architecture is described. Instruments include the Near Infrared Camaera, Near Infrared Spectrograph, Mid-Infrared Instrument, and the Fine Guidance Sensor. Compared to other telescopes the JWST has a 2.7 longer wavelength than the Hubble Telescope (HST), 38 times better sensitivity at K band that the HST NICMOS, and 8-24 times better angular resolution than the Spitzer Telescope. among other features. Engineering or verification models for all telescope instruments are being assembled and tested in the current year. Currently, good progress continues to be made on critical path items and the JWST is on track for a June 2013 launch.

Sabelhaus, Phil↗