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At least 253 records · Page 14
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NASA NTRS1979

The Einstein /HEAO 2/ X-ray Observatory

The Einstein (HEAO 2) X-ray Observatory, launched in 1978, includes a fully imaging focusing X-ray telescope with an angular resolution of a few arc sec, a field of view of up to one deg, and a sensitivity several hundred times greater than previously available in any X-ray astronomy experiment. A high-resolution imager, an imaging proportional counter, a focal plane crystal spectrometer, and a monitor proportional counter are among the principal instruments on board the Einstein X-ray Observatory. About 20% of the total effective observing time in the first year of the X-ray astronomy experiment has been reserved for guest observers.

Giacconi, R.↗
NASA NTRS1979

On-orbit control system performance of the HEAO-2 observatory

The on-orbit performance of the High Energy Astronomy Observatory is described. The control system utilizes precision gyros for attitude reference and skewed reaction wheels controlled by a reprogrammable computer. The observatory points at selected targets, maneuvers automatically and acquires guide stars for updating at each target. Performance data indicates maneuver accuracies less than one arc minute and pointing accuracies of 2-5 arc seconds. Use of 7th-9th magnitude guide stars has resulted in several improper updates caused by 'flat-field' stray light effects in the star trackers. The method used to discriminate true stars from the flat-field is also presented.

Rose, R. E.↗
NASA NTRS1979

Forecasts of geomagnetic activity by Ottawa Magnetic Observatory: Their reliabilty and application

A 27 day forecast of geomagnetic activity based on the forecasts from two locations is presented. To evaluate the reliability of the forecasts, the predicted activity was compared with the actual geomagnetic activity at five geomagnetic observatories located in different magnetic zones: Ottawa (57.0N, 351.5E); Meanook (61.8N, 301.0E); Fort Churchill (68.8N, 322.5E); Cambridge Bay (76.7N, 294.0E); and Resolute Bay (83.1N, 287.7E). Results indicate that the percentage of correct predictions varies with the geomagnetic latitude of the observatory used for comparison. The percentage is on the average highest for lower latitude stations and lowest for the northern stations. The number of incorrect predictions ranges from 4.7% for Ottawa to 8.4% for Churchill.

Hruska, J.↗
NASA NTRS1980

The Space Telescope Observatory

The Space Telescope is an international astronomical observatory which will be placed into a low earth orbit in December 1983. The observatory will provide astronomers the opportunity to use five different instruments (wide field/planetary camera, faint object camera, high-resolution spectrograph, faint-object spectrograph, and high speed photometer), and to do astrometry with the use of the fine guidance sensors used primarily for pointing control. These instruments, the spectral range available above the earth's atmosphere, and the spatial resolution available from the combination of a near-diffraction limited 94-in. primary mirror and the stability provided by the Pointing Control System provide a tremendous potential to the astronomical community.

Bahcall, J. N.↗
NASA NTRS1981

Kuiper Airborne Observatory /Space Science Platform 1/

It is pointed out that jet transport aircraft operating in the stratosphere (often at 45,000 ft) have proved highly cost-effective and convenient as telescope platforms. The Kuiper Airborne Observatory (KAO) 91-cm telescope is described, with attention given to specifications, pointing and tracking, data handling, instrument development, and costs. It is noted that the observatory makes possible important astronomical research, graduate-level instruction, and the development and testing of rugged, remotely controlled instruments. Contributions made by the KAO to planetary astronomy, extragalactic astronomy, the interstellar medium, and to the study of star formation and evolution are enumerated.

Gillespie, C. M., Jr.↗
NASA NTRS1981

Photographic observations of comets at Lowell Observatory

Observations of Halley's comet at Lowell Observatory cover a period from November 10, 1909 to May 17, 1911: 334 direct photographs were taken, 118 objective prism spectra, and 32 slit spectrograms of the nucleus, many of them including 5 arc minutes of the surrounding coma. Just one morning's observations are illustrated as an example of utilizing every possible resource available at the Observatory at the time. Observational improvements developed since then are described and some suggestions for the coming return of Halley's comet are made.

Giclas, H. L.↗
NASA NTRS1981

The recovery of the HEAO-2 observatory

In August 1980, the Second High Energy Astronomy Observatory suffered the simultaneous double failure of two gyros, leaving the observatory with one gyro less than what is required for operation. The function of the missing gyro was replaced to allow restoration of spacecraft operation by reprogramming the on-board computer to derive rate from star and sun sensors, and by utilizing complex procedures. Large sun sensor quantization, jump characteristics of the star tracker, and extremely limited computer memory capacity further complicated the problem. Recovery attempts continued for over three months, during which time a suitable rate algorithm was derived. Final verification of the technique was never completed, however, due to the unexpected revival of one of the failed gyros.

Rose, R. E.↗
NASA NTRS1983

Solar Terrestrial Observatory for future space station program

The Solar Terrestrial Observatory (STO) Science Study Group was established in 1979 to formulate a scientific strategy for the development of a Solar Terrestrial Observatory as an interdependent problem-oriented combination of solar, magnetospheric, and atmospheric instruments. In the scenario formed by the STO Science Study Group, the STO would be mounted on a long-lived Space Platform, carried into orbit, and serviced by the Space Shuttle. The proposed strategy focused on investigations of the physical processes that interlink the major regions of solar-terrestrial space. In reviewing that strategy, one quickly concludes that the STO objectives can be met, and in many ways enhanced, by using a Shuttle-serviced manned Space Station. This conclusion is reinforced by the results of earlier workshops devoted to manned Space Stations.

Roberts, W. T.↗
NASA NTRS1982

AXAF, a permanent orbiting X-ray observatory - Telescope and instrumentation plans

The Advanced X-ray Astrophysics Facility (AXAF) now under study is to be a long-lived X-ray observatory in space. It is to be launched by the Space Shuttle, maintainable on-orbit, and retrievable for ground re-furbishment. The AXAF is conceived as an X-ray telescope with 6 nested grazing incidence X-ray mirrors (with a maximum aperture of 1.2 m) and interchangeable and replaceable focal plane instruments. The optics will provide 0.5 arcsecond imagery over a several arcminute field and somewhat reduced resolution over 1 degree in the X-ray band from 0.1 to 10 keV (1.2 to 120 A). The characteristics and expected performance of the observatory are described.

Zombeck, M. V.↗
NASA NTRS1983

X-ray observations of 4U 1626-67 by the monitor counter on the Einstein /HEAO 2/ observatory

The pulsing X-ray source 4U 1626-67 was observed with the Monitor Proportional Counter (MPC) on board the Einstein X-Ray Observatory on three occasions in early 1979. The MPC is a sealed, argon-filled proportional counter with a 1.5 mil beryllium window and is coaligned with the X-ray telescope on board the observatory. The spectral data spanning the energy range from 1.1 to 21 keV are divided into eight logarithmically spaced energy channels which integrate for 2.56 s. The Time Interval Processor (TIP) circuitry of the MPC measures time intervals between events to within 1 microsecond or 1.6%, whichever is larger, for a count rate dependent fraction of all events in all eight energy channels. It is found that in the energy range from 1 to 21 keV, the spectrum and 7.7 s pulse shape of 4U 1626-67 are variable on a time scale of minutes. The pulse shape variations correlate in a complex way with the intensity variations in this source.

Elsner, R. F.↗
NASA NTRS1982

AXAF, a permanent orbiting X-ray observatory - Telescope and instrumentation plans

The Advanced X-ray Astrophysics Facility (AXAF) now under study is to be a long-lived X-ray observatory in space. It is to be launched by the Space Shuttle, maintainable on-orbit, and retrievable for ground re-furbishment. The AXAF is conceived as an X-ray telescope with 6 nested grazing incidence X-ray mirrors (with a maximum aperture of 1.2 microns) and interchangeable and repleceable focal plane instruments. The optics will provide 0.5 arcsecond imagery over a several arcminute field and somewhat reduced resolution over 1 degree in the X-ray band from 0.1 to 10 keV (1.2 to 120 A). The characteristics and expected performance of the observatory are described.

Zombeck, M. V.↗
NASA NTRS1983

Astronomical observatories

The layout and equipment of astronomical observatories, the oldest scientific institutions of human society are discussed. The example of leading observatories of the USSR allows the reader to familiarize himself with both their modern counterparts, as well as the goals and problems on which astronomers are presently working.

Ponomarev, D. N.↗
NASA NTRS1983

The rings of Uranus - Occultation profiles from three observatories

Occultation profiles for the nine confirmed Uranian rings obtained from Las Campanas, the European Southern Observatory, and Cerro Tololo on 15-16 August 1980 are compared. The alpha ring shows a 'double-dip' structure; the eta ring shows a broad and narrow component (similar to Saturn's F ring); and the epsilon ring shows six features that appear in the data from all three observatories. Diffraction fringes appear at the edges of several of the occultation profiles.

Elias, J. H.↗
NASA NTRS1984

Performance data of US Naval Observatory VLG-11 hydrogen masers since September, 1983

In 1983, two VLC-11 masers were delivered to the U.S. Naval Observatory by the Smithsonian Astrophysical Observatory. Last year the short-term stability of these masers was reported and the effect of this short-term stability on timekeeping performance was examined. Since the date of installation, 13 September 1983, data on the masers' long-term performance have been accumulated. The Allan variance, agma(tau), of the relative frequency between the masers reaches a minimum of about 4 parts in 10 to the 16th power at averaging times 5,000 seconds and rises at longer averaging times due, at least partly, to systematic frequency drift. The systematic frequency drifts, expressed in units of fractional frequency difference per day are discussed.

Vessot, R. F. C.↗
NASA NTRS1984

Options for a new Arizona observatory - Configurations, costs and site

The process of creating a major observatory, with emphasis on the configurations, costs, and site involved, is examined. The premise that cost optimization starts with a modestly priced building block, such as a 7.5-m telescope, is considered. The telescope unit and the configurations in which it is used, ranging from a single telescope or a set of separate telescopes, to an MMT in which the light of all of the telescopes can be phased when desired, are described. It is shown that options exist for using elements in a nonredundant linear array or Michelson interferometer. A means of estimating costs of different facilities, all on the same basis, is provided. The importance of placing the observatory on a site, such as Mt. Graham in Arizona, which maximizes the output per unit cost of the facility is discussed.

Woolf, N. J.↗
NASA NTRS1985

International Ultraviolet Explorer Observatory operations

This volume contains the final report for the International Ultraviolet Explorer IUE Observatory Operations contract. The fundamental operational objective of the International Ultraviolet Explorer (IUE) program is to translate competitively selected observing programs into IUE observations, to reduce these observations into meaningful scientific data, and then to present these data to the Guest Observer in a form amenable to the pursuit of scientific research. The IUE Observatory is the key to this objective since it is the central control and support facility for all science operations functions within the IUE Project. In carrying out the operation of this facility, a number of complex functions were provided beginning with telescope scheduling and operation, proceeding to data processing, and ending with data distribution and scientific data analysis. In support of these critical-path functions, a number of other significant activities were also provided, including scientific instrument calibration, systems analysis, and software support. Routine activities have been summarized briefly whenever possible.

Source record↗
NASA NTRS1985

20-micron transparency and atmospheric water vapor at the Wyoming Infrared Observatory

The atmospheric transparency at 19.5 and 23 microns from the Wyoming Infrared Observatory over the past six years has been examined. It is found that the transparency is largely controlled by the season. Four months: June, July, August, and September have very poor 20-micron transparency. During the rest of the year the transparency is usually quite good at 19.5 microns and moderately good at 23 microns. Using rawinsonde data and theoretical calculations for the expected infrared transparency, the measures of 20-micron transparency were calibrated in terms of atmospheric water-vapor content. The water vapor over the Wyoming Infrared Observatory is found to compare favorably with that above other proposed or developed sites: Mauna Kea, Mount Graham, and Wheeler Peak.

Grasdalen, G. L.↗
NASA NTRS1985

The status of low-energy gamma-ray astronomy and the Gamma-Ray Observatory

A brief sketch of the objectives and status of the various subdisciplines in gamma-ray astronomy (below 10 GeV) are presented. The Gamma-Ray Observatory planned for launch in 1988 is described. This NASA observatory and several planned French-Soviet spacecraft are expected to elevate gamma-ray astronomy into a mature observational science for the Space Station era.

Fishman, G. J.↗