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NASA NTRS1977

An infrared foreoptics adaptor for the Learjet Telescope

A foreoptics adapter has been built for the Learjet telescope which permits simultaneous viewing of the visible star field in the image plane and acquisition of astronomical data at infrared wavelengths (less than 1 micrometer). The device uses an adjustable dichroic beamsplitter to transmit visible wavelengths to an eyepiece (or television camera), and to reflect infrared wavelengths to a port where an infrared detector system can be mounted. The instrument is intended as a multiple user facility for the Learjet telescope. This report describes the adapter and its use.

Erickson, E. F.↗

NASA NTRS1976

A computer-aided telescope pointing system utilizing a video star tracker

The Video Inertial Pointing (VIP) System is being developed to satisfy the acquisition and pointing requirements of astronomical telescopes. VIP employs a single video sensor to generate three-axis pointing error signals and to provide inputs for a cathode ray tube (CRT) display of the star field. The pointing error signals update the telescope's gyro stabilization system. The CRT display facilitates target acquisition and positioning of the telescope by a remote operator. The present paper describes the analysis, simulation, and hardware development of a prototype, advanced VIP system. An early model of the system utilizing a silicon-intensified target vidicon camera has flown on a balloon-borne telescope and is briefly described. The advanced system, which can employ either a vidicon camera or a charge-coupled device video sensor, has been tested using an analog/digital hybrid simulation. The advanced VIP hardware is described, and the simulation results presented.

Lorell, K. R.↗

NASA NTRS1978

A study of the IC 5146 dark cloud complex

The IC 5146 dark cloud complex has been studied in the infrared in order to identify and study associated young stellar objects. Most of the objects detected in the survey appear to be field stars, predominantly late-type giants. Three young objects were detected in the survey: the B0 star BD +46 deg 3474, the Ae star BD +46 deg 3471, and a previously unidentified object which appears to be a heavily obscured FU Orionis star. The properties of the last two objects are examined in detail, and an attempt is made to produce reasonable models for them. It is suggested that FU Orionis stars are binaries, and some consequences of this model are described. Photometry of the brighter stars in the IC 5146 cluster has been used to establish a distance to the cluster of 900 + or - 100 pc.

Elias, J. H.↗

NASA NTRS1979

Control networks for the Galilean satellites, November 1979

Pictures of the four Galilean satellites taken as the two Voyager spacecraft approached Jupiter during March and July 1979 are presented. Control nets of the Galilean satellites, computed photogrammetrically, and measurements of the mean radii are presented. The pictures in the control nets are identified, the coordinates of the control points are given, and identifications of some of the control points are shown on figures. The use of star field pictures to compute the focal lengths of the camera is discussed and the geometric relationship between the narrow and wide and angle cameras is reported. A description of the coordinate systems of the Galilean satellites is presented and the status of the control net computations is reported.

Davies, M. E.↗

NASA NTRS1981

Convective dynamos for rotating stars

Global dynamo theory is applied to the problem of why some stars have field reversing dynamos, and others do not. It is argued that convectively driven dynamos are the most likely source of magnetic fields in stars that have convection zones.

Gilman, P. A.↗

NASA NTRS1982

The relationship between carbon monoxide abundance and visual extinction in interstellar clouds

Carbon monoxide column densities are compared to visual extinctions toward field stars in the rho Oph and Taurus molecular cloud complexes. The relationship of C(0-18) column density to extinction is established, and new determinations for (C-13)O column densities are given for a range of visual extinctions extended to beyond 20 mag. A prescription for determining hydrogen column densities and masses of molecular clouds from observations of CO isotopes is presented and discussed critically. These measurements agree well with the predictions of gas phase chemistry models which include chemical fractionation and selective isotopic photodestruction. The functional dependence of the C(O-18) column density on extinction is characterized by two different regimes separated by a distinct transition observed to occur at 4 mag in both molecular cloud complexes, whereas the functional dependence of (C-13)O is quite different in the two regions. Some saturation is found to occur for C(O-18) emission at high visual extinction and use the rarer isotopic species C(O-17) and (C-13)(O-18) to correct for it.

Frerking, M. A.↗

NASA NTRS1984

Ultraviolet and optical observations of metal deficient red giants and chromospheric models

Three metal deficient field stars were observed in the ultraviolet and optical spectral regions: HD 165195, HD 110281, and HD 232078. High dispersion spectra near H alpha, and low dispersion, long wavelength IUE spectra were obtained. The H alpha profiles have strong asymmetric emission with absorption cores that are frequently asymmetric. The surface flux of Mg II lines is similar to that of luminous Pop I stars in spite of the lower metal abundance. Semi-empirical atmospheric models suggest that the characteristic emission in the wings of the H alpha line can arise within static chromospheres. Radial expansion gives an asymmetric, blue-shifted H alpha core accompanied by greater emission in the red line wing than the blue wing. Wind models with extended atmospheres suggest mass loss rates - 2 billion M/yr. Thus H alpha provides no evidence that steady mass loss is substantial enough to significantly affect the evolution of stars on the red giant branch of globular clusters.

Duprele, A. K.↗

NASA NTRS1984

High-sensitivity IRAS observations of the Chamaeleon I dark cloud

Very sensitive IRAS observations of a region of 0.8 sq deg in the Chamaeleon I cloud have revealed 70 compact sources. Hot sources are field stars; warm sources are associated with pre-main-sequence (PMS) stars in the cloud center; others may be in an even earlier phase of gravitational collapse. Cool sources, detected only at the long wavelengths, surround the main cloud and appear to be associated with small globules. Only a small fraction (less than 20 percent) of the total luminosity of the known PMS objects is emitted in the IRAS bands. This has important implications for the classification of the newly discovered embedded objects.

Baud, B.↗

NASA NTRS1985

Hydrogen-like atoms on the surface of neutron stars - Intense magnetic field effects

It is known that very strong (greater than 1-TG) magnetic fields exist on the surface of some neutron stars. The properties of atoms in fields of this nature are considerably different from those of atoms in field-free regions. Because of the mixing of spherical and cylindrical symmetries, the analytical solution to the problem of a hydrogen atom in a uniform magnetic field is impossible to obtain. In this work, a variational wave function is used to describe the properties of hydrogen like atoms in intense magnetic fields including first-order relativistic effects. Special attention is given to the transition matrix elements for the 2p(0) - 1s(0) transition in Fe XXVI.

Williams, A. C.↗

NASA NTRS1985

The optical polarization of Epsilon Aurigae through the 1982-84 eclipse

About 350 nights observations on the 61-cm telescope at Pine Mt. Observatory were made of the variable polarization of Eps. Aurigae during 1982-85, in the U, B, and V color bands. The V data are the most complete and are shown. In terms of the overall features the curves in all three colors are quite similar. The typical errors per nightly point in the V curves are about 0.015% for either of the two normalized, equatorial Stokes parameters Q and U. Note that there is a large background or constant component of some 2.5%, position angle around 135 deg. This is presumably largely interstellar, and the intrinsic polarization probably does not much exceed the amplitude of the variable component, approx. 0.5%. A few field-star polarizations were measured but a very clear pattern was not obtained in this part of the sky.

Kemp, J. C.↗

NASA NTRS1986

A densitometric analysis of IIaO film flown aboard the space shuttle transportation system STS-3, STS-8, and STS-7

Three canisters of IIaO film were prepared along with packets of color film from the National Geographic Society, which were then placed on the Space Shuttle #3. The ultimate goal was to obtain reasonably accurate data concerning the background fogging effects on IIaO film as it relates to the film's total environmental experience. This includes: the ground based packing, and loading of the film from Goddard Space Flight Center to Cape Kennedy; the effects of the solar wind, humidity, and cosmic rays; the Van Allen Belt radiation exposure; various thermal effect; reentry and off-loading of the film during take off, and 8 day, 3 hour 15 minutes orbits. The total densitometric change caused by all of the above factors were examined. The results of these studies have implications for the utilization of IIaO spectroscopic film on the future shuttle and space lab missions. These responses to standard photonic energy sources will have immediate application for the uneven responses of the film photographing a star field in a terrestrial or extraterrestrial environment with associated digital imaging equipment.

Hammond, E. C., Jr.↗

NASA NTRS1985

The Orbiter camera payload system's large-format camera and attitude reference system

The Orbiter camera payload system (OCPS) is an integrated photographic system carried into earth orbit as a payload in the Space Transportation System (STS) Orbiter vehicle's cargo bay. The major component of the OCPS is a large-format camera (LFC), a precision wide-angle cartographic instrument capable of producing high-resolution stereophotography of great geometric fidelity in multiple base-to-height ratios. A secondary and supporting system to the LFC is the attitude reference system (ARS), a dual-lens stellar camera array (SCA) and camera support structure. The SCA is a 70 mm film system that is rigidly mounted to the LFC lens support structure and, through the simultaneous acquisition of two star fields with each earth viewing LFC frame, makes it possible to precisely determine the pointing of the LFC optical axis with reference to the earth nadir point. Other components complete the current OCPS configuration as a high-precision cartographic data acquisition system. The primary design objective for the OCPS was to maximize system performance characteristics while maintaining a high level of reliability compatible with rocket launch conditions and the on-orbit environment. The full OCPS configuration was launched on a highly successful maiden voyage aboard the STS Orbiter vehicle Challenger on Oct. 5, 1984, as a major payload aboard the STS-41G mission.

Schardt, B. B.↗

NASA NTRS1985

Active-region plages and the Hyades anomaly?

The Hyades are known to differ in their photometric properties (Crawford 1969; Campbell 1984) and spectral properties (Rose 1984) from field stars of similar metal abundance. Using spectra of solar plages, it is demonstrated that the Hyades spectral anomalies are caused by excess emission from magnetic regions (plages) on the surfaces of these cluster stars. It is further speculated that the Hyades photometric anomalies arise from the same cause, but photometric data on solar plages necessary to resolve this issue are not available. The Pleiades stars and a few extreme emission stars show similar spectral anomalies, but of such magnitude to indicate that plages on Pleiades stars have higher surface brightnesses than on the sun and do not merely cover a larger fraction of the stars.

Labonte, B. J.↗

NASA NTRS1987

The calibration of photographic and spectroscopic films. A densitometric analysis of IIaO film flown aboard the space shuttle transportation system STS3, STS8, and STS7

The results of these studies have implications for the utilization of the IIaO spectroscopic film on the future shuttle and space lab missions. These responses to standard photonic energy sources will have immediate application for the uneven responses of the film photographing a star field in a terrestrial or extraterrestrial environment with associated digital imaging equipment.

Hammond, Ernest C., Jr.↗

NASA NTRS1986

Design and development of a Space Station proximity operations research and development mockup

Proximity operations (Prox-Ops) on-orbit refers to all activities taking place within one km of the Space Station. Designing a Prox-Ops control station calls for a comprehensive systems approach which takes into account structural constraints, orbital dynamics including approach/departure flight paths, myriad human factors and other topics. This paper describes a reconfigurable full-scale mock-up of a Prox-Ops station constructed at Ames incorporating an array of windows (with dynamic star field, target vehicle(s), and head-up symbology), head-down perspective display of manned and unmanned vehicles, voice- actuated 'electronic checklist', computer-generated voice system, expert system (to help diagnose subsystem malfunctions), and other displays and controls. The facility is used for demonstrations of selected Prox-Ops approach scenarios, human factors research (work-load assessment, determining external vision envelope requirements, head-down and head-up symbology design, voice synthesis and recognition research, etc.) and development of engineering design guidelines for future module interiors.

Haines, Richard F.↗

NASA NTRS1988

Compact radio sources in the galactic plane

The preliminary results of a search for infrared counterparts to compact continuum radio sources found within 0.5 deg of the Galactic plane are presented. Out of 75 positions searched, nine very red sources, each with a probability of less than 0.01 of being a random field star, were found. Most of the nine sources are characterized by deep silicate absorption features at 10 microns and a red energy distribution that continues to rise beyond 25 microns. Six of the sources are best explained as late O or early B stars exciting a compact H II region. The radio emission is close to that expected for the rate of emission of ionizing photons for a normal main-sequence star. Although these H II regions are compact, they are not sufficiently dusty in the immediate environment of the star to significantly reduce the ionizing flux. Three of the sources show considerably more emission than expected for a main-sequence star, indicating they are either hotter than a main-sequence star with the same luminosity or the radio emision is nonthermal and coming from a more exotic object.

Jones, Terry Jay↗

NASA NTRS1989

The properties of the disk system of globular clusters

A large refined data sample is used to study the properties and origin of the disk system of globular clusters. A scale height for the disk cluster system of 800-1500 pc is found which is consistent with scale-height determinations for samples of field stars identified with the Galactic thick disk. A rotational velocity of 193 + or - 29 km/s and a line-of-sight velocity dispersion of 59 + or - 14 km/s have been found for the metal-rich clusters.

Armandroff, Taft E.↗

NASA NTRS1988

Three-meter balloon-borne telescope

The Three-Meter Balloon-Borne Telescope is planned as a general purpose facility for making far-infrared and submillimeter astronomical observations from the stratosphere. It will operate throughout the spectral range 30 microns to 1 millimeter which is largely obscurred from the ground. The design is an f/13.5 Cassegrain telescope with an f/1.33 3-meter primary mirror supported with a 3-axis gimbal and stabilization system. The overall structure is 8.0 m high by 5.5 m in width by 4.0 m in depth and weighs 2000 kg. This low weight is achieved through the use of an ultra lightweight primary mirror of composite construction. Pointing and stabilization are achieved with television monitoring of the star field, flex-pivot bearing supports, gyroscopes, and magnetically levitated reaction wheels. Two instruments will be carried on each flight; generally a photometric camera and a spectrometer. A 64-element bolometer array photometric camera operating from 30 to 300 microns is planned as part of the facility. Additional instruments will be derived from KAO and other development programs.

Hoffmann, William F.↗