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Charge-coupled devices (CCDs) have now flown successfully in a number of space scientific and engineering instruments, and have rapidly become the preferred technology for most imaging applications. One of their earliest planned applications in space was in the precision (subarcsecond) star tracker for the Astro series of UV missions.
This paper describes the design and performance of the Astro Integrated Radiator System (IRS). The system was recently ground tested and proven successful in rejecting approximately 400 watts of heat. The radiator was constructed from an aluminum panel configured to form two orthogonal planes. Heat pipes were adhesively bonded and riveted to the radiator to isothermalize the surface. The IRS was subjected to a full thermal vacuum test to validate the thermal math model and to qualify the radiator for space flight. The thermal performance met prescribed temperature limits with margins at both extremes, and no mechanical failures occurred.
This report presents the mathematical technique for calculating the amount of time that an astronomical object, e.g., a star, can be observed from a satellite in near Earth orbit. This includes the places and times in the orbit where the object is acquired and where it is lost. Constraints placed on the observation of the object, such as the line-of-sight from observer to the target must not come within less than some specified angle to the limb of the Earth, are included in the calculations. The equations developed within the report are then used for a detailed analysis of the observation possibilities for objects at any place on the celestial sphere for a typical Spacelab ASTRO mission. The results, presented in graphic form, are suitable for use in pre-mission planning and also for use in real-time replanning.
This report describes how guide stars are selected for the Optical Sensor Package (OSP) for the Instrument Pointing System (IPS) when it is operating in the stellar mode on the ASTRO missions. It also describes how the objective loads are written and how the various roll angles are related; i.e., the celestial roll or position angle, the objective load roll angles, and the IPS gimbal angles. There is a brief description of how the IPS operates and its various modes of operation; i.e., IDOP, IDIN, and OSPCAL.
A teacher's guide that concentrates on the electromagnetic spectrum is presented. The subject was chosen because it is part of the middle school curriculum and because an understanding of the different ranges of energy is crucial to an understanding of the high energy astronomy performed by the Astro-1 telescopes to be carried on the Space Shuttle's first astrophysics mission. Various learning activities are outlined.
NASA has recently completed a shuttle-borne stellar ultraviolet astronomy mission known as Astro-1. A three axis instrument pointing system (IPS) was employed to accurately point the science instruments. In order to analyze the pointing control system and verify pointing performance, a simulation of the IPS was developed using the multibody dynamics software TREETOPS. The TREETOPS IPS simulation is capable of accurately modeling the multibody IPS system undergoing large angle, nonlinear motion. The simulation is documented and example cases are presented demonstrating disturbance rejection, fine pointing operations, and multiple target pointing and slewing of the IPS.
ASTRO-D, which is to be launched by a MU-3II vehicle, is a scientific Earth orbiting satellite of the Institute of Space and Astronomical Science (ISAS) of Japan. It will be launched in Uchinoura, Kagoshima Prefecture, Japan. The Deep Space Network will support 4 to 8 contacts per day, depending on the launch and early orbit phase (LEOP) and mission phase, providing only downlink telemetry recording to all stations. Data is given in tabular form for network support, frequency assignments, telemetry, command, and tracking support responsibility.
The Hopkins Ultraviolet Telescope (HUT), flown aboard the Space Shuttle Columbia in the Astro-1 mission, provided the first spectrophotometry in the sub Kyman alpha region for many astronomical sources. Observations of 77 sources were made throughout the far ultraviolet (912 to 1850 A, delta lambda approximately 3 A), and for a few objects in the extreme ultraviolet (415 to 912 A, delta lambda approximately 1.5 A). Among the objects observed were quasars, galaxy clusters, active and normal galaxies, cataclysmic variables, globular clusters, supernova remnants, planetary nebulae, and white dwarfs.
The Ultraviolet Imaging Telescope (UIT), part of the Astro-1 Spacelab Mission, was used to obtain high-resolution surface brightness distribution data in six ultraviolet wavelength bands for the bright reflection nebula NGC 7023. The corresponding data from the visible leads us to conclude that the scattering in the near and far ultraviolet in this nebula is more strongly forward directed than it is in the visible. The UIT also obtained near-UV and far-UV images of the giant OB association NGC 206 in M32. Photometry was obtained for thirty massive stars. We analyzed UV imagery of two Sb bulges and two E galaxies obtained with UIT. For NGC 1275, the measured UV colors indicate a mass function which extends to eight solar masses but no higher. Other aspects of this investigation are discussed.
We present the results from images taken from the region of the light echoes around SN 1987A, as acquired on the first flight of the Astro-1 Ultraviolet Imaging Telescope (UIT). They indicate a weighted-average UV echo surface brightness of about 3 x 10 exp -18 ergs/s sq cm A sq arcsec. This is consistent with earlier results obtained by the IUE when scaled by the optical surface brightness of the two different echoes observed. These results indicate that the UV flux emitted by shock from core collapse penetrating the stellar surface cannot be as strong as that predicted by a large class of theoretical models (cited herein), or that previous results on the optical scattering of echoing dust do not apply to these clouds. Prospects for a more accurate measurements once the echoes have propagated to other regions and a background measurements can be obtained with UIT are discussed. They indicate that a more accurate determination of the above results is probable with another epoch of UIT observations.
The Astro-1 mission obtained observations related to a wide variety of current problems in astronomy during a 9-day flight of the space shuttle Columbia. Early results from one of the instruments, the Hopkins Ultraviolet Telescope, are reviewed here. Among these are new insights concerning the origin of the ultraviolet light from the old stellar population in elliptical galaxies, new evidence for a hot, gaseous corona surrounding the Milky Way, improved views of the physical conditions in active galactic nuclei, and a measurement of the ionization state of the local interstellar medium.
This video explains the ASTRO 1 observatory and its ten day mission aboard SpaceLab on NASA's Space Shuttle, which Marshall Space Flight Center (MSFC) and Goddard Space Flight Center (GSFC) astronomers will use to study distant stars, supernovae, and black holes. The observatory contains ultraviolet and x ray telescopes that will capture images earth-bound observatories can't, due to interference from the earth's atmosphere. The video contains footage of the instrument being loaded on the shuttle, animations of anticipated images to be captured, and scenes of the SpaceLab Control Center at MSFC.
Simultaneous UV and optical observations of the Seyfert galaxy Markarian 335 (z = 0.026) during the Astro-1 mission yield a spectrum spanning the wavelength range of 912-8410 A. In the sub-Ly alpha region a prominent blended emission feature of O VI lambda lambda 1032, 1038, and Ly beta is nearly as strong as C IV wavelength 1549. The continuum flux extends beyond the redshifted Luman limit without a noticeable discontinuity, but a siginificant change in slope exists near the redhsifted Lyman edge. We suggest that such a change may be the signature of a Lyman edge in an accretion disk seen at a small inclination angle. Using a disk model including such an edge, we fit the spectrum with a central black hole mass of 5 x 10(exp 7) solar mass, an accretion rate of 0.07 solar mass/yr, and an optical depth at the Lyman edge of 0.4. To account for the strong O VI emission as well as the soft X-ray excess, we consider the effects of Comptonization on the disk spectrum, which can produce a high-energy tail for the UV bump and also smooth the Lyman edge feature.
The Graphical Observation Scheduling System (GROSS) and its functionality and editing capabilities are reported on. The GROSS system was developed as a replacement for a suite of existing programs and associated processes with the aim of: providing a software tool that combines the functionality of several of the existing programs, and provides a Graphical User Interface (GUI) that gives greater data visibility and editing capabilities. It is considered that the improved editing capability provided by this approach enhanced the efficiency of the second astronomical Spacelab mission's (ASTRO-2) mission planning.
We describe the signal processing system of the Astro-E XRS Instrument. The Calorimeter Analog Processor (CAP) provides bias and power for the detectors and amplifies the detector signals by a factor of 20,000. The Calorimeter Digital Processor (CDP) performs the digital processing of the calorimeter signals, detecting X-ray pulses and analyzing them by optimal filtering. We describe the operation of pulse detection, pulse height analysis, and risetime determination. We also discuss performance, including the three event grades (hi-res, mid-res, and low-res), anticoincidence detection, counting rate dependence, and noise rejection.
XRS is the microcalorimeter X-ray detector aboard the US-Japanese ASTRO-E observatory, which is scheduled to be launched in early 2000. XRS is a high resolution spectrometer- with less than 9 eV resolution at 3 keV and better than 14 eV resolution over its bandpass ranging from about 0.3 keV to 15 keV. Here we present the results of our first calibration of the XRS instrument. We describe the methods used to extract detailed information about the detection efficiency and spectral redistribution of the instrument. We also present comparisons of simulations and real data to test our detector models.
The Astro-E High Resolution X-ray Spectrometer (XRS) was developed jointly by the NASA/Goddard Space Flight Center and the Institute of Space and Astronautical Science in Japan. The instrument is based on a new approach to spectroscopy, the X-ray microcalorimeter. This device senses the energies of individual X-ray photons as heat with extreme precision. A 32 channel array of microcalorimeters is being employed, each with an energy resolution of about 12 eV at 6 keV (the Fe-K region). This will provide spectral resolving power 10 times higher than any other non-dispersive X-ray spectrometer. The instrument incorporates a three stage cooling system capable of operating the array at 60 mK for about two years in orbit. The array sits at the focus of a grazing incidence conical mirror. The quantum efficiency of the microcalorimeters and the reflectivity of the X-ray mirror system combine to give high throughput over the 0.3-12 keV energy band. This new capability will enable the study of a wide range of high-energy astrophysical sources with unprecedented spectral sensitivity. This paper presents the basic design requirements and implementation of the XRS, and also describes the instrument parameters and performance.
We describe the transmission calibration of the Astro-E XRS blocking filters. The XRS instrument has five aluminized polyimide blocking filters. These filters are located at thermal stages ranging from 200 K to 60 mK. They are each about 1000 A thick. XRS will have high energy resolution which will enable it to see some of the extended fine structure around the oxygen and aluminum K edges of these filters. Thus, we are conducting a high spectral resolution calibration of the filters near these energies to resolve out extended flue structure and absorption lines.