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A summary of the Phase A of the High Energy Astronomy Observatory Mission-C (HEAO-C) is presented. The mission, baseline experiments, observatory design, and spacecraft subsystems are described, and the principal mission considerations are discussed. A summary is included of the general recommendations.
The Michigan Airglow Observatory (MAO) was located at Ester Dome Observatory, College, Alaska (latitude: 64 deg 53'N, longitude: 148 deg 03'W) since October, 1971. The MAO houses a 6-inch Fabry-Perot interferometer, a 2-channel monitoring photometer and a 4-channel tilting filter photometer. The Fabry-Perot interferometer was used extensively during the winter observing seasons of 1971-72 and 1972-73 to measure temperature and mass motions of the neutral atmosphere above approximately 90 kilometers altitude. Neutral wind data from the 1971-72 observing season as measured by observing the Doppler shift of the gamma 6300 A atomic oxygen emission line are presented.
This document is a compilation of the weather data collected at the Mt. Hopkins Observatory in southern Arizona from 1968 to 1971. It is the second meteorological report aimed at assisting scientists in the scheduling of experiments at the Observatory site.
System definition studies were conducted of the Earth Observatory Satellite (EOS). The studies show that the concept of an Earth Observatory Satellite in a near-earth, sun-synchronous orbit would make a unique contribution to the goals of a coordinated program for acquisition of data for environmental research with applications to earth resource inventory and management. The technical details for the proposed development of sensors, spacecraft, and a ground data processing system are presented.
The University of Hawaii's Institute for Astronomy is currently constructing a lunar laser ranging observatory at the 3050-meter summit of Mt. Haleakala, Hawaii. The Nd YAG laser system to be employed provides three pulses per second, each pulse being approximately 200 picoseconds in duration. The energy contained in one pulse at 5320 A lies in the range from 250 to 350 millijoules. Details of observatory construction are provided together with transmitter design data and information concerning the lunastat, the feed telescope, the relative pointing system, the receiver, and the event timer system.
Of the three observatories planned in NASA's OAO program, one, OAO-3, is still in orbit and producing scientifically useful data. The prime experiment is the Princeton telescope spectrometer. Following a brief history of the OAO program, a description is given of the Princeton telescope with its 80-cm primary mirror, and of the spectrometer, which yields a resolution of up to 0.05 A. The spacecraft guidance system is also described. This system initially points the observatory to within a few arc minutes of the target, places the 0.3-arc sec slit on the star in less than 3 minutes, and holds on the star for up to 50 minutes with errors less than 0.05 arc sec. The main scientific results are described under the following categories: (1) the widespread presence of molecular hydrogen; (2) the search for other molecules, including detection of CO; (3) the nature of the interstellar medium as inferred from the detection of various atomic lines; (4) the study of chromospheres in late type stars; and (5) the study of mass loss in binaries and single stars.
The results of design/cost tradeoff studies conducted during the Earth Observatory Satellite system definition studies are presented. The studies are concerned with the definition of a basic modular spacecraft capable of supporting a variety of operational and/or research and development missions, with the deployment either by conventional launch vehicles or by means of the space shuttle. The three levels investigated during the study are: (1) subsystem tradeoffs, (2) spacecraft tradeoffs, and (3) system tradeoffs. The range of requirements which the modular concept must span is discussed. The mechanical, thermal, power, data and electromagnetic compatibility aspects of modularity are analyzed. Other data are provided for the observatory design concept, the payloads, integration and test, the ground support equipment, and ground data management systems.
Attitude reference systems for use with the Earth Observatory Satellite (EOS) are described. The systems considered are fixed and gimbaled star trackers, star mappers, and digital sun sensors. Covariance analyses were performed to determine performance for the most promising candidate in low altitude and synchronous orbits. The performance of attitude estimators that employ gyroscopes which are periodically updated by a star sensor is established by a single axis covariance analysis. The other systems considered are: (1) the propulsion system design, (2) electric power and electrical integration, (3) thermal control, (4) ground data processing, and (5) the test plan and cost reduction aspects of observatory integration and test.
A system baseline design oriented to the requirements of the next generation of Earth Observatory Satellite missions is presented. The first mission (EOS-A) is envisioned as a two-fold mission which (1) provides a continuum of data of the type being supplied by ERTS for the emerging operational applications and also (2) expands the research and development activities for future instrumentation and analysis techniques. The baseline system specifically satisfies the requirements of this first mission. However, EOS-A is expected to be the first of a series of earth observation missions. Thus the baseline design has been developed so as to accommodate these latter missions effectively as the transition is made from conventional, expendable launch vehicles and spacecraft to the Shuttle Space Transportation System era. Further, a subset of alternative missions requirements including Seasat, SEOS, SMM and MSS-5 have been analyzed to verify that the spacecraft design to serve a multi-mission role is economically sound. A key feature of the baseline system design is the concept of a modular observatory system whose elements are compatible with varying levels of launch vehicle capability. The design configuration can be used with either the Delta or Titan launch vehicles and will adapt readily to the space shuttle when that system becomes available in the early 1980's.
The design concept and operational aspects of the Earth Observatory Satellite (EOS) are presented. A table of the planned EOS missions is included to show the purpose of the mission, the instruments involved, and the launch date. The subjects considered in the analysis of the EOS development are: (1) system requirements, (2) design/cost trade methodology, (3) observatory design alternatives, (4) the data management system, (5) the design evaluation and preferred approach, (6) program cost compilation, (7) follow-on mission accommodation, and (8) space shuttle interfaces and utilization. Illustrations and block diagrams of the spacecraft configurations are provided.
An analysis of the systems involved in the operation and support of the Earth Observatory Satellite (EOS) is presented. Among the systems considered are the following: (1) the data management system, (2) observatory to primary ground station communications links, (3) local user system, (4) techniques for recognizing ground control points, (5) the central data processing-implementation concept, and (6) program effectiveness analysis.
A new observatory for meteor research which provides data for study of meteor heights, velocities, orbits, and meteoroid abundances is described. The observing equipment is automated to take advantage of the long periods of favorable observing weather common to the region. Four K-24 cameras, electrically operated, provide the triangulation observations, and four Maksutov f/1.3 cameras with blazed transmission grating provide spectral coverage. The patrol cameras have operated for a year and a half, and approximately 6,000 frames have been exposed by 9 March 1975. Meteor trails appear on 260 of these frames. Sixty-eight trails are of meteors photographed from two locations and thus allow trajectory and orbit determinations for 34 meteors. Photoelectric sensors initiate the 2-second spectrograph exposures, and electrical controls open and close the observatory at present times.
An overview is presented of the equipment and data acquisition procedures at La Posta Astrogeophysical Observatory, located in the mountains, east of San Diego, Calif. It is a solar observatory, focusing on solar flares and the effect of solar activity on earth. It makes daily radio and optical observations of solar activity. Radio transmission in the earth atmosphere is monitored with VLF and HF equipment. A magnetometer monitors the state of the geomagnetic field.
Observatory power is generated by a partially deployable solar array which is modularized to facilitate adaptation to three missions having different power requirements. Three nickel-cadmium batteries are controlled independently from dedicated modular chargers to increase subsystem adaptability and decrease sensitivity to temperature differences between batteries. Battery level redundancy is employed, enabling mission completion with two of three battery/charger combinations operational. Bus voltage limiting is accomplished by a modularized shunt regulator which can survive any single part failure and meet all mission requirements. Relatively low shunt electronics power dissipation internal to the observatory is achieved by sequenced operation of linear shunt segments which are coupled to a large area resistive shunt radiator. Summaries of solar array, battery and subsystem breadboard test results are provided.
Measurements of characteristic speckle change times are presented for stars observed with an image-sharpening telescope installed and operated on equatorial mounts at Leuschner Observatory in Lafayette, California, and Lick Observatory at Mount Hamilton, California. Despite the short speckle change times encountered, it was possible to record dramatically improved stellar images on nights when the speckles changes relatively slowly. Sharpened images of Sirius and Arcturus are discussed.
The statistics associated with the successful selection and acquisition of guide stars as attitude benchmarks for use in reorientation maneuvers of the HEAO-B observatory are considered as a function of the maneuver angle, initial attitude uncertainties, and the pertinent celestial region. Success likelihoods in excess of 0.99 are predicted assuming anticipated gyro and star tracker error sources. The maneuver technique and guide star selection constraints are described in detail. The results presented are specialized numerically to the HEAO-B observatory. However, the analytical techniques developed are considered applicable to broader classes of spacecraft requiring celestial targeting.
Based on Spacelab/Shuttle missions plans for a permanently manned Solar Terrestrial Observatory are outlined for low earth orbit, whose primary function will be to measure sun-induced phenomena on earth, e.g., atmospheric and magnetospheric dynamics. Attention is given to the study of magnetospheric storms, and their interaction with the lower atmosphere. Eventually, a geosynchronous solar observatory is foreseen, which will be able to measure atmospheric changes continuously, uninterrupted by breaks caused by a 90 minute orbital period.
A convenient guide to the expected characteristics of the Space Telescope Observatory for astronomers and physicists is presented. An attempt is made to provide enough detail so that a professional scientist, observer or theorist, can plan how the observatory may be used to further his observing programs or to test theoretical models.