High Energy Astronomy Observatory 3
Encyclopedia
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
three High Energy Astronomy Observatories, HEAO 3 was launched 20 September 1979 on an Atlas-Centaur
Atlas-Centaur
The Atlas-Centaur was an American expendable launch system designed and built by General Dynamics Convair Division in San Diego, CA. It was derived from the SM-65 Atlas missile. It was a member of the Atlas family of rockets, and was used for 61 orbital launches between 1962 and 1983. It was...
launch vehicle, into a nearly circular, 43.6 degree inclination low-Earth orbit with an initial perigee of 486.4 km.
The normal operating mode was a continuous celestial scan, spinning approximately once every 20 min about the spacecraft z-axis, which was nominally pointed at the Sun.
Total mass of the observatory at launch was 2660 kilograms (5,864.3 lb).
HEAO 3 included three scientific instruments: the first a cryogenic high-resolution germanium gamma-ray spectrometer
Spectrometer
A spectrometer is an instrument used to measure properties of light over a specific portion of the electromagnetic spectrum, typically used in spectroscopic analysis to identify materials. The variable measured is most often the light's intensity but could also, for instance, be the polarization...
, and two devoted to cosmic-ray observations.
The scientific objectives of the mission's three experiments were:
to study intensity, spectrum, and time behavior of X-ray and gamma-ray sources between 0.06 and 10 MeV; measure isotropy of the diffuse X-ray and gamma-ray background; and perform an exploratory search for X-and gamma-ray line emissions;
to determine the isotopic composition of the most abundant components of the cosmic-ray flux with atomic mass
Atomic mass
The atomic mass is the mass of a specific isotope, most often expressed in unified atomic mass units. The atomic mass is the total mass of protons, neutrons and electrons in a single atom....
between 7 and 56, and the flux of each element with atomic number
Atomic number
In chemistry and physics, the atomic number is the number of protons found in the nucleus of an atom and therefore identical to the charge number of the nucleus. It is conventionally represented by the symbol Z. The atomic number uniquely identifies a chemical element...
(Z) between Z = 4 and Z = 50;
to search for super-heavy nuclei up to Z
Atomic number
In chemistry and physics, the atomic number is the number of protons found in the nucleus of an atom and therefore identical to the charge number of the nucleus. It is conventionally represented by the symbol Z. The atomic number uniquely identifies a chemical element...
= 120 and measure the composition of the nuclei with Z >20.
The Gamma-ray Line Spectrometer Experiment
The HEAO "C-1" instrument (as it was known before launch) was a sky-survey experiment, operating in the hard X-ray and low-energy gamma-ray bands.The gamma-ray spectrometer was especially designed to search for the 511 keV gamma-ray line produced by the annihilation
Annihilation
Annihilation is defined as "total destruction" or "complete obliteration" of an object; having its root in the Latin nihil . A literal translation is "to make into nothing"....
of positron
Positron
The positron or antielectron is the antiparticle or the antimatter counterpart of the electron. The positron has an electric charge of +1e, a spin of ½, and has the same mass as an electron...
s in stars, galaxies, and the interstellar medium
Interstellar medium
In astronomy, the interstellar medium is the matter that exists in the space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, dust, and cosmic rays. It fills interstellar space and blends smoothly into the surrounding intergalactic space...
(ISM), nuclear gamma-ray line emission expected from the interactions of cosmic ray
Cosmic ray
Cosmic rays are energetic charged subatomic particles, originating from outer space. They may produce secondary particles that penetrate the Earth's atmosphere and surface. The term ray is historical as cosmic rays were thought to be electromagnetic radiation...
s in the ISM, the radioactive products of cosmic nucleosynthesis
Nucleosynthesis
Nucleosynthesis is the process of creating new atomic nuclei from pre-existing nucleons . It is thought that the primordial nucleons themselves were formed from the quark–gluon plasma from the Big Bang as it cooled below two trillion degrees...
, and nuclear reactions due to low-energy cosmic rays.
In addition, careful study was made of the spectral and time variations of known hard X-ray sources.
The experimental package contained four cooled, p-type high-purity Ge
Germanium
Germanium is a chemical element with the symbol Ge and atomic number 32. It is a lustrous, hard, grayish-white metalloid in the carbon group, chemically similar to its group neighbors tin and silicon. The isolated element is a semiconductor, with an appearance most similar to elemental silicon....
gamma-ray detectors with a total volume of about 100 cm
, enclosed in a thick (6.6 cm average) caesiumCaesium
Caesium or cesium is the chemical element with the symbol Cs and atomic number 55. It is a soft, silvery-gold alkali metal with a melting point of 28 °C , which makes it one of only five elemental metals that are liquid at room temperature...
iodide (CsI) scintillation
Scintillation counter
A scintillation counter measures ionizing radiation. The sensor, called a scintillator, consists of a transparent crystal, usually phosphor, plastic , or organic liquid that fluoresces when struck by ionizing radiation. A sensitive photomultiplier tube measures the light from the crystal...
shield in active anti-coincidence to suppress extraneous background.
The experiment was capable of measuring gamma-ray energies falling within the energy interval from 0.045 to 10 MeV. The Ge detector system had an initial energy resolution better than 2.5 keV at 1.33 MeV and a line sensitivity from 1.E-4 to 1.E-5 photons/sq cm-s, depending on the energy. Key experimental parameters were (1) a geometry factor of 11.1 sq cm-sr, (2) effective area ~75 cm
at 100 keV, (3) a field of view of ~30 deg FWHMFull width at half maximum
Full width at half maximum is an expression of the extent of a function, given by the difference between the two extreme values of the independent variable at which the dependent variable is equal to half of its maximum value....
at 45 keV, and (4) a time resolution of less than 0.1 ms for the germanium detectors and 10 s for the CsI detectors. The gamma-ray spectrometer operated until 1 June 1980, when its cryogen was exhausted. The energy resolution of the Ge detectors was subject to degradation (roughly proportional to energy and time) due to radiation damage. The primary data are available at from the NASA HESARC and at JPL. They include instrument, orbit, and aspect data plus some spacecraft housekeeping information on 1600-bpi binary tapes. Some of this material has subsequently been archived on more modern media.
The experiment was proposed, developed, and managed by the Jet Propulsion Laboratory
Jet Propulsion Laboratory
Jet Propulsion Laboratory is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. The facility is headquartered in the city of Pasadena on the border of La Cañada Flintridge and Pasadena...
of the California Institute of Technology, under the direction of Dr. Allan S. Jacobson.
The Isotopic Composition of Primary Cosmic Rays Experiment
The HEAO C-2 experiment measured the relative composition of the isotopes of the primary cosmic rays between beryllium and iron (Z from 4 to 26) and the elemental abundances up to tin (Z=50). Cerenkov counters and hodoscopeHodoscope
A hodoscope is a type of detector used in particle physics which makes use of coincident detections to determine the trajectory of an energetic particle. Typically, a hodoscope consists of an array of sub-detectors which can each independently detect a particle passing through it...
s, together with the Earth's magnetic field, formed a spectrometer. They determined charge and mass of cosmic rays to a precision of 10% for the most abundant elements over the momentum range from 2 to 25 GeV/c (c=speed of light). Scientific direction was by Principal Investigators Prof. Bernard Peters and Dr. Lyoie Koch-Miramond. The primary data base has been archived at the Centre Etudes Nuclearires de Saclay and the Danish Space Research Institute. Information on the data products is given by Engelman et al. 1985.
The Heavy Nuclei Experiment
The purpose of the HEAO C-3 experiment was to measure the charge spectrum of cosmic-ray nuclei over the nuclear charge (Z) range from 17 to 120, in the energy interval 0.3 to 10 GeV/nucleon; to characterize cosmic ray sources; processes of nucleosynthesis, and propagation modes. The detector consisted of a double-ended instrument of upper and lower hodoscopes and three dual-gap ion chambers. The two ends were separated by a Cerenkov radiater. The geometrical factor was 4 sq cm-sr. The ion chambers could resolve charge to 0.24 charge units at low energy and 0.39 charge units at high energy and high Z. The Cerenkov counter could resolve 0.3 to 0.4 charge units. Binns et al. give more details.The experiment was proposed and managed by the Space Radiation Laboratory of the California Institute of Technology
California Institute of Technology
The California Institute of Technology is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering...
(Caltech), under the direction of Principal Investigator Prof. Edward C. Stone
Edward C. Stone
Edward Carroll Stone is a professor of physics at Caltech, space scientist, and former director of the NASA Jet Propulsion Laboratory .-Caltech:...
, Jr. of Caltech, and Dr. Martin H. Israel, and Dr. Cecil J. Waddington.
Project
The HEAO 3 Project was the final mission in the High Energy Astronomy ObservatoryHEAO Program
The High Energy Astronomy Observatory Program was a NASA program of the late 1970s and early 1980s that included a series of three large low-Earth-orbiting spacecraft for X-ray and Gamma-Ray astronomy and Cosmic-Ray investigations. After launch, they were denoted HEAO 1, HEAO 2 , and HEAO 3,...
series, which was managed by the NASA Marshall Space Flight Center
Marshall Space Flight Center
The George C. Marshall Space Flight Center is the U.S. government's civilian rocketry and spacecraft propulsion research center. The largest center of NASA, MSFC's first mission was developing the Saturn launch vehicles for the Apollo moon program...
(MSFC), where the Project Scientist was Dr. Thomas A. Parnell, and the Project Manager was Dr. John F. Stone. The prime contractor was TRW
TRW
TRW Inc. was an American corporation involved in a variety of businesses, mainly aerospace, automotive, and credit reporting. It was a pioneer in multiple fields including electronic components, integrated circuits, computers, software and systems engineering. TRW built many spacecraft,...
.
See also
- HEAO ProgramHEAO ProgramThe High Energy Astronomy Observatory Program was a NASA program of the late 1970s and early 1980s that included a series of three large low-Earth-orbiting spacecraft for X-ray and Gamma-Ray astronomy and Cosmic-Ray investigations. After launch, they were denoted HEAO 1, HEAO 2 , and HEAO 3,...
- High Energy Astronomy Observatory 1
- Einstein ObservatoryEinstein ObservatoryEinstein Observatory was the first fully imaging X-ray telescope put into space and the second of NASA's three High Energy Astrophysical Observatories...
(HEAO 2)