astronomy

High Energy Astronomy Observatory 1

High Energy Astronomy Observatory 1 is a astronomy topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand High Energy Astronomy Observatory 1 rather than just read about it. In short: HEAO-1 was an X-ray telescope launched in 1977. HEAO-1 surveyed the sky in the X-ray portion of the electromagnetic spectrum (0.2 keV – 10 MeV), providing nearly constant monitoring of X-ray sources near the ecliptic poles and more detailed studies of a number of objects by observations lasting 3–6 hours.

Key takeaways

High Energy Astronomy Observatory 1 belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect High Energy Astronomy Observatory 1 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of High Energy Astronomy Observatory 1 from memory before moving on to harder problems.

Reference excerpt

HEAO-1 was an X-ray telescope launched in 1977. HEAO-1 surveyed the sky in the X-ray portion of the electromagnetic spectrum (0.2 keV – 10 MeV), providing nearly constant monitoring of X-ray sources near the ecliptic poles and more detailed studies of a number of objects by observations lasting 3–6 hours. It was the first of NASA's three High Energy Astronomy Observatories, launched on August 12, 1977 aboard an Atlas rocket with a Centaur upper stage, operated until 9 January 1979. During that time, it scanned the X-ray sky almost three times HEAO included four X-ray and gamma-ray astronomy instruments, known as A1, A2, A3, and A4, respectively (before launch, HEAO 1 was known as HEAO A). The orbital inclination was about 22.7 degrees. HEAO 1 re-entered the Earth's atmosphere on 15 March 1979.

A1: Large-Area Sky Survey instrument

The A1, or Large-Area Sky Survey (LASS) instrument, covered the 0.25–25 keV energy range, using seven large proportional counters. It was designed, operated, and managed at the Naval Research Laboratory (NRL) under the direction of Principal Investigator Dr. Herbert D. Friedman, and the prime contractor was TRW. The HEAO A-1 X-Ray Source Catalog included 842 discrete X-ray sources.

A2: Cosmic X-ray Experiment

The A2, or Cosmic X-ray Experiment (CXE), from the Goddard Space Flight Center, covered the 2–60 keV energy range with high spatial and spectral resolution. The Principal Investigators were Dr. Elihu A. Boldt and Dr. Gordon P. Garmire.

A3: Modulation Collimator instrument The A3, or Modulation Collimator (MC) instrument, provided high-precision positions of X-ray sources, accurate enough to permit follow-up observations to identify optical and radio counterparts. It was provided by the Center for Astrophysics (Smithsonian Astrophysical Observatory and the Harvard College Observatory, SAO/HCO). Principal Investigators were Dr. Daniel A. Schwartz of SAO and Dr. Hale V. Bradt of MIT.

A4: Hard X-Ray / Low-Energy Gamma-ray experiment

The A4, or Hard X-ray / Low Energy Gamma-ray Experiment, used sodium iodide (NaI) scintillation counters to cover the energy range from about 20 keV to 10 MeV. It consisted of seven clustered modules, of three distinct designs, in a roughly hexagonal array. Each detector was actively shielded by surrounding CsI scintillators, in active-anti-coincidence, so that an extraneous particle or gamma-ray event from the side or rear would be vetoed electronically, and rejected. (It was discovered in early balloon flight by experimenters in the 1960s that passive collimators or shields, made of materials such as lead, actually increase the undesired background rate, due to the intense showers of secondary particles and photons produced by the extremely high energy (GeV) particles characteristic of the space radiation environment.) A plastic anti-coincidence scintillation shield, essentially transparent to gamma-ray photons, protected the detectors from high-energy charged particles entering from the front. For all seven modules, the unwanted background effects of particles or photons entering from the rear was suppressed by a "phoswich" design, in which the active NaI detecting element was optically coupled to a layer of CsI on its rear surface, which was in turn optically coupled to a single photomultiplier tube for each of the seven units. Because the NaI has a much faster response time (~0.25 μs) than the CsI (~1 μs), electronic pulse shape discriminators could distinguish good events in the NaI from mixed events accompanied by a simultaneous interaction in the CsI. The largest, or High Energy Detector (HED), occupied the central position and covered the upper range from ~120 keV to 10 MeV, with a field-of-view (FOV) collimated to 37° FWHM. Its NaI detector was 5 inches (13 cm) in diameter by 3 inches (7.6 cm) thick. The extreme penetrating power of photons in this energy range made it necessary to operate the HED in electronic anti-coincidence with the surrounding CsI and also the six other detectors of the hexagon. Two Low Energy Detectors (LEDs) were located in positions 180° apart on opposite side of the hexagon. They had thin ~3 mm thick NaI detectors, also 5 inches (13 cm) in diameter, covering the energy range from ~10–200 keV. Their FOV was defined to fan-shaped beams of 1.7° x 20° FWHM by passive, parallel slat-plate collimators. The slats of the two LEDs were inclined to ±30° to the nominal HEAO scanning direction, crossing each other at 60°. Thus, working together, they covered a wide field of view, but could localize celestial sources with a precision determined by their 1.7° narrow fields. The four Medium Energy Detectors (MEDs), with a nominal energy range of 80 keV — 3 MeV, had 3 inches (7.6 cm) dia by 1 inch (2.5 cm) thick NaI detector crystals, and occupied the four remaining positions in the hexagon of modules. They had circular FOVs with a 17° FWHM. The primary data from A4 consisted of "event-by-event" telemetry, listing each good (i.e., un-vetoed) event in the NaI detectors. The experiment had the flexibility to tag each event with its pulse height (proportional to its energy), and a one or two byte time tag, allowing precision timing of objects such as gamma-ray bursts and pulsars. Results of the experiment included a catalog of the positions and intensities of hard X-ray (10–200 keV) sources, a strong observational basis for extremely strong magnetic fields (of order 1013 G) on the rotating neutron stars associated with Her X-1 and 4U 0115+634, a definitive diffuse component spectrum between 13 and 200 keV, discovery of the power-law shape of the Cygnus X-1 power density spectrum, and discovery of slow intensity cycles in the X-Ray sources SMC X-1 and LMC X-4, resulting in approximately 15 Ph.D theses and ~100 scientific publications. The A4 instrument was provided and managed by the University of California at San Diego, under the direction of Prof. Laurence E. Peterson, in collaboration with the X-ray group at MIT, where the initial A4 data reduction was performed under the direction of Prof. Walter H. G. Lewin.

Illustrations

Worked examples

Example 1 — a first encounter with High Energy Astronomy Observatory 1

Start with the simplest possible case. Write down what High Energy Astronomy Observatory 1 claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In astronomy, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to High Energy Astronomy Observatory 1 before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about High Energy Astronomy Observatory 1 ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of High Energy Astronomy Observatory 1

In research: High Energy Astronomy Observatory 1 appears in astronomy research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses High Energy Astronomy Observatory 1 in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: High Energy Astronomy Observatory 1 is common in secondary-school and first-year university syllabi. It links to neighbouring topics 1977 in spaceflight, August 1977 in the United States, Gamma-ray telescopes, so understanding it makes those chapters shorter.
In everyday life: Look for High Energy Astronomy Observatory 1 outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study High Energy Astronomy Observatory 1 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what High Energy Astronomy Observatory 1 means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain High Energy Astronomy Observatory 1 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is High Energy Astronomy Observatory 1 in simple terms?

Why does High Energy Astronomy Observatory 1 matter?

Because it connects several astronomy ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study High Energy Astronomy Observatory 1?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on High Energy Astronomy Observatory 1.