76
2 Observations of Radio and X-ray Pulsars
discoveries made by the Copernicus were those of several long-period pulsars, with
the rotation periods of several minutes instead of the more typical seconds or less.
The Astronomical Netherlands Satellite (ANS) jointly funded by the Netherlands
Institute for Space Research and the NASA, a space-based X-ray and ultraviolet
telescope, was launched into the Earth orbit in August 1974. The ANS could measure
X-ray photons in 2–30 keV energy band with a 60 cm
2 detector. The positions of the
Galactic and extra-galactic X-ray sources were found by the ANS. The ANS also
measured their spectra, looked at their variations over time, discovered X-ray bursts
and detected X-rays from Capella, which is one of the brightest stars in the X-ray
band with an X-ray luminosity about 10,000 times that of the Sun. Moreover, the
UK and USA also jointly developed a space observatory dedicated to observing the
sky in the X-ray band, a satellite called Ariel-5, launched from San Marco platform
in the Indian Ocean in October 1974. The satellite has the all-sky monitor composed
of two one-dimensional pinhole cameras, which can scan most of the sky area for
every revolution. Its angular resolution is 10° × 10°, with an effective area of 3 cm
2 ,
and an energy bandpass of 3–6 keV. The Aerial-5 detected the X-ray pulsars whose
rotational periods get to several minutes.
In the late 1970s, NASA started to develop X-ray astronomy research program, the
High Energy Astronomy Observatory (HEAO), which include a series of three large
low-earth-orbiting satellites for X-ray and gamma-ray astronomy and cosmic-ray
investigations. The three satellites were, respectively, denoted by HEAO-1, HEAO-2
(also known as the Einstein Observatory) and HEAO-3 after launching. The satellites
were three-axis stabilized to arc-minute accuracy, with fixed solar panels. The HEAO1 surveyed the sky in the X-ray portion of the electromagnetic spectrum from 0.2 keV
to 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 h. The HEAO-2 carried a single large grazing-incidence focusing X-ray telescope
that provided unprecedented levels of sensitivity and arc-second angular resolution of
point sources and extended objects. There were four focal plane instruments installed
in the HEAO-2, including a high-resolution imaging camera in 0.15–3 keV energy
range, an imaging proportional counter in 0.4–4 keV, a solid-state spectrometer in
0.5–4.5 keV and a Bragg focal plane crystal spectrometer. The HEAO-3 included
three scientific instruments: one cryogenic high-resolution germanium gamma-ray
spectrometer and two devoted to cosmic-ray observations. The normal operating
mode of the HEAO-3 was a continuous celestial scan, spinning approximately once
every 20 min about the satellite’s Z-axis, which was nominally pointed to the Sun.
Thereafter, some countries and international organizations successively developed
and launched a series of X-ray astronomy satellites, such as Aerial-6, Hakucho,
Tenma, European X-ray Observatory Satellite (EXOSAT), Ginga, Kvant/Mir, Granat,
Röntgen Satellite (ROSAT) and Spartan, and the activities continued into the 1990s.
The cosmic X-ray detecting activities since 1970 are listed in Table 2.2,
where famous X-ray astronomy satellites include ROSAT, Advanced Satellite for
Cosmology and Astrophysics (ASCA), Rossi X-ray Timing Explorer (RXTE),
Chandra X-ray Observatory and X-ray Multi-Mirror Mission-Newton (XMMNewton).
2 Observations of Radio and X-ray Pulsars
discoveries made by the Copernicus were those of several long-period pulsars, with
the rotation periods of several minutes instead of the more typical seconds or less.
The Astronomical Netherlands Satellite (ANS) jointly funded by the Netherlands
Institute for Space Research and the NASA, a space-based X-ray and ultraviolet
telescope, was launched into the Earth orbit in August 1974. The ANS could measure
X-ray photons in 2–30 keV energy band with a 60 cm
2 detector. The positions of the
Galactic and extra-galactic X-ray sources were found by the ANS. The ANS also
measured their spectra, looked at their variations over time, discovered X-ray bursts
and detected X-rays from Capella, which is one of the brightest stars in the X-ray
band with an X-ray luminosity about 10,000 times that of the Sun. Moreover, the
UK and USA also jointly developed a space observatory dedicated to observing the
sky in the X-ray band, a satellite called Ariel-5, launched from San Marco platform
in the Indian Ocean in October 1974. The satellite has the all-sky monitor composed
of two one-dimensional pinhole cameras, which can scan most of the sky area for
every revolution. Its angular resolution is 10° × 10°, with an effective area of 3 cm
2 ,
and an energy bandpass of 3–6 keV. The Aerial-5 detected the X-ray pulsars whose
rotational periods get to several minutes.
In the late 1970s, NASA started to develop X-ray astronomy research program, the
High Energy Astronomy Observatory (HEAO), which include a series of three large
low-earth-orbiting satellites for X-ray and gamma-ray astronomy and cosmic-ray
investigations. The three satellites were, respectively, denoted by HEAO-1, HEAO-2
(also known as the Einstein Observatory) and HEAO-3 after launching. The satellites
were three-axis stabilized to arc-minute accuracy, with fixed solar panels. The HEAO1 surveyed the sky in the X-ray portion of the electromagnetic spectrum from 0.2 keV
to 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 h. The HEAO-2 carried a single large grazing-incidence focusing X-ray telescope
that provided unprecedented levels of sensitivity and arc-second angular resolution of
point sources and extended objects. There were four focal plane instruments installed
in the HEAO-2, including a high-resolution imaging camera in 0.15–3 keV energy
range, an imaging proportional counter in 0.4–4 keV, a solid-state spectrometer in
0.5–4.5 keV and a Bragg focal plane crystal spectrometer. The HEAO-3 included
three scientific instruments: one cryogenic high-resolution germanium gamma-ray
spectrometer and two devoted to cosmic-ray observations. The normal operating
mode of the HEAO-3 was a continuous celestial scan, spinning approximately once
every 20 min about the satellite’s Z-axis, which was nominally pointed to the Sun.
Thereafter, some countries and international organizations successively developed
and launched a series of X-ray astronomy satellites, such as Aerial-6, Hakucho,
Tenma, European X-ray Observatory Satellite (EXOSAT), Ginga, Kvant/Mir, Granat,
Röntgen Satellite (ROSAT) and Spartan, and the activities continued into the 1990s.
The cosmic X-ray detecting activities since 1970 are listed in Table 2.2,
where famous X-ray astronomy satellites include ROSAT, Advanced Satellite for
Cosmology and Astrophysics (ASCA), Rossi X-ray Timing Explorer (RXTE),
Chandra X-ray Observatory and X-ray Multi-Mirror Mission-Newton (XMMNewton).