2.8 Development of X-ray Astronomy
79
2.8.3 Advanced Satellite for Cosmology and Astrophysics
The Advanced Satellite for Cosmology and Astrophysics (ASCA), formerly named
ASTRO-D, is the fourth cosmic X-ray astronomy satellite by Japan Aerospace Exploration Agency (JAXA), and the second for which the USA provided a part of the
scientific payloads. On February 20, 1993, the satellite was launched from Kagoshima
Space Center of Japan into an Earth orbit of 523 km perigee, 615 km apogee and
31° inclination. The ASCA operated successfully for over 7 years until its attitude
control was lost on July 14, 2000 during a geomagnetic storm, after which no scientific observations were performed, and finally re-entered the Earth’s atmosphere to
burn out on March 2, 2001.
The ASCA carried four large-area X-ray telescopes, in which at the focal point of
two is a gas imaging spectrometer in 0.7–10 keV energy band and at the focal point
of the other two is a solid-state imaging spectrometer in 0.4–10 keV. The telescope
belongs to Wolter type, with 1.2-m diameter, 3.5-m focal length, and collecting area
of 1300 cm
2 at 1 keV and 600 cm
2 at 7 keV. The ASCA is the first X-ray astronomy
mission to combine imaging capability with a broad passband, good spectral resolution and a large effective area. It also is the first X-ray astronomy satellite using
the CCD. Therefore, the primary scientific objective of the ASCA is the X-ray spectroscopy of astrophysical plasma, especially the analysis of discrete features such
as emission lines and absorption edges. The sensitivity of the instruments carried
by the ASCA allowed for the first detailed, broadband spectra of distant quasars to
be derived. Moreover, the suite of the instruments provided the best opportunity at
the time for identifying the sources whose combined emission makes up the cosmic
X-ray background.
2.8.4 Rossi X-ray Timing Explorer
The Rossi X-ray Timing Explorer (RXTE) is a satellite that observes the time variation of astronomical X-ray sources, named after Italian experimental physicist Bruno
Benedetto Rossi (1905–1993). On December 30, 1995, the satellite was launched
from Cape Canaveral into a nearly circular Earth orbit of 283-km altitude and 23degree inclination, and hereafter operated by the NASA. There were three payloads
installed on the satellite, an All-Sky Monitor (ASK), a Proportional Counter Array
(PCA) and a High-Energy X-ray Timing Experiment (HEXTE), and their performance indicators are, respectively, listed in Table 2.3. The RXTE’s mission is to
observe X-rays from black holes, neutron tars, X-ray pulsars and X-ray bursts. The
significantly scientific results from the observations of RXTE mainly included: to
show an evidence for the existence of the frame-dragging effect predicted by the
theory of general relativity; to locate a candidate intermediate-mass black hole,
named M82 X-1; to prove that the diffuse background X-ray glow in our galaxy
comes from innumerable, previously undetected white dwarfs and from other stars’
79
2.8.3 Advanced Satellite for Cosmology and Astrophysics
The Advanced Satellite for Cosmology and Astrophysics (ASCA), formerly named
ASTRO-D, is the fourth cosmic X-ray astronomy satellite by Japan Aerospace Exploration Agency (JAXA), and the second for which the USA provided a part of the
scientific payloads. On February 20, 1993, the satellite was launched from Kagoshima
Space Center of Japan into an Earth orbit of 523 km perigee, 615 km apogee and
31° inclination. The ASCA operated successfully for over 7 years until its attitude
control was lost on July 14, 2000 during a geomagnetic storm, after which no scientific observations were performed, and finally re-entered the Earth’s atmosphere to
burn out on March 2, 2001.
The ASCA carried four large-area X-ray telescopes, in which at the focal point of
two is a gas imaging spectrometer in 0.7–10 keV energy band and at the focal point
of the other two is a solid-state imaging spectrometer in 0.4–10 keV. The telescope
belongs to Wolter type, with 1.2-m diameter, 3.5-m focal length, and collecting area
of 1300 cm
2 at 1 keV and 600 cm
2 at 7 keV. The ASCA is the first X-ray astronomy
mission to combine imaging capability with a broad passband, good spectral resolution and a large effective area. It also is the first X-ray astronomy satellite using
the CCD. Therefore, the primary scientific objective of the ASCA is the X-ray spectroscopy of astrophysical plasma, especially the analysis of discrete features such
as emission lines and absorption edges. The sensitivity of the instruments carried
by the ASCA allowed for the first detailed, broadband spectra of distant quasars to
be derived. Moreover, the suite of the instruments provided the best opportunity at
the time for identifying the sources whose combined emission makes up the cosmic
X-ray background.
2.8.4 Rossi X-ray Timing Explorer
The Rossi X-ray Timing Explorer (RXTE) is a satellite that observes the time variation of astronomical X-ray sources, named after Italian experimental physicist Bruno
Benedetto Rossi (1905–1993). On December 30, 1995, the satellite was launched
from Cape Canaveral into a nearly circular Earth orbit of 283-km altitude and 23degree inclination, and hereafter operated by the NASA. There were three payloads
installed on the satellite, an All-Sky Monitor (ASK), a Proportional Counter Array
(PCA) and a High-Energy X-ray Timing Experiment (HEXTE), and their performance indicators are, respectively, listed in Table 2.3. The RXTE’s mission is to
observe X-rays from black holes, neutron tars, X-ray pulsars and X-ray bursts. The
significantly scientific results from the observations of RXTE mainly included: to
show an evidence for the existence of the frame-dragging effect predicted by the
theory of general relativity; to locate a candidate intermediate-mass black hole,
named M82 X-1; to prove that the diffuse background X-ray glow in our galaxy
comes from innumerable, previously undetected white dwarfs and from other stars’