The FOV of MAXI slit cameras is defined by the combination
of slat collimator and a slit aperture.
The slat collimator defines a narrow and long field of view
(1.5 FWHM
for a single collimator).
The 1-D position-sensitive X-ray detectors are employed to map the
X-ray sky within the narrow fan-beam FOV.
Three collimated detectors are combined
together to cover a half circle FOV (1.5
) simultaneously.
The ISS will rotate synchronously with its orbit so that one
side will always points towards the center of the Earth and the
opposite side will see the sky all the time.
Figure 1 shows how it scans across the sky in the course of an
orbit. Since observations are not possible at particular regions of
the orbit with high charged particle flux, two fan beams are used to
simultaneously cover two perpendicular fields of view, one centered on
the zenith ("zenith view''), and the other centered at the forward
direction of motion of the space station ("horizon view''). This
will enable MAXI to achieve a more uniform coverage of the sky.
To obtain the maximum scientific outputs within the constraints of the
platform (JEM-EF), we designed the
layout of instruments on MAXI as shown in Fig. 2.
The size is 1.85 m (L)
0.8 m (W)
1.0 m (H) and the
mass is about 500 kg.
It is equipped with two scientific instruments,
GSC (Gas Slit Cameras) and SSC (Solid-state Slit Cameras)
(Mihara et al. 1999).
GSC consists of an 1-D position sensitive proportional
counter with a slat collimator and a slit on top.
The proportional counter is based on the WXM/HETE2 counters
with the gas of 1.4 atm composed of 97% Xe and 3% CO2.
It is sensitive to X-rays in 2-30 keV.
Three identical GSC detectors are combined to cover a fan-beam
field of view with 180
1.5
.There are four such detector sets, of which two cover the zenith view,
and the other two cover the horizon view.
The combined geometrical area is
cm2 with
the angular resolution of better than
1.5
for 3-8 keV photons.
SSC uses
X-ray CCD to achieve soft X-ray response.
The CCD chips will be developed by Osaka University and Hamamatsu Photonics.
It is the full-frame transfer type, with pixel size of 25
m
square, and 1024
1024 pixels per chip.
The energy range is 0.5-10 keV.
Each CCD chip is employed as one-dimensional position sensitive detector
with the fast readout.
In the present design, we use 32 chips in total with an effective area
of 200 cm2.
Copyright The European Southern Observatory (ESO)