Japan's next solar physics mission, Solar-B, will place the first (*)
large (50 cm) solar optical telescope
in space. Launch is scheduled in August 2004.
Whereas Yohkoh (Solar-A) continues
to be highly successful in studying the active Sun, with
emphasis on high-energy phenomena in the corona, Solar-B
will study the connections between fine magnetic field elements
in the photosphere and the structure and dynamics of the
entire solar atmosphere.
The mission will perform three basic types
of observation with high spatial, spectral and temporal resolution
:
- Determination of the photospheric magnetic
vector and velocity fields.
- Observation of the properties of the resulting
plasma structures in the transition region and corona.
- Measurement of the detailed density, temperature
and velocity of these structures.
A coordinated set of instruments will deliver
these observations :
- A 0.5 m optical telescope equipped with a
vector magnetograph, narrow band imager and spectrometer to obtain
photospheric magnetic and velocity fields at 0.2 arc sec (~150
km) resolution.
- An EUV imaging spectrometer to obtain
plasma velocities to an accuracy of <= 10 km s-1 along
with temperatures and densities in the transition region and
corona at <2 arc sec resolution.
- An X-ray/EUV telescope to image transition
region and coronal plasma in the range 0.5 - 20 MK at ~2 arc
sec resolution.
The EUV imaging spectrometer (EIS) will be built by a consortium
led by MSSL.
EIS consists of a multi-layer coated single mirror telescope,
and a stigmatic imaging spectrometer incorporating a multilayer
coated diffraction grating. The image produced by the primary
mirror is imaged onto and entrance slit/slot and the light which
passes through this spectrometer aperture is dispersed and re-imaged
in the focal plane of the CCD detector.
The UK will provide the structure of the EIS instrument,
the CCD camera and its electronics, and the main
instrument electronics system. The CCDs for EUV detection
will be procured from UK industry (Marconi Ltd).
The Naval Research Laboratory,
Washington DC, in association with the NASA
Goddard Space Flight Center,
Greenbelt MD, will provide the instrument's optics and their
mechanisms, including the entrance filter, multilayer-coated
mirror and grating, and the spectrograph slit.
The members of the UK consortium having a hardware role are
MSSL, Birmingham University and
the Rutherford Appleton Laboratory.
Other consortium members are in university research groups in
Cambridge, Imperial
College, and St.
Andrews.
Japan's National Astronomical
Observatory will be involved in the interaction with ISAS, Japan's Institute for
Space and Astronautical Science.