m) observations, and can achieve very deep observations
with high spatial resolution8.
On the other hand, FIRST has its weight on longer wavelengths,
and can make high-resolution spectroscopic observations
as well as photometric observations9.
Two other large missions (NGST8, FIRST9)
for infrared and sub-mm regions
have been proposed to be launched by 2010.
Table 3 summaries characteristics of these missions
together with those of the HII/L2 mission.
Figure 6 compares the sensitivity of the three missions.
Table 3 and Figure 6
shows that each mission has its own
unique capability. NGST has its weight on near-infrared
(1-5 m) observations, and can achieve very deep observations
with high spatial resolution8.
On the other hand, FIRST has its weight on longer wavelengths,
and can make high-resolution spectroscopic observations
as well as photometric observations9.
However, both NGST and FIRST have only moderately cooled telescopes, and thermal radiation from the telescopes degrade the sensitivity very much at mid- and far-infrared (see dotted lines in Figure 6). On the other hand, the HII/L2 mission has good sensitivity throughout the infrared region, and achieves supreme sensitivity especially in mid- to far-infrared region, since it has a cooled telescope. Hence, the HII/L2 mission is complementary with NGST and FIRST, and we need these three missions to cover the whole infrared region with good sensitivity and high spatial resolution. International collaborations are essential to make these important missions possible, and also to make well-organized observations with these three unique missions.
| Mission | Aperture | Temperature of | Core | Launch |
| Size | the Telescope | Wavelength | Year | |
| NGST8 | 6-8 m | < 70 K | 1-5 m | 2007 |
| HII/L2 | 3.5 m | 4.5 K | 5-200 m | 2010 |
| FIRST9 | 3-3.5 m | 80 K | 80-600 m | 2005 |
This paper is based upon stimulating discussions with many people in Japan on the future of infrared astronomy. We would like to thank all of them.
