for diffraction limited resolution. Lf we take into
consideration various degradation factors, for example the
effect of atmosphere, imcompleteness of hardware system, we
must extend the aperture a little more. Therefore, we assumed
l m aperture as an actually required diameter of telescope.
Another assumptions are the glass material BK-7 for correcting
plate and 1.5 for parameter k which determines the radius of
neutral zone. Then, utilizing equation (3), we can fix the
parameters «€ , A and R as follows:
(3.68616 x 1079
(à » 3.92868 x 10713
R = 1.06825 x 10% mm
From these parameters, non-spherical coefficients of correcting
plate are determined, and ray trace, aberrations, spot diagram
and OTF are calculated.
3. Calculation of optical performances
Calculations of aberrations and OTF are performed by wave
optics, so the calculated results will give physical insight of
the system performances. Incidentally geometrical optics
sometimes gives too superior results for such a reflecting
system. The focal plane of Schmidt telescope is spherical as
shown. in PFPig..2,. F. The spot-diagrams of on axis and semi-
field angle 1.65 degree on this curved focal plane are shown in
Fig. 74a), {b)iand-the spot diagram at 1.65 degree on flat
plane F' is shown in Fig. 7, (c) for comparison. The former
two spot diagrams are smaller than the assumed photodiode
aperture 14 um, but the latter spot diagram on flat plane is
large extraordinarily. Fig. 8 is the OTF for Fig. 7 (b). 'It
is clear that ‘the OTF value at the cut off ‘frequency of
photodiode aperture 14 um is about 0.67 for both tangential and
sagital directions. This means that the conical scan utilizes
the curved focal plane itself gives sufficient performance for
100 m spatial resolution from geosynchronous orbit.
4. Conclusion
100 m spatial resolution at l.l um wave length can be realized
with good performance utilizing conical scan on the curved
focal plane of Schmidt telescope. The diameter of the
telescope is 1 m and the focal length is about 5 m. This
dimension is rather small compared to the space telescope and
it's realization is not so difficult. The observation from
geosynchronous orbit is a'staring type and sufficient
integration time for signal will be obtained. By focal plane
construction we can extend the image to surrounding sea area of
the Japan islands and to other area, for example, the Chinese
continent area.
Reference
1. Handbook of Optics, Optical Society Of America, 1978,
McGraw-Hill.
79